Cell-laden 3D bioprinting hydrogel matrix depending on different compositions for soft tissue engineering: Characterization and evaluation.

Cell-printing techniques that can construct three-dimensional (3D) structures with biocompatible materials and cells are of great interest for various biomedical applications, such as tissue engineering and drug-screening studies. For successful cell-printing with cells, bioinks are critical for both the processability of printing and the viability of printed cells. However, the influence of composition on 3D bio-printing with cells has not been well explored. In this study, we investigated different compositions of alginate bioinks by varying the concentrations of high molecular weight alginate (High Alg) and low molecular weight alginate (Low Alg). Bioinks of 3wt% alginate containing High Alg alone or a 1:2 (Low Alg:High Alg) composite allowed for the construction of 3D scaffolds with good processability and shapes. Cell-printing with fibroblasts and in vitro culture studies revealed good viability and growth of the printed cells after up to 7days of culture. Bioinks prepared with High and Low Alg at a 2:1 ratio exhibited better cell growth compared with those of other compositions. This study progresses the design and applications of alginate-based bioinks for cell-printing platforms in soft tissue engineering.

Transdermal thiol-acrylate polyethylene glycol hydrogel synthesis using near infrared light.

Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm(-2)) could induce gelation via a mixed-mode reaction with a small increase in temperature (∼5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications.

Near-Infrared-Light-Assisted Photothermal Polymerization for Transdermal Hydrogelation and Cell Delivery.

Photopolymerization of hydrogels has been widely used to encapsulate cells and support their growth in 3D environments. However, common light sources (i.e., ultraviolet and visible light) strongly interact with biological systems and are therefore inappropriate for in vivo applications, such as transdermal polymerization. Using near infrared (NIR) light that minimally interacts with living tissues, this study investigates NIR light-assisted photothermal polymerization (NAPP) of diacrylated polyethylene glycol (PEGDA), in which interactions between NIR light and gold nanorods activate a thermal initiator (i.e., AIPH), resulting in generation of radicals for polymerization of PEGDA. Gelation parameters, including precursor concentrations and NIR power, are investigated to minimize the use of initiator and temperature increases (<43 °C) during NAPP. Cell viability is as high as 80% after NAPP-based encapsulation. Incorporation of polyethylene glycol (PEG) modified with a cell-adhesive peptide moiety (Arg-Gly-Asp) into the gel system further enables prolongation of cell viability during incubation up to 7 d. NAPP results in successful transdermal gelation and good viability of the transplanted cells. Thus, this new cell encapsulation approach, demonstrated for the first time in this study, will benefit various applications, including cell delivery and remote control over cellular environments.

Porphyrin-peptoid conjugates: face-to-face display of porphyrins on peptoid helices.

Distance, orientation, and number controlled porphyrin-peptoid conjugates (PPCs) were efficiently synthesized. Cofacial (1, 2, and 4), slipped-cofacial (3), and unstructured (5) arrangements of porphyrins provided distinct optical and electronic properties characterized by UV-vis and circular dichroism spectroscopy. In addition, ECCD spectra confirmed the handedness of peptoid helices.