Maksym Krepker

Novel LDPE/halloysite nanotube films with sustained carvacrol release for broad-spectrum antimicrobial activity

The emergence of antibiotic resistance of pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials e.g., essential oils (EOs), as an alternative strategy to reduce microbial contamination. However, the volatile nature of EOs presents a major challenge in their incorporation into polymers by conventional high-temperature processing techniques. Herein, we employ halloysite nanotubes (HNTs) as efficient nano-carriers for carvacrol (a model EO). This pre-compounding encapsulation step imparts enhanced thermal stability to the carvacrol, allowing for its subsequent melt compounding with low-density polyethylene (LDPE). The resulting polymer nanocomposites exhibit outstanding antimicrobial properties with a broad spectrum of inhibitory activity against Escherichia coli, Listeria innocua in biofilms, and Alternaria alternata. Their antimicrobial effectiveness is also successfully demonstrated in complex model food systems (soft cheese and bread). This superior activity, compared to other studied carvacrol containing films, is induced by the significantly higher carvacrol content in the film as well as its slower out-diffusion from the hybrid system. Thus, these new active polymer nanocomposites presents an immense potential in controlling microbial contamination and biofilm related adverse effects, rendering them as excellent candidate materials for a wide range of applications.

Dual-Functionalized Porous Si/Hydrogel Hybrid for Label-Free Biosensing of Organophosphorus Compounds

A multifunctional porous Si (PSi) nanostructure is designed to combine a responsive PSi/hydrogel hybrid interfaced with a biorecognition element to selectively recognize small model molecules, organophosphorus compounds (OPCs), of high biological importance. A pH-responsive poly(2-dimethylaminoethyl methacrylate) [poly(DMAEMA)] hydrogel is synthesized and patterned in situ within an oxidized PSi Fabry-Pérot thin film. The resulting new hybrid displays a well-defined, rapid, and reversible optical response to pH changes. We employ this hybrid as an optical transducer element in a biosensing scheme by integrating it with organophosphorus hydrolase (OPH), capable of selective OPC hydrolysis. The enzyme is immobilized onto the pore walls of the oxidized PSi scaffold, resulting in an array of catalytic nanoscale chambers for the degradation of OPCs. Thus, the biosensor function relies on diffusion of the OPCs hydrolysis products from the catalytic chambers, through the interconnected pores network, to the hybrid region triggering its optical response. Exposure to the model target analyte results in a rapid and reproducible change in the optical reflectivity spectrum of the hybrid, allowing for label-free detection and quantification of OPCs in a simple and reliable manner.