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Surface-tuned nanomaterials: a path towards effective antimicrobial strategies

Karmacharya, Mamata
Cho, Yoon-Kyoung
Issued Date
Antimicrobial resistance is a significant issue associated with biofilms, resulting in an increased need for higher doses of antimicrobial agents. Several hypotheses have been proposed to explain the mechanisms behind biofilm antibiotic resistance. One of these hypotheses suggests that the delayed penetration of antibiotics into the biofilm is a contributing factor. Another hypothesis relates to alterations in the chemical microenvironment within the biofilm such as differences in oxygen and pH levels between the bulk fluid and biofilm interior that can lead to changes in antibiotic activity. Specifically, osmotic stress responses resulting from changes in the biofilm's osmotic environment can also decrease cell envelope permeability to antibiotics and alter antibiotic susceptibility. A third mechanism of antibiotic resistance involves subpopulations of microorganisms within the biofilm matrix, which have different genotypes and phenotypes that affect their antibiotic susceptibility profiles. The complexity of biofilm structures and their presence in sites such as oral cavities and wounds make complete eradication challenging with conventional methods.
To tackle the challenges posed by antimicrobial resistance, there is an urgent requirement for advanced catalysts capable of functioning in the intricate and harsh chemical environments of biofilms. Our solution involves the utilization of mixed-FeCo-oxide-based surface-textured nanostructures (MTex) as highly efficient magneto-catalytic platforms. These MTex structures generate reactive oxygen species (ROS) with defensive properties across a wide pH range. They possess the ability to permeate the biofilm and effectively eliminate bacteria that are embedded within it. Additionally, their magnetic properties enable the removal of biofilm debris from microchannels. The unique surface topography of these nanostructures resembles that of a ploughed field, contributing significantly to their exceptional antifouling effectiveness. The formation of these surfaces occurs during the oxidative annealing and solid-state conversion of β-FeOOH nanocrystals, presenting an avenue for the development of novel enzyme-like properties at the interface between nanomaterials and biology.
Since the onset of the COVID-19 pandemic, the surging demand for surgical masks has had notable ecological and financial repercussions. To tackle this concern, we devised a novel technique involving a dual-channel spray-assisted nanocoating on nonwoven surgical masks, utilizing shellac/copper nanoparticles. This coating effectively enhances the hydrophobicity of the masks, repelling aqueous droplets. Furthermore, the coated surface exhibits exceptional photoactivity, enabling both photocatalytic and photothermal properties to exert antimicrobial effects. This innovation renders the masks reusable and self-sterilizing. When exposed to solar illumination, the photoactive antiviral mask (CAM) rapidly achieves temperatures exceeding 70°C, generating free radicals that disrupt the membranes of virus-like particles at the nanoscale. Consequently, the masks possess self-cleaning properties, rendering them reusable. Our CAM design offers significant protection against the transmission of viral aerosols in the battle against the COVID-19 pandemic, while simultaneously reducing environmental waste and mitigating the economic costs associated with disposable masks.
Next, to develop an innovative therapeutic system that can leverage the platelet-bacteria interactions have shown promise for targeting oral microbiota, but platelet-based delivery has encountered difficulties such as cargo loading, low efficacy in diffusing through biofilms, and regulating release. To overcome these obstacles, we propose a method that employs biorthogonal catalysis within human platelet membrane vesicles (h-PMV) with supramolecular metal catalysts (SMCs) to create "nanofactories" that convert prodrugs into antimicrobial therapeutic molecules in the vicinity of bacteria. Using this approach, we investigate the use of SMCs inside h-PMVs, known as PLT-reactor, to activate pro-antibiotic drugs (pro-ciprofloxacin and pro-moxifloxacin) for efficient killing of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 bacteria. This "bind and kill" strategy demonstrates the potent antimicrobial specificity of PLT-reactors against oral biofilms harboring Streptococcus mutans 3065 through preferential binding and in-situ drug production, resulting in efficient bacterial killing. The analysis indicates that h-PMVs not only provide PLT-reactors with targeting capability but also minimize hemolytic effects. Our findings suggest that platelet membrane-cloaked surfaces possess unique features of robust, multifaceted, and pathogen-specific binding affinity, excellent biocompatibility, and potential as an alternative to antibody-based targeted therapy for infectious diseases.
Taken together, our different compartmentalized nanoreactors provides the novel approaches to cope with the risks of antimicrobial infections and pandemics in the long term.
Ulsan National Institute of Science and Technology
School of Energy and Chemical Engineering (Chemical Engineering)


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