Two‐photon microfabrication of poly(ethylene glycol) diacrylate and a novel biodegradable photopolymer—comparison of processability for biomedical applications

Abstract

Two‐photon polymerization (2PP) is a versatile microfabrication tool for biomedical applications as it provides unparalleled resolution for accurate three‐dimensional (3D) replication of biological microstructures. To widen the selection of biomaterials suitable for 2PP, this paper presents the processing of a methacrylated poly(ε‐caprolactone)‐based oligomer (PCL‐o) and a poly(ethylene glycol) diacrylate (PEGda) hydrogel into microstructures. PCL‐o is a novel biodegradable photopolymer that has not been previously processed with 2PP, and the fabrication of both polymers with an Nd:YAG laser is reported here for the first time. The overall 2PP processability and achievable resolution were studied by polymerizing arbitrary microstructures on glass substrates. The samples were characterized with scanning electron microscopy. Additionally, the effect of photoinitiator concentration on the resolution was investigated. Also, a preliminary cell attachment test was performed with UV cured films in order to investigate the impact of the used material–initiator combination on cell viability and migration. As a result, laser‐induced polymerization of both PCL‐o and PEGda was successfully demonstrated, and the Nd:YAG laser was proven adequate for the 2PP processing of the novel biodegradable photoresist. Resolution in the order of 1 µm was achieved with PCL‐o. With the easy processing of both PEGda and PCL‐o, these materials have great potential for different biomedical applications. Copyright © 2011 John Wiley & Sons, Ltd.

Photocrosslinkable Materials for the Fabrication of Tissue-Engineered Constructs by Stereolithography

“…Fibroblasts, cultured onto spin-coated thin films after photopolymerization, remained viable and showed comparable cell attachment and division regarding cells cultured on glass surfaces (control), which indicates that the developed material do not affect cell proliferation. In a similar work, Koskela et al [53] used the 2PP technique to produce [31] microstructures, using methacrylated PCL-based oligomer (PCL-o) and Irgacure ® 127 as UV photoinitiator. Live/dead staining analysis showed that hESC-derived neuronal cells, cultured on the PCL film for 7 days, were able to attach to the surface, though the material did not allow cell migration.…”

“…However, 2PP systems are very expensive, operating with a single material type that prevents the fabrication of multimaterial constructs [85]. These equipments usually employ a femtosecond titanium:sapphire laser (short pulse width and high peak power) without photo-masks, operating at approximately 800 nm wavelength to induce the polymerization [53,74,82]. A great variety of natural and synthetic photosensitive materials can be used for the 2PP technique, like acrylate-based polymer, zirconium sol-gels, organically modified ceramic materials, aliphatic polyesters and gelatin [52,74,79,105].…”

“…In this process, the laser beam is more precisely focused, reducing the spot size to a few micrometers in diameter, this way enhancing the resolution of the system [13,56]. Today, there is a great interest in the use of 2PP processes for the fabrication of various devices, such as microneedles, sensors and scaffolds for different biological and biomedical applications [39,48,53]. These processes are able to produce 3D structures with submicron resolution, enabling an ultra-fast fabrication process at greater depth [8].…”

Micro additive manufacturing using ultra short laser pulses

“…The most common biomaterials for 2PP stereolithography include gelatin [159], hyaluronic acid [160], PEG [161], PCL [162] and PLA [163]. The capabilities of 2PP stereolithography for the fabrication of 3D cellular hydrogels were also shown by the direct printing of gelatin methacrylamide containing human osteosarcoma cells [159].…”

Two-photon polymerization of hydrogels – versatile solutions to fabricate well-defined 3D structures

“…For example, human embrionic stem cell (hESC)-derived neuronal cells cultured on PEGDA or a poly( P -caprolactone)-based oligomer (PCL-o) were able to attach on both material surfaces, but did not migrate. 103 Only the cells placed inside the structures survived, whereas the ones found outside the scaffolds were dead. Aer a subsequent material functionalization, PEGDA and PCL-o could be used as guidance structures in neural cell culture applications.…”