Drug Release Property of Poly 3-Hydroxybutyrate 4-Hydroxybutyrate (P34HB) as Drug-Eluting Coatings on Metal Coronary Stents

Drug-eluting stents (DES) have become the main method of interventional therapy for coronary heart disease, because their drug coating can effectively reduce the incidence of restenosis after stent implantation. Biodegradable polymers for coatings are the latest development direction for coating polymers, because they can be degraded into small molecules in the human body. In this study, the polymer P34HB(P34HB-1:4HB% = 1 mol%, Mw: 225,000; P34HB-10:4HB% = 10 mol%, Mw: 182,000), the fourth generation of biodegradable Polyhydroxy alkanoates (PHAs), was coated on stents to evaluate the drug release properties of the DES. Both P34HB-1 and P34HB-10 coatings showed increased drug release rates, as the polymer concentrations were gradually increased from 8 mg/mL to 28 mg/mL. Both P34HB-1 and P34HB-10 coatings showed increased drug release rates as the drug polymer ratios were gradually changed from 1:10 to 1:2. The drug release rates of the P34HB-1 coatings became slower than P34HB-10, thus showing sustained drug release effects. The drug release rates of the P34HB-1 coatings decreased when Rates of solution flow increased, decreased when Focusing pressures decreased, and decreased when Mandrel moving speeds increased. P34HB-1 coatings prepared with CHCl(3)/NPA (10:1) mixed solvents had better controlled drug release rates compared to Firebird2(®). The drug release rates of P34HB-1 coatings prepared with CHCl(3) solutions decreased as the outer layer weights were increased from 0 to 800 μg. When the outer layer weights reached 800 μg, the drug release rates of P34HB-1 coatings were slower than Firebird2(®). P34HB-1 coatings prepared with both CHCl(3)/NPA (10:1) mixed solvents and double layers had more effectively controlled drug release rates than P34HB-1 coatings prepared with only mixed solvents or double layers and these effects were far greater than Firebird2(@); thus, P34HB-1 represents a latent polymer for DES.