Biomedical metallic materials can be harmful to the human body in the long term due to the release and accumulation of metallic particles resulting from the degradation and corrosion of the material, a consequence of the wear suffered by the implant. Therefore, biodegradable materials have been studied that reduce the risk to health and the need for a second surgical intervention to remove the implant when the tissue is regenerated.
Magnesium alloys are possible candidates as degradable biomaterials for temporary implants in various specialties such as traumatology, cardiology and dentistry, and as bone fixation and osteosynthesis instruments, cardiovascular devices such as stents or catheters, and even cavity filling materials and as a barrier in dental implants.
In contrast to Ti alloys and stainless steel, magnesium alloys are possible candidates as degradable materials for temporary implants since they can react with the physiological fluids of the body and form soluble and non-toxic products, which can be eliminated through the urine without posing health risks. Additionally, the mechanical properties of magnesium alloys, such as Young's modulus, compressive strength and density, are very close to the properties of human bone, which favors the reduction of failures associated with bone implants. Mg is the metal that is easier to machine and achieve stable final dimensions, therefore, complex parts can be produced and it has the ability to absorb energy from any material, which makes it suitable for use in load-bearing applications.
On the other hand, microalgae have been recently studied the use of microalgae as corrosion inhibitors. Microalgae are photosynthetic microorganisms that can be used to produce different metabolites, such as lipids, proteins, and pigments. These species have high percentages of vitamins, fatty acids, essential amino acids, and polysaccharides, properties that make them excellent as active ingredients for food. The biomass obtained from microalgae, in particular Chlorella sp., can have a protein content between 40-60% depending on the cultivation conditions In recent years, the use of microalgae has been studied in different fields such as the food industry, medical, chemical, and pharmacological applications, as biofuels, as a source of renewable energy and for water treatments, among others, obtaining excellent results.
Calcium phosphate (CaP) and chemical analogues have been extensively studied for biomedical applications since the coatings designed with this ceramic contain elements similar to those present in the mineralized inorganic phase of the human bone. The release of Ca2+ y PO43− ions facilitate cellular interaction on the surface of the implant, so they can encourage the growth of new bone tissue and produce greater stability in vivo over a long period of time.
The use of CaP as a coating on magnesium alloys has been shown to be an effective way to increase the resistance to magnesium corrosion over time, which improves the biocompatibility and osseointegration of the surface.
Despite the excellent qualities of Mg that position it as a possible candidate as a biodegradable material for the design of temporal fixation elements, magnesium alloys can corrode in aqueous solutions causing problems such as osteolysis, loss of minerals, especially calcium, which causes degeneration and weakening of bones, debilitation of mechanical properties, creation of gas bubbles, and the formation of spaces between the tissue and implants.
In recent decades, strategies have been investigated to control the rate of degradation of these alloys, including microstructural and surface modification techniques. The modification of the surface in a chemical way (biofunctionalization) is the most applied in orthopedic implants because it allows establishing stable and strong bonds between the surface and the immobilized molecule because it generates ionic or covalent chemical bonds that can resist the extreme conditions of the human body during and after implantation.
Therefore, the purpose of this work is to biofunctionalized magnesium with calcium phosphate (CaP) and biomass from Chlorella sp. independently (monolayer) and jointly (multilayer). Electrochemical tests (corrosion potential, EIS, TAFEL) and surface characterization (SEM, XRD, optical microscope) will be implemented. The experimental design consists of evaluating three times of immersion in microalgae (1, 3 and 5 hours) and electrodeposition of CaP (20, 60 and 120 minutes). For each monolayer, the time that provides the best corrosion resistance will be selected. Subsequently, the CaP / Microalgae multilayer will be designed. The results obtained show that biofunctionalization with microalgae for 3h and electrodeposition of CaP for 120min considerably improve the corrosion resistance of magnesium. The multilayer design is expected to allow for better performance and surface stability of magnesium. The CaP / Microalgae multilayer is sought to improve the osteoconduction and osseointegration of the substrat
