Page 89 - IJB-9-3

International Journal of Bioprinting Biocompatible 3D printing photosensitive resin

Keywords: Orthopedic surgical guide; Non- isocyanate and brittle, resulting in poor mechanical properties,
polyurethane; 3D printing; Photosensitive resins; which limits the application of NIPU in the 3D printing of
Biocompatibility orthopedic surgical guides [16,17] . Acrylation modulates the
mechanical properties of NIPU. Polyethylene glycol (PEG),
a commonly used biomedical material, is often chemically
modified with acrylate groups to form polyethylene
1. Introduction glycol diacrylate (PEGDA) with photopolymerization
[18]
The orthopedic surgical guide has been widely used in the properties . PEGDA has good flexibility and suitable
clinic to increase surgical accuracy and reduce surgery polarity due to its molecular chain and is well-compatible
[19,20]
time, trauma, pain, and swelling [1,2] . Traditional polymers with acrylic resins . However, the use of PEDGA for the
such as acrylonitrile butadiene styrene (ABS), polylactide acrylation of NIPU to improve mechanical properties for
(PLA), and polyethylene glycol (PEG) are widely used in biomedical applications has not been reported yet.
the field of three-dimensional (3D) printing of biomedical In this study, we synthesized NIPU by the ring-
materials [3-6] . However, these materials-based orthopedic opening reaction of propylene carbonate and isophorone
surgical guides have various disadvantages, such as poor diamine and modified it using methacryloyl chloride. This
accuracy, easy deformation, cytotoxicity, and high cost [2,7] . synthetic route is environmentally friendly and shortens
Therefore, novel, cost-effective polymers with the required the synthesis time of NIPU. The main advantage over the
mechanical properties and excellent biocompatibility are traditional NIPU synthesis route is the avoidance of the
in high demand for the 3D printing of orthopedic surgical toxic isocyanate monomer. As for the synthetic route
guides. without isocyanate monomers, the advantage is the use

Photosensitive resins initiated by polyurethane are of a six-membered ring of amines for the reaction, which
commonly used in the 3D printing of surgical guides [8,9] . adds mechanical strength and intermolecular forces to
The excellent mechanical strength, biocompatibility, the NIPU molecular chain. Meanwhile, non-isocyanate
flexibility, and hydrophobicity of polyurethane are suitable polyurethane acrylate (NIPUA) was obtained by adding
for medical device applications [10,11] . The reaction of polyols PEGDA to improve the mechanical properties. The
with isocyanates produces polyurethanes. The reaction of biocompatibility of NIPUA and commercial resins to bone
amines with highly toxic phosgene compounds produces cells, muscle cells, and macrophages were compared to
isocyanates . These toxic residual compounds continue investigate the possible application of NIPUA in the 3D
[12]
to leach out during surgery, which seriously threatens the printing of orthopedic surgical guides.
patient’s health . Despite recent advances in reducing such
[13]
toxicity, toxic phosgenation of amine-terminated lysine 2 Materials and methods
esters-produced polyisocyanates are still the precursors 2.1. Materials
of polyurethanes. The unreacted polyisocyanates remain Propylene carbonate (PC, 99.7%), isophorone diamine
in the final polymer as a toxic substance. To avoid these (IPDA, 99%), n-Hexane (97%), dichloromethane
challenges, nontoxic methods to produce isocyanate-free (99.5%), anhydrous magnesium sulfate, triethylene glycol
polyurethanes should be developed.
dimethacrylate (TEGDMA, 99%), polyethylene glycol
Non-isocyanate polyurethane (NIPU) is a new type diacrylate (PEGDA), phenothiazine (PTZ, 98%), and
of polyurethane with a similar structure to traditional 2-(Dimethylamino) ethyl-methacrylate (DMAEMA,
polyurethane. There are four main synthetic pathways: 99%) were obtained from Shanghai Aladdin Bio-
condensation polymerization, rearrangement reaction, Chem Technology Company (China). Camphorquinon
ring-opening polymerization, and polyaddition (CQ, 98%) was purchased from Shanghai Yuanye Bio-
polymerization. The first three methods mostly use Technology Company (China). Triethylamine (TEA,
toxic raw materials, produce by-products, and have 99%) and methacryloyl chloride (MAC, 95%) were
harsh reaction conditions. Cyclic carbonates (CCs) and obtained from Shanghai Macklin Bio-Chem Technology
polyfunctional amine polyaddition is the common way Company (China). Sodium chloride (99.5%) and sodium
to obtain NIPU. During this process, the primary and bicarbonate were purchased from Tianjin chemical reagent
secondary –OH groups are formed alongside urethane factory (China). Commercial resin solution with epoxy-
linkages. This method completely avoids the usage of based resin as the main component (Trans, White) was
isocyanates in the synthesis process and eliminates the use purchased from Stratasys company (USA). Triethylamine
of hazardous chemical compounds during synthesis [14,15] . and dichloromethane were dried over 4A molecular sieves
However, the curing process makes hybrid resins hard before use.

Volume 9 Issue 3 (2023) 81 https://doi.org/10.18063/ijb.684