NIR-Light-Active ZnO-Based Nanohybrids for Bacterial Biofilm Treatment

Abstract

Nanomaterials with antimicrobial properties triggered by external stimuli appear to be a promising and innovative substitute for the destruction of antibiotic-resistant superbugs as they can induce multiple disruptions in the cellular mechanism. This study demonstrates the use of squaraine (SQ) dye as the photosensitive material, activated in the near-infrared tissue-transparent therapeutic window. The dye has been covalently attached to the ZnO nanoparticle surface, forming ZnO-SQ nanohybrids. The formation of the nanohybrids is confirmed using Fourier transform infrared and other optical spectroscopic methods. The photoinduced interfacial electron transfer process (as confirmed using the time-resolved fluorescence technique) from the excited state of SQ to the conduction band of ZnO is responsible for the greater reactive oxygen species (ROS) generation ability of the nanohybrid. The production of photoactivated ROS (especially singlet oxygen species) by ZnO-SQ provides remarkable antimicrobial action against clinically significant Staphylococcus aureus. Detailed investigations suggest synergistic involvement of cell membrane disruption and nanoparticle internalization followed by photoinduced intracellular ROS generation, which result in an unprecedented 95% bacterial killing activity by the nanohybrid. Moreover, the efficacy of the nanohybrid for disruption of bacterial biofilms has been examined. The electron microscopic images suggest significant bacterial cell death following structural alteration and reduced adherence property of the biofilms. Nanodimension-driven greater internalization of ZnO-SQ followed by an improved dissolution of ZnO in an acidic environment of the biofilm as well as red-light-driven interfacial charge separation and ROS generation improves the efficacy of the material for biofilm destruction. An artificial medical implant mimicking titanium sheets coated with ZnO-SQ depicts light-triggered disruption in the adherence property of matured biofilms. The cytotoxicity and hemolysis assays show inherent biocompatibility of the photoactive nanohybrid. This study is notably promising for the treatment of life-threatening drug-resistant infections and eradication of biofilms formed within artificial implants.

Wide bandgap semiconductor-based novel nanohybrid for potential antibacterial activity: ultrafast spectroscopy and computational studies

“…Therefore, a faster component indicates the PET (photoinduced electron transfer) from the highest occupied molecular orbital (HOMO) of NF to the conduction band of the ZnO semiconductor NPs. 32 Therefore, the PET interfaced from the HOMO of NF to the CB (conduction band) of ZnO NP scale down the recombination of the electron and hole of the semiconductor. This appreciates the biological antibacterial activity, 32 which will be discussed in the later course of the discussion.…”

“…31 Such kinds of medication could be applied to the affected tissue, while the surrounding cells remain normal, active, healthy and unhurt. 32 This requires the drugs or NH materials to be activated in the targeted organism. Recently, nanotechnology and NP-based materials have adopted important attention in antibiotics, antimicrobial action against bacteria, and more specically for cancer therapy.…”

“…NF has been widely used in the medicinal sector for varicose disease, including urinary tract infection in chronically catheterized patients. 34,35 We chose a wide bandgap semiconductor ZnO NP due to its advantages (compared to other NPs, such as targeted delivery vehicles, non-toxic, chemically reliable, biodegradable, excellent wide bandgap, greater binding energy (60 MeV), lower cost and abundance in nature 32,[36][37][38] ) and developed two different sizes of NF-functionalized nanohybrids (NHs) using ZnO NP ($5 nm and $30 nm) to study the effect of crystal dimension on molecular interaction in NH. We have chosen the uorescence properties of 5 nm ZnO NPs to conrm the NH formation and excited state electron transfer dynamics from ZnO to NF.…”

Enhanced Water Stability and Photoresponsivity in Metal-Organic Framework (MOF): A Potential Tool to Combat Drug-resistant Bacteria

“…The acidic microenvironments chronic infections, or wounds pH value in the range of 4–7 might be exploited to construct pH-sensitive nanotherapeutics 17 . The exceptional dissolution of ZnO (zinc oxide) NPs nanoparticles at lower pH inducted its useful purpose as nanocarriers for drug delivery applications 18 . Recently, ZnO NPs of great biocompatibility loaded with NIR active photosensitizer are shown to provide unprecedented antimicrobial photodynamic therapeutic efficacy 19 .…”

Evolving Technologies and Strategies for Combating Antibacterial Resistance in the Advent of the Postantibiotic Era

“…Therefore, the quest for finding suitable designs for implant coatings that can be triggered with noninvasive stimuli such as the photodynamic approach is still continuing. More recently, Bagchi et al have designed NIR‐light active ZnO‐based nanohybrids and coated them onto implant‐mimicking titanium, and have presented their results on the light‐triggered disruption in the adherence property of matured biofilms 156. In their studies, ZnO‐NPs was conjugated with red‐light‐absorbing dye squaraine (SQ) as the PS for aPDT.…”