Poly(lactic acid) (PLA) suture can be absorbed by the human body, and so have wide applications in modern surgery operations. The degradation period of PLA suture is expected to meet with the healing time of different types of wounds. In order to control the degradation period of the PLA suture, the carbon nanotubes (CNTs) were composited with PLA suture, and the degradation experiment in vitro was performed on sutures. The structure and properties of sutures during degradation, such as surface morphology, breaking strength, elongation, mass and chemical structure, were tracked and analyzed. The results indicated that the degradation brought about surface defects and resulted in 13.5 weeks for the strength valid time of the original PLA suture. By contrast, the strength valid time of the CNTs/PLA suture was increased to 26.6 weeks. Whilst the toughness of both the pure PLA and CNTs/PLA sutures decreased rapidly and almost disappeared after 3 to 4 weeks of degradation. The mass loss demonstrated that the time required for complete degradation of the two sutures was obviously different, the pure PLA suture 49 weeks, while CNTs/PLA sutures 63 to 73 weeks. The research proved that CNTs delayed PLA degradation and prolonged its strength valid time in degradation.

Polylactic acid (PLA) surgical suture can be absorbed by human body. In order to avoid surgical site infections (SSIs), the drug is usually loaded on the PLA suture, and then the drug can release directly to the wound. Because the different types of wounds heal at different times, it is needed to control the drug release rate of PLA suture to consistent to the wound healing time. Two biopolymers, polyglycolide (PGA) and polycaprolactone (PCL), were selected as the carrier of ciprofloxacin (CPFX) drug, and then the CPFX-PCL/PGA was coated on the PLA suture. The degradation rate of drug-carrier can be controlled by adjusting the proportion of PCL/PGA, which can regulate the rate of CPFX drug release from PLA suture. The results show that the surface of PLA suture, coating with PCL/PGA, was very rough, which led to increased stitching resistance when we were suturing the wound. These materials, such as the PLA suture, the PCL/PGA carriers and the CPFX drug, were just physically mixed rather than chemically reacted, which was very useful for ensuring the original efficacy of CPFX drug. With the increasing of PCL in the carriers, both the breaking strength and elongation of these un-degraded sutures increased. During degradation, the breaking strength of all sutures gradually decreased, and the more PCL in the coating materials, the longer effective strength-time for the suture. With the increasing of PCL in the drug-carrier, the rate of drug releasing became lower. The drug release mechanism of CPFX-PCL/PGA was a synergistic effect of drug diffusion and PCL/PGA carrier dissolution.

Basalt fiber (BF) possesses some excellent properties in temperature resistance, chemical stability, sound absorption and so on. It has been applied to create composites with the polylactic acid (PLA) resin, which could be used as medical equipments, bone repairing materials, automobile shells and others. However, the compatibilities between BF and PLA are understood to be poor. In order to solve the problem, BF was treated by sodium hydroxide solution (NaOH) and then by coupling agent KH550, and the optimal concentration of NaOH was found to be 15 g/L, and the optimal KH550 dosage was 2%. The research revealed that one end of KH550 molecule was reacted with the hydroxyl groups on the surface of BF to form chemical link, and the amino group at the other end of KH550 molecule was reacted with the terminal hydroxyl group or the terminal carboxyl group of PLA molecule to form chemical link. Graphical Abstract

Drug loaded PLA suture has been one most potential surgery material to help wounds healing. The loaded drug amounts and sustained drug release effect were a vital part for PLA suture. In this research drug-loaded microspheres and finishing bath were prepared to ensure more drug particles loaded on PLA suture. Moreover, sustained drug release effect and mechanical properties of PLA suture were also observed. The results suggested that PLA concentration and emulsifier amounts had more effect on the size of PLA drug-loaded microspheres and the optimal technology was: 0.03 g/mL of PLA concentration, 0.3 g of amount of emulsifier and the total amount of drug and emulsifier was 3 g. Moreover, drug release test showed a significant sustained release effect of the drug-loaded PLA suture. Mechanical measurements indicated the flexibility and strength were not impaired by such drug-loaded method. This research is expected to benefit the surgery fields further.