It is well known that metal materials, except for noble ones, undergo a process of corrosion when inside a biological organism and therefore, release metal ions. Many heavy metals can induce a hypersensitive reaction. Metals noted as potential allergenics are beryllium, nickel, cobalt, chrome and, occasionally tantalum titanium and vanadium. Nickel is the most common allergen of these metals, followed by cobalt and chrome.

Metal ions, even though they themselves are not allergens, can activate the immune system creating complexes with the proteins already present in the organism. These protein complexes are potential allergens responsible for later provoking hypersensitive responses; cell-mediated immunity. Allergenic phenomenon in patients with implanted metal devices is growing as well as awareness of the orthopedic community towards this problem. The need for a type of anti-allergenic prostheses is therefore continually increasing.

BIOLOY® coating has the objective of creating an inert layer and barrier^[1,2] that acts as an interface between the patient (in reality between the tissues and liquids) and the metal of the prosthesis, consequently impeding the passage of metal ions from the prosthesis to the patient. The principle function is in fact, to create a physical barrier between the metal substrate and the surrounding organic environment impeding the release of metal ions from the substrate: thus permitting a notable reduction of the risk of provoking a hypersensitivity risk or to develop an allergic reaction caused by metal elements from device alloys (i.e. Ni, Co, Cr).

BIOLOY® coating therefore allows the:

1. Possibility of implanting metal prosthetic devices in patients who have noted allergies to one or more metals of which the devices are manufactured;
2. Reduction of the risk of developing an allergic reaction in a patient in which one or more metallic devices is implanted.

A BIOLOY® coating, moreover, thanks to the elevated hardness and resistance to abrasion, improves the tribological performance of the metal alloy’s joint surface thereby reducing polyethylene wear.

The TiNbN coating is a single layer surface coating that esthetically gives a gold color to the surface that is coated.

IThe requirements that must satisfy a BIOLOY® coating are a coating hardness of >2000 HV (Vickers), a thickness of 3÷6 µm and an adhesion characterized by no coating delamination.