A stereolithography-based bioprinting platform for multimaterial fabrication of heterogeneous hydrogel constructs is presented. Dynamic patterning by a digital micromirror device, synchronized by a moving stage and a microfluidic device containing four on/off pneumatic valves, is used to create 3D constructs. The novel microfluidic device is capable of fast switching between different (cell-loaded) hydrogel bioinks, to achieve layer-by-layer multimaterial bioprinting. Compared to conventional stereolithography-based bioprinters, the system provides the unique advantage of multimaterial fabrication capability at high spatial resolution. To demonstrate the multimaterial capacity of this system, a variety of hydrogel constructs are generated, including those based on poly(ethylene glycol) diacrylate (PEGDA) and gelatin methacryloyl (GelMA). The biocompatibility of this system is validated by introducing cell-laden GelMA into the microfluidic device and fabricating cellularized constructs. A pattern of a PEGDA frame and three different concentrations of GelMA, loaded with vascular endothelial growth factor, are further assessed for its neovascularization potential in a rat model. The proposed system provides a robust platform for bioprinting of high-fidelity multimaterial microstructures on demand for applications in tissue engineering, regenerative medicine, and biosensing, which are otherwise not readily achievable at high speed with conventional stereolithographic biofabrication platforms.

Optical fibers are widely used in biomedical applications for sensing, imaging, and therapies. Unlike existing solid-state optical fibers, soft polymer and hydrogel fibers offer physical and chemical properties well suited for functionalization with biomolecules and long-term implantation in the body. Here, hydrogel optical fibers are fabricated with glucose-sensitive moieties and the swelling-induced sensing is demonstrated. The core of the fiber is made of poly(acrylamide-co-poly(ethylene glycol) diacrylate) (p(AM-co-PEGDA)) hydrogel functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis diols of glucose molecules lowers the apparent pKa of the hydrogel network and increases the concentration of the boronate anions that enhances the Donnan osmotic pressure to swell and change the physical size of the hydrogel optical fiber. This mechanism is reversible through ester group dynamic covalent binding of the phenylboronic acid with glucose molecules. Dynamic changes in the effective RI of the hydrogel optical fiber are measured through light propagation loss. The sensor sensitivity to glucose concentration is 1.2 mmol L−1 over a physiological range of 1–12 mmol L−1. The biocompatible hydrogel optical fibers may be subcutaneously implanted for continuous monitoring of interstitial glucose concentrations.

Surgical sealants have been used for sealing or reconnecting ruptured tissues but often have low adhesion, inappropriate mechanical strength, cytotoxicity concerns, and poor performance in biological environments. To address these challenges, we engineered a biocompatible and highly elastic hydrogel sealant with tunable adhesion properties by photocrosslinking the recombinant human protein tropoelastin. The subcutaneous implantation of the methacryloyl-substituted tropoelastin (MeTro) sealant in rodents demonstrated low toxicity and controlled degradation. All animals survived surgical procedures with adequate blood circulation by using MeTro in an incisional model of artery sealing in rats, and animals showed normal breathing and lung function in a model of surgically induced rat lung leakage. In vivo experiments in a porcine model demonstrated complete sealing of severely leaking lung tissue in the absence of sutures or staples, with no clinical or sonographic signs of pneumothorax during 14 days of follow-up. The engineered MeTro sealant has high potential for clinical applications because of superior adhesion and mechanical properties compared to commercially available sealants, as well as opportunity for further optimization of the degradation rate to fit desired surgical applications on different tissues.

Conventional surgical techniques to seal and repair defects in highly stressed elastic tissues are insufficient. Therefore, this study aimed to engineer an inexpensive, highly adhesive, biocompatible, and biodegradable sealant based on a modified and naturally derived biopolymer, gelatin methacryloyl (GelMA). We tuned the degree of gelatin modification, prepolymer concentration, photoinitiator concentration, and crosslinking conditions to optimize the physical properties and adhesion of the photocrosslinked GelMA hydrogels. Following ASTM standard tests that target wound closure strength, shear resistance, and burst pressure, GelMA sealant was shown to exhibit adhesive properties that were superior to clinically used fibrin- and poly(ethylene glycol)-based glues. Chronic in vivo experiments in small as well as translational large animal models proved GelMA to effectively seal large lung leakages without the need for sutures or staples, presenting improved performance as compared to fibrin glue, poly(ethylene glycol) glue and sutures only. Furthermore, high biocompatibility of GelMA sealant was observed, as evidenced by a low inflammatory host response and fast in vivo degradation while allowing for adequate wound healing at the same time. Combining these results with the low costs, ease of synthesis and application of the material, GelMA sealant is envisioned to be commercialized not only as a sealant to stop air leakages, but also as a biocompatible and biodegradable hydrogel to support lung tissue regeneration.

Summary Recent years have seen tremendous advances in the field of hydrogel-based biomaterials. One of the most prominent revolutions in this field has been the integration of elements or techniques that enable spatial and temporal control over hydrogels’ properties and functions. Here, we critically review the emerging progress of spatiotemporal control over biomaterial properties towards the development of functional engineered tissue constructs. Specifically, we will highlight the main advances in the spatial control of biomaterials, such as surface modification, microfabrication, photo-patterning, and three-dimensional (3D) bioprinting, as well as advances in the temporal control of biomaterials, such as controlled release of molecules, photocleaving of proteins, and controlled hydrogel degradation. We believe that the development and integration of these techniques will drive the engineering of next-generation engineered tissues.

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This article describes a paper-based microfluidic system that quantifies the concentrations of tear electrolytes using a smartphone-based reader.

The aim of the study herein reported was to review mobile health (mHealth) technologies and explore their use to monitor and mitigate the effects of the COVID-19 pandemic. Methods: A Task Force was assembled by recruiting individuals with expertise in electronic Patient-Reported Outcomes (ePRO), wearable sensors, and digital contact tracing technologies. Its members collected and discussed available information and summarized it in a series of reports. Results: The Task Force identified technologies that could be deployed in response to the COVID-19 pandemic and would likely be suitable for future pandemics. Criteria for their evaluation were agreed upon and applied to these systems. Conclusions: mHealth technologies are viable options to monitor COVID-19 patients and be used to predict symptom escalation for earlier intervention. These technologies could also be utilized to monitor individuals who are presumed noninfected and enable prediction of exposure to SARS-CoV-2, thus facilitating the prioritization of diagnostic testing.