PLGA-PEG-supported Pd nanoparticles as efficient catalysts for Suzuki-Miyaura coupling reactions in water

Article abstract of DOI:10.2533/chimia.2016.252

Chemical transformations that can be performed selectively under physiological conditions are highly desirable tools to track biomolecules and manipulate complex biological processes. Here, we report a new nanocatalyst consisting of small palladium nanoparticles stabilized on the surface of PLGA-PEG nanoparticles that show excellent catalytic activity for the modification of biological building blocks through Suzuki-Miyaura cross-coupling reactions in water. Brominated or iodinated amino acids were coupled with aryl boronic acids in phosphate buffer in good yields. Interestingly, up to 98% conversion into the coupled amino acid could be achieved in 2 h at 37°C using the stable, water-soluble cyclic triolborate as organometallic partner in the presence of only 1 mol% of palladium. These results pave the way for the modification of biomolecules in complex biological systems such as the intracellular space.

Full text of DOI:10.2533/chimia.2016.252

252 CHIMIA 2016, 70, No. 4
doi:10.2533/chimia.2016.252
Laureates: Junior Prizes of the sCs faLL Meeting 2015
Chimia 70 (2016) 252–257 © Swiss Chemical Society
PLGA-PEG-supported Pd Nanoparticles
as Efficient Catalysts for Suzuki-Miyaura
Coupling Reactions in Water
Anaëlle Dumas§*, Arnaud Peramo, Didier Desmaële, and Patrick Couvreur
§SCS-DSM Award for best poster presentation in Chemical Biology
Abstract: Chemical transformations that can be performed selectively under physiological conditions are highly
desirable tools to track biomolecules and manipulate complex biological processes. Here, we report a new
nanocatalyst consisting of small palladium nanoparticles stabilized on the surface of PLGA-PEG nanoparticles
that show excellent catalytic activity for the modification of biological building blocks through Suzuki-Miyaura
cross-coupling reactions in water. Brominated or iodinated amino acids were coupled with aryl boronic acids
in phosphate buffer in good yields. Interestingly, up to 98% conversion into the coupled amino acid could
be achieved in 2 h at 37 °C using the stable, water-soluble cyclic triolborate as organometallic partner in the
presence of only 1 mol% of palladium. These results pave the way for the modification of biomolecules in
complex biological systems such as the intracellular space.
Keywords: Amino acid chemistry · Palladium nanoparticles · Suzuki-Miyaura cross-coupling
ful of reactions have been developed that logical settings.[6d,9] Palladium-catalysed
fulfil all of these criteria.[3] Among them, cross-coupling reactions involving protein
Introduction
the Staudinger ligation (azide-phosphine), substrates suffered from low yields until
The tracking and manipulation of in-
copper-catalysed or strain-promoted Davis and coworkers reported the 2-ami-
azide-alkyne cycloadditions and tetrazine no-4,6-dihydroxypyrimidine (ADHP)-
dividual cellular components provide un-
precedented opportunities to understand
complex cellular processes and may open
new avenues for the treatment of human
disease.[1] Among the functional tools
available for the manipulation of biolog-
ical systems, ‘bioorthogonal reactions’
offer versatile platforms for the selective
and controlled modification of biomole-
ligation approaches are the most widely based catalyst [Pd(OAc)2(ADHP) ] ena-
utilised bioorthogonal reactions to date.[4] bling efficient Suzuki-Miyaura r2eaction
While these transformations have been of halogenated amino acids and peptides
helpful addressing a number of funda- with boronic acids.[10] This system proved
mental biological questions,[1b,5] toxicity, its efficacy in the preparation of struc-
cross-reactivity with endogenous thiols or turally-defined protein-conjugates with
other biomolecules, and poor stability of excellent conversions at chemically-in-
cules of interest.[1] These transformations
the reagents in biological environments, stalled or genetically-encoded aryl iodides
complicate their application in a number on purified proteins and on the surface
involve covalent bond formation between
non-native chemical tags that react highly
chemoselectively together under physio-
logical conditions, while remaining inert
towards the myriad of other functional
groups found in biological environments.
of settings.[6] Therefore, the design of truly of bacteria.[10,11] In parallel, the analogue
bioorthogonal reactions, involving stable, N,N’-dimethyl ADHP-palladium(ii) com-
selective and synthetically accessible re- plex was reported by Li et al. to promote
action partners remains an area of active copper-free Sonogashira cross-coupling
investigation in chemical biology.[3,7]
Palladium-mediated
reactions on alkyne-labelled proteins in-
The major difficulty resides in finding
cross-coupling side bacterial cells.[12]
reactions provide new possibilities for
These results propelled palladium-me-
diated reactions in the very demanding bio-
non-perturbing chemical handles that react
rapidly, while generating no or non-toxic
side products.[2] As a result, only a hand-
chemical reporter strategies.[8] The reac-
tive groups associated with these process- orthogonal chemistry toolbox. However,
es are rarely found in natural systems and these transformations still suffer from
cross-coupling reactions proceed with high drawbacks as the non-specific interactions
specificity and broad functional group tol- of the homogenous palladium complexes
erance. However, the poor stability under with nitrogen-, sulphur-, or oxygen-con-
aerobic conditions of most palladium(0) taining biological building blocks may
complexes used as catalysts, and the high cause cytotoxicity[12] and require the re-
temperatures required for activation, have moval of the palladium catalyst after reac-
restricted these reactions to the convention- tion using metal scavengers.[11] The use of
al organic synthesis of small molecules. heterogeneous palladium catalysts could
*Correspondence: Dr. A. Dumas
Institut Galien Paris-Sud
UMR 8612, CNRS, Univ. Paris-Sud
Université Paris‐Saclay
Faculté de Pharmacie
5 rue JB Clément
In the last decade, efforts to develop wa- overcome these problems by reducing
ter- and air-stable catalytic systems active non-specific binding to biomolecules.[8]
within the narrow biologically-relevant Palladium nanoparticles (Pd NPs) stabi-
pH and temperature windows, have ena- lised by organic polymers, or inorganic
bled the use of palladium reactions in bio- supports have already demonstrated their
92296 Châtenay-Malabry, France
E-mail: anaelle.dumas@u-psud.fr

Laureates: Junior Prizes of the sCs faLL Meeting 2015
CHIMIA 2016, 70, No. 4 253
activity in Suzuki-Miyaura coupling with eter (Fig. 1D) positioned on the surface of preparation (Fig. 1C). Macroscopic aggre-
small molecules. In this context, they pres- the polymeric nanoparticles. Inductively- gation was, however, observed after six
ent attractive alternatives to homogenous coupled plasma mass spectrometry (ICP- days of storage.
catalysts owing to their facile separation MS) quantified the presence of 4.8 atoms
from final products, possible reusability of palladium/polymer chain (Pd/polymer Catalytic Activity of Pd-PLGA-PEG
and cost-effectiveness as no elaborate li- mass ratio = 0.01). DLS analysis revealed Nanoassemblies in Suzuki-Miyaura
gand is necessary for their stabilisation.[13] that palladium loading resulted in an in- Cross-coupling
However, most reported Pd NPs-mediated crease in diameter going from 157.9 ± 7.8
The catalytic activity of the prepared
reactions require the use of organic co-sol- nm for PLGA-PEG NPs to 176.3 ± 6.8 assemblies was tested on model Suzuki-
vents, surfactants, strong bases and/or high nm for Pd-PLGA-PEG nanoassemblies. Miyaura reactions involving halogenated
temperatures, which are not compatible Reduction of the negative surface charge phenylalanine and tyrosine analogues in
with biological applications.[14] In our con- (Zeta potential) from –14.32 ± 0.45 mV to the presence of 1 mol% palladium in the
tinued effort to develop efficient nanotech- –7.68 ± 5.71 mV was also observed upon form of Pd-PLGA-PEG nanoassemblies
nologies to promote biologically compati- palladium loading (Table 1).
and in pH 8.0 phosphate buffer at 37 °C
ble reactions, we report here the elabora- Despite their low absolute surface (Table 2). In these conditions, the reac-
tion of palladium nanoparticles (ca. 5.6 nm charge, the Pd-PLGA-PEG nanoassem- tion of N-Boc-4-iodo-l-phenylalanine (1)
diameter) stabilized on the surface of larg- blies showed reasonable stability, with no with phenyl boronic acid reached 42% and
er poly(d,l-lactide–co–glycolide)–block– significant aggregation at least 3 days after 68% conversion after 2 and 18 h respec-
poly(ethylene glycol) copolymer nano-
particles (PLGA–PEG NPs, ca. 158 nm
diameter) as catalysts for the Suzuki-
Miyaura cross-coupling reaction between
halogenated amino acids and aryl-boron
reagents under physiologically-relevant
conditions. The prepared palladium-PL-
GA-PEG (Pd-PLGA-PEG) nanoassem-
blies (176 nm mean diameter) were found
to be good catalysts for the coupling of
brominated or iodinated amino acids with
aryl boronic acids in phosphate buffer.
Interestingly, the coupling with a stable
water-soluble cyclic triolborate was even
more efficient, yielding up to 98% con-
version in 2 h at 37 °C in the presence of
only 1 mol% of palladium, even at slightly
acidic pH. The remarkable activity of these
palladium-loaded nanoassemblies even in
the absence of added base, the stability
and the water-solubility of the cyclic triol-
borate[15] make these reaction conditions a
potential tool for the modification of bio-
logical systems through carbon–carbon
bond formation.
Results and Discussion
Preparation of Palladium-loaded
Nanoassemblies
The palladium-loaded PLGA-PEG na-
noparticles were assembled according to a
straightforward two-step process. Stable
PLGA-PEG nanoparticles (157.9 nm ± 7.8
nm hydrodynamic diameter, as revealed
by dynamic light scattering (DLS) analy-
Fig. 1. Cryo-TEM images of (A) a representative sample and (B) a zoom of Pd-PLGA-PEG nano-
assemblies. (C) Evolution of the mean diameter of Pd-PLGA-PEG nanoassemblies upon incuba-
tion at 25 °C in water for several days after resuspension (PLGA-PEG concentration = 0.2 mg/
sis) were prepared according to the emul-
mL), (D) Size distribution of the palladium nanoparticles on the PLGA-PEG (304 randomly chosen
sion-evaporation method. These polymeric
samples on cryo-TEM images, mean diameter: 5.59 nm ± 1.17nm)
nanoparticles were then incubated with an
aqueous solution of K2PdCl4. The mixture
was stirred vigorously for 15 h at 25 °C.
Table 1. Physicochemical characterisation of PLGA-PEG NPs and Pd-PLGA-PEG nanoassemblies
Excess palladium was then removed from (NAs). Each value represents the average of more than six experiments ± standard deviation.
the stable palladium-loaded nanoassem-
blies by ultracentrifugation. Cryogenic
transmission electron microscopy (cryo-
Hydrodynamic
diameter [nm]
Polydispersity
index
Zeta potential
[mV]
TEM) images of the Pd-PLGA-PEG nano-
PLGA-PEG NPs
157.9 ± 7.8
176.3 ± 6.8
0.094 ± 0.016
0.113 ± 0.039
–14.32 ± 0.45
–7.68 ± 5.71
assemblies (Fig. 1A and B) showed palla-
dium nanoparticles of 5.6 ± 1.2 nm diam-
Pd-PLGA-PEG NAs

254 CHIMIA 2016, 70, No. 4
Laureates: Junior Prizes of the sCs faLL Meeting 2015
1
Table 2. Suzuki-Miyaura cross-coupling reactions between halogenated amino acid and phenyl
boronic acid derivatives catalyzed by Pd-PLGA-PEG nanoassemblies.
tively as determined by H-NMR (Table
2, entry 1). Surprisingly, reaction with
the 4-bromo-analog (2) showed 43% and
98% conversion efficiency after 2 and 18 h
respectively under the same conditions
(Table 2, entry 2). Although aryl bromides
are usually less reactive than their iodinat-
ed analogues in the Suzuki-Miyaura re-
action,[16] the poor solubility of N-Boc-4-
iodo-l-phenylalanine in phosphate buffer
might explain the reversed reactivity pat-
tern observed here. However, coupling of
the chlorinated analogue (3) did not give
the desired product under the mild condi-
No
R1-X
R2
Time [h]
Conversion [%]a
2
18
42
68
1
H
tions used here (Table 2, entry 3). When
applied to N-Boc-3-iodo-l-tyrosine (4),
our standard conditions yielded the ex-
pected coupling product in 67% and 70%
conversion after 2 and 18 h respectively
(Table 2, entry 4).
2
18
43
98
2
H
Exploring the electronic effect of sub-
stituents on the phenyl boronic acid re-
vealed that, as expected, substitution on
the 3-position of the phenyl ring with an
electron-withdrawing nitro group, sig-
nificantly slowed down the reaction rate,
probably due to a decreased nucleophilic-
ity of the boron reagent, disfavouring the
transmetallation step. In this case, no re-
action was observed with N-Boc-4-bromo-
l-phenylalanine (2) whereas, the coupling
with N-Boc-4-iodo-l-phenylalanine (1)
afforded the corresponding adduct in 35%
2
18
0
0
3
4
H
H
2
18
67
70
conversion in 2 h (Table 2, entry 5). By
X = Br 18
X = I
0
35
5
3-NO2
contrast, an electron-donating methoxy
group on the 4-position of the phenyl bo-
2
ronic acid facilitated the reaction. Thus, as
expected from an increased nucleophilici-
ty of the boron coupling partner, coupling
of N-Boc-4-bromo-l-phenylalanine (2)
with 4-methoxyphenylboronic acids was
found more efficient than in the absence of
substituent, giving 62% conversion in 2 h
6
4-OMe
2
62
1 equiv. R1-X, 3 equiv. R-B(OH)2, 1mol% Pd on PLGA-PEG nanoparticles. aThe conversion was
determined by 1H-NMR spectroscopy on the crude reaction mixture.
(Table 2, entry 6).
Aryl boronic acids are the most wide-
ly used coupling partners in the Suzuki-
Miyaura cross-coupling reaction, never-
theless they can suffer from a poor stability
and give side reactions such as protode-
boronation, di- and trimerization leading
to the formation of byproducts, reducing
yields and demanding laborious purifica-
tion processes.[17] Alternative organoboron
reagents, such as pinacol esters, potassium
trifluoroborates, or boronates, display im-
proved physico-chemical properties pro-
viding clear advantages over standard bo-
ronic acids under specific Suzuki-Miyaura
6-methyl-2-phenyl-1,3,6,2-dioxazaboro- to react in the Suzuki-Miyaura cross-cou-
cane-4,8-dione (phenyl boronic MIDA pling reaction even in the absence of added
esters) are known partners of the Suzuki- base. The phenyl cyclic triolborate deriva-
Miyaura cross-coupling reaction with the tive (7) was prepared from phenyl boronic
advantage of being monomeric, crystalline acid following a reported procedure.[15b]
and air- and moisture-stable reagents.[18] Interestingly, thereactionofthiscompound
Although usually more efficient than the with N-Boc-4-iodo-l-phenylalanine (1) in
corresponding boronic acids in some reac- the presence of the catalytic Pd-PLGA-
tion settings,[15a] little or no reaction was PEG nanoassemblies led to excellent con-
observed with our system after 18 h (Table
3, entry 1 & 2). 37 °C (Table 3, entry 3). The reaction with
The air- and moisture-stable tetraco- the less reactive 4-bromo-phenylalanine
version in 2 h in pH 8.0 phosphate buffer at
coupling conditions. To investigate the
ordinated boronate complex 7 was then analogue (2) led to 90% and 98% conver-
effect of the boron species on the reaction
outcome, different water-soluble boronic
coupling partners were tested in a model
system involving the halogenated N-Boc-
l-phenylalanine derivatives 1–3 with
phenyl-boron reagents 5–7 in the pres-
ence of 1 mol% of PLGA-PEG-supported
palladium. Aryltrifluoroborate salts and
tested. These reagents were reported as sion in 2 and 18 h respectively (Table 3,
useful reaction partners in Suzuki-Miyaura entry 4). However, by analogy with the ob-
cross-couplings as the quaternization of servation made with the arylboronic acids,
the boron centre with the anionic ligand no reaction was observed with N-Boc-4-
enhanced significantly the nucleophilicity chloro-l-phenylalanine (3) (Table 3, entry
of the organic groups attached, facilitating 5). Remarkably, although Suzuki-Miyaura
transmetallation on the metal centre.[15] As cross-couplings with aryl boronic acids
a result, such reagents have been reported usually require the addition of an exoge-

Laureates: Junior Prizes of the sCs faLL Meeting 2015
CHIMIA 2016, 70, No. 4 255
Table 3. Suzuki-Miyaura cross-coupling reactions between halogenated phenylalanine and
various organoboron reagents catalysed by Pd-PLGA-PEG nanoassemblies
surfactants. Noteworthy is the remarkable
efficiency of the coupling process when
using cyclic triolborate reagents as boron
partners. Indeed, the reaction of N-Boc-
4-iodo-l-phenylalanine (1) with a phenyl
cyclic triolborate derivative 7 led to 98%
conversion in 2 h in the presence of 1 mol%
palladium in aqueous phosphate buffer at
37 °C, near-physiological pH and on a syn-
thetically relevant scale.
The Suzuki-Miyaura cross-coupling
variant reported here works even at slight-
No.
X
Y2-B-Ph
pH
Time [h]
Conversion [%]a
ly acidic pH. This will present a significant
1
I
8.0
18
4
advantage compared to the original version
of the reaction in environments where the
pH cannot be controlled, such as in the in-
tracellular space. In addition, the chelating
effect of the polymer chains stabilising
the metal may reduce non-specific inter-
actions with surrounding biomolecules,
and thus minimize toxicity as compared
to small-molecule-stabilized homogenous
catalysts. In this context, we believe that
the present approach will contribute to the
design of a catalytic system able to selec-
tively achieve an irreversible carbon–car-
bon bond formation in complex biological
systems.
2
3
I
I
8.0
8.0
18
0
2
18
98
100
2
18
90
98
4
5
6
7
Br
Cl
I
8.0
8.0
7.0
6.0
Material and Methods
18
2
0
Materials
Unless otherwise stated, all reagents
and solvents were purchased from Sigma-
Aldrich. Potassium tetrachloropalladate
(II) (K PdCl4) 99.99% trace metal basis
(Sigma2-Aldrich, Lot N° MKBL2083V)
was used as a palladium source.
97
97
N-Boc-4-iodo-l-phenylalanine,
N-Boc-4-bromo-l-phenylalanine
N-Boc-4-chloro-l-phenylalanine
and
were
I
2
purchased from Alfa Aesar. N-Boc-3-iodo-
l-tyrosine was prepared as reported else-
where.[19] PLGA-PEG (poly(ethylene gly-
col)-poly(dl-lactide-co-glycolide) 50:50
Resomer® PEG type RGP d 50105 (MW
50000 g/mol) (diblock, 10% PEG with
5000 Dalton, Evonik IndustriesAG, Essen,
Germany) was generously donated by the
1 equiv. R1-X, 3 equiv. Y2B-Ph, 1 mol% Pd on PLGA-PEG nanoparticles. aThe conversion was
determined by 1H-NMR spectroscopy on the crude reaction mixture.
nous base, the reaction between N-Boc- Pd-PLGA-PEG nanoassemblies (1mol%
4-iodo-l-phenylalanine (1) and the triol- palladium) showed complete conversion
group of Prof. Elias Fattal, Université
borate (7) catalysed by the palladium-as- after 2 h at 37 °C in phosphate buffer. The
Paris-Saclay. Deionized MilliQ purified
water was used for all chemical reactions
semblies gave excellent conversions in 2 h coupled product was isolated by column
even in neutral and slightly acidic buffers chromatography in 81% yield validating
and for nanoparticles synthesis. Proton nu-
(97% conversion at pH 7.0 and 6.0) (Table
the usefulness of our process for synthet-
clear magnetic resonance (1H NMR) spec-
3, entries 6 & 7). The remarkable activity
ic transformations of polyfunctional, wa-
of these palladium-loaded nanoassemblies ter-soluble substrates under mild condi-
in the absence of added bases represents tions.
tra were recorded on a Bruker AV500 (500
MHz) or Bruker AV400 (400 MHz). All
chemical shifts are quoted on the δ scale in
ppm using residual solvent as the internal
standard. Ultracentrifugation was achieved
using Optima LE-80K Ultracentrifuge
a significant advantage over standard
Suzuki-Miyaura coupling conditions for
reactions involving base-sensitive reaction Conclusion and Perspectives
partners or where little control over the pH
Beckman Coulter apparatus.
is possible.
The Pd-PLGA-PEG nanoassemblies
Interestingly, the process is not limit- reported here showed excellent catalytic
ed to the micromolar scale but could be activities for the coupling of halogenated
PLGA-PEG Nanoparticle (PLGA-
PEG NPs) Preparation
scaled to afford milligram quantities. The
amino acid analogues via Suzuki-Miyaura
Plain
PLGA-PEG
nanoparticles
reaction of 33 mg of N-Boc-4-iodo-l- reaction in water and mild conditions with-
phenylalanine (1) with 7 in the presence of out the need for additional co-solvents or
were prepared by emulsion-evaporation.

256 CHIMIA 2016, 70, No. 4
Laureates: Junior Prizes of the sCs faLL Meeting 2015
Practically, PLGA-PEG (50 mg) was dis- Camera System Camera at a nominal mag- citric acid solution 10% (5 mL). The aque-
solved into CH Cl (4 mL). The organic nification of 80x at a defocus level of 2 µm. ous solution was extracted with EtOAc (5 x
phase was emul2sifi2ed into 10 mL of 1.5%
5 mL). The combined organic layers were
sodium cholate (w/v) aqueous solution us- Determination of Pd Encapsulation then washed with brine (10 mL), dried over
ing a vortex for 1 min and then a vibrating Efficacy by ICP-MS MgSO4, filtered and concentrated. The res-
metallic tip at 180V, at 30% amplitude for The association of Pd to PLGA-PEG idue was purified by chromatography on
1 min at 0 °C. The organic solvent was nanoparticles (i.e. encapsulation efficacy) silica gel column (100/0 to 95/5 DCM/
evaporated by magnetic stirring for 4 h. was determined by inductively coupled MeOH) to provide the expected N-Boc-4-
The nanoparticles were recovered by ul- plasma-mass spectrometry (ICP-MS) by phenyl-l-phenylalanine (22.1 mg, 81%).
tracentrifugation (1 h, 27 440 g, 4 °C) and Antellis (Parc technologique du Canal, 3 1H NMR (500 MHz, MeOD) δ 7.47 (d, J =
the pellet was resuspended in MilliQ water rue des satellites, 31400 Toulouse). 7.3 Hz, 2H), 7.40 (d, J = 7.7 Hz, 2H), 7.30
(t, J = 7.6 Hz, 2H), 7.20 (d, J = 7.4 Hz, 3H),
to form a stock suspension of 5 mg PLGA-
PEG / mL.
Potassium 4-methyl-1-phenyl-
2,6,7-trioxa-1-borate-bicyclo[2.2.2]
octane (7)
4.21 (m, 1H), 3.11 (dd, J = 13.6, 4.8 Hz,
1H), 2.86 (dd, J = 13.6, 8.0 Hz, 1H), 1.24
(s, 9H). MS (ESI+) m/z (%): 364.1 (100%)
Pd-loading on PLGA-PEG
Nanoparticles (Pd-PLGA-PEG NPs)
A mixture of phenylboronic acid [M+Na]+.
PLGA-PEG NPs stock suspension (200 (1 mmol, 121.9 mg, 1 equiv.) and
µL, 1 mg PLGA-PEG, 0.02 µmol) was di- 1,1,1-tris(hydroxymethyl)ethane (1 mmol,
luted with 990 µL MilliQ water. K PdCl4 120.1 mg, 1 equiv.) in toluene (2 mL) was
stock solution (10 µL, 100 mM, 1 2µmol) heated under reflux with azeotropic distil-
was added and the mixture was briefly vor- lation using a Dean-Stark apparatus for 4
Acknowledgements
This work is supported by a public grant
overseen by the French National Research
Agency (ANR) as part of the ‘Investissements
d’Avenir’ program (Labex NanoSaclay, ref-
texed and then incubated on a thermostated h. The solvent was removed under reduced
erence: ANR-10-LABX-0035). We thank
shaker (bioSan TS-100) at 25 °C and 800
pressure and the residue taken up into tolu-
rpm for 15 h. The resulting nanoassemblies ene (2 mL) and solid KOH (0.9 mmol, 50.4
were recovered by ultracentrifugation (1 h, mg, 0.9 equiv.) was added. The reaction
Jean-François Gallard (Institut de Chimie
des Substances Naturelles, CNRS-ICSN
UPR 2301, Université Paris-Sud) and
Camille Dejean (BioCIS, UMR-CNRS-8076,
moved and the pellet was resuspended in of the water by the Dean-Stark method for Université Paris-Sud) for technical assistance
24 696 g, 4 °C), the supernatant was re- mixture was heated at reflux with removal
on NMR measurements; The Service d’Ana-
lyse des Médicaments et Métabolites (SAMM)
450 µL MilliQ water.
4 h. The solid that precipitated was filtered,
washed with acetone and dried under re-
and Stéphanie Nicolaÿ for technical assis-
duced pressure to afford the expected salt
Size and Zeta Potential
tance on mass spectrometry measurements;
Ghislaine Frébourg (Service de Microscopie
Electronique de l’IFR de Biologie Intégrative,
la FRM 2006, SESAME 2005 et le CNRS-
INSB) and Julie Mougin (Institut Galien, UMR
CNRS 8612, Université Paris-Sud) for techni-
cal assistance on cryo-TEM measurements. AD
1
The hydrodynamic diameter (dH) and
7 (219.6 mg, 90% yield). H NMR (300
polydispersity index (PDI) of the PLGA- MHz, DMSO) δ 7.30 (d, J = 7.2 Hz, 2H),
PEG NPs and Pd-PLGA-PEG nanoassem- 6.92 (m, 3H), 3.56 (s, 6H), 0.47 (s, 3H). 13C
blies were measured by quasi elastic light NMR (75 MHz, DMSO) δ 132.61, 125.86,
scattering, using a Zetasizer Nano ZS in- 124.31, 74.19, 16.76, (C-B signal was not
strument (Malvern, France). Suspensions detected).
were diluted in water and filtered over a
1 µm-pore glass filter. Measurements were General Method for Suzuki–
performed in triplicate at 20 °C, at an angle Miyaura Coupling on Small Scale
thanks the Swiss National Science Foundation
for funding.
of 173° to avoid multiple scattering. The
In an Eppendorf tube, the arylhalide
counting time was set at 60 s. Zeta poten- (0.008 mmol, 1 equiv.) and the boronic ac-
tial measurements were carried out with id (0.024 mmol, 3 equiv.) were suspended
the same instrument, at 25 °C, in 1 mM in phosphate buffer pH 8.0 (200 mM, 50
Received: January 15, 2016
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