In this study, poly(lactic acid) (PLA) scaffolds were prepared by selective enzymatic degradation using poly(3-hydrobutyrate-co-4-hydrobutyrate) [P(3HB-co-4HB)] depolymerase. The porous morphology and properties of the scaffolds were investigated to clarify whether the microstructure of the biomimetic extracellular matrix is suitable for cell proliferation and differentiation. When the P(3HB-co-4HB) composition of PLA/P(3HB-co-4HB) blends was changed from 50 wt% to 60 wt%, the mean pore diameter of the porous PLA scaffolds increased from 64.15 µm to 80.01 µm, the porosity significantly improved from 68.45% to 79.88%, and the compressive modulus decreased from 9.34 MPa to 6.94 MPa. PLA40 with 60% P(3HB-co-4HB) blending was used in in vitro degradation and mouse embryo fibroblast (MEF) cell culture tests. The results demonstrated that the PLA scaffolds were degraded completely into harmless products in simulated body fluid (SBF) solution at a slow degradation rate, and the weight loss of the scaffolds could reach 80% after 8 months of in vitro degradation. Meanwhile, the PLA scaffolds showed the largest swelling value of 157.4% after immersion in SBF solution for 14 days. Cell viability was determined through scanning electron microscopy (SEM) and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) tests. The results showed that the PLA scaffolds supported the attachment and growth of MEF cells. Compared with the PLA scaffolds without any modification, the PLA scaffolds modified by poly-L-lysine exhibited a better biocompatibility to MEF cells. These results indicate that selective enzymatic degradation has a potential application in scaffold manufacturing.

Poly(ε-caprolactone) (PCL) is an artificial polyester with commercially promising application. In this study, two novel PCL-degrading enzymes named PCLase I and PCLase II were purified to homogeneity from the culture supernatant of an effective polyester-degrading bacterium, Pseudomonas hydrolytica sp. DSWY01^T. The molecular masses of PCLase I and PCLase II were determined to be 27.5 and 30.0 kDa, respectively. The optimum temperatures for the enzyme activities were 50 and 40°C, and the optimum pH values were 9.0 and 10.0, respectively. The two enzymes exhibited different physical and chemical properties, but both enzymes could degrade PCL substrates into monomers and oligomers. Weight loss detection and scanning electron microscopy revealed that PCLase I had more effective degradation ability than PCLase II. The genes of the two enzymes were cloned on the basis of the peptide fingerprint analysis results. The sequence analysis and substrate specificity analysis results showed that PCLase I and PCLase II were cutinase and lipase, respectively. Interface activation experiment also confirmed this conclusion. Structural analysis and modeling were further performed to obtain possible insights on the mechanism.