Yu Fu,Qingrong Wu,Wanying Yang,Jiaqi Wang,Zechen Liu,Hao Shi,Shouxin Liu
Medical titanium alloy Ti-6Al-4V (TC4) has been widely used in the medical field, especially in human tissue repair. However, TC4 has some shortcomings, which may cause problems with biocompatibility and mechanical compatibility in direct contact with the human body. To solve this problem, physical gels are formed on the surface of TC4, and the storage modulus of the formed physical gel matches that of the human soft tissue. 2-bromoisobutyryl bromide (BIBB) and dopamine (DA) were used to form initiators on the surface of hydroxylated medical titanium alloy. Different initiators were formed by changing the ratio of BIBB and DA, and the optimal one was selected for subsequent reactions. Under the action of the catalyst, L-lactide and D-lactide were ring-opened polymerized with hydroxyethyl methacrylate (HEMA), respectively, to form macromolecular monomers HEMA-PLLA29and HEMA-PDLA29with a polymerization degree of 29. The two macromolecular monomers were stereo-complexed by ultrasound to form HEMA-stereocomplex polylactic acid (HEMA-scPLA29). Based on two monomers, 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo (ethylene oxide) methacrylate (OEGMA), and the physical crosslinking agent HEMA-scPLA29,physical gels are formed on the surface of TC4 attached to the initiator via Atom Transfer Radical Addition Reaction (ATRP) technology. The hydrogels on the surface of titanium alloy were characterized and analyzed by a series of instruments. The results showed that the storage modulus of physical glue was within the range of the energy storage modulus of human soft tissue, which was conducive to improving the mechanical compatibility of titanium alloy and human soft tissue.Keywords:hydrogels;medical titanium alloy;dopamine;mechanics
Biodegradable polymersomes that can potentially be employed in drug delivery systems were fabricated by blending poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide) (PLLA-PEG-PLLA) and poly(d-lactide)-b-poly(ethylene glycol)-b-poly(d-lactide) (PDLA-PEG-PDLA) block copolymers in a weight ratio of 1:1 in an aqueous solution. A series of amphiphilic PLLA-PEG-PLLA and PDLA-PEG-PDLA triblock copolymers were synthesized with different hydrophobic chain lengths through ring-opening polymerization. The self-assembly of pure PLLA-PEG-PLLA and an equimolar mixture of enantiomers of PLLA-PEG-PLLA and PDLA-PEG-PDLA was investigated by transmission electron microscopy, X-ray diffraction, and dynamic light scattering. Various nanostructures including spherical micelles, worm-like micelles, and vesicles were obtained by controlling the hydrophobic chain length and the incubation temperature. In the pure PLLA-PEG-PLLA systems, the hydrophobic–hydrophilic balance dominated the self-assembled morphologies. In equimolar enantiomer mixtures, self-assembled morphologies were greatly affected by the formation of the PLLA-PDLA stereocomplex (SC). There was an inverse correlation between the SC crystallinity and the curvature of the self-assembled structures─the higher the SC content, the smaller the curvature. This rule was not applicable when the SC content was too high (≳50%), which produced spherical micelles as the main nanostructures. Since the SC-induced self-assembly could be controlled by changing the incubation temperature, the polymersomes can potentially be used in many applications, such as nanoreactors and nanovehicles.
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