Characterisation of PAMAM/PAA polyelectrolyte complexes and the growth profile of their multilayer assemblies on functionalised PLA nonwoven fabric: Impact of drying and amine density

•Optimization of polyelectrolytes’ pH and concentration ratio in liquid–liquid phase to apply in liquid–solid phase.•Investigation of adsorption–desorption behavior of a dendritic polycation and a linear polyanion multilayer on textile materials.•Investigation of the growth profile of polyelectrolyte multilayers based on ninhydrin assay.•Tailoring polyelectrolyte multilayer assemblies’ density and growth profile by applying simple air-drying between LBL.•100 % antibacterial activity of multilayered-PLA nonwoven against both Gram-negative and Gram-positive strain of bacterium. A comprehensive study was conducted to characterise and optimise the polyelectrolyte complex (PEC) formation of polyacrylic acid (PAA) (−) and poly(amidoamine) (PAMAM) (+) in liquid–liquid phase, as well as their multilayer construction on pre-treated polylactide (PLA) nonwoven fabric using the layer-by-layer (LBL) technique in liquid–solid phase. Based on the studies of PEC formation in the liquid–liquid phase, the results showed that PAMAM at pH 8 and PAA at pH 4 exhibit compact and globular conformations, respectively, leading to high aggregated PEC concentrations. A concentration ratio of 7:7 (10−4 g/mL) at the obtained optimal pH resulted in the highest PEC formation in the liquid–liquid phase and consequently the highest polyelectrolyte (PE) multilayer growth in the liquid–solid phase. The LBL technique revealed complex adsorption–desorption behaviour of the dendritic PAMAM and linear PAA system, with intermediate drying stabilising the PAA layer. This led to a divergent growth profile with increased amine density on the even layers, resulting in a less compact structure of the PE multilayer assemblies than those constructed with a converging profile. Interestingly, higher amine density did not translate into higher interaction with guest molecules, indicating a threshold for a stable layer with optimal host–guest properties. Mechanical and antibacterial analyses indicated that integrating PE multilayers enhances the substrate performance and imparts bactericidal activity, as no bacterial growth was observed compared to the aminolysed PLA. In conclusion, understanding the PE multilayer growth and controlling density is crucial for designing advanced nonwoven fabric for applications like drug delivery, where microbial contamination is a concern.