Enzyme-enabled responsive surfaces for anti-contamination materials

Recent developments in smart antibacterial surfaces to inhibit biofilm formation and bacterial infections

Since their development over 70 years, antibiotics are still the most effective strategy to treat bacterial biofilms and infections.

Bacterial infection microenvironment-responsive enzymatically degradable multilayer films for multifunctional antibacterial properties

The adhesion of bacteria is one of the most important stages in biofilm formation and bacterial infection. Once bacteria have adhered to a biomaterial surface, it is hard to eliminate them, and bacterial growth and infection are inevitable. In the current study, we have designed and constructed enzymatically degradable (hyaluronic acid/chitosan)n-(hyaluronic acid/polylysine)n ((HA/CHI)n-(HA/PLL)n) composite multilayer films via a layer-by-layer self-assembly method. Spectroscopic ellipsometry and scanning electron microscopy cross section measurements showed the exponential growth behavior of (HA/CHI)10-(HA/PLL)10 multilayer films (∼2 μm). The increased secretion of hyaluronidase and chymotrypsin in the bacterial infection microenvironment led to the fast degradation of the outer (PLL/HA)n multilayer films in the first 24 h. Enzymatic degradation of the multilayer films efficiently reduced the adhesion of both Staphylococcus aureus and Escherichia coli (>99%). Bacterial live/dead staining demonstrated the bactericidal action of the remaining bottom (CHI/HA)n multilayer films against the two kinds of bacteria. In vivo subcutaneous tests on New Zealand white rabbits, wound appearance and histopathology analysis showed that the implantation of composite multilayer film-modified PDMS promoted wound healing and the materials demonstrated a self-defense antibacterial effect. The material demonstrated both anti-adhesive and bactericidal properties and could be used to modify biomedical implants.

A self-defensive antibacterial coating acting through the bacteria-triggered release of a hydrophobic antibiotic from layer-by-layer films

Drug delivery systems play important roles in the construction of antibacterial coatings on the surfaces of biomaterials. However, excessive release of antibiotics in the environment can lead to the generation of resistant bacteria. A methoxy poly(ethylene glycol)-poly(ε-caprolactone)-chitosan (MPEG-PCL-CS) block polymer was prepared through covalent grafting of CS onto MPEG-PCL. MPEG-PCL-CS micelles were prepared and showed a high load capacity for the hydrophobic antibiotic triclosan (TCA) (∼5 wt%). Multilayer films were constructed through self-assembling TCA/MPEG-PCL-CS cationic micelles with poly(acrylic acid) (PAA). Transmission and scanning electron microscopy analyses confirmed the presence of micelles on the surface (20-40 nm). As barriers for the antibiotic, the (TCA/MPEG-PCL-CS)/PAA multilayer films contained a high load of TCA (255 μg cm-2). Importantly, the multilayer films showed both bacteria-triggered and pH-responsive release properties and can be used as self-defensive antibacterial coatings. Bacterial adhesion caused a local acidic environment and altered the permeability of the multilayer films, promoting drug release. Both in vitro and in vivo antibacterial tests indicated a high bactericidal activity of drug-loaded multilayer films against both E. coli and S. aureus.

Enzymatic waterborne polyurethane towards a robust and environmentally friendly anti-biofouling coating

A simple, green, robust and efficient method has been developed for the preparation of an anti-biofouling coating by directly mixing antifouling enzymes with a castor oil-based waterborne polyurethane (WPU) dispersion.

Antifouling activity of enzyme-functionalized silica nanobeads

The amelioration of biofouling in industrial processing equipment is critical for performance and reliability. While conventional biocides are effective in biofouling control, they are potentially hazardous to the environment and in some cases corrosive to materials. Enzymatic approaches have been shown to be effective and can overcome the disadvantages of traditional biocides, however they are typically uneconomic for routine biofouling control. The aim of this study was to design a robust and reusable enzyme-functionalized nano-bead system having biofilm dispersion properties. This work describes the biochemical covalent functionalization of silica-based nanobeads (hereafter referred to as Si-NanoB) with Proteinase K (PK). Results showed that PK-functionalized Si-NanoB are effective in dispersing both protein-based model biofilms and structurally altering Pseudomonas fluorescens biofilms, with significant decreases in surface coverage and thickness of 30.1% and 38.85%, respectively, while increasing surface roughness by 19 % following 24 h treatments on bacterial biofilms. This study shows that enzyme-functionalized nanobeads may potentially be an environmentally friendly and cost effective alternative to pure enzyme and chemical treatments.

Printed microwells with highly stable thin-film enzyme coatings for point-of-care multiplex bioassay of blood samples

A paper-based colorimetric biosensor suitable for point-of-care bioassay of blood samples is developed using highly stable enzyme thin-film coatings confined within inkjet printed polymeric microwells.