Effects of UV wavelength on cell damages caused by UV irradiation in PC12 cells

Radiation Damage to a Three-Dimensional Hydrogel Model of the Brain Perivascular Niche

Glioblastoma (GBM) is a highly aggressive and recurrent brain cancer characterized by diffuse metastasis at the tumor margins. Radiation therapy is a standard component of current treatment and offers potential for improved patient outcomes. While radiation therapy targets GBM cells in the tumor margins, it may also significantly damage adjacent noncancerous tissues, leading to reduced quality of life and potentially creating a tumor-supportive microenvironment. The perivascular niche (PVN) in the tumor margins is believed to play a significant role in regulating the glioblastoma stem cell subpopulation as well as serving as a site for cancer recurrence and migration. Understanding the impact of radiation on the PVN can better inform radiation schemes and improve our understanding of GBM recurrence, but is difficult in vivo. Here, we adapt a previously developed three-dimensional hydrogel model of the brain PVN to investigate the impact of radiation dosage and delivery rate on PVN properties in vitro. Effects of radiation on vessel architecture can be measured in this hydrogel-based model, suggesting an approach that can provide insight into the effects of radiation on a shorter time scale relative to in vivo experiments.

Radical-free photopolymerizable composites of hyaluronic acid and gelatin for tissue engineering

Photopolymerization is widely used in tissue engineering and biofabrication to pattern specific geometries and modulate physical properties. Commonly employed photochemistries rely on a photoinitiator that generates reactive free radicals when exposed to light, which can lead to cytotoxic effects due to interactions with biomolecules and cellular components. To mitigate these issues, we have developed hyaluronic acid and gelatin derivatives of umbelliferone, which can form dimers thanks to cyclobutene ring formation when exposed to long-wavelength UV light (365 nm). These reactions occur efficiently with reduced cytotoxicity and without the need of a photoinitiator. Ligation to the biopolymers was carried out with the incorporation of a triethylene glycol or n-octyl linker that enhances the conformational flexibility of umbelliferone and contributes to improve the rheological properties. By heat annealing these derivatives, we produced double network hydrogels with various compositions. We assessed their physical properties using rheological and uniaxial compression tests, evaluated their cytocompatibility by encapsulating articular chondrocytes, and conducted preliminary printability tests to determine their suitability for injection and extrusion-based biofabrication. The materials exhibited good cytocompatibility and cell adhesion, were successfully extrudable using a pneumatic bioprinter while maintaining cell viability and were compatible with regulatory-approved steam sterilization. Due to their unique properties, these umbelliferone derivatives are well-suited for tissue engineering and biofabrication applications, offering crucial advantages for future clinical translation. STATEMENT OF SIGNIFICANCE: This study introduces a method for preparing novel bioinks from coumarin derivatives of hyaluronic acid and gelatin, key biopolymers in tissue engineering. These derivatives enable photoinitiator-free photocrosslinking without generating free radicals, thereby reducing cytotoxic risks and facilitating easier clinical translation compared to existing approaches. They are compatible with steam sterilization and show promise for extrusion-based techniques like bioprinting and injectability. Through mechanical characterization and biological assessments, the interactions between the biopolymers at different ratios and their effect on encapsulated cells were studied, providing insights for optimizing future tissue engineering applications.

Radiation damage to a three-dimensional hydrogel model of the brain perivascular niche

Glioblastoma (GBM) is a highly aggressive and recurrent brain cancer characterized by diffuse metastasis at the tumor margins. Radiation therapy is a standard component of current treatment and offers potential for improved patient outcomes. While radiation therapy targets GBM cells in the tumor margins, it may also significantly damage adjacent non-cancerous tissues, leading to reduced quality of life and potentially creating a tumor-supportive microenvironment. The perivascular niche (PVN) in the tumor margins is believed to play a significant role in regulating the glioblastoma stem cell subpopulation as well as serving as a site for cancer recurrence and migration. Understanding the impact of radiation on the PVN can better inform radiation schemes and improve our understanding of GBM recurrence, but is difficult in vivo. Here we adapt a previously developed three-dimensional hydrogel model of the brain perivascular niche to investigate the impact of radiation dosage and delivery rate on perivascular niche properties in vitro. Effects of radiation on vessel architecture can be measured in this hydrogel-based model, suggesting an approach that can provide insight into the effects of radiation on a shorter time scale relative to in vivo experiments.

Dynamically changing extracellular matrix stiffness drives Schwann cell phenotype

Schwann cells (SCs) hold key roles in axonal function and maintenance in the peripheral nervous system (PNS) and are a critical component to the regeneration process following trauma. Following PNS trauma, SCs respond to both physical and chemical signals to modify phenotype and assist in the regeneration of damaged axons and extracellular matrix (ECM). There is currently a lack of knowledge regarding the SC response to dynamic, temporal changes in the ECM brought on by swelling and the development of scar tissue as part of the body's wound-healing process. Thus, this work seeks to utilize a biocompatible, mechanically tunable biomaterial to mimic changes in the microenvironment following injury and over time. Previously, we have reported that ECM cues such as ligand type and substrate stiffness impact SC phenotype and plasticity, which was demonstrated by SCs on mechanically stable biomaterials. However, to better realize SC potential for plasticity following traumatic injury, a UV-tunable polydimethylsiloxane (PDMS) substrate with dynamically changing stiffness was utilized to mimic changes over time in the microenvironment. The dynamic biomaterial showed an increase in stress fibers, greater YAP expression, and fluctuations in c-Jun production in SCs in comparison to stiff and soft static controls. Utilizing biomaterials to better understand the role between temporal mechanical dynamics and SC phenotype holds a very high potential for developing future PNS therapies.

Evaluating the polymerization effectiveness and biocompatibility of bio-sourced, visible light-based photoinitiator systems

The use of photopolymerization is expanding across a multitude of biomedical applications, from drug delivery to bioprinting. Many of these current and emerging photopolymerization systems employ visible light, as motivated by safety and energy efficiency considerations. However, the "library" of visible light initiators is limited compared with the wealth of options available for UV polymerization. Furthermore, the synthesis of traditional photoinitiators relies on diminishing raw materials, and several traditional photoinitiators are considered emerging environmental contaminants. As such, there has been recent focus on identifying and characterizing biologically sourced, visible light-based photoinitiator systems that can be effectively used in photopolymerization applications. In this regard, several bio-sourced molecules have been shown to act as photoinitiators, primarily through Type II photoinitiation mechanisms. However, whether bio-sourced molecules can also act as effective synergists in these reactions remains unknown. In this study, we evaluated the effectiveness of bio-sourced synergist candidates, with a focus on amino acids, due to their amine functional groups, in combination with two bio-sourced photoinitiator molecules: riboflavin and curcumin. We tested the effectiveness of these photoinitiator systems under both violet (405 nm) and blue (460-475 nm) light using photo-rheology. We found that several synergist candidates, namely lysine, arginine, and histidine, increased the polymerization effectiveness of riboflavin when used with both violet and blue light. With curcumin, we found that almost all tested synergist candidates slightly decreased the polymerization effectiveness compared with curcumin alone under both light sources. These results show that bio-sourced molecules have the potential to be used as synergists with bio-sourced photoinitiators in visible light photopolymerization. However, more work must be done to fully characterize these reactions and to investigate more synergist candidates. Ultimately, this information is expected to expand the range of available visible light-based photoinitiator systems and increase their sustainability.

Linoleic Acid Induces Metabolic Reprogramming and Inhibits Oxidative and Inflammatory Effects in Keratinocytes Exposed to UVB Radiation

Linoleic acid (LA), the primary ω-6 polyunsaturated fatty acid (PUFA) found in the epidermis, plays a crucial role in preserving the integrity of the skin's water permeability barrier. Additionally, vegetable oils rich in LA have been shown to notably mitigate ultraviolet (UV) radiation-induced effects, including the production of reactive oxygen species (ROS), cellular damage, and skin photoaging. These beneficial effects are primarily ascribed to the LA in these oils. Nonetheless, the precise mechanisms through which LA confers protection against damage induced by exposure to UVB radiation remain unclear. This study aimed to examine whether LA can restore redox and metabolic equilibria and to assess its influence on the inflammatory response triggered by UVB radiation in keratinocytes. Flow cytometry analysis unveiled the capacity of LA to diminish UVB-induced ROS levels in HaCaT cells. GC/MS-based metabolomics highlighted significant metabolic changes, especially in carbohydrate, amino acid, and glutathione (GSH) metabolism, with LA restoring depleted GSH levels post-UVB exposure. LA also upregulated PI3K/Akt-dependent GCLC and GSS expression while downregulating COX-2 expression. These results suggest that LA induces metabolic reprogramming, protecting against UVB-induced oxidative damage by enhancing GSH biosynthesis via PI3K/Akt signaling. Moreover, it suppresses UVB-induced COX-2 expression in HaCaT cells, making LA treatment a promising strategy against UVB-induced oxidative and inflammatory damage.

Cracking the Code: Reprogramming the Genetic Script in Prokaryotes and Eukaryotes to Harness the Power of Noncanonical Amino Acids

Over 500 natural and synthetic amino acids have been genetically encoded in the last two decades. Incorporating these noncanonical amino acids into proteins enables many powerful applications, ranging from basic research to biotechnology, materials science, and medicine. However, major challenges remain to unleash the full potential of genetic code expansion across disciplines. Here, we provide an overview of diverse genetic code expansion methodologies and systems and their final applications in prokaryotes and eukaryotes, represented by Escherichia coli and mammalian cells as the main workhorse model systems. We highlight the power of how new technologies can be first established in simple and then transferred to more complex systems. For example, whole-genome engineering provides an excellent platform in bacteria for enabling transcript-specific genetic code expansion without off-targets in the transcriptome. In contrast, the complexity of a eukaryotic cell poses challenges that require entirely new approaches, such as striving toward establishing novel base pairs or generating orthogonally translating organelles within living cells. We connect the milestones in expanding the genetic code of living cells for encoding novel chemical functionalities to the most recent scientific discoveries, from optimizing the physicochemical properties of noncanonical amino acids to the technological advancements for their in vivo incorporation. This journey offers a glimpse into the promising developments in the years to come.

Light-based 3D bioprinting technology applied to repair and regeneration of different tissues: A rational proposal for biomedical applications

3D bioprinting technology, a subset of 3D printing technology, is currently witnessing widespread utilization in tissue repair and regeneration endeavors. In particular, light-based 3D bioprinting technology has garnered significant interest and favor. Central to its successful implementation lies the judicious selection of photosensitive polymers. Moreover, by fine-tuning parameters such as light irradiation time, choice of photoinitiators and crosslinkers, and their concentrations, the properties of the scaffolds can be tailored to suit the specific requirements of the targeted tissue repair sites. In this comprehensive review, we provide an overview of commonly utilized bio-inks suitable for light-based 3D bioprinting, delving into the distinctive characteristics of each material. Furthermore, we delineate strategies for bio-ink selection tailored to diverse repair locations, alongside methods for optimizing printing parameters. Ultimately, we present a coherent synthesis aimed at enhancing the practical application of light-based 3D bioprinting technology in tissue engineering, while also addressing current challenges and future prospects.

Mutually Orthogonal Bioorthogonal Reactions: Selective Chemistries for Labeling Multiple Biomolecules Simultaneously

Bioorthogonal click chemistry has played a transformative role in many research fields, including chemistry, biology, and medicine. Click reactions are crucial to produce increasingly complex bioconjugates, to visualize and manipulate biomolecules in living systems and for various applications in bioengineering and drug delivery. As biological (model) systems grow more complex, researchers have an increasing need for using multiple orthogonal click reactions simultaneously. In this review, we will introduce the most common bioorthogonal reactions and discuss their orthogonal use on the basis of their mechanism and electronic or steric tuning. We provide an overview of strategies to create reaction orthogonality and show recent examples of mutual orthogonal chemistry used for simultaneous biomolecule labeling. We end by discussing some considerations for the type of chemistry needed for labeling biomolecules in a system of choice.

Three-Dimensional Bioprinting in Vascular Tissue Engineering and Tissue Vascularization of Cardiovascular Diseases

In the 21st century, significant progress has been made in repairing damaged materials through material engineering. However, the creation of large-scale artificial materials still faces a major challenge in achieving proper vascularization. To address this issue, researchers have turned to biomaterials and three-dimensional (3D) bioprinting techniques, which allow for the combination of multiple biomaterials with improved mechanical and biological properties that mimic natural materials. Hydrogels, known for their ability to support living cells and biological components, have played a crucial role in this research. Among the recent developments, 3D bioprinting has emerged as a promising tool for constructing hybrid scaffolds. However, there are several challenges in the field of bioprinting, including the need for nanoscale biomimicry, the formulation of hydrogel blends, and the ongoing complexity of vascularizing biomaterials, which requires further research. On a positive note, 3D bioprinting offers a solution to the vascularization problem due to its precise spatial control, scalability, and reproducibility compared with traditional fabrication methods. This paper aims at examining the recent advancements in 3D bioprinting technology for creating blood vessels, vasculature, and vascularized materials. It provides a comprehensive overview of the progress made and discusses the limitations and challenges faced in current 3D bioprinting of vascularized tissues. In addition, the paper highlights the future research directions focusing on the development of 3D bioprinting techniques and bioinks for creating functional materials.

Target identification of small molecules: an overview of the current applications in drug discovery

Target identification is an essential part of the drug discovery and development process, and its efficacy plays a crucial role in the success of any given therapy. Although protein target identification research can be challenging, two main approaches can help researchers make significant discoveries: affinity-based pull-down and label-free methods. Affinity-based pull-down methods use small molecules conjugated with tags to selectively isolate target proteins, while label-free methods utilize small molecules in their natural state to identify targets. Target identification strategy selection is essential to the success of any drug discovery process and must be carefully considered when determining how to best pursue a specific project. This paper provides an overview of the current target identification approaches in drug discovery related to experimental biological assays, focusing primarily on affinity-based pull-down and label-free approaches, and discusses their main limitations and advantages.

Light-regulated RNA interference induced by p-hydroxyphenacyl-modified siRNA in mammalian cells

siRNA is an important tool for modulating gene expression in current biomedical research. It would be highly desirable for siRNA to respond to an external stimulus. In this paper, we report a convenient, photolabile caging agent to regulate siRNA functions. 2-bromo-4'-hydroxyacetophenone (BHAP) can readily modify phosphorothioate backbones and inhibit siRNAs. Mild UV irradiation will cleave the modifying moiety to generate natural nucleic acid backbones, thus activating siRNA functions. Such modification is conveniently conducted in an aqueous solution with high efficiency and is cost-effective and scalable. This approach provides a convenient tool for the controlled regulation of gene expression by deploying minimal usage of complex organic synthesis for site-specific installation of the caging group to siRNA unlike previous reported works that required a series of intricate organic synthesis and cumbersome purification techniques to achieve similar aims. This study will open new doors for optochemical regulation of a variety of genes by pHP caging group in mammalian cell culture.

Advanced strategies to overcome the challenges of bacteriophage-based antimicrobial treatments in food and agricultural systems

Bacteriophages (phages), highly prevalent in aquatic and terrestrial environments, have emerged as novel antimicrobial agents in food and agricultural systems. Owing to their efficient and unique infection mechanism, phages offer an alternative to antibiotic therapy as they specifically target their host bacteria without causing antibiotic resistance. However, the real-world applications of phages as antimicrobials are still limited due to their low survivability under harsh conditions and reduced antimicrobial efficacy. There is an unmet need to understand the challenges of using phages in food and agricultural systems and potential strategies to enhance their stability and delivery. This review overviews the challenges of using phages, including acidic conditions, improper temperatures, UV-light irradiation, desiccation, and inefficient delivery. It also summarizes novel strategies such as encapsulation, embedding, and immobilization, which enable improved viability and enhanced delivery. The protein capsid and nucleic acid components of phages are delicate and sensitive to physicochemical stresses. Incorporating phages into biocompatible materials can provide a physical barrier for improving phage stability and enhancing phage delivery, resulting in a high antimicrobial efficacy. In conclusion, the development of phage delivery systems can significantly overcome the challenges associated with phage treatments and reduce the risk of foodborne diseases in the industry.

Preclinical Testing Techniques: Paving the Way for New Oncology Screening Approaches

Prior to clinical trials, preclinical testing of oncology drug candidates is performed by evaluating drug candidates with in vitro and in vivo platforms. For in vivo testing, animal models are used to evaluate the toxicity and efficacy of drug candidates. However, animal models often display poor translational results as many drugs that pass preclinical testing fail when tested with humans, with oncology drugs exhibiting especially poor acceptance rates. The FDA Modernization Act 2.0 promotes alternative preclinical testing techniques, presenting the opportunity to use higher complexity in vitro models as an alternative to in vivo testing, including three-dimensional (3D) cell culture models. Three-dimensional tissue cultures address many of the shortcomings of 2D cultures by more closely replicating the tumour microenvironment through a combination of physiologically relevant drug diffusion, paracrine signalling, cellular phenotype, and vascularization that can better mimic native human tissue. This review will discuss the common forms of 3D cell culture, including cell spheroids, organoids, organs-on-a-chip, and 3D bioprinted tissues. Their advantages and limitations will be presented, aiming to discuss the use of these 3D models to accurately represent human tissue and as an alternative to animal testing. The use of 3D culture platforms for preclinical drug development is expected to accelerate as these platforms continue to improve in complexity, reliability, and translational predictivity.

Fast Reconfigurable Electrode Array Based on Titanium Oxide for Localized Stimulation of Cultured Neural Network

Planar microelectrode arrays have become standard tools for in vitro neural-network analysis. However, these predefined micropatterned devices lack adaptability to target-specific cells within a cultured network. Herein, we fabricated a reconfigurable TiO₂ electrode array with an anatase-brookite bicrystalline polymorphous mesoporous layer. Because of its selective absorption of ultraviolet (UV) light and corresponding photoconductivity, TiO₂ electrode array was identified as a promising tool for high-resolution light-addressing. The TiO₂ film was used as a semitransparent semiconductor with a high R_off/R_on ratio of 10⁵ and a fast response time of 400 ms. In addition, the effect of UV radiation on the resistance of the TiO₂ film over 30 d in an aqueous environment was analyzed, with the film exhibiting high stability. An arbitrary UV pattern was applied to a reconfigurable TiO₂ electrode using a digital micromirror device (DMD), affording highly localized neural stimulation at the single-cell level. The reconfigurable TiO₂ electrode with a patterned indium tin oxide (ITO) substrate enabled the independent connection of up to 60 points with external stimulators and signal recorders. We believe this technique would be helpful for electrophysiological research requiring the analysis of cell and neural-network features using a highly localized neural interface.

Study of cell protective effects of alcohols against UV-C radiation and comparison to gamma radiation

A singlet oxygen production was monitored using a singlet oxygen sensor green chemical probe; reaction of chemical probe with singlet oxygen produces a fluorescent endoperoxide. Adding ethanol to the irradiated system resulted in decrease of the fluorescence signal, which indicates a decrease in concentration of singlet oxygen formed under UV-C irradiation. Thus, ethanol was likely to quench singlet oxygen in a system under study. This quenching did not occur with the use of methanol. When irradiating E. coli cells in the presence of ethanol and Rose Bengal for higher singlet oxygen production, there was a greater reduction in the radiation sensitivity of the cells compared to the system without Rose Bengal. Higher concentration of ethanol caused greater protection of cells; thus, it is likely that ethanol can scavenge singlet oxygen and provide a partial protection of bacteria from the effects of UV-C radiation. These results were compared with previously published data where the bacteria were irradiated by gamma radiation in presence of alcohols.

Integration of hydrogels in microfabrication processes for bioelectronic medicine: Progress and outlook

Recent research aiming at the development of electroceuticals for the treatment of medical conditions such as degenerative diseases, cardiac arrhythmia and chronic pain, has given rise to microfabricated implanted bioelectronic devices capable of interacting with host biological tissues in synergistic modalities. Owing to their multimodal affinity to biological tissues, hydrogels have emerged as promising interface materials for bioelectronic devices. Here, we review the state-of-the-art and forefront in the techniques used by research groups for the integration of hydrogels into the microfabrication processes of bioelectronic devices, and present the manufacturability challenges to unlock their further clinical deployment.

Improving printability of hydrogel-based bio-inks for thermal inkjet bioprinting applications via saponification and heat treatment processes

Material jetting bioprinting is a highly promising three-dimensional (3D) bioprinting technique that facilitates drop-on-demand (DOD) deposition of biomaterials and cells at pre-defined positions with high precision and resolution. A major challenge that hinders the prevalent use of the material jetting bioprinting technique is due to its limited range of printable hydrogel-based bio-inks. As a proof-of-concept, further modifications were made to gelatin methacrylate (GelMA), a gold-standard bio-ink, to improve its printability in a thermal inkjet bioprinter (HP Inc. D300e Digital Dispenser). A two-step modification process comprising saponification and heat treatment was performed; the GelMA bio-ink was first modified via a saponification process under highly alkali conditions to obtain saponified GelMA (SP-GelMA), followed by heat treatment via an autoclaving process to obtain heat-treated SP-GelMA (HSP-GelMA). The bio-ink modification process was optimized by evaluating the material properties of the GelMA bio-inks via rheological characterization, the bio-ink crosslinking test, nuclear magnetic resonance (NMR) spectroscopy and the material swelling ratio after different numbers of heat treatment cycles (0, 1, 2 and 3 cycles). Lastly, size-exclusion chromatography with multi-angle light scattering (SEC-MALS) was performed to determine the effect of heat treatment on the molecular weight of the bio-inks. In this work, the 4% H2SP-GelMA bio-inks (after 2 heat treatment cycles) demonstrated good printability and biocompatibility (in terms of cell viability and proliferation profile). Furthermore, thermal inkjet bioprinting of the modified hydrogel-based bio-ink (a two-step modification process comprising saponification and heat treatment) via direct/indirect cell patterning is a facile approach for potential fundamental cell-cell and cell-material interaction studies.

Measuring and modeling the influence of salinity change on the transport behaviour of Escherichia coli through quartz sand

Pathogenic bacteria can be discharged in the environment through natural as well as anthropogenic activities. Once in the environment, they may contaminate soil and sediments and migrate towards water bodies. Transient chemical conditions may occur in soil/sediments and favor mobilization of bacteria, e.g., upon the reduction of salinity (or ionic strength). However, the magnitude of this phenomenon and its relationship with particle size is not well understood, yet. In this work, we investigated the transport of Escherichia coli under variable salinity conditions (between 1 and 20 part per thousand, ppt) and for different soil grain sizes (between 150 and 710 μm). A model developed in our group was applied in this work. It couples bacteria and salinity transport equations in order to account for transient water composition in the description of bacteria migration. The model was calibrated and validated with laboratory experiments. The tests were monitored continuously with UV-Vis spectroscopy, which allowed to record highly resolved concentration fronts. The results show that salinity increases the retardation of the bacteria. Upon salinity drop, a release of bacteria occurs forming a peak whose magnitude increases with salinity change. This effect becomes more important as the grain size decreases. Simulations suggest that the dominant retention mechanism is attachment for coarse sand and straining for fine sand. The retention can be reversed as the salinity is reduced causing a sudden bacteria mobilization. Such a behaviour may have important implications on microbial contamination of water bodies when soil/sediments undergo transient chemical conditions.

Light-induced high-efficient cellular production of immune functional extracellular vesicles

Extracellular vesicle (EV)-based therapies and vaccines are emerging. However, employment at the scale for population-based dose development is always a huge bottleneck. In order to overcome such a roadblock, we introduce a simple and straightforward approach for promoting cellular production of dendritic cell derived EVs (DEVs) by leveraging phototherapy based light induction. Under the optimization of light wavelengths, intensities, and exposure times, we achieved more than 13-fold enhancement in DEV production rate, while maintaining good integral quality and immune function from produced EVs. The LED light at 365 nm is optimal to reliably trigger enhanced cellular production of EVs no matter cell line types. Our observation and other reported studies support longer near UV wavelength does not impair cell growth. We conducted a series of investigations in terms of size, zeta potential, morphology, immune surface markers and cytokines, biocompatibility, cellular uptake behaviour, and immune-modulation ability on eliciting cellular responses in vitro. We also validated the biodistribution, immunogenicity, and administration safety using light-promoted DEVs in mice models from both male and female genders. Overall data supports that light promoted DEVs are highly immune functional with great biocompatibility for serving as good therapeutic platforms. The in vivo animal study also demonstrated light-promoted DEVs are as well tolerated as native DEVs, with no safety concerns. Taken together, the data supports that light promoted DEVs are in excellent quality, high biocompatibility, in vivo tolerant, and viable for serving as an ideal therapeutic platform in scalable production.

Enhanced fluorescence from semiconductor quantum dot-labelled cells excited at 280 nm

Semiconductor quantum dots (QDs) have significant advantages over more traditional fluorophores used in fluorescence microscopy including reduced photobleaching, long-term photostability and high quantum yields, but due to limitations in light sources and optics, are often excited far from their optimum excitation wavelengths in the deep-UV. Here, we present a quantitative comparison of the excitation of semiconductor QDs at a wavelength of 280 nm, compared to the longer wavelength of 365 nm, within a cellular environment. We report increased fluorescence intensity and enhanced image quality when using 280 nm excitation compared to 365 nm excitation for cell imaging across multiple datasets, with a highest average fluorescence intensity increase of 3.59-fold. We also find no significant photobleaching of QDs associated with 280 nm excitation and find that on average, ~80% of cells can tolerate exposure to high-intensity 280 nm irradiation over a 6-hour period.

Tuning Superfast Curing Thiol-Norbornene-Functionalized Gelatin Hydrogels for 3D Bioprinting

Photocurable gelatin-based hydrogels have established themselves as powerful bioinks in tissue engineering due to their excellent biocompatibility, biodegradability, light responsiveness, thermosensitivity and bioprinting properties. While gelatin methacryloyl (GelMA) has been the gold standard for many years, thiol-ene hydrogel systems based on norbornene-functionalized gelatin (GelNB) and a thiolated crosslinker have recently gained increasing importance. In this paper, a highly reproducible water-based synthesis of GelNB is presented, avoiding the use of dimethyl sulfoxide (DMSO) as organic solvent and covering a broad range of degrees of functionalization (DoF: 20% to 97%). Mixing with thiolated gelatin (GelS) results in the superfast curing photoclick hydrogel GelNB/GelS. Its superior properties over GelMA, such as substantially reduced amounts of photoinitiator (0.03% (w/v)), superfast curing (1-2 s), higher network homogeneity, post-polymerization functionalization ability, minimal cross-reactivity with cellular components, and improved biocompatibility of hydrogel precursors and degradation products lead to increased survival of primary cells in 3D bioprinting. Post-printing viability analysis revealed excellent survival rates of > 84% for GelNB/GelS bioinks of varying crosslinking density, while cell survival for GelMA bioinks is strongly dependent on the DoF. Hence, the semisynthetic and easily accessible GelNB/GelS hydrogel is a highly promising bioink for future medical applications and other light-based biofabrication techniques.

Wearable patch delivery system for artificial pancreas health diagnostic-therapeutic application: A review

The advanced stimuli-responsive approaches for on-demand drug delivery systems have received tremendous attention as they have great potential to be integrated with sensing and multi-functional electronics on a flexible and stretchable single platform (all-in-one concept) in order to develop skin-integration with close-loop sensation for personalized diagnostic and therapeutic application. The wearable patch pumps have evolved from reservoir-based to matrix patch and drug-in-adhesive (single-layer or multi-layer) type. In this review, we presented the basic requirements of an artificial pancreas, surveyed the design and technologies used in commercial patch pumps available on the market and provided general information about the latest wearable patch pump. We summarized the various advanced delivery strategies with their mechanisms that have been developed to date and representative examples. Mechanical, electrical, light, thermal, acoustic and glucose-responsive approaches on patch form have been successfully utilized in the controllable transdermal drug delivery manner. We highlighted key challenges associated with wearable transdermal delivery systems, their research direction and future development trends.

A highly efficient microwave-assisted synthesis of an LED-curable methacrylated gelatin for bio applications

This study deals with the development of an LED-curable methacrylated gelatin (GelMA) synthesis via microwave (MW) irradiation with a reaction and purification time-, energy-, and methacrylation reagent-saving approach. To investigate the efficiency of MW irradiation in GelMA synthesis, characteristics of the GelMAs prepared by using glycidyl methacrylate (GMA) or methacrylic anhydride (MA) via the MW-assisted (MWA) method were compared comprehensively with those synthesized via the conventional heating method. Moreover, MWA reaction conditions were optimized in terms of methacrylation reagent concentrations (C), reaction time (t), and MW power (P). Characterization and assessment of the GelMAs were conducted with 1H NMR, FT-IR, and Raman spectroscopy along with physical-mechanical, thermal, and hydrophilicity analysis. The results demonstrated that the MWA synthesized GMA-GelMA hydrogels were possessed of increased methacrylation degree (MD), gel fraction (GF), tensile strength (TS), elongation at break (EB), glass transition temperature (T g), and water contact angle (WCA) as well as decreased swelling degree (SD) values in comparison to those of MA-GelMA and GMA-GelMA hydrogels prepared via the MWA and conventional method, respectively. Enhanced properties of the MWA synthesized GMA-hydrogels suggested an effective methacryloyl conjugation leading to a greater amount of covalent crosslinking density justified by the dipolar moment calculations. Optimal GMA C, t, P, and purification time for a highly crosslinked GelMA hydrogel (MD: 96.1%, GF: 98.3%, SD: 10.11%, TS: 6.7 MPa, EB: 175.2%, T g: 75.34 °C, and WCA: 72.22°) were found to be a 5 times molar excess over the primary amine groups of gelatin, 5 min, 500 W, and 24 h, respectively. Thus, the optimized MW conditions offer a promising green method to prepare GelMAs for bio applications.

Monitoring the biochemical changes occurring to human keratinocytes exposed to solar radiation by Raman spectroscopy

Solar radiation exposure is recognised to be a significant contributor to the development of skin cancer. Monitoring the simultaneous and consecutive mechanisms of interaction could provide a greater understanding of the process of photocarcinogenesis. This work presents an analysis of the biochemical and morphological changes occurring to immortalised human epithelial keratinocyte (HaCaT) cell cultures exposed to simulated solar radiation (SSR). Cell viability was monitored with the aid of the Alamar Blue assay, morphological examination was done with haematoxylin and eosin staining (H&E) and changes to the biochemical constituents (nucleic acids and proteins) as a result of the radiation insult were demonstrated through a combination of Raman microspectroscopy and multivariate analysis of spectral patterns. The spectral results suggest that SSR induces changes to the conformational structure of DNA as an immediate result of the radiation, whereas alteration in the protein signature is mostly seen as a later response.

Fundamentals of light-cell-polymer interactions in photo-cross-linking based bioprinting

Biofabrication technologies that use light for polymerization of biomaterials have made significant progress in the quality, resolution, and generation of precise complex tissue structures. In recent years, the evolution of these technologies has been growing along with the development of new photocurable resins and photoinitiators that are biocompatible and biodegradable with bioactive properties. Such evolution has allowed the progress of a large number of tissue engineering applications. Flexibility in the design, scale, and resolution and wide applicability of technologies are strongly dependent on the understanding of the biophysics involved in the biofabrication process. In particular, understanding cell–light interactions is crucial when bioprinting using cell-laden biomaterials. Here, we summarize some theoretical mechanisms, which condition cell response during bioprinting using light based technologies. We take a brief look at the light–biomaterial interaction for a better understanding of how linear effects (refraction, reflection, absorption, emission, and scattering) and nonlinear effects (two-photon absorption) influence the biofabricated tissue structures and identify the different parameters essential for maintaining cell viability during and after bioprinting.

One-Step Photoactivation of a Dual-Functionalized Bioink as Cell Carrier and Cartilage-Binding Glue for Chondral Regeneration

Cartilage defects can result in pain, disability, and osteoarthritis. Hydrogels providing a chondroregeneration-permissive environment are often mechanically weak and display poor lateral integration into the surrounding cartilage. This study develops a visible-light responsive gelatin ink with enhanced interactions with the native tissue, and potential for intraoperative bioprinting. A dual-functionalized tyramine and methacryloyl gelatin (GelMA-Tyr) is synthesized. Photo-crosslinking of both groups is triggered in a single photoexposure by cell-compatible visible light in presence of tris(2,2'-bipyridyl)dichlororuthenium(II) and sodium persulfate as initiators. Neo-cartilage formation from embedded chondroprogenitor cells is demonstrated in vitro, and the hydrogel is successfully applied as bioink for extrusion-printing. Visible light in situ crosslinking in cartilage defects results in no damage to the surrounding tissue, in contrast to the native chondrocyte death caused by UV light (365-400 nm range), commonly used in biofabrication. Tyramine-binding to proteins in native cartilage leads to a 15-fold increment in the adhesive strength of the bioglue compared to pristine GelMA. Enhanced adhesion is observed also when the ink is extruded as printable filaments into the defect. Visible-light reactive GelMA-Tyr bioinks can act as orthobiologic carriers for in situ cartilage repair, providing a permissive environment for chondrogenesis, and establishing safe lateral integration into chondral defects.

On Demand Light-Degradable Polymers Based on 9,10-Dialkoxyanthracenes

Light induced degradation of polymers has drawn increasing interest due to the need for externally controllable modulation of materials properties. However, the portfolio of polymers, that undergo precisely controllable degradation, is limited and typically requires UV light. A novel class of backbone-degradable polymers that undergo aerobic degradation in the presence of visible light, yet remain stable against broad-spectrum light under anaerobic conditions is reported. In this design, the polymer backbone is comprised of 9,10-dialkoxyanthracene units that are selectively cleaved by singlet oxygen in the presence of green light as confirmed by NMR and UV/vis spectroscopy. The resulting polymers have been processed by electrohydrodynamic (EHD) co-jetting into bicompartmental microfibers, where one hemisphere is selectively degraded on demand.

Zweigelt and Niagara skin extracts suppress cyclobutane pyrimidine dimer formation due to UV irradiation in NHEK cells: first attempt

The grape skins after pressing the juice are a major problem for winery. However, because it contains a large amount of polyphenols, development of effective usages are expected to construct sustainable waste use. In this study, we examined whether grape skin extract is effective for recovery of DNA damage caused by UV irradiation. Extract from Zweigelt and Niagara skin was prepared by methanol, and UV irradiation was performed at 10 mJ/cm² (250 nm) and 15 mJ/cm² (290 nm) using human normal skin cells. As results, the decreased cell viability due to UV irradiation was improved by adding Niagara or Zweigelt skin extract. On the other hand, cyclobutane pyrimidine dimer production due to UV irradiation decreased significantly by Niagara or Zweigelt extract. In addition, the effects of grape skin extracts on the expression of sirtuin gene were also examined.

Vat polymerization-based bioprinting-process, materials, applications and regulatory challenges

Over the years, the field of bioprinting has attracted attention for its highly automated fabrication system that enables the precise patterning of living cells and biomaterials at pre-defined positions for enhanced cell-matrix and cell-cell interactions. Notably, vat polymerization (VP)-based bioprinting is an emerging bioprinting technique for various tissue engineering applications due to its high fabrication accuracy. Particularly, different photo-initiators (PIs) are utilized during the bioprinting process to facilitate the crosslinking mechanism for fabrication of high-resolution complex tissue constructs. The advancements in VP-based printing have led to a paradigm shift in fabrication of tissue constructs from cell-seeding of tissue scaffolds (non-biocompatible fabrication process) to direct bioprinting of cell-laden tissue constructs (biocompatible fabrication process). This paper, presenting a first-time comprehensive review of the VP-based bioprinting process, provides an in-depth analysis and comparison of the various biocompatible PIs and highlights the important considerations and bioprinting requirements. This review paper reports a detailed analysis of its printing process and the influence of light-based curing modality and PIs on living cells. Lastly, this review also highlights the significance of VP-based bioprinting, the regulatory challenges and presents future directions to transform the VP-based printing technology into imperative tools in the field of tissue engineering and regenerative medicine. The readers will be informed on the current limitations and achievements of the VP-based bioprinting techniques. Notably, the readers will realize the importance and value of highly-automated platforms for tissue engineering applications and be able to develop objective viewpoints towards this field.

ETHANOL AS A MODIFIER OF RADIATION SENSITIVITY OF LIVING CELLS AGAINST UV-C RADIATION

The protection of Escherichia coli bacteria and the yeast Saccharomyces cerevisiae against UV-C radiation by ethanol was studied. It was found that the fraction of surviving cells increases with increasing ethanol concentration. The specific protection depends on the dose rate, concentration range of ethanol, and it is higher for yeast compared to the bacteria.

Recent Strategies in Extrusion-Based Three-Dimensional Cell Printing toward Organ Biofabrication

Reconstructing human organs is one of the ultimate goals of the medical industry. Organ printing utilizing three-dimensional cell printing technology to fabricate artificial living organ equivalents has shed light on the advancement of this field into a new era. Among three currently applied techniques (inkjet, laser-assisted, and extrusion-based), extrusion-based cell printing (ECP) has evoked the majority of interest due to its low cost, wide range of applicable materials, and ease of spatial and depositional controllability. Major challenges in organ reconstruction include difficulties in precisely fabricating complex structural features, creating perfusable and functional vasculatures, and mimicking biophysical and biochemical characteristics in the printed constructs. In this review, we describe the merits and limitations of ECP for organ fabrication and discuss its recent advances aimed at overcoming these challenges. In addition, we delineate the expected future techniques for printing live tissue or organ substitutes.

Spatio-Temporal Control of Cell Adhesion: Toward Programmable Platforms to Manipulate Cell Functions and Fate

Biophysical and biochemical signals of material surfaces potently regulate cell functions and fate. In particular, micro- and nano-scale patterns of adhesion signals can finely elicit and affect a plethora of signaling pathways ultimately affecting gene expression, in a process known as mechanotransduction. Our fundamental understanding of cell-material signals interaction and reaction is based on static culturing platforms, i.e., substrates exhibiting signals whose configuration is time-invariant. However, cells in-vivo are exposed to arrays of biophysical and biochemical signals that change in time and space and the way cells integrate these might eventually dictate their behavior. Advancements in fabrication technologies and materials engineering, have recently enabled the development of culturing platforms able to display patterns of biochemical and biophysical signals whose features change in time and space in response to external stimuli and according to selected programmes. These dynamic devices proved to be particularly helpful in shedding light on how cells adapt to a dynamic microenvironment or integrate spatio-temporal variations of signals. In this work, we present the most relevant findings in the context of dynamic platforms for controlling cell functions and fate in vitro. We place emphasis on the technological aspects concerning the fabrication of platforms displaying micro- and nano-scale dynamic signals and on the physical-chemical stimuli necessary to actuate the spatio-temporal changes of the signal patterns. In particular, we illustrate strategies to encode material surfaces with dynamic ligands and patterns thereof, topographic relieves and mechanical properties. Additionally, we present the most effective, yet cytocompatible methods to actuate the spatio-temporal changes of the signals. We focus on cell reaction and response to dynamic changes of signal presentation. Finally, potential applications of this new generation of culturing systems for in vitro and in vivo applications, including regenerative medicine and cell conditioning are presented.

3D-Bioprinted Osteoblast-Laden Nanocomposite Hydrogel Constructs with Induced Microenvironments Promote Cell Viability, Differentiation, and Osteogenesis both In Vitro and In Vivo

An osteoblast-laden nanocomposite hydrogel construct, based on polyethylene glycol diacrylate (PEGDA)/laponite XLG nanoclay ([Mg5.34Li0.66Si8O20(OH)4]Na0.66, clay)/hyaluronic acid sodium salt (HA) bio-inks, is developed by a two-channel 3D bioprinting method. The novel biodegradable bio-ink A, comprised of a poly(ethylene glycol) (PEG)-clay nanocomposite crosslinked hydrogel, is used to facilitate 3D-bioprinting and enables the efficient delivery of oxygen and nutrients to growing cells. HA with encapsulated primary rat osteoblasts (ROBs) is applied as bio-ink B with a view to improving cell viability, distribution uniformity, and deposition efficiency. The cell-laden PEG-clay constructs not only encapsulated osteoblasts with more than 95% viability in the short term but also exhibited excellent osteogenic ability in the long term, due to the release of bioactive ions (magnesium ions, Mg2+ and silicon ions, Si4+), which induces the suitable microenvironment to promote the differentiation of the loaded exogenous ROBs, both in vitro and in vivo. This 3D-bioprinting method holds much promise for bone tissue regeneration in terms of cell engraftment, survival, and ultimately long-term function.

Ultraviolet B Light Emitting Diodes (LEDs) Are More Efficient and Effective in Producing Vitamin D3 in Human Skin Compared to Natural Sunlight

Vitamin D, the sunshine vitamin is important for health. Those with fat malabsorption disorders malabsorb vitamin D and thus must rely on cutaneous production of vitamin D₃. Vitamin D₃ is generated secondary to exposure to ultraviolet B (UVB) radiation (whether from the sun or from an artificial source). Light emitting diodes (LEDs) have been developed to emit ultraviolet radiation. Little is known about the efficiency of UVB emitting LEDs tuned to different wavelengths for producing vitamin D₃ in human skin. Ampoules containing 7-dehydrocholesterol were exposed to a LED that emitted a peak wavelength at 293, 295, 298 or 305 nm to determine their efficiency to produce previtamin D₃. The 293 nm LED was best suited for evaluating its effectiveness for producing vitamin D in human skin due to the shorter exposure time. This LED was found to be 2.4 times more efficient in producing vitamin D₃ in human skin than the sun in less than 1/60^th the time. This has significant health implications for medical device development in the future that can be used for providing vitamin D supplementation to patients with fat malabsorption syndromes as well as patients with other metabolic abnormalities including patients with chronic kidney disease.

Wavelength-normalized spectroscopic analysis of Staphylococcus aureus and Pseudomonas aeruginosa growth rates

Optical density (OD) measurements are the standard approach used in microbiology for characterizing bacteria concentrations in culture media. OD is based on measuring the optical absorbance of a sample at a single wavelength, and any error will propagate through all calculations, leading to reproducibility issues. Here, we use the conventional OD technique to measure the growth rates of two different species of bacteria, Pseudomonas aeruginosa and Staphylococcus aureus. The same samples are also analyzed over the entire UV-Vis wavelength spectrum, allowing a distinctly different strategy for data analysis to be performed. Specifically, instead of only analyzing a single wavelength, a multi-wavelength normalization process is implemented. When the OD method is used, the detected signal does not follow the log growth curve. In contrast, the multi-wavelength normalization process minimizes the impact of bacteria byproducts and environmental noise on the signal, thereby accurately quantifying growth rates with high fidelity at low concentrations.

Biomarkers of mercury exposure in the Amazon

Mercury exposure in the Amazon has been studied since the 1980s decade and the assessment of human mercury exposure in the Amazon is difficult given that the natural occurrence of this metal is high and the concentration of mercury in biological samples of this population exceeds the standardized value of normality established by WHO. Few studies have focused on the discovery of mercury biomarkers in the region's population. In this way, some studies have used genetics as well as immunological and cytogenetic tools in order to find a molecular biomarker for assessing the toxicological effect of mercury in the Amazonian population. Most of those studies focused attention on the relation between mercury exposure and autoimmunity and, because of that, they will be discussed in more detail. Here we introduce the general aspects involved with each biomarker that was studied in the region in order to contextualize the reader and add information about the Amazonian life style and health that may be considered for future studies. We hope that, in the future, the toxicological studies in this field use high technological tools, such as the next generation sequencing and proteomics skills, in order to comprehend basic questions regarding the metabolic route of mercury in populations that are under constant exposure, such as in the Amazon.

Effect of Tinospora cordifolia on the reduction of ultraviolet radiation-induced cytotoxicity and DNA damage in PC12 cells

The safety of Tinospora cordifolia and its potential to protect against ultraviolet radiation-induced cytotoxicity and DNA damage in PC12 cells were investigated. To evaluate the safety of T. cordifolia, cell viability and agarose gel electrophoresis were carried out using PC12 cells treated with 0 to 100 μg mL(-1) of methanol extract of T. cordifolia. T. cordifolia extracts did not show cytotoxicity ranging 0 to 100 μg mL(-1). In addition, T. cordifolia extracts significantly increased cell viability at 1 ng, 10 ng and 1 μg mL(-1) concentrations in serum-deprived medium compared to control. To confirm the protective role against UV-induced damage, PC12 cells alone or in the presence of 10 ng, 100 ng, or 1 μg mL(-1) of T. cordifolia extract were exposed to 250, 270 and 290 nm of UV radiation, which corresponded to doses of 120, 150 and 300 mJ cm(-2), respectively. Treatment with T. cordifolia extracts significantly increased the cell survival rate irradiated at 290 nm. In addition, T. cordifolia extracts significantly reduced cyclobutane pyrimidine dimer formation induced by UV irradiation at all wavelengths. In conclusion, T. cordifolia is not toxic and safe for cells. Our findings can support its application as phototherapy in the medical sector.