Efficiency of liquid tin(ii) n-alkoxide initiators in the ring-opening polymerization of l-lactide: kinetic studies by non-isothermal differential scanning calorimetry

Biodegradable and 3D printable lysine functionalized polycaprolactone scaffolds for tissue engineering applications

Tissue engineering (TE) has sparked interest in creating scaffolds with customizable properties and functional bioactive sites. However, due to limitations in medical practices and manufacturing technologies, it is challenging to replicate complex porous frameworks with appropriate architectures and bioactivity in vitro. To address these challenges, herein, we present a green approach that involves the amino acid (l-lysine) initiated polymerization of ɛ-caprolactone (CL) to produce modified polycaprolactone (PCL) with favorable active sites for TE applications. Further, to better understand the effect of morphology and porosity on cell attachment and proliferation, scaffolds of different geometries with uniform and interconnected pores are designed and fabricated, and their properties are evaluated in comparison with commercial PCL. The scaffold morphology and complex internal micro-architecture are imaged by micro-computed tomography (micro-CT), revealing pore size in the range of ~300-900 μm and porosity ranging from 30 to 70 %, while based on the geometry of scaffolds the compressive strength varied from 143 ± 19 to 214 ± 10 MPa. Additionally, the degradation profiles of fabricated scaffolds are found to be influenced by both the chemical nature and product design, where Lys-PCL-based scaffolds with better porosity and lower crystallinity degraded faster than commercial PCL scaffolds. According to in vitro studies, Lys-PCL scaffolds have produced an environment that is better for cell adhesion and proliferation. Moreover, the scaffold design affects the way cells interact; Lys-PCL with zigzag geometry has demonstrated superior in vitro vitality (>90 %) and proliferation in comparison to other designs. This study emphasizes the importance of enhancing bioactivity while meeting morphology and porosity requirements in the design of scaffolds for tissue engineering applications.

Syntheses of polylactides by means of tin catalysts

Reaction mechanisms and synthetic methods used for the preparation of homo- and copolylactides based on tin(ii) and tin(iv) catalysts are reviewed.

Development of an Antimicrobial-Coated Absorbable Monofilament Suture from a Medical-Grade Poly(l-lactide-co-ε-caprolactone) Copolymer

In this study, a medical-grade poly(l-lactide-co-ε-caprolactone) (PLC) copolymer with a monomer ratio of l-lactide (L) to ε-caprolactone (C) of 70:30 mol % for use as an absorbable surgical suture was synthesized via ring-opening polymerization (ROP) using a novel soluble liquid tin(II) n-butoxide (Sn(OnC4H9)2) as an initiator. In fiber fabrication, the process included copolymer melt extrusion with a minimal draw followed by sequential controlled hot-drawing and fixed-annealing steps to obtain oriented semicrystalline fibers with improved mechanical strength. For healing enhancement, the fiber was dip-coated with "levofloxacin" by adding the drug into a solution mixture of acetone, poly(ε-caprolactone) (PCL), and calcium stearate (CaSt) in the ratio of acetone/PCL/CaSt = 100:1% w/v:0.1% w/v. The tensile strength of the coated fiber was found to be increased to ∼400 MPa, which is comparable with that of commercial polydioxanone (PDS II) of a similar size. Finally, the efficiency of the drug-coated fiber regarding its controlled drug release and antimicrobial activity was investigated, and the results showed that the coated fiber was able to release the drug continuously for as long as 30 days. For fiber antimicrobial activity, it was found that a concentration of 1 mg/mL was sufficient to inhibit the growth of Staphylococcus aureus (MRSA), Escherichia coli O157:H7, and Pseudomonas aeruginosa, giving a clear inhibition zone range of 20-24 mm for 90 days. Cytotoxicity testing of the drug-coated fibers showed a %viability of more than 70%, indicating that they were nontoxic.

Novel Poly(Methylenelactide-g-L-Lactide) Graft Copolymers Synthesized by a Combination of Vinyl Addition and Ring-Opening Polymerizations

In this work, a novel poly (methylenelactide-g-L-lactide), P(MLA-g-LLA) graft copolymer was synthesized from poly(methylenelactide) (PMLA) and L-lactide (LLA) using 0.03 mol% liquid tin(II) n-butoxide (Sn(OnBu)2) as an initiator by a combination of vinyl addition and ring-opening polymerization (ROP) at 120 °C for 72 h. Proton and carbon-13 nuclear magnetic resonance spectroscopy (1H- and 13C-NMR) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the grafted structure of P(MLA-g-LLA). The P(MLA-g-LLA) melting temperatures (Tm) range of 144-164 °C, which was lower than that of PLA (170-180 °C), while the thermal decomposition temperature (Td) of around 314-335 °C was higher than that of PLA (approx. 300 °C). These results indicated that the grafting reaction could widen the melt processing range of PLA and in doing so increase PLA's thermal stability during melt processing. The graft copolymers were obtained with weight-average molecular weights (M¯w) = 4200-11,000 g mol-1 and a narrow dispersity (Đ = 1.1-1.4).