Enhanced ligand-free attachment of osteoblast to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanoparticles.

Polymeric nanoparticles have previously been used as substrates for cell attachment and proliferation due to their ability to mimic the extracellular matrix, but in general, they require surface chemical modifications to achieve this purpose. In this study, polymeric nanoparticles were developed and used without any matrix ligands functionalized on their surface to promote cell attachment and proliferation of human osteoblasts (MG63s). First, telechelic, reduced molar mass and diol-functionalized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was prepared by transesterification using ethylene glycol. Then, PHBV-diol was used to prepare biodegradable nanoparticles via the solvent evaporation technique. MG63s were cultured in the presence of PHBV nanoparticles and growth kinetics were compared to that on tissue culture polystyrene (TCPS). Cell attachment on non-tissue culture polystyrene pre-coated with nanoparticles was assessed and compared to attachment on TCPS. The cell attachment study demonstrated that cells readily attached and were well spread onto the nanoparticle surfaces compared to non-tissue culture polystyrene. These findings reveal the potential of PHBV nanoparticles for cell attachment and growth to be used in tissue engineering.

Synthesis and Self-Assembly of Poly(N-Vinylcaprolactam)-b-Poly(ε-Caprolactone) Block Copolymers via the Combination of RAFT/MADIX and Ring-Opening Polymerizations.

Well-defined amphiphilic, biocompatible and partially biodegradable, thermo-responsive poly(N-vinylcaprolactam)-b-poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by combining reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerizations (ROP). Poly(N-vinylcaprolactam) containing xanthate and hydroxyl end groups (X-PNVCL-OH) was first synthesized by RAFT/macromolecular design by the interchange of xanthates (RAFT/MADIX) polymerization of NVCL mediated by a chain transfer agent containing a hydroxyl function. The xanthate-end group was then removed from PNVCL by a radical-induced process. Finally, the hydroxyl end-capped PNVCL homopolymer was used as a macroinitiator in the ROP of ε-caprolactone (ε-CL) to obtain PNVCL-b-PCL block copolymers. These (co)polymers were characterized by Size Exclusion Chromatography (SEC), Fourier-Transform Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance spectroscopy (1H NMR), UV-vis and Differential Scanning Calorimetry (DSC) measurements. The critical micelle concentration (CMC) of the block copolymers in aqueous solution measured by the fluorescence probe technique decreased with increasing the length of the hydrophobic block. However, dynamic light scattering (DLS) demonstrated that the size of the micelles increased with increasing the proportion of hydrophobic segments. The morphology observed by cryo-TEM demonstrated that the micelles have a pointed-oval-shape. UV-vis and DLS analyses showed that these block copolymers have a temperature-responsive behavior with a lower critical solution temperature (LCST) that could be tuned by varying the block copolymer composition.

Synthesis of amphiphilic pullulan-graft-poly(ε-caprolactone) via click chemistry.

Chemical modification of natural polymers has been commonly employed for the development of new bio-based materials, aiming at adjusting specific properties such as solubility, biodegradability, thermal stability and mechanical behavior. Among all natural polymers, polysaccharides are promising materials, in which biodegradability, processability and bioreactivity make them suitable for biomedical applications. In this context, this work describes the synthesis and characterization of a novel amphiphilic pullulan-g-poly(ε-caprolactone) (Pull-g-PCL) graft copolymer. In a first step, pullulan was chemically modified with 2-bromopropionyl bromide to obtain bromo-functionalized pullulan (PullBr). Then, this precursor was modified with sodium azide, leading to azide pullulan (PullN3). In parallel, propargyl-terminated poly(ε-caprolactone) was prepared via ring-opening polymerization (ROP). These preliminary steps involved the synthesis of azide and alkyne compounds, capable of being linked together via alkyne-azide cycloaddition reaction catalyzed by copper (Cu (I)), which leads to Pull-g-PCL. The chemical structures of the polymers were assessed by Proton Nuclear Magnetic Resonance (1H NMR) and Fourier Transform Infrared (FTIR).