In situ gel forming stereocomplex composed of four-arm PEG-PDLA and PEG-PLLA block copolymers

Stereocomplexed Functional and Statistical Poly(lactide-carbonate)s via a Simple Organocatalytic System

The stereocomplexation of polylactide (PLA) has been widely relied upon to develop degradable, sustainable materials with increased strength and improved material properties in comparison to stereopure PLA. However, forming functionalized copolymers of PLA while retaining high crystallinity remains elusive. Herein, the controlled ring-opening copolymerization (ROCOP) of lactide (LA) and functionalized cyclic carbonate monomers is undertaken. The produced polymers are shown to remain crystalline up to 25 mol % carbonate content and are efficiently stereocomplexed with homopolymer PLA and copolymers of opposite chirality. Polymers with alkene and alkyne pendent handles are shown to undergo efficient derivatization with thiol-ene click chemistry, which would allow both the covalent conjugation of therapeutic moieties and tuning of material properties.

Drug delivery systems based on polyethylene glycol hydrogels for enhanced bone regeneration

Drug delivery systems composed of osteogenic substances and biological materials are of great significance in enhancing bone regeneration, and appropriate biological carriers are the cornerstone for their construction. Polyethylene glycol (PEG) is favored in bone tissue engineering due to its good biocompatibility and hydrophilicity. When combined with other substances, the physicochemical properties of PEG-based hydrogels fully meet the requirements of drug delivery carriers. Therefore, this paper reviews the application of PEG-based hydrogels in the treatment of bone defects. The advantages and disadvantages of PEG as a carrier are analyzed, and various modification methods of PEG hydrogels are summarized. On this basis, the application of PEG-based hydrogel drug delivery systems in promoting bone regeneration in recent years is summarized. Finally, the shortcomings and future developments of PEG-based hydrogel drug delivery systems are discussed. This review provides a theoretical basis and fabrication strategy for the application of PEG-based composite drug delivery systems in local bone defects.

The isothermal crystallization kinetic of poly(L-lactide)-block-poly(ethylene glycol) block copolymers (PLLA-PEG): Effect of block lengths of PEG and PLLA

Poly(ethylene glycol)-block-poly(L-lactide) (PEG-PLLA) is a biodegradable copolymer which widely applied to medicine and drug system, and the morphology, organization and mechanical properties were extensively investigated. However, the crystallization kinetic were...

Synthesis and characterizations of in situ cross-linkable gelatin and 4-arm-PPO-PEO hybrid hydrogels via enzymatic reaction for tissue regenerative medicine

In situ cross-linkable hybrid hydrogels composed of gelatin and 4-arm-polypropylene oxide-polyethylene oxide (Tetronic) was developed as an injectable scaffold for tissue regeneration. The gelatin was modified by hydroxyphenyl propionic acid (HPA) and the Tetronic was conjugated with tyramines (Tet-TA). The hydrogels were rapidly formed by mixing the polymer solutions containing horseradish peroxidase (HRP) and hydrogen peroxide (H(2)O(2)). The gelation time and mechanical properties of the hydrogels could be controlled by varying the HRP and H(2)O(2) concentrations. In vitro degradation study of the hybrid hydrogels was carried out using collagenase and the prolonged proteolytic degradation was obtained due to the presence of the Tetronic. Human dermal fibroblast (hDFB) was cultured in the hydrogel matrices to evaluate the cyto-compatibility. The encapsulated cells were shown to be highly viable and spread over the gel matrices, suggesting that the hybrid hydrogels have an excellent cyto-compatibility. The hydrogels were also subcutaneously injected in the back of mice and the results demonstrated that the hydrogels were rapidly formed at the injected site. From these results, we demonstrate that the in situ cross-linkable hydrogels formed by hybridization of gelatin and Tetronic via enzyme-mediated reactions hold great promise for use as injectable matrices for tissue regenerative medicine due to their tunable physico-chemical properties and excellent bioactivity.

Intracellular delivery and anti-cancer effect of self-assembled heparin-Pluronic nanogels with RNase A

A novel self-assembled nanogel was prepared for the intracellular delivery of ribonuclease A (RNase A) and the anti-cancer efficacy of RNase A delivery was investigated. The physical properties of self-assembled heparin-Pluronic (HP) nanogels incorporating RNase A (HPR nanogels) were characterized by dynamic light scattering (DLS), ξ-potential, and transmission electron microscopy (TEM). RNase A showed a strong affinity for the HP nanogel, resulting in a high loading efficiency (>78%) and significantly decreased hydrodynamic size (from 89 to ~29). HPR nanogels were efficiently internalized into HeLa cells and localized in the cytosol as well as the nucleus. In the mechanism study of cellular uptake, treating with methoxy β-cyclodextrin (Mβ-CD) decreased the uptake efficiency of HP nanogel, indicating that internalization occurs via caveolae/lipid-raft mediated endocytosis. Localization in the nucleus most likely occurred because the conjugated heparin facilitated nucleus penetration. The cytotoxicity of HPR nanogels was significantly increased when the RNase A concentration was increased, which resulted from the degradation of single stranded RNAs in the cytosol and the nucleus due to the intracellular localization of the HPR nanogels. These results demonstrate that self-assembled HP nanogels are a remarkable vehicle for intracellular protein delivery and hold promise for use as cancer chemotherapeutics.