The role of salicylate as dopant in polypyrrole matrix deposited on biocompatible substrates

DANIEL O. FLAMINI; ALEJANDRA L. MARTÍNEZ; MELISA SAUGO; MARÍA B. GONZÁLEZ; ANA P. LOPERENA; IVANA L. LEHR; SILVANA B. SAIDMAN

Advances in Materials Science Research

Nova Science Publishers

Año: 2023; p. 1 - 267

Salicylates are used as substitutes for nonsteroidal anti-inflammatory drugs (NSAIDs). The most commonly used and well-known salicylate is aspirin. Several studies suggest that aspirin not only relieves fever, inflammation, and pain, but also reduces the risk of stroke, heart attack, and some cancers [1-3].In our time, great efforts are being made to produce metal implants with drug-releasing systems [4]. It is important to deliver drugs locally near the implanted material to achieve high efficacy of therapeutic agents [5]. In addition, coating the surface of the metallic implant to protect it from corrosion is a widely studied topic. Polypyrrole (PPy) is a conductive polymer and a suitable material for biomedical applications [6] with many advantages such as its relatively easy electrosynthesis in aqueous solutions, biocompatibility and good stability [7]. Specifically, the salicylate (Sa) molecule plays a dual role in the electrosynthesis of PPy on various biocompatible substrates. First, Sa acts as a dopant of the polymer and second, it is a promoter for the formation of rectangular microtubules [8]. The microtubular structures provide a large active surface area and, under certain experimental conditions, the Sa anion can be released from the film. In this way, the anti-inflammatory effect of Sa can be exploited in the vicinity of the substrate. Another interesting feature of Sa molecule is that it behaves as a passivating agent, inhibiting the dissolution of active metals such as iron or magnesium and also allowing a stable PPy formation.In addition, implant-related infections are a tragic problem, and revision surgery is often required for individuals with severe infections [9]. To prevent this, surface modifications are also used. For example, the addition of metal ions such as Ag+, Cu2+, and Zn2+ is suitable because they exert antimicrobial activity at the implant site. Ti-6Al-4V and Nitinol are Ti-based widely used biomaterials. PPy films were synthesized from aqueous solution with Sa onto both alloys. The microstructured polymer matrix was used for the immobilization of Zn and Ag species, respectively. These modifications provide antimicrobial properties against Staphylococcus aureus [10, 11].Stainless steel 316L (SS 316 L) is the most commonly used alloy for medical implants and was coated with salicylate-doped PPy with microtubular morphology to improve the corrosion properties. The PPy coating was able to immobilize silver and copper particles [12, 13].AZ91D is a biodegradable magnesium alloy used for temporary implants. To retard corrosion, the substrate was coated with a double film consisting of a molybdate-based film and a PPy film obtained from a salicylate solution. The duplex film was modified with silver and exhibits good antibacterial activity against Escherichia coli [14].In the present chapter, the role of salicylate concentration in the electroformation of PPy on different alloys such as Ti-6Al-4V, Nitinol, SS 316 L and AZ91D is investigated. The obtained corrosion protection of the coatings was analyzed in Ringer solutions and the role of salicylate in immobilizing metals on PPy matrix for antibacterial properties was also studied.