Objectives Because of its excellent biocompatibility, non-toxicity and biodegradability, polylactide (PLA) is a natural choice for various types of biomaterials, for example as a drug carrier. However, the use of PLA as a base substance for nitric oxide (NO) used as the donor has not been previously reported. On the other hand, high pressure gas foaming preparation of porous polylactide for tissue engineering or other biomedical applications has been developed for decades and proven to be a successful method to manipulate PLA. We employed nitric oxide as the pressure gas injected into amorphous amino acid modified-PLA solid to obtain a gas-solid solution, while the amino acids provided the amino group for EDTA modification, which may serve as a candidate for donating NO.
Methods We synthesized poly-(la-serine)-esters to introduce the diazo-group on the side chain, which can be loaded with NO and acts as a NO donor (diazeniumdiolate). The bulk poly-(la-serine)-ester was formed by high pressure NO and CO2 gas to obtain a NO-loaded porous scaffold (Figure 1).
Results The block ratio of LA:serine 50:50 is feasible for fine products with both good properties and NO capacity. Thermal and mechanical characterization shows good thermal, tensile and processing properties. SEM observation confirms the porous structure induced by gas foaming. The Griess method applied to measure NO release in PBS (pH 7.4) showed 1082 mol/mg release in 7 hours.
Conclusions The results indicate this methodology is feasible. The block-polyester we synthesized shows a practical NO capacity with a convenient loading process, while good thermal and mechanical properties are maintained, and therefore may serve as a candidate for donating NO.
Acknowledgments This work was financially supported by the Innovation Cultivation Project of Zhuhai College of Jilin University (Grant No. 2016XJCQZD06).