Controllable protein delivery from coated surgical sutures

Abstract

In contemporary tissue engineering there is a need for drug delivery approaches that offer controllable release kinetics from common surgical devices, particularly at healing tissue interfaces. We describe a generally applicable approach to release therapeutic proteins from sutures in a controllable manner. Results demonstrated that several common, commercially available surgical sutures could be coated with nano-porous hydroxyapatite mineral layers using a biomimetic process. The nanoscale morphology, composition, and dissolution rate of these coatings were controlled by varying the degree of carbonate substitution during calcium phosphate (CaP) mineral growth. Coated sutures could efficiently bind both an acidic protein and a basic protein, and subsequent sustained protein release was controllable by varying the coating composition. Interestingly, decreases in pH could trigger enhanced coating dissolution and, in turn, increased protein release kinetics. Importantly, CaP coatings on Orthocord sutures were robust enough to endure under clinically relevant conditions, as protein-containing coatings remained intact after multiple passages through sheep tendon and meniscus tissues. The use of CaP-coated Orthocord sutures in a sheep rotator cuff repair model demonstrated that suture coatings did not negatively impact their utility at a bone–tendon interface. Considering the ubiquitous use of sutures and their proximity to damaged tissue, the approach described in this study may provide an efficient, site-specific way of regulating new tissue formation in emerging tissue engineering schemes.