Pendant groups fine-tuning thermal gelation of poly(ε -caprolactone)-b -poly(ethylene glycol)-b -poly(ε-caprolactone) aqueous solution

An injectable thermosensitive hydrogel self-supported by nanoparticles of PEGylated amino-modified PCL for enhanced local tumor chemotherapy

We synthesized amino-modified poly(ε-caprolactone) PCN-b-PEG-b-PCN (PECN) triblock copolymers and studied the contribution of the introduced amino groups to the drug delivery efficiency of PECN nanoparticles (NPs) and their injectable thermosensitive hydrogels. PECN15 with an optimal amino group content was obtained. Firstly, the hydrophobic drug paclitaxel (PTX) was loaded into PECN15 up to 5.91% and formed PTX/PECN NPs 90 nm in size and with a slightly positive charge (7.3 mV). Furthermore, the injectable PTX/PECN NPs aqueous solution (25 wt%) at ambient temperature could undergo fast gelation at 37 °C and sustainedly release PTX/PECN NPs in 10 days. More importantly, compared with our previously reported PECT NPs, the PECN NPs without an increase in toxicity could improve the cell uptake and enhance intracellular drug release by responding to the acidic environment of the endosome. Thus, the PTX/PECN NPs presented a lower IC50 of 3.14 μg mL-1 than that of the PTX/PECT NPs (7.67 μg mL-1) and free PTX (4.65 μg mL-1). Moreover, through peritumoral injection, the PTX/PECNGel showed 94.27% inhibition rate of tumor growth on day 19, higher than PTX/PECTGel (72.28%) and Taxol® (47.03%). Therefore, the PECN NPs hydrogel provided a more effective injectable platform to enhance local cancer chemotherapy, and also provided the possibility of further functionalization by the reactive amino groups.

Self-Assemblable Polymer Smart-Blocks for Temperature-Induced Injectable Hydrogel in Biomedical Applications

Self-assembled temperature-induced injectable hydrogels fabricated via self-assembly of polymer smart-blocks have been widely investigated as drug delivery systems and platforms for tissue regeneration. Polymer smart-blocks that can be self-assembly play an important role in fabrication of hydrogels because they can self-assemble to induce the gelation of their copolymer in aqueous solution. The self-assembly occurs in response to an external stimulus change, such as temperature, pH, glucose, ionic strength, light, magnetic field, electric field, or their combination, which results in property transformations like hydrophobicity, ionization, and conformational change. The self-assembly smart-block based copolymers exist as a solution in aqueous media at certain conditions that are suitable for mixing with bioactive molecules and/or cells. However, this solution turns into a hydrogel due to the self-assembly of the smart-blocks under exposure to an external stimulus change in vitro or injection into the living body for a controllable release of loaded bioactive molecules or serving as a biomaterial scaffold for tissue regeneration. This work reports current scenery in the development of these self-assembly smart-blocks for fabrication of temperature-induced injectable physically cross-linked hydrogels and their potential application as drug delivery systems and platforms for tissue engineering.

Synthesis and gelation of copolypept(o)ides with random and block structure

Copolypept(o)ides of polysarcosine (PSar) and poly(N-isopropyl-L-glutamine) (PIGA) with random and block sequence structures were synthesized by ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCA) and γ-benzyl-l-glutamate N-carboxyanhydrides (BLG-NCA) and post modification. With different distribution of Sar along the main chain, H-bonding pattern and secondary structure of polypeptides were turned, as well as aggregation and gelation behavior. Both copolypept(o)ides formed hydrogels above their critical gelation concentrations (CGCs) without thermo-sensitivity, which was normally reserved for PEG copolypeptides (eg, PEG-b-PIGA). In particular, a different mechanism from previously reported micellar percolation or fibrillar entanglement was suggested for gelation of the random copolypept(o)ide. Therefore, hydrogels from copolymers of PSar and PIGA represented a new approach to construct easy-handling, biocompatible, biodegradable and thermo-stable gels that could potentially be applied in biomedical fields.