# Electrospun Poly(vinyl alcohol) Composites Containing pH-Fractionated Kraft Lignin: Structural Characterization, Biocompatibility, and Immunomodulation

## TL;DR

This paper explores how pH-fractionated lignin affects the properties of electrospun PVA composites, showing their potential for biomedical uses due to biocompatibility and immune response modulation.

## Contribution

The study introduces pH-guided lignin fractionation as a novel method to control the physicochemical and immunological properties of PVA/lignin composites.

## Key findings

- Lignin fractionated at pH 5 showed optimal colloidal stability and particle size (339 nm, -38 mV).
- PVA-lignin composites at pH 5 selectively increased TNF-α production without affecting IL-10 levels.
- All composites were cytocompatible with Vero cells, maintaining over 90% viability after 24 hours.

## Abstract

Lignin and its derivatives
exhibit attractive physicochemical and
biological properties, including antioxidant, antimicrobial, and immunomodulatory
activities; however, the relationship between lignin fractionation
conditions and these biological effects remains poorly understood.
Filling this gap is fundamental for the advancement of lignin-based
materials in biomedical applications. In this study, Kraft lignin
was fractionated by precipitation at three pH values (2, 5, and 8)
and incorporated into poly­(vinyl alcohol) (PVA) matrices, which were
subsequently processed by electrospinning. The components and the
resulting composites were systematically characterized in terms of
molar mass distribution, chemical structure, surface morphology, and
colloidal properties using GPC, FTIR, SEM, zeta potential, and particle
size analyses. The results demonstrated that pH-controlled fractionation
significantly altered the molecular characteristics of lignin, dispersion
behavior, surface charge, and filament morphologies. Notably, the
lignin fraction obtained at pH 5 exhibited a favorable balance between
particle size and colloidal stability, 339 nm and −38 mV, respectively.
Biological evaluation revealed that all composites were cytocompatible
with Vero cells, showing no significant reduction (less than 10%)
in cell viability after 24 h of exposure. In contrast, immunological
assays using human peripheral blood mononuclear cells (PBMCs) revealed
distinct pH-dependent immune responses. The composite containing lignin
fractionated at pH 5 preserved cell viability and selectively increased
TNF-α production (p-value = 0.0008) without affecting IL-10
levels (p-value >0.05), indicating a controlled pro-inflammatory
response.
Overall, these results demonstrate that pH-guided fractionation is
an effective strategy for adjusting the physicochemical and immunological
behavior of electrospun PVA/lignin composites and identify the PVA-lignin
system fractionated at pH 5 as a promising platform for biomedical
applications requiring immunological modulation.