As acrylated polymers become more widely used in additive manufacturing, their potential applications toward biomedicine also raise the demand for biodegradable, photocurable polymeric materials. Polycaprolactone diacrylate (PCLDA) and poly(ethylene glycol) diacrylate (PEGDA) are two popular choices of materials for stereolithography (SLA) and digital light processing additive manufacturing (DLP-AM), and have been applied to many biomedical related research. However, both materials are known to degrade at a relatively low rate in vivo, limiting their applications in biomedical engineering. In this work, biodegradable, photocurable copolymers are introduced by copolymerizing PCLDA and/or PEGDA with poly(glycerol sebacate) acrylate (PGSA) to form a network polymer. Two main factors are discussed: the effect of degree of acrylation in PGSA and the weight ratio between the prepolymers toward the mechanical and degradation properties. It is found that by blending prepolymers with various degree of acrylation and at various weight ratios, the viscosity of the prepolymers remains stable, and are even more 3D printable than pure substances. The formation of various copolymers yielded a database with selectable Young’s moduli between 0.67–10.54 MPa, and the overall degradation rate was significantly higher than pure substance. In addition, it is shown that copolymers fabricated by DLP-AM fabrication presents higher mechanical strength than those fabricated via direct UV exposure. With the tunable mechanical and degradation properties, the photocurable, biodegradable copolymers are expected to enable a wider application of additive manufacturing toward tissue engineering.

The regeneration of damaged or lost tissue is considered to be a critical step toward realizing full organ regeneration in modern medicine. Although surgical techniques continue to advance, treatment for missing tissues in irregular wounds remains particularly difficult. With increasing interest in the application of additive manufacturing in tissue engineering, the fabrication of customized scaffolds for the regeneration of missing tissue via three-dimensional (3D) printing has become especially promising. Amongst the work on the regeneration of many important organs, liver regeneration is particularly interesting because liver diseases are increasingly prevalent in many countries around the world, resulting in a greater need for liver transplantation. The generation of hexagonal scaffolds for the regeneration of liver lobules is highly demanding, but their 3D structure has been proved difficult to reproduce by traditional fabrication methods. In this work, various hexagonal scaffolds are developed for liver lobule regeneration via 3D printing using novel biodegradable polymeric materials, including poly(glycerol sebacate) acrylate and poly(ethylene glycol) diacrylate. Through fine-tuning of printing parameters, a series of hexagonal scaffolds were designed and printed to mimic liver lobule units. The scaffolds were printed with various structures together with varying surface areas and 3D structures to enhance cell seeding density and diffusivity of the culture medium. Analysis of cell metabolic activities showed that the high-diffusion staircase (HDS) scaffold could support potential differences in cell proliferation rate. Furthermore, the HDS scaffolds composed of different copolymers were cultured with cells for up to 16 days to investigate the relationship between physical properties and hepatocyte proliferation. The results indicate that the combination of the high flexibility 3D printing with biodegradable, photocurable copolymers shows great promise for the regeneration of 3D liver lobules.

Digital light processing additive manufacturing (DLP-AM) technology has received a lot of attention in the field of biomedical engineering due to its high precision and customizability. However, some photoinitiators, as one of the key components in DLP-AM, may present toxicity and limit the application of DLP-AM toward biomedical applications. In order to gain further insights into the correlation between biocompatibility and photoinitiators in photoresins, a study on the selection of photoinitiators used in DLP-AM is conducted. The light absorbance range and cytocompatibility of four photoinitiators, vitamin B2 combined with triethanolamine (B2/TEOA), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2-dimethoxy-2-phenylacetophenone (DMPA), and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), are characterized. Each photoinitiator is then combined with poly(glycerol sebacate) acrylate (PGSA) and poly(εcaprolactone) diacrylate (PCLDA), to evaluate their miscibility and film formation ability through photopolymerization. The mechanical properties, in vitro and in vivo biocompatibility studies on bulk films are investigated. It is found that B2/TEOA and TPO exhibit a wider light absorbance range than I2959 and DMPA.PGSA films with B2/TEOA (PGSA-B2/TEOA) is capable of sustaining cell proliferation up to 10 days and showing low immune responses after 14 days post implantation, proving its biocompatibility. Although B2/TEOA requires longer photopolymerization time, the mechanical strength of PGSA-B2/TEOA is comparable to PGSA films with TPO and DMPA, and this combination is 3D-printable through DLP-AM at the rate of 100 s per layer. In summary, B2/TEOA is a promising photoinitiator for 3D printing.