6.4. Medical Devices
Seriously ill patients with respiratory distress, and also other patients with other conditions such as cardiovascular disease often require intimate contact with medical devices. Examples of devices include prosthetic heart valves, orthopedic implants, intravascular catheters, artificial hearts, cardiac pacemakers, etc. [185]. Wettability of the surfaces has been shown to play a crucial role in the adhesion of viruses to whichever surface is present. Glass slides were successfully coated with silanes of various hydrophobicity and showed that more hydrophobic surfaces were most efficient in capturing influenza A viruses. This points again to a form of nanotrapping and inactivation of the virus by surface interactions [186]. Glass slides were also LbL coated with polyanionic and polycationic chitosan to eliminate S. aureus. It was implied that this LbL process will benefit medical devices with antibacterial properties [187].
Vascular prostheses were coated successfully with alternating layers of human serum albumin and the GAG, heparin, and other carbohydrates such as dextran sulfate. These multilayered contacts prevented the clotting factor, fibrinogen from causing thrombosis which is a serious complication of contact with the medical device [188].
Although not always disclosing full information, self-eliminating coatings on medical devices that comprise mainly of polypeptides were successfully applied to medical devices that could deliver biological substances after implantation into the human body [189], applied to urethral catheters and stents to prevent mucosal tissue of the urethra to block openings of the catheter or stent that will lead to prevention of fluid drainage. These coatings also released antimicrobials although antivirals were not mentioned specifically [190,191]. In a comprehensive review, the future of LbL nanocoating in the medical profession was pointed out, however, antiviral LbL applications were not mentioned [192].
It was interesting to find that LbL-nanocoating of medical devices also revealed very few literature entries and even fewer regarding coating with polysaccharides or antiviral coating.
It was reported that catheter silicon tubes that contained chlorohexidine-containing PEG-micelles were coated with poly(acrylic acid) as polyanion. Again the purpose of this study was to afford antibacterial action to the silicon tubes [193].
Dental implants are another medical device that benefited from antibacterial LbL coating with PSS and PAH. Metronidazole was coated in the final bilayer and this provided the antibacterial effect to prevent periodontal infections [194].
It is again apparent, at the time of writing, that antiviral coatings of medical devices have not been the main focus of research or innovation efforts. Figure 5 depicts a summary of our suggested methods of contributing in an almost crude, passive way to curb viral infections.