Salicylaldehyde-functionalized polyethyleneimine precursor: Synthesis, characterization, and encapsulation in electrospun nonwoven for moisture-triggered release applications

Abstract

Salicylaldehyde (SAL) is a natural flavoring agent with broad-spectrum antimicrobial activities but susceptible to degradation. To enhance its stability, SAL was conjugated with branched polyethyleneimine to form a SAL precursor (SALP) for controlled release applications. SAL molecules formed covalent bonds with BrPEI via imine linkages and imidazolidine rings, as confirmed by 1D and 2D NMR and FTIR spectroscopies. SALP was metastable under dry conditions but susceptible to acid-hydrolysis, triggering the release of SAL vapor, as revealed by the 1H NMR analysis. To facilitate end-use applications, SALP was encapsulated in poly(lactic acid)/poly(ethylene oxide) (PLA/PEO) nonwovens prepared by a free-surface electrospinning process. The release of SAL vapor from SALP-loaded nonwovens was studied using a citric acid (CA) solution of different concentrations. Additionally, a tri-layer nonwoven comprised of a SALP-loaded nonwoven sandwiched between two layers of CA-loaded fibers was developed. When exposed to 100 % RH, the composite nonwoven released SAL at a level of 0.046 ± 0.011 mg SAL/mg nonwoven in 4 h. The composite nonwoven exhibited antimicrobial properties against Escherichia coli K12, showing an 8-log reduction after a 4 h exposure to SAL vapor released from a 3 × 3 cm2 nonwoven. The antimicrobial nonwoven could be promising for limiting the proliferation of spoilage and pathogenic microorganisms to enhance the safety and reduce the wastage of food products.