Functionally graded PLGA-nano apatite-lauric acid biocomposite membrance for potential clinical applications

Abstract

Bone healing is a challenge in orthopaedics and dentistry. An occlusive membrane is used for the reconstruction of bone defects in guided bone regeneration (GBR) technique. Infection is the major cause for GBR membrane failure in which multiple antibiotics have been used to prevent bacterial colonisation in regenerative clinical practice. An anti-infective membrane with alternative antimicrobial agent to substitute antibiotics is paramount to overcome the incidence of bacterial resistance and side-effects. In this study, a composite membrane was developed by incorporating lauric acid (LA), a naturally derived antimicrobial substance. Poly(lactic-co-glycolic acid) (PLGA) based composite membrane was successfully fabricated using a combination of solvent casting-thermally induced phase separation (TIPS)-solvent leaching technique. The triple-layered membrane structure was attained via solvent casting of the composite solutions which then immediately phase separated by freezing at -18±1°C for 24 h. Then, the solvent in phase separated membrane was removed by immersing in precooled water at 3±1°C for 26 h, after which the membrane was air dried at 25°C for 3 days. The triple-layered construct of the PLGA composite membrane was developed with a gradient structure of LA and non-stoichiometric nanoapatite (NAp), to deliver the antimicrobial and osteconductive properties, respectively. The surface morphology and phase composition of the membrane were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The resulting graded membrane consisted of small pore size layer-1 containing 10wt% NAp + 1-3wt% LA, an intermediate labyrinth layer-2 with 20-50wt% NAp + 1wt% LA, and a large pore size layer-3 containing 30-100wt% NAp without LA. The existence of chemical interaction between PLGA, NAp and LA was identified using Fourier transform infrared spectrophotometry (FTIR) analysis. The synergistic effects of 10-30wt% NAp and 1wt% LA in dry membranes demonstrated higher tensile strength (0.61±0.17 MPa) and elastic modulus (23.15± 6.19 MPa). However, a more pliable behavior with a decrease in elastic modulus (12.50± 4.32MPa) was observed in 3wt% LA added membrane compared to the pure PLGA (20.17±2.21 MPa). The addition of LA resulted in a plasticizing effect at 3wt% due to weak intermolecular interactions in PLGA chains, caused by LA (-OH) and PLGA (C-O) bondings. These results were corroborated by the FTIR peak shift (1-3 cm-1) and glass transition temperature (Tg) reduction as detected using differential scanning calorimeter (DSC). The composite membrane retained its structural integrity with only 22% weight loss after incubation for 24 weeks in phosphate buffered saline (PBS), which indicates its potential use as a physical barrier. The 1-3wt% LA loaded composite membranes had good cell viability toward mouse fibroblasts and showed increased bacterial reduction with increased LA loadings against S. aureus. These results demonstrate the potential of LA loaded biocomposite membrane to provide anti-infective surfaces, useful in clinical applications.