Microbial degradation of poly(p-dioxanone) I. Isolation of degrading microorganisms and microbial decomposition in pure culture

Study onin vivoandin vitrodegradation of polydioxanone weaving tracheal stents

The appropriate degradation characteristics of polydioxanone (PDO) are necessary for the safety and effectiveness of stents. This study aimed to investigate the degradation of PDO weaving tracheal stents (PW stents)in vitroandin vivo. The degradation solution ofS. aureus(SAU),E. coli(ECO),P. aeruginosa(PAE), and control (N) were prepared, and the PW stents were immersed for 12 weeks. Then, the radial support force, weight retention, pH, molecular structure, thermal performance, and morphology were determined. Furthermore, the PW stents were implanted into the abdominal cavity of rabbits, and omentum was embedded. At feeding for 16 weeks, the mechanical properties, and morphology were measured. During the first 8 weeks, the radial support force in all groups was progressively decreased. At week 2, the decline rate of radial support force in the experimental groups was significantly faster compared to the N group, and the difference was narrowed thereafter. The infrared spectrum showed that during the whole degradation process, SAU, ECO and PAE solution did not lead to the formation of new functional groups in PW stents.In vitroscanning electron microscope observation showed that SAU and ECO were more likely to gather and multiply at the weaving points of the PW stents, forming colonies.In vivoexperiments showed that the degradation in the concavity of weaving points of PW stents was more rapid and severe. The radial support loss rate reached more than 70% at week 4, and the radial support force was no longer measurable after week 8. In omentum, multinuclear giant cells and foreign giant cells were found to infiltrate. PW stents have good biocompatibility. The degradation rate of PW stents in the aseptic conditionsin vivowas faster than in the bacteriological environmentin vitro.

3D-Printed Poly (P-Dioxanone) Stent for Endovascular Application: In Vitro Evaluations

Rapid formation of innovative, inexpensive, personalized, and quickly reproducible artery bioresorbable stents (BRSs) is significantly important for treating dangerous and sometimes deadly cerebrovascular disorders. It is greatly challenging to give BRSs excellent mechanical properties, biocompatibility, and bioabsorbability. The current BRSs, which are mostly fabricated from poly-l-lactide (PLLA), are usually applied to coronary revascularization but may not be suitable for cerebrovascular revascularization. Here, novel 3D-printed BRSs for cerebrovascular disease enabling anti-stenosis and gradually disappearing after vessel endothelialization are designed and fabricated by combining biocompatible poly (p-dioxanone) (PPDO) and 3D printing technology for the first time. We can control the strut thickness and vessel coverage of BRSs by adjusting the printing parameters to make the size of BRSs suitable for small-diameter vascular use. We added bis-(2,6-diisopropylphenyl) carbodiimide (commercial name: stabaxol^®-1) to PPDO to improve its hydrolytic stability without affecting its mechanical properties and biocompatibility. In vitro cell experiments confirmed that endothelial cells can be conveniently seeded and attached to the BRSs and subsequently demonstrated good proliferation ability. Owing to the excellent mechanical properties of the monofilaments fabricated by the PPDO, the 3D-printed BRSs with PPDO monofilaments support desirable flexibility, therefore offering a novel BRS application in the vascular disorders field.

Biological compatibility, thermal and in vitro simulated degradation for poly(p-dioxanone)/poly(lactide-co-glycolide)/poly(ethylene succinate-co-glycolide)

Bio-absorbable polymers are widely desired to be applied and used as biomaterials for surgery hemostatic and medical tissue engineering devices. Ring-opening copolymerization reaction was applied to synthesize poly(ethylene succinate-co-glycolide) (PES-b-PGA). Stannous octoate was used as a catalyst whereas poly(ethylene succinate) was used as a macro-initiator to react with glycolide. PES-b-PGA was then used as a compatibilizer to prepare the blend biomaterial of PPDO/PLGA/PES-b-PGA by melt blending poly(p-dioxanone) (PPDO) with poly(lactide-co-glycolide) (PLGA). This would enhance the interactions of the inter-molecular chains and intra-molecular segments thus improving the compatibility. To obtain the biomaterial of PPDO/PLGA/PES-b-PGA with a regulated and controlled degradation and/or hydrolysis period, various ratios of PPDO, PLGA, and PES-b-PGA was blended. Behaviors of the thermal and in vitro simulated degradation, biological compatibility, cytotoxicity and subcutaneous implantation of PPDO/PLGA/PES-b-PGA were investigated. The results show that the in vitro hydrolytic degradation cycle is consistent with the wound healing time and that the biomaterial has slight cytotoxicity and it will do good to the cell proliferation, with 1 grade of cytotoxicity and the relative growth rate being the range from 92.5% to 96.2%. The implantation of the biomaterial into the rabbits' ears will not adversely affect the wound healing and the tissues surrounding the implanted sites. Therefore, the biomaterial has good biocompatibility and potential applications in medical tissue engineering devices.

A novel biocompatible polymeric blend for applications requiring high toughness and tailored degradation rate

Finding the right balance in mechanical properties and degradation rate of biodegradable materials for biomedical applications is challenging, not only at the time of implantation but also during biodegradation. For instance, high elongation at break and toughness with a mid-term degradation rate are required for tendon scaffold or suture application, which cannot be found in each alpha polyester individually. Here, we hypothesise that blending semi-crystalline poly(p-dioxanone) (PDO) and poly(lactide-co-caprolactone) (LCL) in a specific composition will enhance the toughness while also enabling tailored degradation times. Hence, blends of PDO and LCL (PDO/LCL) were prepared in varying concentrations and formed into films by solvent casting. We thoroughly characterised the chemical, thermal, morphological, and mechanical properties of the new blends before and during hydrolytic degradation. Cellular performance was determined by seeding mouse fibroblasts onto the samples and culturing for 72 hours, before using proliferation assays and confocal imaging. We found that an increase in LCL content causes a decrease in hydrolytic degradation rate, as indicated by induced crystallinity, surface and bulk erosions, and tensile properties. Interestingly, the noncytotoxic blend containing 30% PDO and 70% LCL (PDO3LCL7) resulted in small PDO droplets uniformly dispersed within the LCL matrix and demonstrated a tailored degradation rate and toughening behaviour with a notable strain-hardening effect reaching 320% elongation at break; over 3 times the elongation of neat LCL. In summary, this work highlights the potential of PDO3LCL7 as a biomaterial for biomedical applications like tendon tissue engineering or high-performance absorbable sutures.