Bulk Erosion Degradation Mechanism for Poly(1,8-octanediol-co-citrate) Elastomer: An In Vivo and In Vitro Investigation

Abstract

As a biodegradable elastomer, poly(1,8-octanediolco-citrate) (POC) has been widely applied in tissue engineering and implantable electronics. However, the unclear degradation mechanism has posed a great challenge for the better application and development of POC. To reveal the degradation mechanism, here, we present a systematic investigation into in vivo and in vitro degradation behaviors of POC. Initially, critical factors, including chemical structures, hydrophilic and water-absorbency characteristics, and degradation reaction of POC, are investigated. Then, various degradation-induced changes during in vitro degradation of POC-x (POC with different cross-linking densities) are monitored and discussed. The results show that (1) cross-linking densities exponentially drop with degradation time; (2) mass loss and PBSabsorption ratio grow nonlinearly; (3) the morphology on the cross-section changes from flat to rough at a microscopic level; (4) the cubic samples keep swelling until they collapse into fragments from a macro view; and (5) the mechanical properties experience a sharp drop at the beginning of degradation. Finally, the in vivo degradation behaviors of POC-x are investigated, and the results are similar to those in vitro. The comprehensive assessment suggests that the in vitro and in vivo degradation of POC occurs primarily through bulk erosion. Inflammation responses triggered by the degradation of POC-x are comparable to poly(lactic acid), or even less obvious. In addition, the mechanical evaluation of POC in the simulated application environment is first proposed and conducted in this work for a more appropriate application. The degradation mechanism of POC revealed will greatly promote the further development and application of POC-based materials in the biomedical field.

Biodegradation Behavior Control for Shape Memory Polyester Poly(Glycerol-Dodecanoate): An In Vivo and In Vitro Study

“…We employed crosslink density to indirectly reflect the network density in PGD. The crosslink density of PGD was calculated based on its Young’s modulus at 37 °C, as previously mentioned. , The crosslink density increased linearly with the cure time, which was fitted by the linear formula shown in Figure e. The crosslink rate of PGD was faster when MR H/C was closer to 1.00 and vice versa.…”

“…For micromorphology changes during degradation, erosion holes were observed on the surfaces of the PGD samples but did not further expand inside the samples. The water absorbability of each PGD group was lower than 7%, which made it difficult for liquid to penetrate the PGD samples after implantation; thus, the depolymerization of ester bonds tended to occur on its surface, as previously mentioned. , In contrast, typical bulk erosion polymers, such as PCL, poly­(lactic acid), poly­(lactic- co -glycolic acid), and poly­(1,8-octanediol- co -citrate), did not undergo dimensional changes during degradation. , The high swelling nature of the bulk erosion polymer resulted in the easy penetration of liquid inside the polymer, which allowed hydrolysis to occur inside and on the surface of the polymer . Thus, the degradation rates of bulk erosion polymers generally showed exponential trends; that of surface erosion polymers, such as poly­(glycerol sebacate) and poly­(ethylene carbonate), tended to be constant. ,, Linearly fitting the mass loss of each PGD group in our in vivo study, their coefficients of determination R 2 were all higher than 0.95, indicating a relatively constant degradation rate.…”

“…30,31 In contrast, typical bulk erosion polymers, such as PCL, poly(lactic acid), poly(lactic-co-glycolic acid), and poly(1,8octanediol-co-citrate), did not undergo dimensional changes during degradation. 20,23 The high swelling nature of the bulk erosion polymer resulted in the easy penetration of liquid inside the polymer, which allowed hydrolysis to occur inside and on the surface of the polymer. 32 Thus, the degradation rates of bulk erosion polymers generally showed exponential trends; that of surface erosion polymers, such as poly(glycerol sebacate) and poly(ethylene carbonate), tended to be constant.…”

“…The crosslink density ( n , mol/m 3 ) of PGD was calculated from the following formula, as previously mentioned: ,, n = E 3 R T where R represents the universal gas constant (8.3114 J/mol K), T represents the absolute temperature during testing (K), and E represents Young’s modulus of PGD from the tensile test ( E , Pa). Young’s modulus of PGD was measured according to ISO527 using a universal testing machine (IPBF-300, CARE) equipped with a 300 N load cell and temperature controller.…”

Citrate-Based Polyester Elastomer with Artificially Regulatable Degradation Rate on Demand

“…The resulting POCSS films were again placed in the vacuum oven at 100 °C for 0, 0.5, and 1 day, respectively, to obtain POCSS-0d, POCSS-0.5d, and POCSS-1d (including POCSS-yd). Equimolar CA and OD were directly reacted to obtain POC-0d by the one-step method, referring to our previous research . All films were cut into disk specimens with 6 mm diameter and for the various tests.…”