A comparative study on in vitro degradation behavior of PLLA-based copolymer monofilaments

A review of recent advances of piezoelectric poly-L-lactic acid for biomedical applications

Poly-L-lactic acid (PLLA), recognized as a piezoelectric material, not only demonstrates exceptional piezoelectric properties but also exhibits commendable biocompatibility and biodegradability. These properties render PLLA highly promising for diverse applications, including sensors, wearable devices, biomedical engineering, and related domains. This review offers a comprehensive overview of the distinctive piezoelectric effect of PLLA-based material and delves into the latest advancements in its preparation strategies as a piezoelectric material. It further presents recent research progress in PLLA-based piezoelectric materials, particularly in the realms of health monitoring, skin repair, nerve regeneration, and tissue repair. The discourse extends to providing insights into potential future trajectories for the development of PLLA-based piezoelectric materials.

Understanding the hydrolysis mechanism on segments and aggregate structures: Corrosion-tailored poly (lactic acid) deriving copolymers with δ-valerolactone

Poly (L-lactic acid) (PLLA) based copolymers modified with δ-valerolactone (DVL) through random copolymerization (PVLA-R) and block copolymerization (PVLA-B) with various DVL content were prepared to investigate their degradation regulation and mechanism. Chemical structure, thermal properties, hydrophilicity, crystallization as well as the crystal defects of the obtained copolymers were respectively confirmed. Degradation regulation of both PVLA-R and PVLA-B, such molecular weight and pH value changes of PLLA based copolymers were investigated via vitro degradation method. In order to further explore the degradation principle of the two copolymers, their degradation residues at different stages were systematically studied. The addition and increasing content of DVL disturbs the regularity of original PLLA molecular structure, resulting in accelerating degradation of copolymers. Compared with amorphous region, the crystalline region of both two copolymers has better corrosion resistance, which could be confirmed by increased melting point and crystallinity of both PVLA-R and PVLA-B degradation residues. PVLA-B copolymers show relatively superior degradation resistance mainly due to their higher molecular weight, crystallinity and hydrophobic index than PVLA-R copolymers.

Mechanical and hydrolytic properties of thin polylactic acid films by fused filament fabrication

Thin polymeric films are widely used as medical applications such as cell culture, stent, drug delivery and mechanical fixation. One of the most commonly used materials is polylactic acid (PLA) - a material, which is non-toxic, biodegradable and biocompatible. Fused filament fabrication (FFF) is a preferable additive manufacturing technique to manufacture polymers, where PLA is one of the most common materials. FFF is a promising technique for customised biomedical applications due to its relatively low cost and geometrical flexibility where biomedical applications are patient tailored. This study is the first to consider FFF monolayered thin films of PLA in terms of mechanical and hydrolytic properties at 37 °C in vitro degradation. Throughout degradation, the reduction in mechanical properties was examined by analysing molecular weight and thermal properties. FFF monolayered PLA underwent autocatalytic bulk degradation with no proof of significant mass loss. Young's modulus, ultimate tensile strength and molecular weight reduced by approximately 60%, 86%, and 80% after 280 days, respectively, while the degree of crystallinity increased by 143% in comparison to benchmark thin films at day 0. It was found that the decrease in mechanical properties was more sensitive to the increase in crystallinity in the early stage of the degradation, while the molecular weight was more dominant in the late stage of the degradation. This study provides practical information in terms of mechanical properties to support medical device designers in a range of potential end-use biomedical applications to achieve safe functional products over the required degradation lifetime.

Biodegradable atrial septal defect occluders: A current review

Atrial septal defect (ASD) is a common structural congenital heart disease. With the development of interventional closure devices and transcatheter techniques, interventional closure therapy has become the most well-accepted therapeutic alternative worldwide, as it offers a number of advantages over conventional therapies such as improved safety, easier operation, lower complication rates and invasiveness, and shorter anesthetic time and hospitalizations. During the past decades, various types of occluders based on nondegradable shape memory alloys have been used in clinical applications. Considering that the permanent existence of foreign nondegradable materials in vivo can cause many potential complications in the long term, the research and development of biodegradable occluders has emerged as a crucial issue for interventional treatment of ASD. This review aims to summarize partially or fully biodegradable occlusion devices currently reported in the literature from the aspects of design, construction, and evaluation of animal experiments. Furthermore, a comparison is made on the advantages and disadvantages of the materials used in biodegradable ASD occlusion devices, followed by an analysis of the problems and limitations of the occlusion devices. Finally, several strategies are proposed for future development of biodegradable cardiac septal defect occlusion devices. STATEMENT OF SIGNIFICANCE: Although occlusion devices based on nondegradable alloys have been widely used in clinical applications and saved numerouspatients, biodegradable occlusion devices may offer some advantages such as fewer complications, acceptable biocompatibility, and particularly temporary existence, thereby leaving "native" tissue behind, which will certainly become the development trend in the long term. This review summarizes almost all partially or fully biodegradable occlusion devices currently reported in the literature from the aspects of design, construction, and evaluation of animal experiments. Furthermore, a comparison is made on the advantages and disadvantages of the materials used in biodegradable ASD occlusion devices, followed by an analysis of the problems and limitations of the occlusion devices. Finally, several strategies are proposed for future development of biodegradable cardiac septal defect occlusion devices.

Design and evaluation of a novel biodegradable inferior vena cava filter

Inferior vena cava filter has been increasingly applied in clinical practice to prevent pulmonary embolism. Nowadays, various complications after implanting conventional filters seriously hinder clinical applications. Therefore, in this paper, a novel biodegradable inferior vena cava filter was designed based on biodegradable materials, which is an hourglass-like filter anchored inside a stent structure fixed by connecting fibers. Firstly, mechanical tests in crimp were performed to study the expansion properties of the filter, showing that the biodegradable inferior vena cava filter could achieve self-expansion easily. Furthermore, the biodegradable inferior vena cava filters and fibers were incubated in phosphate buffer media (pH = 7.4 ± 0.2) at 37°C for six months. Scanning electron microscope micrograph showed that the stents exhibited no significant dimensional and structural changes and had enough radial force to support the vessel. During the degradation period, the results of scanning electron microscope, gel permeation chromatography, differential scanning calorimetry and tensile strength analysis confirmed that the degradation rate of the hourglass-like filter was faster than the connecting fibers, achieving progressive degradation and thus avoiding the polymer fragments from blocking vessel. Cytotoxicity and hemolysis assay demonstrated good biocompatibility of the filter. For 5 mm × 10 mm sized thrombus, in vitro simulated thrombus capture test showed that the mean trapping efficiency of the filter was 90%, which was comparable to traditional inferior vena cava filter. In conclusion, all results exhibited that the as-designed biodegradable inferior vena cava filter has a potential in clinical application for patients who are at temporary high risk of venous thromboembolism.