Ingus Skadins , Aigars Reinis , Juta Kroica , Agnese Pura , Liga Berzina-Cimdina , Dmitrijs Jakovlevs , Dagnija Rostoka , Natalija Berza , Janis Vetra
Introduction: The use of biomaterial implants in medicine is becoming ever more popular, and on many occasions the use of biomaterial implants becomes a lifesaving procedure. A primary obstacle to a wider use of biomaterial implants is their risk of infection and unsuccessful tissue integration with the surface of biomaterials. For the creation of new substances various combinations of materials are used nowadays, thus forming composite materials. Composite materials are materials which consist of two or more components or phases, which according to their characteristics vary considerably, but they are mutually dissolvent or little solvent, and they have a distinct border surface.1 Most often titanium (Ti) and titanium fused implants are covered, as they are bioinert materials.2-4 HAp/TiO2 composite ceramic layer shows better linkage strength with the material if compared with pure HAp. By increasing TiO2 amount in the composite, its strengths also enhances, as well as TiO2 addition can decrease attachment of bacteria to the biomaterial, thus decreasing the possible infection risk of the implant; however infection risk around TiO2 containing implant is still a problem in medicine.5
Objective: The objective of the study was to determine Staphylococcus epidermidis (S.epidermidis) and Pseudomonas aeruginosa (Ps.aeruginosa) adhesion and colonisation intensity on hydroxyapatite (HAp) and titanium dioxide (TiO2) commercial composite material surfaces originally synthesised by Biomaterial Development and Innovation Centre of Riga Technical University. Materials used: Composite material samples used: No 1 100% HAp – burned 1000oC, No 2 50% HAp and 50% TiO2 – burned at 1000oC, No 3 80% HAp and 20% TiO2 – burned at 1000oC, No 4 100% TiO2 – burned at 1000oC, No 5 20% HAp and 80% TiO2 – burned at 1000oC, No 6 100% TiO2 – burned at 1200oC, No 7 20% HAp and 80% TiO2 – burned at 1200oC, No 8 80% HAp and 20% TiO2 – burned at 1200oC, No 9 50% HAp and 50% TiO2 – burned at 1200oC, No 10 100% HAp – burned at 1200oC
Method: Ps.aeruginosa ATCC 27853, S.epidermidis ATCC 12228 reference cultures were used in the study. Bacterial suspensions were prepared from bacterial pure cultures of 1 ml TSB (Trypto-Casein-Soy Broth) volume with a concentration of 10, 102 and 103 CFU/ml (colony forming units). Samples were cultivated at 37oC temperature for 2 h in order to determine adhesion intensity, and a sample with a concentration of 102 CFU/ml for 24 h – to determine colonisation intensity. For adhesion evaluation and determination of colonisation amount, sonication and culture method was used. For determination of colonisation intensity sonicationculture method was used as well as scanning electron microscope.
Result: In general, adhesion intensity on HAp and TiO2 composite material surface is not big. S.epidermidis adhesion starts at 10 CFU/ml/2h/37oC exposition only for biomaterial types 2, 3, 4 (from 0.0027-0.003 CFU/mm2), at 102 CFU/ml/2h/37oC – better adhesion is observed on surfaces of biomaterials 3 and 4, and worse adhesion on surfaces of biomaterials 6, 7, 8. At 103 CFU/ml/2h/37oC exposition the greatest adhesion is observed on surfaces of biomaterials 3 and 10 (0.093 and 0.094 CFU/mm2 respectively). Ps.aeruginosa adhesion intensity was lower than S.epidermidis and at 10 CFU/ml/2h/37oC exposition happened only on biomaterial surfaces 1 and 4 (0.028 and 0.001 CFU/mm2 respectively). At 102 CFU/ml/2h/37oC exposition also demonstrated a low adhesion level, and at 103 CFU/ml/2h/37oC exposition the lowest adhesion intensity was demonstrated on biomaterials 3, 6, 9, 10, and the greatest one on biomaterial 1.
Conclusion: Used bacteria have low adhesion abilities on HAp and TiO2 containing biomaterials. Pseudomonas aeruginosa show even lower adhesion ability on biomaterials with HAp and TiO2 mixture. Optimal HAp/TiO2 composite ceramics composition, which ensures the lowest contamination risk of microorganisms is with a 50% and 80% TiO2 content after a thermal processing at 1200 ?C.
