The development of new nanomaterials with high biomedical performance and low toxicity is essential to obtain more efficient therapy and precise diagnostic tools and devices. Recently, scientists often face issues of balancing between positive therapeutic effects of metal oxide nanoparticles and their toxic side effects. In this review, considering metal oxide nanoparticles as important technological and biomedical materials, the authors provide a comprehensive review of researches on metal oxide nanoparticles, their nanoscale physicochemical properties, defining specific applications in the various fields of nanomedicine. Authors discuss the recent development of metal oxide nanoparticles that were employed as biomedical materials in tissue therapy, immunotherapy, diagnosis, dentistry, regenerative medicine, wound healing and biosensing platforms. Besides, their antimicrobial, antifungal, antiviral properties along with biotoxicology were debated in detail. The significant breakthroughs in the field of nanobiomedicine have emerged in areas and numbers predicting tremendous application potential and enormous market value for metal oxide nanoparticles.

https://www.mdpi.com/2313-7673/5/2/27/pdf

Metal Oxide Nanoparticles as Biomedical Materials

Nanoparticle technology is rapidly advancing and is used for a wide range of applications in medicine. The potential of metal nanoparticles as antimicrobial agents is widely studied and is considered as an alternative approach to overcome the challenge posed by multidrug resistance in bacteria. This review discusses novel approaches to nanoparticle synthesis including green synthesis and the antimicrobial spectrum of nanoparticles. Approaches for enhancing antimicrobial potential of nanoparticles by surface modification and its potential as a vehicle for antibiotic delivery are also explored.

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Antimicrobial Nanoparticles: applications and mechanisms of action

Copper-doped TiO2 was prepared with a sol–gel chemical method Various concentrations (3, 6, and 9 wt%) of Cu dopant were employed Several techniques were implemented to assess the structural, optical, morphological and chemical properties of the synthesized samples Evaluation of elemental composition using SEM-EDS and XRF techniques showed the presence of dopant element in the prepared samples XRD analysis confirmed the presence of anatase (TiO2) phase with interstitial doping Incorporation of dopant was observed to enhance the crystallinity and increase the crystallite size of the synthesized products SAED profiles revealed a high degree of crystallinity in the prepared specimens, which was also evident in the XRD spectra Optical properties studied using UV-vis spectroscopy depicted a shift of the maximum absorption to the visible region (redshift) that signified a reduction in the band gap energy of Cu-doped TiO2 samples Examination of morphological features with scanning and high-resolution transmission electron microscopes revealed the formation of spherical nanoparticles with a tendency to agglomerate with increasing dopant concentration Molecular vibrations and the formation of Ti–O–Ti bonds were revealed through FTIR spectra PL spectroscopy recorded the trapping efficiency and migration of charge carriers, which exhibited electron–hole recombination behavior Doped nanostructures showed enhanced bactericidal performance and synergism against S aureus and E coli In summary, Cu-doped TiO2 nanostructures were observed to impede bacteria effectively, which is deemed beneficial in overcoming ailments caused by pathogens such as microbial etiologies Furthermore, molecular docking analysis was conducted to study the interaction of Cu-doped TiO2 nanoparticles with multiple proteins namely β-lactamase (binding score: −491 kcal mol−1), ddlB (binding score: −567 kcal mol−1) and FabI (binding score: −613 kcal mol−1) as possible targets with active site residues Dye degradation/reduction of control and Cu-doped samples were studied through absorption spectroscopy The obtained outcomes of the performed experiment indicated that the photocatalytic activity of Cu-TiO2 enhanced with increasing dopant concentration, which is thought to be due to a decreased rate of electron–hole pair recombination Consequently, it is suggested that Cu-TiO2 can be exploited as an effective candidate for antibacterial and dye degradation applications

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Dye degradation performance, bactericidal behavior and molecular docking analysis of Cu-doped TiO2 nanoparticles

The increasing use of antibiotics is being driven by factors such as the aging of the population, increased occurrence of infections, and greater prevalence of chronic diseases that require antimicrobial treatment. The excessive and unnecessary use of antibiotics in humans has led to the emergence of bacteria resistant to the antibiotics currently available, as well as to the selective development of other microorganisms, hence contributing to the widespread dissemination of resistance genes at the environmental level. Due to this, attempts are being made to develop new techniques to combat resistant bacteria, among them the use of strictly lytic bacteriophage particles, CRISPR-Cas, and nanotechnology. The use of these technologies, alone or in combination, is promising for solving a problem that humanity faces today and that could lead to human extinction: the domination of pathogenic bacteria resistant to artificial drugs. This prospective paper discusses the potential of bacteriophage particles, CRISPR-Cas, and nanotechnology for use in combating human (bacterial) infections.

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Prospects for the Use of New Technologies to Combat Multidrug-Resistant Bacteria.

Recently, titanium dioxide (TiO2) nanomaterials have gained increased attention because of their cost-effective, safe, stable, non-toxic, non-carcinogenic, photocatalytic, bactericidal, biomedical, industrial and waste-water treatment applications. The aim of the present work is the synthesis of electrospun TiO2 nanofibers (NFs) in the presence of different amounts of air–argon mixtures using sol-gel and electrospinning approaches. The physicochemical properties of the synthesized NFs were examined by scanning and transmission electron microscopies (SEM and TEM) coupled with energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible spectroscopy and thermogravimetric analyzer (TGA). The antibacterial and antibiofilm activity of synthesized NFs against Gram-negative Pseudomonas aeruginosa and Gram-positive methicillin-resistant Staphylococcusaureus (MRSA) was investigated by determining their minimum bacteriostatic and bactericidal values. The topological and morphological alteration caused by TiO2 NFs in bacterial cells was further analyzed by SEM. TiO2 NFs that were calcined in a 25% air-75% argon mixture showed maximum antibacterial and antibiofilm activities. The minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) value of TiO2 NFs against P. aeruginosa was 3 and 6 mg/mL and that for MRSA was 6 and 12 mg/mL, respectively. The MIC/MBC and SEM results show that TiO2 NFs were more active against Gram-negative P. aeruginosa cells than Gram-positive S. aureus. The inhibition of biofilm formation by TiO2 NFs was investigated quantitatively by tissue culture plate method using crystal violet assay and it was found that TiO2 NFs inhibited biofilm formation by MRSA and P. aeruginosa in a dose-dependent manner. TiO2 NFs calcined in a 25% air-75% argon mixture exhibited maximum biofilm formation inhibition of 75.2% for MRSA and 72.3% for P. aeruginosa at 2 mg/mL, respectively. The antibacterial and antibiofilm results suggest that TiO2 NFs can be used to coat various inanimate objects, in food packaging and in waste-water treatment and purification to prevent bacterial growth and biofilm formation.

Synthesis of Electrospun TiO2 Nanofibers and Characterization of Their Antibacterial and Antibiofilm Potential against Gram-Positive and Gram-Negative Bacteria.

The antibacterial activity of 21 nm TiO2 nanoparticles (NPs) and particles modified with Garcinia zeylanica (G. zeylanica) against Methicillin resistant Staphylococcus aureus was investigated in the presence and absence of light. Surface modification of TiO2 NPs with the adsorption of G. zeylanica extract, causes to shift the absorption edge of TiO2 NPs to higher wavelength. TiO2 NPs, G. zeylanica pericarp extract showed significant bactericidal activity which was further enhanced in contact with the TiO2 modified G. zeylanica extract. The antimicrobial activity was enhanced in the presence of TiO2 NPs modified with G. zeylanica and with longer contact time.

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H. D. Siriwardena

Papers

Enhanced antibacterial activity of TiO 2 nanoparticle surface modified with Garcinia zeylanica extract