Photodynamic antimicrobial chemotherapy activities of modified carbocyanine-zinc oxide nanoparticle- and nanoflower-based nanoconjugates

Abstract

The continuously rising cases of antibiotic resistance and pathogenic bacterial mutations pose a serious medical problem. Microorganisms are ubiquitous because they can adapt to conditions in any environment. They can colonize all types of environments, including water, air, soils, and the bodies of plants and animals. When pathogenic microorganisms are prevalent in such situations, they are harmful because they promote degeneration and degradation of the matrix, which harms the ecosystem and humans by harming individual health. This calls for environmental decontamination efforts to protect the ecology and human health. Several chemical and physical methods have been applied for the treatment of different environments where pathogenic microbes have been contaminated. The use of physical methods includes the employment of heat and filtrations, whereas chemical methods include chlorination, antibiotics and photocatalyst. Although these methods have been used more often, they are associated with limitations, including a lack of effectiveness that contributes to the problem of the development of antimicrobial-resistant strains. Furthermore, using physical agents does not eradicate all the microbes since some are suitably adapted to extreme conditions through mutation phenomena. Due to these drawbacks, scientists and researchers have embarked on research to find alternative methods and approaches that can eliminate the microbes while avoiding mechanisms that can develop resistance within the strains. However, photodynamic antimicrobial chemotherapy (PACT) has been reported to be an attractive alternative method that can be employed to counter the limitations of the classical approaches for dealing with microbial contaminants in the environment. Among the pathogenic bacteria are Gram-negative bacteria. These Gram-negative bacteria are less likely to be denatured by chemical treatment because of the intricate construction of their bacterial cell membrane, it functions as an efficient barrier to the penetration of many photosensitizing compounds like dyes. For them to be effectively denatured, only cationic dyes can cause effective photo-induced inactivation of Gram-negative bacteria. In addition, nanostructures have been used as drug delivery platforms for photodynamic therapy (PDT) and as strategies to improve photosensitizers' efficiency in producing reactive oxygen species (ROS) when exposed to light. Thus, in this dissertation, photodynamic antimicrobial chemotherapy has been employed to study the photodynamic antimicrobial chemotherapy activities of functionalized zinc oxide-based nanomaterials and nanoconjugates against E. coli. This dissertation, thus, reports on the fabrication of zinc oxide nanoparticles (ZnO-NPs) and nanoflowers (ZnO-NFs), their functionalized forms (GSH-ZnO-NPs and GSH-ZnO-NFs), as well as the modified carbocyanine (SHBS-IR-791 iodide). It also reports on the conjugations of GSH-ZnO-NPs and GSH-ZnO-NFs with SHBS-IR-791 iodide, labelled as follows: GSH-ZnO-NPs-SHBS-IR-791 iodide and GSH-ZnO-NFs-SHBS-IR-791 iodide conjugates. The analysis of the materials mentioned above using various instruments is also presented in this dissertation. The resulting GSH-ZnO-NPs, GSH-ZnO-NFs and SHBS-IR-791 iodide, as well as GSH-ZnO-NPs-SHBS-IR-791 iodide and GSH-ZnO-NFs-SHBS-IR-791 iodide conjugates, were used for PACT against E. coli. The PACT activities of the as-prepared materials show that the ranking of photo-inactivation depends on the attentiveness of the complex and the presence of light. The results show that GSH-ZnO-NFs-SHBS-IR-791 iodide has higher phototoxicity against E. coli than the other complex, with the trend observed as follows: GSH-ZnO-NFs-SHBS-IR-791 iodide > ZnO-NPs-SHBS-IR-791 iodide > SHBS-IR-791-iodide > GSH-ZnO-NFs> GSH-ZnO-NPs.