Ciprofloxacin conjugated to diphenyltin(iv): A novel formulation with enhanced antimicrobial activity

Article abstract of DOI:10.1039/d0dt01665a

The metalloantibiotic of formula Ph2Sn(CIP)2 (CIPTIN) (HCIP = ciprofloxacin) was synthesized by reacting ciprofloxacin hydrochloride (HCIP·HCl) (an antibiotic in clinical use) with diphenyltin dichloride (Ph2SnCl2DPTD). The complex was characterized in the solid state by melting point, FT-IR, X-ray Powder Diffraction (XRPD) analysis, 119Sn M?ssbauer spectroscopy, X-ray Fluorescence (XRF) spectroscopy, and Thermogravimetry/Differential Thermal Analysis (TG-DTA) and in solution by UV-Vis, 1H NMR spectroscopic techniques and Electrospray Ionisation Mass Spectrometry (ESI-MS). The crystal structure of CIPTIN and its processor HCIP was also determined by X-ray crystallography. The antibacterial activity of CIPTIN, HCIP·HCl, HCIP and DPTD was evaluated against the bacterial species Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), by the means of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Inhibition Zones (IZs). CIPTIN shows lower MIC values than those of HCIP·HCl (up to 4.2-fold), HCIP (up to 2.7-fold) or DPTD (>135-fold), towards the tested microbes. CIPTIN is classified into bactericidal agents according to MBC/MIC values. The developing IZs are 40.8 ± 1.5, 34.0 ± 0.8, 36.0 ± 1.1 and 42.7 ± 0.8 mm, respectively which classify the microbes P. aeruginosa, E. coli, S. aureus and S. epidermidis to susceptible ones to CIPTIN. These IZs are greater than the corresponding ones of HCIP·HCl by 1.1 to 1.5-fold against both the tested Gram negative and Gram positive bacteria. CIPTIN eradicates the biofilm of P. aeruginosa and S. aureus more efficiently than HCIP·HCl and HCIP. The in vitro toxicity and genotoxicity of CIPTIN were tested against human skin keratinocyte cells (HaCaT) (IC50 = 2.33 μM). CIPTIN exhibits 2 to 9-fold lower MIC values than its IC50 against HaCaT, while its genotoxic effect determined by micronucleus assay is equivalent to the corresponding ones of HCIP·HCl or HCIP.

Full text of DOI:10.1039/d0dt01665a

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N. Banti, N. Kourkoumelis, E. Moushi, A. Tasiopoulos, A. P. Douvalis, C. Papachristodoulou, A.
Hatzidimitriou, T. Bakas and S. K. Hadjikakou, Dalton Trans., 2020, DOI: 10.1039/D0DT01665A.
Volume 46
Number 10
14 March 2017
Pages 3073-3412
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DOI: 10.1039/D0DT01665A
Ciprofloxacin conjugated to diphenyltin(IV); A novel formulation with enhanced
antimicrobial activity.
M.P. Chrysouli[a], C.N. Banti[a],*, N. Kourkoumelis[b], E.E. Moushi[c], A.J. Tasiopoulos[d], A.
Douvalis[e], C. Papachristodoulou[f], A.G. Hatzidimitriou[g], T. Bakas[e], S.K. Hadjikakou[a,h],
*
[a] Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110
Ioannina, Greece
[b] Medical Physics Laboratory, Medical School, University of Ioannina, Greece
[c] Department of Life Sciences, The School of Sciences, European University Cyprus, Cyprus
[d] Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus
e
[ ]
Mössbauer Spectroscopy and Physics of Material Laboratory, Department of Physics, University
of Ioannina, Greece
f
[ ]
Department of Physics, University of Ioannina, Greece
[g] Department of Chemistry, Aristotle University of Thessaloniki, Greece;
[h] University Research Center of Ioannina (URCI), Institute of Materials Science and Computing,
Ioannina, Greece
*All correspondence should be addressed to:
Dr. C.N. Banti (Postdoctoral Fellow); email: cbanti@uoi.gr
Dr. S.K. Hadjikakou (Professor); e-mail: shadjika@uoi.gr; tel. x30-26510-08374, x30-26510-08362
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Abstract
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DOI: 10.1039/D0DT01665A
The metalloantibiotic of formula Ph2Sn(CIP)2 (CIPTIN) (HCIP= ciprofloxacin) was
synthesized by reacting ciprofloxacin hydrocloride (HCIP·HCl) (an antibiotic in clinical use) with
the diphenyltin dichloride (Ph2SnCl2 DPTD). The complex was characterized in solid state by
melting point, FT-IR, X-ray Powder Diffraction (XRPD) analysis, 119Sn Mössbauer spectroscopy,
X-ray Fluorescence (XRF) spectroscopy, Thermogravimetry/Differential Thermal Analysis (TG-
1
DTA) and in solution by UV-Vis, H-NMR spectroscopic techniques and Electrospray Ionisation
Mass Spectrometry (ESI-MS). The crystal structure of CIPTIN and its processor HCIP were also
determined by X-ray crystallography.
The antibacterial activity of CIPTIN, HCIP·HCl, HCIP and DPTD was evaluated against
the bacterial species Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli),
Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), by the means
of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and
Inhibition Zones (IZs). CIPTIN shows lower MIC values than those of HCIP·HCl (up to 4.2-
folds), HCIP (up to 2.7-folds) or DPTD (>135-folds), towards the tested microbes. CIPTIN is
classified to bactericidal agents according to MBC/MIC values. The developing IZs are 40.8±1.5,
34.0±0.8, 36.0±1.1 and 42.7±0.8 mm, respectively which classify the microbe’s P. aeruginosa, E.
coli, S. aureus and S. epidermidis to susceptible ones to CIPTIN. These IZ’s are greater to the
corresponding ones of the HCIP·HCl by 1.1 to 1.5-folds against both Gram negative and positive
bacteria tested. CIPTIN eradicates the biofilm of P. aeruginosa and S. aureus more efficiently than
HCIP·HCl and HCIP. The in vitro toxicity and genotoxicity of CIPTIN were tested against
human skin keratinocyte cells (HaCaT) (IC50= 2.33 μΜ). CIPTIN exhibits 2 to 9-folds lower MIC
values against than its IC50 against HaCaT, while its genotoxic effect determined by micronucleus
assay is equivalent to the corresponding ones of HCIP·HCl or HCIP.
Keywords: Bioinorganic Chemistry; Organotin(IV) Compounds; Crystal Structure; Antibacterial
Studies; Ciprofloxacin
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Introduction
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DOI: 10.1039/D0DT01665A
Ciprofloxacin, a second-generation fluoroquinolone, is effective against both Gram-positive
and Gram-negative pathogenic bacteria [1]. It exhibits good bioavailability or tissue permeability,
low incidence of toxic effects and bacteriostatic activity [2]. Generally, the bacteriocidal agents are
preferred than bacteriostatic ones, against infections, since they limit the development of resistance
towards bacteria [3]. However, microbes such as P. aeruginosa, E. coli, S. aureus and S. epidermidis
are reported to have developed resistance towards ciprofloxacin [4]. Hence efforts were made in
recent years to modify ciprofloxacin with metal ions, in order to increase its antibacterial activity
against resistant strains [5-8]
.
The conjugation of metals with drugs (CoMeDs), is a new research area being investigated
for discovery of new synergistic therapeutic modalities. The term “conjugation” is used for
[9-10]
polymeric drug formulations, to emphasize the synergistic effect of a metal with a drug
.
CoMeDs combine metals with specific classes of drugs aiming to create new agents possessing
altogether new properties than the drugs from which they were prepared [9-10]. From this point of
view, organotin(IV) compounds which contain active drugs as ligands are expected to exhibit
enhance effectiveness due to the synergy which is developing between the RnSn(IV) (R= alkyl or
aryl group; n=1 to 3) moiety and the drug. Besides, organotin compounds are commercially used as
agricultural biocides [11-12]. Recently, Pokharia et.al have shown that triorganotin(IV) complexes of
ciprofloxacin (R3Sn(CIP) (R= Me-, Cy-)) exhibit better antibacterial effect than free ciprofloxacin
against E. faecalis, S. aureus, K. pneumoniae, E. coli, P. aeruginosa, and P. mirabilis [13]
.
With the aim to develop new antimicrobial agents with enhanced activity capable of
overcoming bacterial resistance [9,10,14-17], the metalloantibiotic of ciprofloxacin (HCIP, (Scheme
1)), having the formula Ph2Sn(CIP)2 (CIPTIN) was synthesized, characterized and evaluated
against bacterial strains P. aeruginosa, E. coli, S. aureus and S. epidermidis. Moreover, the
combination of an antibiotic, ciprofloxacin, which possesses pharmacological significance and a
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metal with known biological activity, tin(IV), are expected to throw light on principles that govern
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the synergy between metals and drugs in these metallodrugs.
O
OH
Cl-
F
8
O
6
2
5
b
N
N
a
+H2N
Scheme 1. The used ligand hydrocloride ciprofloxacin
Results and discussion
General aspects: A solution of HCIP·HCl in water was initially treated with an excess of KOH in
1:1.5 molar ratio to form KCIP. A solution of DPTD (Ph2SnCl2, diphenyltin dichloride) in MeOH
(1:2 metal to KCIP) was added to the previous one under continues stirring for 30 min, (Scheme 2)
and the suspension was filtered off.
O
O-
O
O
K+
F
KCl
F
O
O
KOH
HCIP·HCl + KOH
N
N
N
N
H2O
HN
H2N
KCIP
HCIP
Ph2SnCl2
HN
F
O
N
O
N
Ph
Sn
Ph
O
O
O
N
O
N
F
NH
CIPTIN
Scheme 2. Preparation reaction of CIPTIN
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Crystals of CIPTIN were grown by slow evaporation of ddH2O/MeOH solution. Besides, crystals
of the HCIP were isolated from the filtrate of the intermediate solution (Scheme 2). CIPTIN is
stable when it is stored at ambient condition and it is soluble in MeOH, CH2Cl2, DMSO and
acetone.
Solid state studies
Crystal and molecular structure of CIPTIN and HCIP: Here we report the crystal structures of the
zwitterionic form of HCIP (anhydrous) and that of CIPTIN using single crystal X-Ray
crystallography for the first time. Unit cell parameters (only) of anhydrous HCIP was determined
earlier from powder X-Ray diffraction data by Fabbiani et al. [18]. The reported unit cell parameters
reveal HCIP crystallizes in P-1 space group with a = 7.9606(2), b = 8.5798(2) and c = 10.7739(3)
Å, α = 87.868(4), β = 87.868(4), γ = 88.212(4)ο, V = 732.43(4) Å3 [18]. In our study we found HCIP
(anhydrous) crystallizes in P-1 space group with almost identical unit cell parameters: a =
7.8945(7), b = 8.5010(8) and c = 10.7522(9) Å and α= 87.440(7), β= 84.496(7) γ= 88.912(7)ο, V=
717.47 Å3. Since synthesis of CIPTIN requires HCIP HCl as starting material, HCIP is an
intermediate of the methodology for the preparation. For this reason, a complete refinement of the
crystal structure of HCIP was attempted independently to clarify the route followed. ORTEP
diagrams of CIPTIN and HCIP along with their selected bond distances and angles are shown in
Figures 1-2.
Figures 1-2
CIPTIN is a covalent organotin compound. It consists of two ciprofloxacin ligands and one
Ph2Sn(IV) moiety. Ciprofloxacin coordinates to tin(IV) through the anionic oxygen atom of its de-
protonated carboxylic group and the oxygen atom of its keto group. Thus, two oxygen atoms from
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each ciprofloxacin and two carbon atoms from the phenyl groups form a distorted octahedral (Oh)
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arrangement around the Sn(IV) ion. The equatorial plane of the octahedron around the Sn(IV) is
constituted by two keto oxygen atoms (O3, O3a) and two carbons of phenyl groups (O3-Sn1-O3a=
80.96(11)o, O3-Sn1-C18a= 166.12(15) o). The axial positions are occupied by the two carboxylic
oxygen atoms (O1 and O1a) (O1-Sn1-O1a= 155.64(11)o). The final arrangement of the ligands in
CIPTIN lead to the Δ-cis-[Ph2Sn(CIP)2] stereoisomer (Figure 1B). Only the Δ-cis-[Ph2Sn(CIP)2]
isomer has been isolated in the crystal lattice indicating stereo-selectivity of the preparation reaction
(Figure 1B).
The two C-O bond distances of the carboxylic group (O1-C6= 1.298(5) and O2-C6=
1.216(5) Å) are almost equivalent, in CIPTIN, confirming the deprotonation which it undergoes.
The O1-C6 bind is slightly longer than the corresponding O2-C6 one due to the donation of O1
atom towards Sn(IV). The C-O bond length of keto group (O3-C2= 1.284(5) Å) suggesting the
retention of the double nature of this bond.
The Sn-O bond distances (Sn1-O1= 2.135(3) and Sn1-O3= 2.158(3) Å) are in accordance to
the corresponding ones found previously in [(n-Bu-)2Sn(nap)2] (napH= naproxen) (Sn1-O1=
2.136(7) and Sn1-O2= 2.506(6) Å) [19], in [Me2Sn(salH)2] (salH2= salicylic acid)) (Sn1-O171=
2.1069(18), Sn1-O271= 2.1087(15), Sn1-O172= 2.5145(15) and Sn1-O272= 2.5773(15) Å) [20] and
in [(n-Bu)2Sn(salH)2] (Sn1-O172= 2.121(3), Sn1-O272= 2.105(4), Sn1-O171= 2.565(4) and Sn1-
O271= 2.632(4) Å) [20]. However, in the cases of [(n-Bu-)2Sn(nap)2], [Me2Sn(salH)2] and [(n-
Bu)2Sn(salH)2] the ligands chelate to Sn(IV), through their carboxylic groups.
Strong hydrogen bonding interactions N3[H3]···O2= 2.733(6) Å lead to 2D layers (Figure
3). The layers are consisted of squares which are formed by four CIPTIN molecules
(Sn···Sn=13.969 Å and Sn-Sn-Sn= 87.03o).
Figure 3
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The two C-O bond distances of the carboxylic group in anhydrous HCIP (O1-C14=
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1.247(3) and O2-C14 (1.266(3) Å) are equivalent suggesting its de-protonation (Figure 2). The
corresponding C1-O1, C1-O2 bond lengths of the HCIP hexahydrate (HCIP·6H2O) are 1.259(2)
and 1.255(2) Å respectively [8]. Moreover, the O1-C14-O2 angle is 125.3(2)°. This is in accordance
to the corresponding bond angle found in HCIP·6H2O (125.11(12)o) [8]. The N3-C11 and N3-C12
bond distances, on the other hand, are 1.481(3) and 1.485(3) Å, respectively, suggesting single N-C
bonds (Figure 2). This is further supported by the C11-N3-C12 bond angle of 109.0(2)°, which is
close to the ideal 108° 28’ of sp3 hybrid. Given that two hydrogen atoms are bind to this nitrogen, a
positive charge is concluded for the ([-NH2-])+ group. Therefore, the charge distribution of the
zwitterionic anhydrous HCIP is shown in Scheme 2.
Hydrogen bonds N3[H3]···O2= 2.623(3) Å and N3[H3]···O1= 2.882(3) Å lead to 1D
ribbon assembly (Figure 2B).
Vibrational spectroscopy: The characteristic vibration bands of the free ligand (HCIP·HCl) at 1710
cm−1, 1620 cm−1 and 1385 cm−1 are assigned to the C=O, νasym(COO) and νsym(COO) vibrations,
respectively (Figure S1). The absence of the vibration band at 1710 cm−1 in the spectrum of
CIPTIN, suggests the coordination of the ligand through the oxygen atom of the keto C=O group
(Figure S1). The νasym(COO) and νsym(COO) vibration bands are shifted at 1622 cm−1 and at 1381
cm−1, respectively in the spectrum of CIPTIN. The presence of C=N band of CIPTIN at 1272
cm−1, suggests that this N atom is not involving in the coordination sphere of the metal. The
absence of (O-H) vibration at 3520 cm−1 in CIPTIN spectrum indicates the deprotonation of the
carboxyl group. Therefore ciprofloxacin is coordinated to the tin metal ion via the keto and the
carboxyl oxygen atom (Figure S1).
X-ray Powder Diffraction (XRPD) analysis: The XRPD spectrum of the powder of CIPTIN is
identical to the simulated one which is derived by using single crystal XRD data (Figure S2). This
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indicates that the formula of the molecular structure of CIPTIN remains unchanged throughout the
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sample.
119Sn Mössbauer spectroscopy: 119Sn Mössbauer spectrum at 77 K of CIPTIN is shown in Figure 4.
The spectrum of CIPTIN, consists of one asymmetric Lorentzian doublet. The occurrence of one
Lorentzian double, indicates either the existence of one type of Sn atom in CIPTIN or one
structural isomer [11,21-22]. The value of the Isomer Shift (I.S.) of CIPTIN is +0.804 mm×s-1 which
corresponds to the (4+) oxidation state [11,21-22]. The I.S. for R2Sn(IV) species lie between +0.737 to
+1.777 mm×s-1 [11,21-22]. The quadrupole splitting parameter (ΔEq) value is 2.242 mm×s-1.
Therefore, cis-octahedral geometry should be concluded for tin(IV) ion in the case of CIPTIN,
since ΔEq value lies between 1.3-2.5 mm×s-1 [11,21-22]. This value indicates an octahedral geometry
with cis-R2Sn(IV) (R= alkyl), around the tin atom of CIPTIN in accordance to X-ray structure.
Figure 4
X-ray Fluorescence (XRF) spectroscopy: The content of CIPTIN in Sn is 15.5 ± 2.3% wt, while the
calculated for C46H44F2N6O6Sn is 12.75 %.
Thermal analysis: The TG-DTA analysis of CIPTIN shows decomposition within 6 steps (112.6-
617.4 °C) with total mass losses 57.92% (Figure S3). The remaining 42.08% is due to the [(SnO2)2]
(which corresponds to Sn: 13.68 %; calc for C46H44F2N6O6Sn: 12.75 %).
Solution studies
Stability studies: The stability of CIPTIN was tested in DMSO and DMSO/water solutions by UV
1
spectroscopy (Figures S4–S5) and H-NMR for a period of 96 h (Figure S6). This period was
chosen for the stability testing, since the biological experiments require 24 or 48 h of incubation
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with CIPTIN. No changes were observed between the initial UV or H-NMR spectra and the
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corresponding ones after 96 h, confirming the retention of CIPTIN in solution (Figures S4–S6).
1
1H NMR studies: A broad resonance signal in the H-NMR spectrum of HCIP·HCl at 9.45 ppm is
[8]
attributed to H[Npiperazine ring
]
(Figure S7). This signal is shifted at 8.87 ppm in CIPTIN. The
resonance signals at 8.68, 7.97-7.92, 7.62-7.59 ppm, in the spectrum of HCIP·HCl are assigned to
the H[2C], H[5C] and H[8C], respectively (Scheme 1) [8]. These signals are observed at 8.67, 7.95-
7.92, 7.79-7.81 ppm in the spectrum of CIPTIN. The resonance signals of H[aC], H[bC],
cyclopropyl (–CH2–) in the spectrum of HCIP·HCl are appeared at 3.85, 3.47, 1.33-1.19 ppm,
respectively [8]. These signals undergo no shift in the case of the CIPTIN. The resonance signals of
DPTD at 8.05-7.80 and 7.42-7.28 ppm are shifted in the spectrum of CIPTIN at 7.72-7.58 and
7.31-7.16 ppm, respectively, indicates the coordination of tin to the antibiotic. Moreover, the
resonance signal in the spectrum of CIPTIN, at 3.16 ppm is attributed to methanol, which was used
as a solvent for the synthesis reaction.
Electrospray Ionisation Mass Spectrometry (ESI-MS): In order to confirm the retention of the
formula of CIPTIN in methanol solution, its ESI-MS spectrum was recorded. The ESI-MS
spectrum of CIPTIN is dominated by the fragment at m/z 600.0-609.0 which is attributed to the
[Ph2Sn(CIP)]+ (calculated for [C29H27N3O3FSn]+: m/z: 599.1 to 609.1) (Figure S8). The presence of
this specie which is derived from CIPTIN by cleavage of the one Sn-C(Ph) bond as part of the
decomposition pattern of [Ph2Sn(CIP)2-H+], assumes the existence of CIPTIN in the solution,
initially.
Antimicrobial studies
Minimum inhibitory concentration (MIC): The Gram-negative (P. aeruginosa and E. coli) and
Gram-positive (S. aureus and S. epidermidis) are among the most concerning pathogens in human
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involved in antibiotic resistance [23-24]. The antimicrobial ability of CIPTIN was evaluated towards
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these strains, in terms of MIC values. The MIC is defined as the lowest concentration for the
bacterial growth inhibition [8-10,14-17]
.
The broth dilution method was used for the determination of the MIC values of CIPTIN,
HCIP·HCl, HCIP and DPTD, upon incubation of Gram-negative (P. aeruginosa and E. coli) or
Gram-positive (S. aureus and S. epidermidis) bacteria for 20 h (Table 1).
Table 1
The MIC values of CIPTIN lie in the range of nanomolar concentrations against P.
aeruginosa, E. coli, S. aureus and S. epidermidis, (0.741±0.035, 0.301±0.062, 1.179±0.083 and
0.255±0.041 μM respectively) (Table 1, Figure S9). The corresponding MIC values of the drug in
HCIP·HCl and HCIP are: 1.174±0.221 μM and 1.048±0.037 μM (P. aeruginosa), 0.938±0.347 μM
and 0.443±0.041 μM (E. coli), 1.454±0.123 μM and 1.459±0.013 μM (S. aureus) and 1.079±0.121
μM and 0.699±0.025 μM (S. epidermidis), respectively (Figure S10-S11) [8]. The MIC values of
DPTD, on the other hand, lie in the micromolar range of concentrations for the tested bacteria:
>100 μΜ, 25.713±1.535 μM, 47.529±8.761 μM and 13.743±0.263 μM towards P. aeruginosa, E.
coli, S. aureus and S. epidermidis, respectively (Figure S12). Thus, CIPTIN shows 1.2 to 4.2-folds
stronger antimicrobial activity than those of HCIP·HCl or HCIP towards both Gram negative and
positive bacteria. The strongest antimicrobial effect of CIPTIN is observed towards S. epidermidis,
which is 4.2-fold higher than that of HCIP·HCl and 2.7 fold than that of HCIP. Moreover CIPTIN
activity rises up to 135-folds than DPTD stronger activity against these bacteria. Therefore,
CIPTIN exerts superior activity than both its ingredients (antibiotic and DPTD).
Microbes are classified to susceptible (MIC< 50 μM) or resistant (MIC> 100 μM) towards
an antimicrobial agent by their MIC values [8,10]. Thus, all tested strains here are considered as
susceptible to CIPTIN.
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Table 1
Minimum bactericidal concentration (MBC): The MBC values for CIPTIN were also evaluated.
MBC is defined as the lowest concentration of an antibacterial agent that kills the 99.9% of the
initial bacterial inoculums [8,10,14-17]
.
The MBC values of CIPTIN for Gram negative P. aeruginosa and E. coli are 0.800±0.195
μM and 0.445±0.040 μM respectively, and against Gram positive bacteria S. aureus, and S.
epidermidis are 1.600±0.110 μM and 0.667±0.045 μM, respectively (Table 1, Figure S13). The
corresponding MBC values of HCIP·HCl and HCIP are 1.200-2.225 μM against both Gram
negative and positive bacteria (Table 1, Figures S14-S15). In the case of DPTD, the MBC values
are higher than 100 μΜ (Figure S16). Thus, CIPTIN exhibits higher bactericidal activity than those
of free drugs which rises up to 3.6-fold in respect of HCIP·HCl or up to 2.8-fold for HCIP. DPTD
has no bactericidal activity.
Since the MBC/MIC values of CIPTIN lie between 1.08-2.62, against the tested microbial
strains, (Table 1) the CIPTIN is classified as bactericidal agent. This is because when the
MBC/MIC value is ≤2, an agent is considered as bactericidal one, while when MBC/MIC value is
≥4, as bacteriostatic one [8,10,14-17]. The MBC/MIC values of HCIP·HCl and HCIP varied between
1.22-2.82 and they are bactericidal drugs.
Inhibition zone (IZ): The IZ was evaluated with agar disk-diffusion method [8,10,14-17]. The calculated
diameter of IZ is used to determine the effectiveness of an antibiotic. Therefore, the bacterial strains
might be classified as susceptible to an agent based on the IZ developed [8,10,14-17]. Thus, Shungu
et.al [25] classified the microbes in three categories according to the size of IZ caused by antibiotics.
(i) those strains where the antibiotic causes IZ ≥17 mm and they are consider as susceptible, (ii)
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those where the antibiotic creates IZ between 13 to 16 mm (13 ≤ IZ ≤ 16 mm) are intermediate, (iii)
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those where the antibiotic causes IZ ≤ 12 mm, and they are considered as resistant strain [25]
.
The IZs caused by CIPTIN determined against P. aeruginosa, E. coli, S. aureus and S.
epidermidis are 40.8±1.5, 34.0±0.8, 36.0±1.1 and 42.7±0.8 mm, respectively classifying these
strains to susceptible ones towards CIPTIN (Figure 5). The ranges of IZs, which were caused by
HCIP·HCl and HCIP lie between 32.0-35.5 mm (against Gram negative bacteria) and 24.0-39.2
mm (against Gram positive). These values are classifying the bacteria tested to susceptible ones
against HCIP·HCl and HCIP (Table 1, Figure S17). The corresponding IZs developed by DPTD
lie between 10.0-18.7 mm against the tested bacteria classifying them to the resistance or
intermediate ones towards DPTD. Generally, CIPTIN causes greater inhibition zones than the
commercial antibiotic or the DPTD, against both negative and positive bacterial strains.
Figure 5
Effect on biofilm formation by CIPTIN: The effect of CIPTIN on biofilm eradication was tested
against biofilm-positive strains (P. aeruginosa, S. aureus) by the Biofilm Elimination Concentration
(ΒΕC) values with crystal violet assay 8-10,14-17]. The ΒΕC is the required concentration to reduce
[
the viability of biofilm bacteria by 99.9%, at least [8-10,14-17]. The ΒΕC value of CIPTIN for P.
aeruginosa is 656 μΜ and for S. aureus is 752 μΜ (Figure 6). We have recently determined the
BEC value of HCIP·HCl against P. aeruginosa (670 μΜ) and S. aureus (952 μΜ) [8]. The
corresponding BEC values of HCIP are: 2140 μΜ (P. aeruginosa) and 2463 μΜ (S. aureus)
(Figure S19). CIPTIN eliminates the biofilm of P. aeruginosa and S. aureus more efficiently than
the neutral drug HCIP, while its BEC value is comparable with the corresponding one of
HCIP·HCl.
Figure 6
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Evaluation of the in vitro toxicity of CIPTIN: Immortalized human keratinocytes (HaCaT) cells
were used to test the in vitro cytotoxic effect of CIPTIN, HCIP·HCl, HCIP and DPTD, by
sulforhodamine B (SRB) assay, upon their incubation with the agents by 48h. The IC50 value of
CIPTIN is 2.33±0.2 μΜ. The corresponding IC50 values of HCIP·HCl, HCIP are >30 μΜ, while
that of DPTD is 1.09±0.1 μΜ.
The therapeutic window of an agent is defined by the selectivity index (SI) [8,26]
SI= IC50(against HaCaT cells)/MIC (against tested bacteria)
:
The higher SI is, the greater antimicrobial effect and lower the cellular toxicity is. The SI values of
CIPTIN values are 3.1 (P. aeruginosa) 7.7 (E. coli), 2.0 (S. aureus) and 9.1 (S. epidermidis). These
values constitute a wide therapeutic window for CIPTIN. The SI values of DPTD are: >0.01, 0.04,
0.02 and 0.08 against P. aeruginosa, E. coli, S. aureus and S. epidermidis respectively.
Evaluation of in vitro genotoxicity by micronucleus assay: The micronucleus assay is frequently
]
used to evaluate the mutagenic, genotoxic or teratogenic effect of metallodrugs [27 . In the presence
of a genotoxic factor, micronuclei (MN) appear as small membrane-bound DNA fragments in the
cytoplasm of interphase cells and they are formed during the metaphase-anaphase transition of the
mitotic cycle [28]. The micronucleus assay has been widely used in monitoring genetic damage in
order to avoid the screening of drugs on animals.
In order to evaluate the genotoxicity of CIPTIN,·HCIP·HCl, HCIP and DPTD, HaCaT
cells were treated by the agents at their IC50 values (Figure 7). The corresponding frequency of
micronucleus after treatment of HaCaT cells by CIPTIN is 2.60±0.15 %, while the frequency
without treatment of the cells is 2.17±0.05 %. Therefore CIPTIN exhibits negligible genotoxicity.
The micronucleus frequencies of HaCaT cells after treatment by the HCIP·HCl (2.44±0.2)% or
HCIP (2.48±0.1)% which is close to that of CIPTIN. The MN formed upon treatment of HaCaT
cells by DPTD is (3.05±0.2) %, which is significantly higher than that of CIPTIN.
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Figure 7
Conclusions
The design and the development of antimicrobial agents are of great importance. The new
metalloantibiotic CIPTIN, has been synthesized and characterized within this work. The crystal
structure reveals that the geometry around the metal center is octahedral (Figure 1B). The
stereoselective synthesis results to the Δ-cis-[Ph2Sn(CIP)2] isomer only (Figure 1B). 2D layers
supramolecular assemblies are established based on strong hydrogen bonding interactions (Figure
3). Four molecules form squares planes with their tins atoms to occupy its acnes of each square.
These constitute the building blocks of the layers (Figure 3). The area is covered by each square is
195.133 Å2.
CIPTIN has been evaluated towards the Gram negative microbes P. aeruginosa, E. coli and
Gram positive ones S. aureus, S. epidermidis. CIPTIN is classified as a bactericidal agent against
P. aeruginosa, E. coli, S. aureus and S. epidermidis (Table 1), while these microbes, are ranked
among the susceptible ones to it (IZ values) (Table 1).
The antibacterial activity of CIPTIN (Δ-cis-[Ph2Sn(CIP)2]) is compared with those of
[13]
CIPAG with formula ({[Ag(HCIP)2]NO3∙}) [8], [Me3Sn(CIP)], [Cy3Sn(CIP)]
and PenAg with
[9]
formula [Ag(Pen)(CH3OH)]2, (HPen= penicillin)
and their ingredients HCIP·HCl, HCIP,
PenNa, DPTD and AgNO3 (Table 1, Figure 8).
CIPTIN exhibits stronger activity than ciprofloxacin against both Gram positive and
negative bacteria tested as well as the [Me3Sn(CIP)], [Cy3Sn(CIP)] [13] suggesting that the presence
of the tin(IV) ion enhances ciprofloxacin’s effectiveness even more (Table 1, Figure 8). While
DPTC’s activity is significant lower than that of CIPTIN, this should be attributed to the
synergistic effect of both the organotin moiety and ciprofloxacin. CIPTIN exerts superior activity
than penicillin against Gram negative, as expected since penicillin is inactive against Gram negative
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bacteria microbes (Figure 8). Against Gram positive microbes, CIPTIN exhibits stronger activity
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against S. epidermidis while penicillin shows higher one on S. aureus (Figure 8). Given that
ciprofloxacin exhibits stronger activity than penicillin against S. epidermidis, while penicillin
against S. aureus, CIPTIN follows the relative efficiency of ciprofloxacin towards penicillin.
Among the compounds of ciprofloxacin, CIPTIN exhibits higher activity from CIPAG against S.
epidermidis, which however is more effective against S. aureus and P. aeruginosa (Figure 8).
Therefore, the antibiotic activity is differentiated by the type of the metal ion which is coordinating
[13]
on the drug. Moreover, among organotins, the [Me3Sn(CIP)] and the [Cy3Sn(CIP)]
show
stronger activity than CIPTIN against P. aeruginosa and S. aureus (Table 1). However this should
be assigned to the higher toxicity of tri- than di-organotin moieties. Although PenAg shows better
activity against S. aureus, CIPTIN, however is more drastic against S. epidermidis and P.
aeruginosa where ciprofloxacin itself shows better activity than free penicillin (Figure 8). Therefore
the activity of the metallodrug is following the corresponding efficiency of the antibiotic, regardless
the type of the metal ion Sn(IV) or Ag(I). Moreover CIPTIN shows superior activity than silver(I)
nitrate against all microbes tested (Figure 8) confirming the conclusion which is already withdrawn
for the synergy of the metal ion with the drug on the activity of the metallodrug. CIPTIN eliminates
the biofilm in a similar manner with the drug (Table 1). The in vitro toxicity of the CIPTIN against
HaCaT cells shows a selectivity index (SI) higher than 1 suggesting wide therapeutic window,
while its in vitro genotoxicity is even lower than that of HCIP·HCl or HCIP.
In conclusion, the coordination of a drug on a metal ion strongly enhances its activity. The
antimicrobial information which has been stored in a drug, affects the activity of the metallodrug
and it is affected by the coordination demands stored in the metal ion, creating a combination of a
new entity with enhance and novel biological properties.
Figure 8
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16
Experimental
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DOI: 10.1039/D0DT01665A
Materials and instruments: All solvents used were of reagent grade. Tryptone tryptophan medium,
beef extract powder, peptone bacteriological, soy peptone were purchased from Biolife. Agar and
yeast extract were purchased from Fluka Analytical. Sodium chloride, D(+)-Glucose, di Potassium
hydrogen phosphate trihydrate were purchased from Merck. Dulbecco’s modified Eagle’s medium,
(DMEM), fetal bovine serum, glutamine and trypsin were purchased from Gibco, Glasgow, UK.
Phosphate buffer saline (PBS) was purchased from Sigma-Aldrich. Melting points were measured
in open tubes with a Stuart Scientific apparatus and are uncorrected. IR spectra in the region of
4000-370 cm-1 were obtained on Cary 670 FTIR spectrometer, Agilent Technologies. A UV-1600
1
PC series spectrophotometer of VWR was used to obtain electronic absorption spectra. The H-
NMR spectra were recorded on a Bruker AC 250, 400 MHFT-NMR instrument in DMSO-d6. ESI-
MS spectra were measured with an Agilent 1100/LC−MS system. 119Sn Mössbauer spectra were
collected at various sample temperatures (85 K), with a constant-acceleration spectrometer
equipped with a CaSnO3 source kept at room temperature. The calibration of the spectrometer was
57
carried out with a Co source and an Fe absorber at room temperature. The line widths were very
close to the natural width (0.28 mm/s). The content of the tin samples was calculated to be
approximately 4 mg Sn in the 2-cm2 area of the sample holder. XRF measurements were carried out
using an Am-241 radio isotopic source (exciting radiation 59.5 keV). Thermal Gravimetric–
Differential Thermal Analysis (TG–DTA) of CIPTIN was carried out on a Seiko SII TG/DTA 7200
apparatus under N2 flow (40 cm3 min−1) with a heating rate of 10 K min−1.
Synthesis and crystallization of CIPTIN: A clear solution of 0.5 mmol ciprofloxacin hydrochloride
(HCIP·HCl) (0.184 gr) in dd water (8 mL) was treated with 0.75 mmol KOH (750 μL 1 N). A
solution of 0.25 mmol diphenyltin dichloride (DPTD) (0.086 gr) in methanol (3 mL) was added to
the previous one under continues stirring for 30 min and the resulting white precipitation was
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immediately filtered off. Crystals of CIPTIN suitable for X-ray analysis were grown from slow
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DOI: 10.1039/D0DT01665A
evaporation of the solution after one day.
CIPTIN: Yellowish crystal, melting point: > 300 °C; elemental analysis found: C: 59.55; H: 4.92,
N: 9.23%; calculated for C46H44N6O6F2Sn: C: 59.19; H: 4.75; N:9.00 %. IR (cm-1), (KBr): 3906w,
2965w, 2698w, 2487w, 2111w, 1918w, 1604w, 1474w, 1265s, 1142s, 1025s, 944vs, 809s, 739vs,
1
628s, 446s; H-NMR (ppm) in DMSO-d6: 8.87 (s, H[Npiperazine ring]), 8.67 (s, H[2C]), 7.95-7.92
(d, H[5C]), 7.79-7.81 (d, H[8C]), 7.72-7.58 (m, Ph-), 7.31-7.16 (m, Ph-), 3.85 (s, H[aC]), 3.47 (d,
H[cC]), 1.33 (m, cyclopropyl CH2), 1.19 (m, cyclopropyl CH2); UV-vis (DMSO): λ= 284 nm (logε=
4.68), λ= 320 nm (logε= 4.21), 331 nm, (logε= 4.20).
X-ray Structure Determination: Intensity data for the crystals of CIPTIN and HCIP were collected
on an Oxford Diffraction CCD instrument, using graphite monochromated Mo radiation (λ=0.71073
Å). Cell parameters were determined by least-squares refinement of the diffraction data from 25
reflections. All data were corrected for Lorentz-polarization effects and absorption [29]. The
[30]
structures were solved with direct methods with SHELXS97
and refined by full-matrix least-
squares procedures on F2 with SHELXL97 [31]. All non-hydrogen atoms were refined
anisotropically, hydrogen atoms were located at calculated positions and refined via the “riding
model” with isotropic thermal parameters fixed at 1.2 (1.3 for CH3 groups) times the Ueq value of
the appropriate carrier atom.
CIPTIN: C46H44N6O6F2Sn, MW= 933.612, monoclinic, space group I2/a, a= 14.7410(6), b=
20.2602(5), c= 18.8558(7) Å, α= 90, β= 111.400(4), γ= 90°, V= 5243.1(3) Å3, Z= 4, T= 100 K, ρ
(calc)= 1.183 g cm−3, μ= 4.320 mm−1, F(000)= 1912. 10180 reflections measured, 4682 unique
(Rint = 0.052). The final R1= 0.0523 (for 3818 reflections with I > 2s(I)) and wR(F2)= 0.1428 (all
data) S= 0.99.
HCIP: C17H18FN3O3, MW= 331.34, triclinic, space group P-1, a= 7.8945(7), b= 8.5010(7), c=
10.7522(9) Å, α= 87.440(7), β= 84.496(7), γ= 88.912(7)°, V= 717.47(11) Å3, Z= 2, T= 100 K, ρ
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(calc)= 1.534 g cm−3, μ= 0.967 mm−1, F(000)= 348. 4189 reflections measured, 2531unique (Rint =
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DOI: 10.1039/D0DT01665A
0.041). The final R1= 0.0511 (for 1996 reflections with I > 2s(I)) and wR(F2)= 0.1440 (all data) S=
1.07.
Crystallographic data (excluding structure factors) for the structure reported in this paper has been
deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos.
CCDC-1993746 (CIPTIN), CCDC-2002394 (HCIP). Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (+44) 1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk).
Biological tests:
Bacterial Strains: The strains used were: Pseudomonas aeruginosa (P. aeruginosa), Escherichia
coli Dh5a (E. coli), Staphylococcus aureus (S. aureus) subsp. aureus (ATCC® 25923™) and
Staphylococcus epidermidis (ATCC® 14990™).
Solvents used: The biological experiments for antibacterial studies were carried in DMSO/Broth
solutions of CIPTIN, HCIP and DPTD and in H2O/Broth solutions for HCIP·HCl. The biological
experiments for the cell viability and for the micronucleus assay were carried in DMSO/DMEM
solutions 0.0005-0.03% v/v DMSO in DMEM for the tested compounds. Stock solutions of
CIPTIN, HCIP·HCl, HCIP and DPTD (0.01 M) in DMSO were freshly prepared and diluted in
broth or cell culture medium to the desired concentration.
Minimum inhibitory concentration (MIC) testing: This study was performed according standard
procedure, as described previously [8-10,14-17]. Briefly, the bacterial strains were streaked onto in
o
trypticase soy agar plates, which were incubated for 18-24 h at 37 C. Then, three to five isolated
colonies were selected of the same morphological appearance from the fresh agar plate using a
sterile loop and transferred into a tube containing 2 mL of sterile saline solution. The optical density
at 620 nm is 0.1, which corresponds in to 108 cfu/mL. The final inoculum size for broth dilution is
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5×105 cfu/mL. The total volume of the culture solution treated by CIPTIN, HCIP·HCl, HCIP or
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DPTD, and the total volumes of the positive and negative controls, were 2 mL. The range of
concentrations of CIPTIN was 100-1600 nM, of HCIP·HCl was 100-800 nM, of CIPH was 200-
1600 nM and of DPTD was 5000-100000 nM. The growth was assessed after incubation for 20 h.
The MIC value was determined as the concentration of the compound which inhibits the visible
growth of the bacterium being investigated, while it confirmed by measuring the solution optical
density at 620 nm vs concentrations [8-10,14-17]
.
Minimum bactericidal concentration testing: In order to determine MBC values of CIPTIN, the
bacteria were initially cultivated in the presence of CIPTIN, HCIP·HCl, HCIP or DPTD in broth
for 20 h. Afterwards, MBC value was determined in duplicate, by subculturing 4 μL of the broth
with bacteria and CIPTIN, HCIP·HCl, HCIP or DPTD in an agar plate. Bactericidal activity
occurs when no colony formation is observed. The lowest concentration at which the tested
[8-10,14-
compounds could give complete inhibition of microbes’ growth was defined as MBC value
17]
.
Determination of the inhibition zone (IZ) through the agar disk-diffusion method: As described
previously [8-10,14-17], agar plates were inoculated with a standardized inoculum (108 cfu/mL) of the
tested microorganism. Filter paper disks (9 mm in diameter), which had been previously soaked by
CIPTIN, HCIP·HCl, HCIP or DPTD (10-3 M), were placed on the agar surface. The Petri dishes
were incubated for 20 h, and then the diameters of the inhibition zones were measured.
Effects on biofilm formation: Bacterial strains of P. aeruginosa or S. aureus with a density of
6.7×106 cfu/mL were inoculated into LB medium (total volume= 1500 μL) and cultured for 24 h at
37 oC. Afterwards, the content of each tube was carefully removed and the tubes are washed with 1
mL dH2O. Negative control contained broth only. Then, the bacteria were incubated with CIPTIN
at concentrations between 25 to 500 μΜ (total volume= 2000 μL) for 20 hrs, at 37 oC. The content
of each tube was aspirated, each tube was washed three times with 1 mL methanol and 2 mL ddH2O
and left to dry. Then, the tubes were stained for 15 min with crystal violet solution (0.1% w/v).
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Excess stain was rinsed off with 1 mL methanol and 2 mL ddH2O. The tubes are left to dry for 24
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hand the bounded crystal violet was released by adding 30% glacial acetic acid (2 mL) and after 3
mL ddH2O. The optical density of the solution yielded is measured at 550 nm, to give the biofilm
biomass [8-10,14-17]
.
In vitro toxicity evaluation
Sulforhodamine B Assay: These studies were performed in accordance with the previous reported
method [10,15]. Briefly, HaCaT cells were seeded in 96-well plate in a density of 8000 cells and after
24 h of cell incubation, the compounds were added in the range of concentration 0.25-3 μΜ (for
CIPTIN and DPTD) and 0.5-30 μΜ (for HCIP·HCl and HCIP). After of 48 h incubation of
HaCaT cells with the compounds, the culture medium was aspirated and the cells were fixed with
50 μL of 10% cold trichloroacetic acid (TCA). The plate was left for 30 min at 4 °C, washed five
times with deionized water, and left to dry at room temperature for at least 24 h. Subsequently, 70
μL of 0.4% (w/v) sulforhodamine B (Sigma) in 1% acetic acid solution was added to each well and
left at room temperature for 20 min. SRB was removed, and the plate was washed five times with
1% acetic acid before air drying. Bound SRB was solubilised with 200 μL of 10 mM un-buffered
Tris-base solution. Absorbance was read in a 96-well plate reader at 540 nm.
Evaluation of genotoxicity by micronucleus assay: The micronucleus assay was carried out as
previously described [27]. Briefly HaCaT cells were seeded (at a density of 240000 cells/well) in
glass cover slips which were afterwards placed in six-well plates, with 3 mL of cell culture medium
and incubate for 24 h. HaCaT cells exposed with compounds in IC50 values for a period of 48 h.
The number of micronucleated cells per 1000 cells was determined.
Acknowledgements
[i] This research has been co-financed by the European Union and Greek national funds through the
Operational Program Competitiveness, Entrepreneurship and Innovation, under the call
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RESEARCH – CREATE – INNOVATE (project code:T1EDK- 02990). [ii] This research is also
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DOI: 10.1039/D0DT01665A
co-financed by Greece and the European Union (European Social Fund- ESF) through the
Operational Programme «Human Resources Development, Education and Lifelong Learning» in the
context of the project “Strengthening Human Resources Research Potential via Doctorate Research”
(MIS-5000432), implemented by the State Scholarships Foundation (ΙΚΥ). [iii] Professor T.
Vaimakis is acknowledged for the useful discussions and the recording of TG-DTA/DSC diagrams.
[iv] The COST Action CA15114 "Anti-Microbial Coating Innovations to prevent infectious
diseases (AMICI)" is acknowledged for the stimulating discussions.
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[24] M. Otto, Staphylococcus epidermidis – the “accidental” pathogen, Nat Rev Microbiol. 2009,
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7, 555–567
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[26] M.P. Pereira, S.O. Kelley, Maximizing the therapeutic window of an antimicrobial drug by
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[27] C.N. Banti, S.K. Hadjikakou, Evaluation of Genotoxicity by Micronucleus Assay in vitro and
by Allium cepa Test in vivo, Bio-protocol, 2019, 9, e3311
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Methods Mol. Biol., 2008, 410, 185–216
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CrysAlis171.NET), Oxford Diffraction, Crysalis CCD and Crysalis RED, Version p171.29.2,
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[30] G.M. Sheldrick, Phase annealing in SHELX-90: direct methods for larger structures, Acta
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of Göttingen, Göttingen, Germany, 1997
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26
Figure Captions
Figure 1.
View Article Online
DOI: 10.1039/D0DT01665A
(A) Molecular diagram together with the numbering scheme of CIPTIN. Selected
bond lengths (Å) and angles [°]: Sn1-O1= 2.135(3), Sn1-O3= 2.158(3), Sn1-C18=
2.120(5), Sn1-O1_a= 2.135(3), Sn1-O3_a= 2.158(3), Sn1-C18_a= 2.120(5), O3-C2=
1.284(5), O1-C6= 1.298(5), O2-C6= 1.216(5), O1-Sn1-O3= 79.93(11), O1-Sn1-
O1_a= 155.64(11), O1-Sn1-O3_a= 81.60(11), O1_a-Sn1-O3= 81.60(11), O3-Sn1-
O3_a= 80.96(11), O1_a-Sn1-O3_a= 79.93(11). (B) Δ-cis-[Ph2Sn(CIP)2] stereoisomer
(A) Molecular diagram together with the numbering scheme of HCIP. Selected bond
lengths (Å) and angles [°]:O1-C14= 1.247(3), O2-C14= 1.266(3), C1-C2= 1.453(3),
O3-C2= 1.241(3), N3-C11= 1.481(3), N3-C12= 1.485(3), O1-C14-O2= 125.3(2),
O3-C2-C1= 125.0(2), C11-N3-C12= 109.0(2) (B) 1D ribbon assembly established by
hydrogen bonds
Figure 2.
Figure 3
Figure 4
Figure 5.
Strong hydrogen bonding interactions O2[H2]···N3 lead to 2D layer architecture.
119Sn Mössbauer spectrum of CIPTIN at 77 K.
Inhibition zones of CIPTIN against P. aeruginosa (A), E. coli (B), S. aureus (C) and
S. epidermidis (D)
Figure 6.
Figure 7.
Crystal violet staining revealing biofilm P. aeruginosa (A) and S. aureus (B) with
increasing concentrations of CIPTIN. Biofilm inhibition (%) of P. aeruginosa and
S. aureus versus pC=-log(C) (M) of CIPTIN (C).
Representative snapshots of micronucleus formed in untreated HaCaT cells (A) and
upon their treatment with CIPTIN (B), HCIP·HCl (C), HCIP (D) or DPTD (E) at
2.33 μΜ for 48 h.
Figure 8.
Istogramm of pMIC (-log(MIC)) values of CIPTIN (Δ-cis-[Ph2Sn(CIP)2]),
[9]
({[Ag(HCIP)2]NO3∙}) [8], PenAg [Ag(Pen)(CH3OH)]2, (HPen= penicillin)
,
HCIP·HCl, HCIP, PenNa, DPTD and AgNO3, against S. aureus, S. epidermidis, P.
aeruginosa and E. coli.
26

Page 27 of 36
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27
Table 1. MIC, MBC values, Inhibition Zones, of CIPTIN, CIPAG, PenAg, HCIP·HCl, HCIP,
View Article Online
DOI: 10.1039/D0DT01665A
DPTD and AgNO3 against P. aeruginosa, E. coli, S. aureus and S. epidermidis
Compound
P. aeruginosa
E. coli
MIC (μM)
S. aureus
S. epidermidis
Ref.
Ph2Sn(CIP)2 CIPTIN
Me3SnCIP
0.741±0.035
0.253
0.301±0.062
1.179±0.083
0.125
0.255±0.041
-
*
[13]
1.012
1.432
-
-
[13]
[8]
Cy3SnCIP
0.089
0.179
-
Ag(CIP)2NO3 CIPAG
[Ag(Pen)](DMSO)]2
HCIP·HCl
0.612±0.142
23.0±2.290
1.174±0.221
1.048±0.037
>2000
0.537±0.067
0.080±0.020
1.454±0.123
1.459±0.013
0.140±0.020
47.529±8.761
79.500
0.458±0.083
2.410±0.880
1.079±0.121
0.699±0.025
3.760±1.140
13.743±0.263
39.400
[9]
[8]
0.938±0.347
0.443±0.041
HCIP
PenNa
Ph2SnCl2 DPTD
AgNO3
*
[9]
-
> 100
60.0
25.713±1.535
-
*
[8]
MBC (μM)
Ph2Sn(CIP)2 CIPTIN
Me3SnCIP
0.800±0.195
0.506
0.445±0.040
1.600±0.110
0.506
0.358
1.000
-
2.000
2.225±0.050
-
0.667±0.045
*
[13]
1.012
2.863
-
-
-
[13]
[8]
Cy3SnCIP
0.716
0.700
46.6
1.6
-
0.800
-
Ag(CIP)2NO3 CIPAG
[Ag(Pen)](DMSO)]2
HCIP·HCl
[9]
[8]
1.624±0.127
1.250±0.098
-
1.600
1.200±0.160
-
HCIP
PenNa
1.280±0.096
2000
*
[9]
Ph2SnCl2 DPTD
AgNO3
> 100
91.5
> 100
> 100
95.0
> 100
140.0
*
[8]
MBC/MIC
Ph2Sn(CIP)2 CIPTIN
Me3SnCIP
Cy3SnCIP
Ag(CIP)2NO3 CIPAG
HCIP·HCl
1.08
2.0
1.48
1.0
2.0
-
1.73
2.82
1.36
4.05
2.0
1.86
1.38
1.53
1.19
2.62
-
-
1.75
1.48
1.72
3.55
*
[13]
[13]
[8]
8.04
1.14
1.36
1.22
1.53
[8]
HCIP
AgNO3
*
[8]
IZ (mm)
Ph2Sn(CIP)2 CIPTIN
Ag(CIP)2NO3 CIPAG
[Ag(Pen)](DMSO)]2
HCIP·HCl
40.8 ± 1.5
32
17
32.0
35.5 ± 0.6
10
34.0 ± 0.8
36.0 ±1.1
28
57
24.0
30.5 ± 0.6
60
42.7 ± 0.8
34
34
36.0
39.2 ± 0.9
34
*
[8]
-
-
[9]
[8]
32.0 ± 0.8
33.0 ± 0.8
-
HCIP
PenNa
*
[9]
Ph2SnCl2 DPTD
AgNO3
10.0± 0.0
13
18.7 ± 0.9
13.1 ± 0.6
12
*
[8]
15.8± 0.4
14
* This study, PenNa= sodium salt of penicillin
27

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View Article Online
DOI: 10.1039/D0DT01665A
(A)
(B)
Figure 1
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Page 29 of 36
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View Article Online
DOI: 10.1039/D0DT01665A
(A)
(B)
Figure 2
29