Biomolecule-polymer conjugates are widely used in bio-related fields, but their synthesis is often tricky, especially the introduction of a single biomolecule at one chain end. This paper describes a new straightforward approach to prepare such conjugates via RAFT polymerization. By designing appropriate bio-related RAFT agents, polymer chains of controlled chain length (Mn = 10 000-40 000 and PDI < 1.1) carrying a single biomolecule as an alpha-end group (a sugar or a biotin) linked by a stable amide bond are obtained. Considering the versatility of the RAFT process, this strategy appears to be very attractive for the design of a variety of conjugates.

The reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐acryloylmorpholine (NAM) is performed using three dithioesters (DT) as chain transfer agents (CTA) that incorporate a morpholine (morpholine‐DT), a biotin (biotin‐DT), or a sugar (sugar‐DT) moiety in the R group. PolyNAM chains of controlled characteristics are synthesized. An unexpected behavior is observed with morpholine‐DT, described as an ‘additional retardation’, which is especially visible when low molar masses are targeted ($\overline M _{\rm n} $ < 5 000 g · mol−1). In that particular case, further investigations using MALDI‐TOF mass spectrometry show the presence of terminated intermediate radicals (IRs), which corroborates the assumption based on a specific protection of IR according to the nature of the α‐chain‐end.magnified image

Dispersion polymerization of n‐butyl acrylate has been performed in a mixture of ethanol and water in the presence of poly(N‐acryloylmorpholine) (polyNAM). These hydrophilic polymer chains are synthesized by the RAFT process and thus incorporate well‐defined chain ends. The dithioester ω‐end group is used as an efficient chain transfer agent under dispersion polymerization conditions to produce hairy poly(n‐butyl acrylate) latex particles. Moreover, pre‐functionalization of the polyNAM chains on the α‐end by a carbohydrate derivative is also achieved to obtain directly functionalized particles according to the same strategy.magnified image

A functional dithioester including a phospholipids moiety (Lipid-DT) has been synthesized in a high yield (71% after purification) from a precursor chain transfer agent (CTA) and fully characterized. The RAFT polymerization of an acrylamide derivative, Nacryloylmorpholine (NAM), mediated by this Lipid-DT exhibits a prolonged induction period in comparison with a non-functional dithioester. This phenomenon is discussed in terms of steric shielding induced by the bulky lipid moiety of the CTA. Moreover, the lipid moiety located at the -end of the chains has a strong influence on the size exclusion chromatography analyses in THF using a standard-based calibration, with the suspicion of a retention phenomenon. The well-defined structure of the lipid-end-functionalized polymer chains has been evidenced by MALDI-TOF mass spectrometry. Finally, these chains have been successfully incorporated into lipid/polymer particle assemblies (LipoParticles) that resulted in an improved stabilization in aqueous medium at relatively high ionic strength (300 mM). 4902 6569 8245 9922 Mass (m/z) M n = 4900 g.mol-1 PDI = 1.10

International audienceMany biosensing and imaging systems use fluorescence detection. We present the synthesis of biotin-end-functionalized highly fluorescent water-soluble polymers for potential use in biotin-avidin systems. Statistical polymers of N-acryloylmorpholine (NAM) and N-acryloxysuccinimide (NAS) were prepared by RAFT polymerization using a biotinylated chain transfer agent that ensured 95% end-functionalization of the chains. They were further labeled with a lucifer yellow (LY) dye, yielding 7 to 62 LY fluorophores per polymer chain. The resulting polymers exhibited reduced fluorescence self-quenching, with 7- to 43-fold higher brightness than free LY dye. In addition, they featured low pH sensitivity and very good photobleaching resistance. Moreover, we showed that a more extended polymer conformation was beneficial to the binding of the terminal biotin with streptavidin. This work paves the way for the development of polymers for signal amplification in biosensing assays, labeling of biotin-receptors at cell surfaces in some cancer studies, labeling of antibodies and microscopy imaging purposes

Summary: Encapsulation of hydrophobic compounds in non ionic nanoparticles can easily be performed directly by miniemulsion polymerization of vinyl acetate or styrene with Pluronic F68 as nonionic surfactant and AIBN as initiator. Triglycerides from fatty acid (Miglyol®) or mixture of benzyl benzoate and oligocaprolactones have been used as the hydrophobe component in order to get biocompatible systems. Latexes containing 50% organic phase have been obtained with up to 50% Mygliol engulfed in the nanoparticles. The influence of these hydrophobic compounds on kinetics and molecular weight distribution has been investigated, emphasizing a particular behavior with each one of the two different monomers and compared with the classical hexadecane. magnified image

Using aminoglycoside antibiotics as drug models, it was shown that electrostatic complexes between hydrophilic drugs and oppositely charged double-hydrophilic block copolymers can form ordered mesophases. This phase behavior was evidenced by using poly(acrylic acid)-block-poly(ethylene oxide) block copolymers in the presence of silica precursors, and this allowed preparing drug-loaded mesoporous silica directly from the drug-polymer complexes. The novel synthetic strategy of the hybrid materials is highly efficient, avoiding waste and multistep processes; it also ensures optimal drug loading and provides pH-dependence of the drug release from the materials.

The syntheses of three poly(ethylene oxide)-based (PEO) double-hydrophilic block copolymers (DHBCs) of different second block nature (thermosensitive poly(N-isopropylacrylamide) (PNIPAM) block, anionic poly(vinylbenzyl phosphonic di-acid) block, and cationic poly(vinylbenzyl triethyl ammonium chloride) block) are described. The synthesis strategy depends on the synthesis of a single 5kD-PEO-based macrochain transfer agent that is able to control the RAFT polymerizations of various functional monomers.Low molecular weights of the second block were targeted to obtain asymmetric structures for the DHBCs. Their ability to form micelles under appropriate conditions (specified temperature, pH and nature of the auxiliary of micellization) and the reversibility of the micellization process were checked. Finally, a nanostructured hybrid silica material was obtained using the PNIPAM-based copolymer as a structuredirecting agent (SDA), which yielded well-organized mesoporous silica after template removal.