Injectable PLGA Microscaffolds with Laser-Induced Enhanced Microporosity for Nucleus Pulposus Cell Delivery.

Intervertebral disc (IVD) degeneration is a leading cause of lower back pain (LBP). Current treatments primarily address symptoms without halting the degenerative process. Cell transplantation offers a promising approach for early-stage IVD degeneration, but challenges such as cell viability, retention, and harsh host environments limit its efficacy. This study aimed to compare the injectability and biocompatibility of human nucleus pulposus cells (hNPC) attached to two types of microscaffolds designed for minimally invasive delivery to IVD. Microscaffolds are developed from poly(lactic-co-glycolic acid) (PLGA) using electrospinning and femtosecond laser structuration. These microscaffolds are tested for their physical properties, injectability, and biocompatibility. This study evaluates cell adhesion, proliferation, and survival in vitro and ex vivo within a hydrogel-based nucleus pulposus model. The microscaffolds demonstrate enhanced surface architecture, facilitating cell adhesion and proliferation. Laser structuration improved porosity, supporting cell attachment and extracellular matrix deposition. Injectability tests show that microscaffolds can be delivered through small-gauge needles with minimal force, maintaining high cell viability. The findings suggest that laser-structured PLGA microscaffolds are viable for minimally invasive cell delivery. These microscaffolds enhance cell viability and retention, offering potential improvements in the therapeutic efficiency of cell-based treatments for discogenic LBP.

Influence of Hydroxyapatite Surface Functionalization on Thermal and Biological Properties of Poly(l-Lactide)- and Poly(l-Lactide-co-Glycolide)-Based Composites.

Novel biocomposites of poly(L-lactide) (PLLA) and poly(l-lactide-co-glycolide) (PLLGA) with 10 wt.% of surface-modified hydroxyapatite particles, designed for applications in bone tissue engineering, are presented in this paper. The surface of hydroxyapatite (HAP) was modified with polyethylene glycol by using l-lysine as a linker molecule. The modification strategy fulfilled two important goals: improvement of the adhesion between the HAP surface and PLLA and PLLGA matrices, and enhancement of the osteological bioactivity of the composites. The surface modifications of HAP were confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), TGA, and elemental composition analysis. The influence of hydroxyapatite surface functionalization on the thermal and in vitro biological properties of PLLA- and PLLGA-based composites was investigated. Due to HAP modification with polyethylene glycol, the glass transition temperature of PLLA was reduced by about 24.5 °C, and melt and cold crystallization abilities were significantly improved. These achievements were scored based on respective shifting of onset of melt and cold crystallization temperatures and 1.6 times higher melt crystallization enthalpy compared with neat PLLA. The results showed that the surface-modified HAP particles were multifunctional and can act as nucleating agents, plasticizers, and bioactive moieties. Moreover, due to the presented surface modification of HAP, the crystallinity degree of PLLA and PLLGA and the polymorphic form of PLLA, the most important factors affecting mechanical properties and degradation behaviors, can be controlled.

Diverse nature of femtosecond laser ablation of poly(L-lactide) and the influence of filamentation on the polymer crystallization behaviour.

Over the past few years we have witnessed growing interest in ultrafast laser micromachining of bioresorbable polymers for fabrication of medical implants and surface modification. In this paper we show that surface structuring of poly(L-lactide) with 300 fs laser pulses at 515 and 1030 nm wavelength leads to formation of defects inside the polymer as a result of laser beam filamentation. Filament-induced channels have diameter around 1 µm and length of hundreds of micrometers. SEM images of microchannels cross-sections are presented. The influence of wavelength and pulse spacing on bulk modification extent was investigated and parameters limiting filamentation were determined. We show that filamentation can be used for controlling properties of PLLA. The presence of filament-induced modifications such as empty microchannels and pressure wave-induced stress lead to increased ability of polymer to crystallize at lower temperature. Crystallization behaviour and crystal morphology after laser treatment was investigated in details using different analytical techniques such as WAXD, DSC and FTIR/ATR. Hydrolytic degradation experiment was performed. Presented method can be applied for controllable, spatially distributed modification of polymer crystallinity, crystalline phase structure and hydrolytic degradation profile.