Current challenges in the biomedical field are the organism’s antibiotic resistance, product development processes and its utility in terms of toxicity, healing duration and adverse effects on human cells. . In addition, detecting infections that cause non-bacterial pathogens, monitoring infection control and preventing nosocomial infections are key tasks for the scientific community .
HAIs are well known as nosocomial infections that occur in hospitals and health care centers. There are many factors that cause HAIs, such as reduced patient immunity, multi-step patient treatment leading to increased infection, spread of drug-resistant bacteria and less attention to the use of protocol for bacterial infection.
Figure 4 shows the various factors that are responsible for the HAI. A worldwide survey conducted by WHO found that an average of 8.7% of people have hospital infections and about 1.4 million people are affected with HAIs. The Eastern Mediterranean and Southeast Asian regions are more susceptible to such infections than the Western world. Nosocomial infections include urinary tract infection, surgical wound, and lower respiratory tract infection .
Prevention of hospital infections requires an integrated and monitoring program in which different aspects are needed to be considered. The transfer of microorganisms from patient to caregiver has been minimized due to personal hygiene including hand washing, gloves, face masks, work clothes, footwear and disinfection of hospital equipment  .
Furthermore, the increase in bacterial resistance has a major effect on health and an enhanced economic burden. A large number of policies have been adopted to lobby against the HAIs. In particular, the use of nano-silver (AgNP) is emerging to control HAI and fight multidrug-resistant bacteria . Biologically synthesized metal NPs are more beneficial than those prepared by physical and chemical methods. This is due to the cheaper treatment cost and the environmentally friendly nature of the biological method. In the biological process, biomass is formed around the metal to neutralize its toxic effects. The bio-modulated silver nanoparticles using Bacillus marisflavi showed high antimicrobial activity against the bacteria that caused HAIs .
Their uncontrolled and overuse of antibiotics as well as their resistance are a current threat to the medical community, which is also addressed by the synergistic combination of antibiotics with nano silver [ 35 ].
The combination of allicin and Ag NPs has been studied for skin infections that occur due to methicillin-resistant staphylococcus aureus. This study shows lower Minimum Inhibitory Concentration (MIC) and Minimum Microbial Concentration (MBC) values for this drug combination and is therefore useful in treating skin to avoid skin infections. Various medical devices used in hospitals are also potential sources of infection. They are coated with silver nanoparticles to avoid bacterial contamination. Silver nano is effectively used in catheters for better antimicrobial activity and does not cause thrombosis . The effects of silver nanoparticles due to a higher surface-to-volume ratio and silver ion release on coagulation of exposed blood have been studied.
Visible light-assisted disinfection using an antimicrobial agent is another way to reduce infection. The antibacterial effect of silver-coated titania film was detected under indoor light on bacterial activation.
Completely killing of MRSA bacteria has been observed by the synergistic effect of silver nanoparticles as a visible light and optical catalyst [37, 38]. Stents and catheters used in cardiovascular applications must be coated with antimicrobial agents such as nano-silver to prevent thrombosis. The silver nanoparticles had higher long-term activity, bactericidal and bacteriostatic properties, and lower biocompatibility and vivo toxicity .
Bone cement is used in knee and hip replacement surgery, where infection rates are lower with nano-silver plus poly (methyl methacrylate) (PMMA) to reduce the risk of bacterial infections. It did not show any cytotoxicity in mouse fibroblasts or human osteoblasts indicating good biological compatibility .
Wound dressing is another area in which nanocrystalline silver has been used commercially since this decade. In clinical trials, the wound healing effect of 1% silver sulfadiazine secretion was compared with the new nanocrystalline silver chitosan.
The cure rate of chitosan-nanocrystalline silver after 13 days was higher than the control 98.98 ± 6.09%, compared with 1% sulfadiazine silver which was 81.67 ± 6.30%. In addition, the cure time was 13.51 ± 4.56 days and 17.45 ± 6.23 days respectively for the crystal silver chitosan-nano group and 1% sulfadiazine silver group. It was found that the antimicrobial efficacy and wound healing properties were significantly high against the silver nanocrystalline chitosan .
Chronic infections mainly involve the formation of biofilm on the surface of medical devices, in which these bacteria are resistant to antibiotic agents. Such biofilms are effectively degraded using nano-silver. After isolating the biofilm from the wound, the anti-biofilm effect of nano-silver was examined.
A lower range of MIC values observed was 11.25–45 μg / mL and the anti-biofilm efficacy of NP Ags was higher at concentrations lower than 50 μg / mL . Silver nanoparticles are incubated into a polymer matrix exhibiting hydrophilic properties, reducing the surface adhesion of microorganisms, forming biofilm and accumulating proteins.
Consequently, frequent dispersion of activated silver nanoparticles on the inner and outer catheter avoids biofilm formation and shows higher antimicrobial properties in a series of in vitro studies  . In addition, human infections are caused by C. The albicans correspond to the fungi commonly found on the skin, oral cavity, vagina and gastrointestinal tract.
Candida biofilm is mainly studied on the abiotic surfaces of medical devices but it has been found that the lower dosage has limited effect. To improve its effectiveness, using a higher dose than needed leads to damage to various organs such as the kidneys, liver, etc. To overcome these problems, bio-silver nanoparticles were used to control biofilm formation on the surface of the catheter at a lower dose .
Nano silver impregnated external ventricular drainage catheters are a new way to avoid catheter-related ventriculitis in patients with neurasthenia. It is confirmed with recent test-tube studies on biomedical devices showing that the separation of silver ions in the catheter is lower than acceptable levels . In conclusion, in vitro and animal studies showed that the NP Ags have a significant degree of toxicity. In vivo studies have shown that long-term exposure increases argyremia. Later, nano-silver was used for wound dressings for safety and broad spectrum. Therefore, Ag NP or its composites is useful material for different purposes to control various infections occurring in hospitals. In addition, appropriate precautions should be taken to avoid their toxic effects on humans.