Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility

Anatase TiO2 co-doped with silver and ceria for antibacterial application

Anatase TiO2 co–doped with Ag and CeO2 (Ag/CeO2–TiO2) was prepared by the peroxo sol-gel method for antibacterial application. The as-prepared materials were characterised by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The antibacterial activities of the samples were tested against two different bacteria: Escherichia coli (OP50), a Gram-negative organism and Staphylococcus aureus (USA300), a Gram-positive organism. The antibacterial effectiveness of the Ag/CeO2–TiO2 coating was >99.99%, i.e. it was extremely effective against both E. coli (OP50) and S. aureus (USA300) after either 30 min of illumination with UVA radiation or 24-h of incubation in the dark. The Ag/CeO2–TiO2 coating was found to be significantly more active than pure TiO2 and TiO2 doped with CeO2 or Ag alone. Therefore, Ag/CeO2–TiO2 can be used as a coating material for the disinfection of both Gram-positive and Gram-negative bacteria

CeO2–TiO2 mixed oxide thin films with enhanced photocatalytic degradation of organic pollutants

A series of CeO2–TiO2 mixed oxides were prepared by the peroxo sol–gel method. X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to investigate the characteristics of CeO2–TiO2 sols and thin films in order to determine the influence of adding CeO2 to TiO2 on the photocatalytic degradation of methylene blue aqueous solution under both ultraviolet and visible light irradiation. The pH values of the as-prepared CeO2–TiO2 sols were neutral; the as-prepared sols contained nanocrystals in colloidal suspensions, and there was no subsequent calcination process. It was observed that the highest photocatalytic degradation activities with respect to methylene blue under both UV and visible light irradiation were exhibited for an optimum CeO2–TiO2 weight ratio of 0.05. The high photocatalytic activity was because of changes in the spectral absorption of material, which was attributed to the heterojunction formed by TiO2 and CeO2 networks via Ti–O–Ce bonds after addition of CeO2. Thus, the presence of CeO2 in TiO2 significantly enhanced the photocatalytic activity

Anatase TiO2 co-doped with silver and ceria for antibacterial application

Anatase TiO2 co–doped with Ag and CeO2 (Ag/CeO2–TiO2) was prepared by the peroxo sol-gel method for antibacterial application. The as-prepared materials were characterised by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The antibacterial activities of the samples were tested against two different bacteria: Escherichia coli (OP50), a Gram-negative organism and Staphylococcus aureus (USA300), a Gram-positive organism. The antibacterial effectiveness of the Ag/CeO2–TiO2 coating was >99.99%, i.e. it was extremely effective against both E. coli (OP50) and S. aureus (USA300) after either 30 min of illumination with UVA radiation or 24-h of incubation in the dark. The Ag/CeO2–TiO2 coating was found to be significantly more active than pure TiO2 and TiO2 doped with CeO2 or Ag alone. Therefore, Ag/CeO2–TiO2 can be used as a coating material for the disinfection of both Gram-positive and Gram-negative bacteria

CeO2–TiO2 mixed oxide thin films with enhanced photocatalytic degradation of organic pollutants

A series of CeO2–TiO2 mixed oxides were prepared by the peroxo sol–gel method. X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to investigate the characteristics of CeO2–TiO2 sols and thin films in order to determine the influence of adding CeO2 to TiO2 on the photocatalytic degradation of methylene blue aqueous solution under both ultraviolet and visible light irradiation. The pH values of the as-prepared CeO2–TiO2 sols were neutral; the as-prepared sols contained nanocrystals in colloidal suspensions, and there was no subsequent calcination process. It was observed that the highest photocatalytic degradation activities with respect to methylene blue under both UV and visible light irradiation were exhibited for an optimum CeO2–TiO2 weight ratio of 0.05. The high photocatalytic activity was because of changes in the spectral absorption of material, which was attributed to the heterojunction formed by TiO2 and CeO2 networks via Ti–O–Ce bonds after addition of CeO2. Thus, the presence of CeO2 in TiO2 significantly enhanced the photocatalytic activity

Antiviral and antibacterial effects of silver-doped TiO₂ prepared by the peroxo sol-gel method

A series of multifunctional silver-doped titanium dioxide (Ag/TiO₂) nanocomposites with various silver contents were synthesized by the peroxo sol-gel method using TiCl4 as a precursor and H₂O₂ as a peptizing agent. The sol was used to coat a glass substrate, thereby forming a thin film. The antiviral and antibacterial activities of the Ag/TiO₂ films and their use in the photocatalytic degradation of an aqueous solution of methylene blue were investigated. The as-prepared materials were characterized using high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The antiviral and antibacterial activities of the samples were tested against Escherichia coli, the influenza A virus (H1N1), and enterovirus. It was observed that an optimum Ag:TiO₂ weight ratio of 1:100 enabled the highest activity in the photocatalytic degradation of an aqueous solution of methylene blue under irradiation with either ultraviolet or visible light. Moreover, the same composition remarkably exhibited extremely high antibacterial and virucidal effectivenesses greater than 99.99% against E. coli and infectious viruses after illumination with ultraviolet A. The presence of silver on TiO₂ significantly enhanced its photocatalytic activity. Thus, the excellent photocatalytic activities and reusability of the Ag/TiO₂ nanocomposite render it applicable as a coating material for several purposes

Photocatalytic Antibacterial Effectiveness of Cu-Doped TiO2 Thin Film Prepared via the Peroxo Sol-Gel Method

Cu-doped titanium dioxide thin films (Cu/TiO2) were prepared on glass substrate via peroxo sol-gel method and dip-coating process with no subsequent calcination process for the degradation of organic dye and use as an antibacterial agent. The as-prepared materials were characterised using transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). For photocatalytic degradation of methylene blue in water, the samples were subjected to Ultraviolet C (UVC) and visible light irradiation. Degraded methylene blue concentration was measured using UV-Vis spectrophotometer. The antibacterial activities of the samples were tested against the gram-negative bacteria Escherichia coli (ATCC25922). Copper species were present in the form of CuO on the surface of modified TiO2 particles, which was confirmed using TEM and XPS. The optimal observed Cu/TiO2 weight ratio of 0.5 represents the highest photocatalytic activities under both UVC and visible light irradiation. Moreover, the same composition remarkably exhibited high antibacterial effectiveness against E. coli after illumination with ultraviolet A. The presence of CuO on TiO2 significantly enhanced photocatalytic activities. Therefore, active Cu-doped TiO2 can be used as a multipurpose coating material