Wheat straw-derived lignin nanoparticles combined with postbiotics for antimicrobial, antibiofilm, and antioxidant applications in topical formulations

Introduction Plant-derived bionanomaterials have emerged as an important interest as a sustainable platform for new drug delivery and antimicrobial applications. In this study, biopolymer-based lignin nanoparticles were synthesized using wheat straw lignin. Method Lignin from wheat straw was extracted and used for the preparation of nanoparticles. The lignin nanoparticles (LNPs) were then characterized using UV–visible spectroscopy, scanning electron microscopy, Fourier transform infrared, and the engineered LNPs were then mixed with cell-free supernatant (CFS) of Lactiplantibacillus plantarum to build a multifunctional, antibiotic-free nanotherapeutic system against dermatological pathogens Cutibacterium acnes using Aloe vera gel. All the combinations were checked for growth and biofilm inhibition of the pathogen. Results Spherical to subspherical LNPs were formed with a mean diameter ranging between 53 and 107 nm. These LNPs in combination with the postbiotic showed excellent growth inhibition of C. acnes (95.5%) in broth assays, compared to the postbiotic CFS alone (63.6%) and the conventional antibiotic azithromycin (35.9%). Quantitative fluorescence microscopy also confirmed a significant decrease in the amount of bacteria associated with the biofilm (47.5% relative fluorescent compared to 58.0% for azithromycin). The formulated nanocomposite gel also demonstrated strong 2, 2-diphenyl-1-picrylhydrazyl free radical-scavenging activity, with an in vitro sun protection factor (SPF) of 10.0, compared to an SPF of 0.53 for the base gel. Discussion The improved antimicrobial and antibiofilm activities of the LNP–postbiotic formulation indicate a combined interaction between wheat straw-derived lignin nanoparticles and L . plantarum postbiotic metabolites, leading to greater C. acnes inhibition than the individual components and the tested azithromycin control. The antioxidant and photoprotective properties of the nanocomposite gel provide additional proof of its potential as a multifunctional, sustainable, antibiotic-free topical biomaterial for acne treatment. However, further investigation may be required to assess its physicochemical stability, skin compatibility, permeation, and in vivo therapeutic efficacy.