Surface Modification of Nickel/Titanium Alloy and Titanium Surfaces via a Polyelectrolyte Multilayer/Calcium Phosphate Hybrid Coating

Abstract

The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20° for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material). magnified image

Calcium Phosphate Mineralization beneath a Polycationic Monolayer at the Air–Water Interface

“…In summary, the study shows that calcium phosphate formation beneath polycationic monolayers is significantly different from calcium phosphate formation on polymer multilayers on solid substrates 18, 20–22. Earlier studies either show the formation of small, rather dense particles or very large fluffy aggregates.…”

“…The unique feature of the current study is indeed that the effect of polycations at the air–water interface is for the first time evaluated at different pH values, including non‐physiological conditions. Open questions, therefore, concern the role of the pH on calcium phosphate mineralization on polymer films such as those just discussed 18, 20–22, 24. Unfortunately there are no data available on this topic at the moment, yet our work suggests that the degree of charging, also in polycations, is a key influence in calcium phosphate formation.…”

“…The current study evaluates the potential of amphiphilic block copolymer monolayers with a cationic block for calcium phosphate mineralization at the air–water interface. The major goal of this study is to provide a model system, which is comparable to the earlier study by Casse et al,25 yet enables the investigation of polycationic surfaces on calcium phosphate mineralization in much more detail than previously achieved 18, 20–22…”

“…Spoerke et al have shown that polyelectrolyte coatings are also viable for the modification of titanium surfaces 21. More recently, Schweizer et al have shown that polyelectrolyte multilayers modified with calcium phosphate could be interesting coatings for cardiovascular stents 22…”

Water-Soluble Cellulose Derivatives Are Sustainable Additives for Biomimetic Calcium Phosphate Mineralization

“…Schweizer, et al prepared hybrid films from chitosan/heparin multilayers and calcium phosphate and demonstrated that the specific composition of these hybrid films strongly affects their water contact angle [16]. Fratzl and coworkers used a coprecipitation process for the synthesis of chitosan-based hybrids [17].…”