Smart nano-inks based on natural food colorant for screen-printing of dynamic shelf life of shrimp

Intelligent packaging embedded with food freshness indicators can monitor food quality and be deployed for food safety and cutting food waste. The innovative nano-inks for dynamic shelf-life printing based on natural food colorant with application in real-time monitoring of shrimp freshness were prepared. Co-assembly of saffron petal anthocyanin (SPA) with hydrophobic curcumin (Cur) into chitin nano-scaffold (particle sizes around 26 ± 8 nm) could deliver hindering SPA leaching, confirmed by FT-IR, FE-SEM, AFM, and color stability test. The best response to pH-sensitivity was found in a ratio of (1:4) Cur/SPA (30% (v/w) in ChNFs that was correlated with the chemical and microbial changes of shrimp during shrimp freshness. However, smart screen-printed inks signified higher responsiveness to pH changes than FFI films. Therefore, smart-printed indicators introduced the excellent potential for a short response time, easy, cost-effective, eco-friendly, co-assembly, great color stabilities, and lifetime for nondestructively freshness monitoring foods and supplements.

Effect of a collagen peptide-fish oil high internal phase emulsion on the printability and gelation of 3D-printed surimi gel inks

The effect of a high internal phase emulsion (HIPE) on three-dimensional-printed surimi gel inks was studied. Increasing the concentration of collagen peptide decreased the particle size of HIPE droplets and improved the viscoelasticity and stability. For example, when the collagen peptide concentration was 5 wt%, the viscoelasticity of the HIPE was high, as indicated by the presence of small and uniform particles, which formed a monolayer in the outer layer of the oil droplets to form stable a HIPE. A HIPE was used as the filling material to fill the surimi gel network, which reduced the porosity of the network. Surimi protein and peptides have dual emulsifying effects on the stabilization of oil. After adding the emulsion, the texture, gel properties and rheological properties of the surimi were reduced, and its printing adaptability was improved. This study provides new ideas for the production of surimi and its application in 3D printing.

Graphene derivative-based ink advances inkjet printing technology for fabrication of electrochemical sensors and biosensors

The field of biosensing would significantly benefit from a disruptive technology enabling flexible manufacturing of uniform electrodes. Inkjet printing holds promise for this, although realizing full electrode manufacturing with this technology remains challenging. We introduce a nitrogen-doped carboxylated graphene ink (NGA-ink) compatible with commercially available printing technologies. The water-based and additive-free NGA-ink was utilized to produce fully inkjet-printed electrodes (IPEs), which demonstrated successful electrochemical detection of the important neurotransmitter dopamine. The cost-effectiveness of NGA-ink combined with a total cost per electrode of $0.10 renders it a practical solution for customized electrode manufacturing. Furthermore, the high carboxyl group content of NGA-ink (13 wt%) presents opportunities for biomolecule immobilization, paving the way for the development of advanced state-of-the-art biosensors. This study highlights the potential of NGA inkjet-printed electrodes in revolutionizing sensor technology, offering an affordable, scalable alternative to conventional electrochemical systems.

Modulus-tunable multifunctional hydrogel ink with nanofillers for 3D-Printed soft electronics

Seamless integration and conformal contact of soft electronics with tissue surfaces have emerged as major challenges in realizing accurate monitoring of biological signals. However, the mechanical mismatch between the electronics and biological tissues impedes the conformal interfacing between them. Attempts have been made to utilize soft hydrogels as the bioelectronic materials to realize tissue-comfortable bioelectronics. However, hydrogels have several limitations in terms of their electrical and mechanical properties. In this study, we present the development of a 3D-printable modulus-tunable hydrogel with multiple functionalities. The hydrogel has a cross-linked double network, which greatly improves its mechanical properties. Functional fillers such as XLG or functionalized carbon nanotubes (fCNT) can be incorporated into the hydrogel to provide tunable mechanics (Young's modulus of 10-300 kPa) and electrical conductivity (electrical conductivity of ∼20 S/m). The developed hydrogel exhibits stretchability (∼1000% strain), self-healing ability (within 5 min), toughness (400-731 kJ/m3) viscoelasticity, tissue conformability, and biocompatibility. Upon examining the rheological properties in the modulated region, hydrogels can be 3D printed to customize the shape and design of the bioelectronics. These hydrogels can be fabricated into ring-shaped strain sensors for wearable sensor applications.

Recent advances on enhancing 3D printing quality of protein-based inks: A review

3D printing is an additive manufacturing technology that locates constructed models with computer-controlled printing equipment. To achieve high-quality printing, the requirements on rheological properties of raw materials are extremely restrictive. Given the special structure and high modifiability under external physicochemical factors, the rheological properties of proteins can be easily adjusted to suitable properties for 3D printing. Although protein has great potential as a printing material, there are many challenges in the actual printing process. This review summarizes the technical considerations for protein-based ink 3D printing. The physicochemical factors used to enhance the printing adaptability of protein inks are discussed. The post-processing methods for improving the quality of 3D structures are described, and the application and problems of fourth dimension (4D) printing are illustrated. The prospects of 3D printing in protein manufacturing are presented to support its application in food and cultured meat. The native structure and physicochemical factors of proteins are closely related to their rheological properties, which directly link with their adaptability for 3D printing. Printing parameters include extrusion pressure, printing speed, printing temperature, nozzle diameter, filling mode, and density, which significantly affect the precision and stability of the 3D structure. Post-processing can improve the stability and quality of 3D structures. 4D design can enrich the sensory quality of the structure. 3D-printed protein products can meet consumer needs for nutritional or cultured meat alternatives.

Rheological insights into 3D printing of drug products: Drug nanocrystal-poloxamer gels for semisolid extrusion

The importance of ink rheology to the outcome of 3D printing is well recognized. However, rheological properties of printing inks containing drug nanocrystals have not been widely investigated. Therefore, the objective of this study was to establish a correlation between the composition of nanocrystal printing ink, the ink rheology, and the entire printing process. Indomethacin was used as a model poorly soluble drug to produce nanosuspensions with improved solubility properties through particle size reduction. The nanosuspensions were further developed into semisolid extrusion 3D printing inks with varying nanocrystal and poloxamer 407 concentrations. Nanocrystals were found to affect the rheological properties of the printing inks both by being less self-supporting and having higher yielding resistances. During printing, nozzle blockages occurred. Nevertheless, all inks were found to be printable. Finally, the rheological properties of the inks were successfully correlated with various printing and product properties. Overall, these experiments shed new light on the rheological properties of printing inks containing nanocrystals.

Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status

Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.

Time-temperature indicator of hydroxyethyl cellulose ink labels for assessing pork freshness

Pork is widely consumed worldwide, and many consumers now utilize sensory evaluation techniques to determine the freshness of pork when buying it. A color-changing ink label utilizing bromocresol purple (BCP) and N-hydroxyphthalimide (NHPI) had been created to help consumers better and more rapidly determine the freshness of pork while it is stored. The ink was easy to prepare and could be readily transferred to A4 paper using screen printing technology. This study delved deeper into the impact of hydroxyethyl cellulose (HEC) on the functional properties of inks to enhance printing performance. The experiment demonstrated that a 1 % mass fraction of HEC improved thixotropy and facilitated the even distribution of ink on A4 paper, as confirmed by scanning electron microscopy. Screen-printed labels with varying concentrations displayed distinct color change rates when stored at different temperatures, indicating their capability to assess pork freshness. FT-IR, laboratory, and stability tests verified the ink's exceptional color change capabilities and printing attributes. An analysis using the Arrhenius equation revealed a substantial synergistic effect between BCP and NHPI, resulting in improved sensitivity and accuracy of the ink. This study offers a practical and feasible method to monitor the storage quality of pork effectively.

Tattoo inks: evaluation of cellular responses and analysis of some trace metals

After tattoo application, inks remain in the skin, mostly in the dermal layer, and manufacturers use inks that have not been adequately evaluated for safety in tattoo production. In this study, the metal contents (Cd, Hg, Pb, and Cr) of tattoo inks available in the Turkish market were determined and the relationship between cell viability and inflammatory response of the detected metal levels was investigated. Nine tattoo inks (3 colors) from 3 different brands abbreviated as E, I, and W were examined. ICP-MS was used for element analysis. The viability of human keratinocyte cells was determined by the WST-1 assay following ink exposures at various dilutions. IL-18 levels were measured in cell culture supernatant by ELISA method following ink or metal (Cd, Cr, Hg, and Pb) exposures. The concentrations of trace elements were found in inks as follows: Cd, 0.0641-1.3857; Hg, 0.0204-0.2675; Pb, 0.8527-6.5981; Cr, 0.1731-45.3962 µg mL-1. It was observed that the levels of Pb and especially Cr in the samples exceeded the limit values. Tattoo inks reduced the cell viability in a dose- and color-dependent manner. IL-18 release was significantly increased in all groups except Cr and black ink of brand I treated cells (p < 0.05). Our results show that the metal contents of tattoo inks exceed Council of Europe Resolution values in some samples and some inks induce immune system activation (IL-18 secretion) and cytotoxic effects. It is thought that these findings may contribute to the toxic/adverse effects of tattoo inks commonly used.

Novel-Ink-Based Direct Ink Writing of Ti6Al4V Scaffolds with Sub-300 µm Structural Pores for Superior Cell Proliferation and Differentiation

Ti6Al4V scaffolds with pore sizes between 300 and 600 µm are deemed suitable for bone tissue engineering. However, a significant proportion of human bone pores are smaller than 300 µm, playing a crucial role in cell proliferation, differentiation, and bone regeneration. Ti6Al4V scaffolds with these small-sized pores are not successfully fabricated, and their cytocompatibility remains unknown. The study presents a novel ink formula specifically tailored for fabricating Ti6Al4V scaffolds featuring precise and unobstructed sub-300 µm structural pores, achieved by investigating the rheological properties and printability of five inks containing 60-77.5 vol% Ti6Al4V powders and bisolvent binders. Ti6Al4V scaffolds with 50-600 µm pores are fabricated via direct ink writing and subjected to in vitro assays with MC3T3-E1 and bone marrow mesenchymal stem cells. The 100 µm pore-sized scaffolds exhibit the highest cell adhesion and proliferation capacity based on live/dead assay, FITC-phalloidin/4',6-diamidino-2-phenylindole staining, and cell count kit 8 assay. The alizarin red staining, real-time quantitative PCR assay, and immunocytochemical staining demonstrate the superior osteogenic differentiation potential of 100 and 200 µm pore-sized scaffolds. The importance of sub-300 µm structrual pores is highlighted, redefining the optimal pore size for Ti6Al4V scaffolds and advancing bone tissue engineering and clinical medicine development.

From voice to ink (Vink): development and assessment of an automated, free-of-charge transcription tool

BACKGROUND

Verbatim transcription of qualitative audio data is a cornerstone of analytic quality and rigor, yet the time and energy required for such transcription can drain resources, delay analysis, and hinder the timely dissemination of qualitative insights. In recent years, software programs have presented a promising mechanism to accelerate transcription, but the broad application of such programs has been constrained due to expensive licensing or "per-minute" fees, data protection concerns, and limited availability of such programs in many languages. In this article, we outline our process of adapting a free, open-source, speech-to-text algorithm (Whisper by OpenAI) into a usable and accessible tool for qualitative transcription. Our program, which we have dubbed "Vink" for voice to ink, is available under a permissive open-source license (and thus free of cost).

RESULTS

We conducted a proof-of-principle assessment of Vink's performance in transcribing authentic interview audio data in 14 languages. A majority of pilot-testers evaluated the software performance positively and indicated that they were likely to use the tool in their future research. Our usability assessment indicates that Vink is easy-to-use, and we performed further refinements based on pilot-tester feedback to increase user-friendliness.

CONCLUSION

With Vink, we hope to contribute to facilitating rigorous qualitative research processes globally by reducing time and costs associated with transcription and by expanding free-of-cost transcription software availability to more languages. With Vink running on standalone computers, data privacy issues arising within many other solutions do not apply.

Toughening 3D printed biomimetic hydroxyapatite scaffolds: Polycaprolactone-based self-hardening inks

The application of 3D printing to calcium phosphates has opened unprecedented possibilities for the fabrication of personalized bone grafts. However, their biocompatibility and bioactivity are counterbalanced by their high brittleness. In this work we aim at overcoming this problem by developing a self-hardening ink containing reactive ceramic particles in a polycaprolactone solution instead of the traditional approach that use hydrogels as binders. The presence of polycaprolactone preserved the printability of the ink and was compatible with the hydrolysis-based hardening process, despite the absence of water in the ink and its hydrophobicity. The microstructure evolved from a continuous polymeric phase with loose ceramic particles to a continuous network of hydroxyapatite nanocrystals intertwined with the polymer, in a configuration radically different from the polymer/ceramic composites obtained by fused deposition modelling. This resulted in the evolution from a ductile behavior, dominated by the polymer, to a stiffer behavior as the ceramic phase reacted. The polycaprolactone binder provides two highly relevant benefits compared to hydrogel-based inks. First, the handleability and elasticity of the as-printed scaffolds, together with the proven possibility of eliminating the solvent, opens the door to implanting the scaffolds freshly printed once lyophilized, while in a ductile state, and the hardening process to take place inside the body, as in the case of calcium phosphate cements. Second, even with a hydroxyapatite content of more than 92 wt.%, the flexural strength and toughness of the scaffolds after hardening are twice and five times those of the all-ceramic scaffolds obtained with the hydrogel-based inks, respectively. STATEMENT OF SIGNIFICANCE: Overcoming the brittleness of ceramic scaffolds would extend the applicability of synthetic bone grafts to high load-bearing situations. In this work we developed a 3D printing ink by replacing the conventional hydrogel binder with a water-free polycaprolactone solution. The presence of polycaprolactone not only enhanced significantly the strength and toughness of the scaffolds while keeping the proportion of bioactive ceramic phase larger than 90 wt.%, but it also conferred flexibility and manipulability to the as-printed scaffolds. Since they are able to harden upon contact with water under physiological conditions, this opens up the possibility of implanting them immediately after printing, while they are still in a ductile state, with clear advantages for fixation and press-fit in the bone defect.

What's in My Ink: An Analysis of Commercial Tattoo Ink on the US Market

As tattoos continue to rise in popularity, the demand for tattoo ink has surged. Historically, tattoo inks have been underregulated in the US market. This study analyzes inks from nine different brands that are common in the United States, ranging from major to small manufacturers. Out of 54 inks, 45 contained unlisted additives and/or pigments. Major, unlisted adulterants include poly(ethylene glycol), propylene glycol, and higher alkanes. Many of the adulterants pose possible allergic or other health risks. Taken together, the results from this study highlight the potential for a significant issue around inaccurate tattoo ink labeling in the United States.

Undaria pinnatifida gel inks for food 3D printing are developed based on the colloidal properties of Undaria pinnatifida slurry and protein/colloidal/starch substances

Currently, people eat Undaria pinnatifida (UP) in a single way, and processing homogeneity is serious. However, UP has not gained any traction in the 3D printing industry to date. This study explored the incorporation of soy protein isolate (SPI), pea protein (PP), xanthan gum (XG), guar gum (GG), corn starch (CS), and potato starch (PS) into UP slurry liquid, the primary component of the study, to formulate a UP gel ink. The UP gel 3D printing ink system based on UP paste was established and characterized. The results show that hydrogen bonds are formed, and three-dimensional gel network structure is formed in all UP gel inks. UP gel inks containing high concentrations of SPI and GG exhibited good texture and rheological qualities and good 3D printing effect, with storage modulus (G') values of 8440.405 ± 3.893 and 8111.730 ± 3.585 Pa. The loss of modulus (G″) values were 1409.107 ± 3.524 and 1071.673 ± 3.669 Pa. Unfortunately, the properties of other UP gel inks are not suitable, resulting in poor 3D printing results. The food 3D printing method developed in this study provides valuable insights for expanding food 3D printing material choices and achieving high-value applications of UP.

Integrated Ink Printing Paper Based Self-Powered Electrochemical Multimodal Biosensing (IFP-Multi ) with ChatGPT-Bioelectronic Interface for Personalized Healthcare Management

Personalized healthcare management is an emerging field that requires the development of environment-friendly, integrated, and electrochemical multimodal devices. In this study, the concept of integrated paper-based biosensors (IFP-Multi ) for personalized healthcare management is introduced. By leveraging ink printing technology and a ChatGPT-bioelectronic interface, these biosensors offer ultrahigh areal-specific capacitance (74633 mF cm-2 ), excellent mechanical properties, and multifunctional sensing and humidity power generation capabilities. More importantly, the IFP-Multi devices have the potential to simulate deaf-mute vocalization and can be integrated into wearable sensors to detect muscle contractions and bending motions. Moreover, they also enable monitoring of physiological signals from various body parts, such as the throat, nape, elbow, wrist, and knee, and successfully record sharp and repeatable signals generated by muscle contractions. In addition, the IFP-Multi devices demonstrate self-powered handwriting sensing and moisture power generation for sweat-sensing applications. As a proof-of-concept, a GPT 3.5 model-based fine-tuning and prediction pipeline that utilizes recorded physiological signals through IFP-Multi is showcased, enabling artificial intelligence with multimodal sensing capabilities for personalized healthcare management. This work presents a promising and ecofriendly approach to developing paper-based electrochemical multimodal devices, paving the way for a new era of healthcare advancements.

Macrophage-like rapid uptake and toxicity of tattoo ink in human monocytes

Macrophages play a critical role for the persistence of tattoo ink in human skin. However, a comparison to other skin-resident and blood circulating immune cells and a profound analysis of REACH-compliant tattoo ink are unmet medical needs. We hence characterized the size distribution of ink particles using physicochemical methods. We studied the uptake of tattoo ink by key human skin cells and blood-derived immune cells using optical and electron microscopy as well as flow cytometry. Scanning electron microscopy of ink revealed its crystalline structure, and a tendency towards aggregations was indicated by size changes upon diluting it. Flow cytometric analyses of skin and immune cells after incubation with tattoo ink demonstrated an increase in cellular granularity upon uptake and red ink additionally evoked fluorescent signals. Human macrophages were most potent in internalizing ink in full thickness 3D skin models. Macrophage cultures demonstrated that the ink did not lead to elevated inflammatory mediators, and showed no indications for toxicity, even after nice days. Strikingly, monocytes were most efficient in ink uptake, but displayed reduced viability, whereas granulocytes and lymphocytes showed only temporary ink uptake with flow cytometric signals declining after 1 day. Mechanistic studies on ink retention by corticosteroids or dexpanthenol in macrophage cultures demonstrated that these compounds do not lead to ink excretion, but even slightly increase the ink load in macrophages. The highly motile monocytes, precursors of macrophages, may play an underrated role for tattoo ink translocation from dermal blood vessels into internal organs.

Wax screen-printable ink for massive fabrication of negligible-to-nil cost fabric-based microfluidic (bio)sensing devices for colorimetric analysis of sweat

Fabric-based microfluidic analytical devices (μADs) have emerged as a promising material for replacing paper μADs thanks to their superior properties in terms of stretchability, mechanical strength, and their wide scope of applicability in wearable devices or embedded in garments. The major obstacle in their widespread use is the lack of a technique enabling their massive fabrication at a negligible-to-nil cost. In response, we report the development of a wax ink with proper thixotropic and hydrophobic properties, fully compatible with automatic screen-printing that allows the one step massive fabrication of microfluidics on a cotton/elastane fabric, with a printing resolution 400 μm (hydrophilic channel) and 1000 μm (hydrophobic barrier), without being necessary any post curing. The cost of the ink (50 g) and of each microfluidic device is ca. 2.3 and 0.007 €, respectively. The active component of the ink was a refined beeswax in a matrix based on ethyl cellulose in 2-butoxy ethyl acetate. Screen-printed fabric μADs were used for the simultaneous colorimetric determination of pH and urea in untreated human sweat by using multivariate regression analysis. This method enabled the direct measurement of urea using urease, regardless of the sweat's pH, and shows strong agreement with a reference method.

Tattoo Pigment Biokinetics in vivo in a 28-Day Porcine Model: Elements Undergo Fast Distribution to Lymph Nodes and Reach Steady State after 7 Days

INTRODUCTION

Pigments of tattoo inks may over time migrate to other parts of the body. Inks kinetics are still poorly understood and little studied. The aim of this first study was to investigate the kinetics of tattoo inks pigment in tattooed porcine skin, which is closer to human skin than mouse skin studied in the past.

METHODS

Three animals were tattooed on the inner thigh and one animal served as untreated control. Skin biopsies were taken on days 7, 14, and 28 after tattooing. Animals were sacrificed on day 28 and homogenate samples of the liver, spleen, kidney, and brain, as well the local lymph nodes were prepared. All samples were analyzed for ink components using inductively coupled plasma-mass spectrometry. The ink itself was characterized by dynamic light scattering and matrix-assisted laser desorption-ionization mass analysis.

RESULTS

Titanium (212 g/kg), copper (6 mg/kg), aluminum (1 mg/kg), zirconium (1 mg/kg), and chromium (3 mg/kg) were found in the ink. Significant deposits of ink elements were detected in the tattooed skin when compared to non-tattooed skin from the same animal (mean ± standard deviation: titanium 240 ± 81 mg/kg, copper 95 ± 39 mg/kg, aluminum 115 ± 63 mg/kg, zirconium 23 ± 12 mg/kg, and chromium 1.0 ± 0.2 mg/kg; p < 0.05). Lymph node concentrations of titanium, copper, aluminum, zirconium, and chromium were 42 ± 2 mg/kg, 69 ± 25 mg/kg, 49 ± 18 mg/kg, 0.3 ± 0.2 mg/kg, 0.5 ± 0.2 mg/kg, respectively.

CONCLUSION

Deposits in skin were unchanged from days 7-28 indicating no redistribution or elimination. No significant deposits of ink elements were found in the liver, spleen, kidney, and brain. In conclusion, our findings confirmed distribution of elements from tattoos to regional lymph nodes, but neither to excretory organs, e.g., liver and kidney, nor to spleen and brain. Thus systemic internal organ exposure was not found.

From biomaterials to biotherapy: cuttlefish ink with protoporphyrin IX nanoconjugates for synergistic sonodynamic-photothermal therapy

Biologically produced nanomaterials capable of therapeutic purposes have received increasing interest in tumor therapy because of their intrinsic biocompatibility. In this study, we made cuttlefish ink (extracted from cuttlefish) and protoporphyrin IX (PpIX) nanoconjugates (CIPs) where PpIX was an endogenous organic compound. In the case of CIPs, PpIX could be triggered by ultrasound (US) for sonodynamic therapy (SDT), and the cuttlefish ink could be excited by a near-infrared laser for photothermal therapy (PTT). Thereafter, tumor growth was greatly inhibited through synergistic SDT-PTT in comparison to single SDT or PTT. In addition, in vivo administration of CIPs showed no noticeable side effects for mouse blood and chief organs, providing an effective strategy for developing biologically produced biomaterials and using them for biotherapy.

Three-Dimensional Extrusion Printed Urinary Specific Grafts: Mechanistic Insights into Buildability and Biophysical Properties

The compositional formulations and the optimization of process parameters to fabricate hydrogel scaffolds with urological tissue-mimicking biophysical properties are not yet extensively explored, including a comprehensive assessment of a spectrum of properties, such as mechanical strength, viscoelasticity, antimicrobial property, and cytocompatibility. While addressing this aspect, the present work provides mechanistic insights into process science, to produce shape-fidelity compliant alginate-based biomaterial ink blended with gelatin and synthetic nanocellulose. The composition-dependent pseudoplasticity, viscoelasticity, thixotropy, and gel stability over a longer duration in physiological context have been rationalized in terms of intermolecular hydrogen bonding interactions among the biomaterial ink constituents. By varying the hybrid hydrogel ink composition within a narrow compositional window, the resulting hydrogel closely mimics the natural urological tissue-like properties, including tensile stretchability, compressive strength, and biophysical properties. Based on the printability assessment using a critical analysis of gel strength, we have established the buildability of the acellular hydrogel ink and have been successful in fabricating shape-fidelity compliant urological patches or hollow cylindrical grafts using 3D extrusion printing. Importantly, the new hydrogel formulations with good hydrophilicity, support fibroblast cell proliferation and inhibit the growth of Gram-negative E. coli bacteria. These attributes were rationalized in terms of nanocellulose-induced physicochemical changes on the scaffold surface. Taken together, the present study uncovers the process-science-based understanding of the 3D extrudability of the newly formulated alginate-gelatin-nanocellulose-based hydrogels with urological tissue-specific biophysical, cytocompatibility, and antibacterial properties.

4D-Printable Photocrosslinkable Polyurethane-Based Inks for Tissue Scaffold and Actuator Applications

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and ≈50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research.

Direct ink writing of biocompatible chitosan/non-isocyanate polyurethane/cellulose nanofiber hydrogels for wound-healing applications

The demand for new biocompatible and 3D printable materials for biomedical applications is on the rise. Ideally, such materials should exhibit either biodegradability or recyclability, possess antibacterial properties, and demonstrate remarkable biocompatibility with no cytotoxic effects. In this research, we synthesized biocompatible and 3D printable hydrogels tailored for biomedical applications, such as wound healing films, by combining antibacterial double-quaternized chitosan (DQC) with cystamine-based non-isocyanate polyurethane (NIPU-Cys) - a material renowned for enhancing both the flexibility and mechanical properties of the hydrogels. To improve the rheological behavior, swelling attributes, and printability, cellulose nanofibrils were introduced into the matrix. We investigated the impact of DQC on degradability, swelling capacity, rheological behavior, printability, and cell biocompatibility. The slightly cytotoxic nature associated with quaternary chitosan was evaluated, and the optimal concentration of DQC in the hydrogel was determined to ensure biocompatibility. The resulting hydrogels were found to be suitable materials for 3D printing via a direct ink writing technique (DIW), producing porous, biocompatible hydrogels endowed with valuable attributes suitable for various wound-healing applications.

Innovations in hydrogel-based manufacturing: A comprehensive review of direct ink writing technique for biomedical applications

Direct ink writing (DIW) stands as a pioneering additive manufacturing technique that holds transformative potential in the field of hydrogel fabrication. This innovative approach allows for the precise deposition of hydrogel inks layer by layer, creating complex three-dimensional structures with tailored shapes, sizes, and functionalities. By harnessing the versatility of hydrogels, DIW opens up possibilities for applications spanning from tissue engineering to soft robotics and wearable devices. This comprehensive review investigates DIW as applied to hydrogels and its multifaceted applications. The paper introduces a diverse range of printing techniques while providing a thorough exploration of DIW for hydrogel-based printing. The investigation aims to explain the progress made, challenges faced, and potential trajectories that lie ahead for DIW in hydrogel-based manufacturing. The fundamental principles underlying DIW are carefully examined, specifically focusing on rheological attributes and printing parameters, prompting a comprehensive survey of the wide variety of hydrogel materials. These encompass both natural and synthetic variations, all of which can be effectively harnessed for this purpose. Furthermore, the review explores the latest applications of DIW for hydrogels in biomedical areas, with a primary focus on tissue engineering, wound dressing, and drug delivery systems. The document not only consolidates the existing state of DIW within the context of hydrogel-based manufacturing but also charts potential avenues for further research and innovative breakthroughs.

Application of Indian ink markers for locating gastric varices under endoscopic ultrasonography

OBJECTIVE

The present study aimed to investigate the accuracy of endoscopic ultrasonography (EUS) combined with Indian ink in locating target vessels of gastric varices (GVs) compared with conventional endoscopic techniques. Additionally, the characteristics of GVs under conventional endoscopy were also explored.

METHODS

All 50 cirrhotic patients with GVs between August 2021 and December 2022 were included in the study. Firstly, conventional endoscopy was employed to identify GVs and to record the expected injection sites. Subsequently, EUS was used to locate the perforated vessel and the injection site was them marked with India ink followed by injection with cyanoacrylate (CYA). Finally, conventional endoscopy was used to examine GVs, to identify the marker points of Indian ink and to compare whether the injection points under conventional endoscopy were consistent with those marked with Indian ink. Furthermore, patients with consistent and inconsistent distribution of endoscopic markers and injection sites were divided into two groups.

RESULTS

EUS could detect the perforating vessels in real time and intuitively. The distribution of markers using EUS was significantly different compared with the injection points obtained by conventional endoscopy (P < 0.001). Therefore, 20 cases were allocated to the consistent group and 30 cases to the non-consistent group. 16 patients who showed red wale signs were obtained in the consistent group and 11 patients in the non-consistent group (P = 0.048). The diameter of the largest GVs was 13.5 (10-15) mm in the consistent group compared with 10 (7.5-10) mm in the non-consistent group (P = 0.006).

CONCLUSION

EUS could provide the exact location of GVs, thus more accurately describing the endoscopic characteristics of the GVs. Furthermore, the red wale signs and diameter of the largest GVs obtained using conventional endoscopy were helpful in determining the location of target GVs.

Effect of polymethyl methacrylate on in situ patterning of perovskite quantum dots by inkjet printing

The preparation of perovskite quantum dots (PQDs) using an in situ inkjet printing method is beneficial for improving the problems of aggregation and photoluminescence (PL) quenching during long-term storage. However, the stability of PQDs prepared using this method is still not ideal, and the morphology of in situ-printed patterns needs to be optimized. To address these problems, this study introduced polymethyl methacrylate (PMMA) into the process of in situ inkjet printing of PQDs and explored the effect of PMMA on the in situ patterning effect of PQDs. The results showed that using a mixed precursor solution containing a small amount of PMMA as the printing ink can slow down the shrinkage process of ink droplets and improve the uniformity of film formation. As the printing substrate, PMMA provided a suitable high-viscosity environment for the in situ growth of PQDs. This could effectively suppress the coffee ring effect. In addition, the interaction between the C=O=C group in PMMA and metal ion Pb2+ in the CsPbBr3 precursor molecules was favourable to enhancing the density of PQDs. The prepared PMMA-coated CsPbBr3 quantum dots (QDs) pattern had high stability and could maintain at 90.08% PL intensity after 1 week of exposure to air.

Development and optimization of starch-based biomaterial inks and the effect of infill patterns on the mechanical, physicochemical, and biological properties of 3D printed scaffolds for tissue engineering

Plant-based hydrogels have wide application as scaffolds in tissue engineering and regenerative medicine due to their low cost and excellent biocompatibility. Scaffolds act as vehicles for cell-based therapeutics and regenerating diseased tissue. While there is a plethora of methods to generate hydrogels with tunable properties to mimic the tissue of interest, 3D bioprinting is a novel emerging technology with the capability to generate versatile patient-specific scaffolds typically embedded with tissue specific cells. Starch-based hydrogels are garnering attention in extrusion-based 3D printing, however owing to their poor mechanical strength and degradation render this material inefficient in its native form. Additionally, the effect of various printing process parameters on mechanical strength and bioactivity is poorly understood. In the present study, we investigate the use of starch and gelatin as composite biomaterial ink and its effect on mechanical, physical and biological properties. We also investigated printability of composite hydrogels with the aim to understand the correlation between two infill patterns and its effect on mechanical, physicochemical, and biological properties. Our results showed that the composite hydrogels had competent mechanical properties and suitable bioactivity when seeded with H9C2 cardiomyocytes. Rheometric analyses provided a broader insight into the required viscosity for printing and has a direct correlation with the composition of the hydrogel. Thus, the composite materials are found to have tissue-specific mechanical properties and may serve as a better, cheaper and personalized alternative to existing scaffolds for the fabrication of engineered cardiac tissue.

Interaction between creation and appreciation: How linguistic art creation impacts the aesthetic evaluation of haiku poetry and ink paintings

In the psychology of aesthetics, compared with appreciation, there are fewer studies on art creation. This study aims to examine the influence of art creation on appreciation using haiku poetry with reference to the Mirror Model-a process model combining creation and appreciation. Although the model has been primarily used to examine visual arts, we examine its applicability to linguistic arts. In addition, we use ink painting to examine whether a generalisation across artistic genres can occur. The 115 participants were divided into two conditions-creation and control. The former created haiku before and after appreciation, while the latter did not create any haiku. The results showed no improvement in evaluation through creation. Additionally, recognising the difficulty related to creation leads to aesthetic evaluation, and this relationship is mediated by awe. These results expand the existing information regarding the Mirror Model in terms of the different art genres.

Aloe vera-based biomaterial ink for 3D bioprinting of wound dressing constructs

This study emphasizes the development of a multifunctional biomaterial ink for wound healing constructs. The biomaterial ink benefits from Aloe vera's intrinsic biocompatible, biodegradable, antioxidant, antimicrobial, anti-inflammatory, and immunomodulatory attributes, thus alleviating the need for supplementary substances employed to combat infections and stimulate tissue regeneration. Moreover, this biomaterial ink seeks to address the scarcity of standardized printable materials possessing adequate biocompatibility and physicochemical properties, which hinder its widespread clinical adoption. The biomaterial ink was synthesized via ionic crosslinking to enhance its rheological and mechanical characteristics. The findings revealed that Aloe vera substantially boosted the hydrogel's viscoelastic behavior, enabling superior compressive modulus and the extrusion of fine filaments. The bioprinted constructs exhibited desirable resolution and mechanical strength while displaying a porous microstructure analogous to the native extracellular matrix. Biological response demonstrated no detrimental impact on stem cell viability upon exposure to the biomaterial ink, as confirmed by live/dead assays. These outcomes validate the potential of the developed biomaterial ink as a resource for the bioprinting of wound dressings that effectively foster cellular proliferation, thereby promoting enhanced wound healing by leveraging Aloe vera's inherent properties.

Therapeutic potential of enzymatically extracted eumelanin from squid ink in type 2 diabetes mellitus ICR mice: Multifaceted intervention against hyperglycemia, oxidative stress and depression

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a prevalent metabolic disease that poses significant health risks due to its numerous complications. However, the effects of eumelanin on oxidative stress, hyperglycemia and depression in diabetic mice have not been extensively studied.

RESULTS

Our study employed an enzymatic approach to extract eumelanin from squid ink and characterized it using spectroscopic techniques. Remarkably, eumelanin extracted with alkaline-neutral-flavor protease (ANF) displayed superior inhibitory activity against α-glucosidase and α-amylase, while enhancing glucose utilization and hepatic glycogen synthesis in human hepatocellular carcinoma cell line (HepG2) insulin resistance model. Further evaluation of ANF in a T2DM ICR mouse model demonstrated its significant potential in alleviating hyperglycemia, reducing glycosylated serum protein levels, improving glucose tolerance and modulating total cholesterol and low-density lipoprotein levels, as well as antioxidant indices at a dosage of 0.04 g kg-1 . Additionally, ANF exhibited positive effects on energy levels and reduced immobility time in antidepressant behavioral experiments. Moreover, ANF positively influenced the density and infiltration state of renal cells, while mitigating inflammatory enlargement and deformation of liver cells, without inducing any adverse effects in mice.

CONCLUSION

Overall, these findings underscore the significant therapeutic potential of ANF in the treatment of T2DM and its associated complications. By augmenting lipid and glucose metabolism, mitigating oxidative stress and alleviating depression, ANF emerges as a promising candidate for multifaceted intervention. © 2023 Society of Chemical Industry.

Electrostatically Cross-Linked Bioinks for Jetting-Based Bioprinting of 3D Cell Cultures

It has been acknowledged that thousands of drugs that passed two-dimensional (2D) cell culture models and animal studies often fail when entering human clinical trials. Despite the significant development of three-dimensional (3D) models, developing a high-throughput model that can be reproducible on a scale remains challenging. One of the main challenges is precise cell deposition and the formation of a controllable number of spheroids to achieve more reproducible results for drug discovery and treatment applications. Furthermore, when transitioning from manually generated structures to 3D bioprinted structures, the choice of material is limited due to restrictions on materials that are applicable with bioprinters. Herein, we have shown the capability of a fast-cross-linking bioink that can be used to create a single spheroid with varying diameters (660, 1100, and 1340 μm) in a high-throughput manner using a commercialized drop-on-demand bioprinter. Throughout this work, we evaluate the physical properties of printable ink with and without cells, printing optimization, cytocompatibility, cell sedimentation, and homogeneity in ink during the printing process. This work showcases the importance of ink characterization to determine printability and precise cell deposition. The knowledge gained from this work will accelerate the development of next-generation inks compatible with a drop-on-demand 3D bioprinter for various applications such as precision models to mimic diseases, toxicity tests, and the drug development process.

Electrogeneration of H2O2 through carbon-based ink on Al foam for electro-Fenton treatment of micropollutants in water

In the present work, the catalytic efficiency of inks based on different carbon materials, namely activated carbon (AC), carbon graphite (CG), and carbon black (CB) was investigated for the oxygen reduction reaction (ORR). Additionally, we explored the feasibility of using this ink as a coating for an Aluminum foam (Alfoam) cathode in an electrochemical cell. The goal was to utilize this setup to produce hydrogen peroxide (H2O2) in the electro-Fenton (EF) process, targeting for treating water contaminated with contaminants of emerging concern (CECs). Among the materials investigated, all of them exhibited the ability to facilitate the ORR. However, AC proved to be the most suitable material due to its optimal balance between physical and electrocatalytic properties, thus enabling the formation of H2O2. When the different inks were applied to the surface of aluminum foam, it was observed that only the ink based on carbon black CB achieved a homogeneous distribution with the same ink quantity. As a result, it was observed that the Alfoam/CB electrode exhibited the highest H2O2 generation capacity, producing 45.6 mg L-1, followed by electro-generation of 5.1 mg L-1 using Alfoam/AC and 11 mg L-1 using Alfoam/CG. Furthermore, the application of Alfoam/CB in EF processes allowed for the almost complete degradation of 15 emerging contaminants of concern (CECs) present in secondary effluent. The innovative outcome of this study positions the developed technology as a promising and effective alternative for the treatment of water contaminated with CECs, demonstrating significant potential for industrial-scale application.

The effects of pen ink and surface disinfectants on red blood cells stored in plasticized polyvinylchloride transfusion bags

BACKGROUND

Each unit of red blood cells (RBCs) produced represents a significant cost to the healthcare system. Unnecessary blood wastage should be minimized. In clinical settings, alterations to blood component bags after issue from the protected setting of the blood bank include pen markings, and those that are exposed to an infectious environment require surface disinfecting. These units may be discarded due to unclear effects on RBC quality. In this study, we investigate whether pen markings or surface disinfection negatively affects the quality of packed RBCs and whether pen ink diffuses through the blood bag.

STUDY DESIGN AND METHODS

RBC bags were marked with pens (water, oil, or alcohol-based) or subjected to surface disinfection (ethanol, hydrogen peroxide [Preempt wipes], or benzalkonium chloride-based wipes [CaviWipes]) and sampled 24 h after applying the treatment and at day 42 post collection (n = 3 for each condition). The samples were analyzed for RBC in vitro quality markers. The presence of any ink in the RBC bags was investigated using mass spectrometry (n = 2).

RESULTS

Data from 24 h and day 42 time points indicated no differences in RBC count, mean corpuscular volume, morphology, deformability, potassium content, or hemolysis for either pen markings or disinfectants when compared with their untreated controls (p > .05). No trace of ink was detected inside the bag.

CONCLUSION

RBC units marked with ballpoint, gel, or Sharpie pens do not suffer a loss of in vitro quality, nor do RBC units which have been surface disinfected with 70% ethanol, Preempt wipes or CaviWipes.

Persistent Localized Descemet Membrane Endothelial Keratoplasty Detachments Secondary to Corneal Ink Stain Marks

PURPOSE

The aim of this study was to describe 2 cases of persistent endothelial graft detachments secondary to corneal gentian violet ink stain marks.

METHODS

This study included a case review of hospital records of 2 eyes with localized Descemet's membrane detachments after Descemet membrane endothelial keratoplasty (DMEK) surgery.

RESULTS

Two patients underwent consecutive uncomplicated DMEK surgery for Fuchs endothelial dystrophy with identical techniques. The grafts were marked with an ink marker through a stromal window to ensure correct orientation during donor graft preparation. Both patients had localized detachments around the ink mark on day 1, week 1, and up to 1 month at postoperative review. The persistent detachment was believed to be due to the gentian violet marker used which had a higher concentration of isopropyl alcohol solvent than the standard marking pen routinely used.

CONCLUSIONS

Ink markers with higher concentrations of isopropyl solvent may result in higher DMEK detachment rates and caution is advised when using these markers.

Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis

In situ analysis of sweat biomarkers potentially provides noninvasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, a skin-attachable paper fluidic patch is reported for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, and uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns-multiplexed detection zones and a longitudinal sweat rate channel-are directly printed by an automated ink dispenser from a specially developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic-ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the color homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture sensitive by incorporating a metal-salt-based dye. The change in saturation/color of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. A cost-effective way is provided to fabricate paper fluidic sensor patches, successfully demonstrating on-body multiplexed evaluation of sweat analytes. Such skin wearables offer on-site analysis, meaningful to an increasingly health-conscious population.

Plant-based ink properties and storage stability for inkjet printing

In this sustainability-oriented research, the properties of plant-based inks were evaluated denoting the viscosity range of 8.5 to 10 cP, the relative density of 1.06, conductivity value of 2.51 mS/cm, and the surface tension of 60 mN/m and pH of 4.9 to be most effective for inkjet printing. The changes in these properties to the one-month storage phase are detailed as determined with attenuated total reflectance - Fourier transform infrared spectroscopy, viscometer, and tensiometer. The varied colours of plant-based inks were stable to storage time except for the blue colour ink made from bio indigo herb that displayed agal-like sediments. After the storage phase, the plant-based inks exhibited anti-thixotropic viscosity except for yellow colour plant-based ink demonstrating thixotropic behaviour. High conductivity values of 18.5 and 15.6 mS/Cm were noted for blue and black colour plant-based inks, indicating their potential for constituting conducting inks; however, the conductivity values dropped to 7.5 and 9.5, respectively, after 1 month. The pH and surface tension were found steady during the storage period. The study of the life cycle analysis of plant-based inks is suggested for future work. The significance of this work in developing plant-based inks for inkjet printing of textiles lies in the convergence of sustainability and innovation. Plant-based inks can offer an eco-friendly alternative to traditional synthetic inks that are used currently, which provides a knowledge base for good practises meeting the environmentally conscious in the digital printing of the textile industry. These developed inks from this study can not only reduce the environmental impact but also promote a healthier ecosystem.

Investigation of 3D printing of toddler foods with special shape and function based on fenugreek gum and flaxseed protein

The practicability of using corn and flaxseed protein as printing inks for manufacture of printed products specifically designed for toddlers as a dysphagia diet with high precision and special shapes with addition of fenugreek gum (FGG) was investigated. 3D printing was used to process grains and dysphagia-compatible food (corn) into a dietary product with attractive appearance which was also easy to swallow. Rheological measurements shown that appropriate amount of flaxseed protein (FP, 0-10 %) can reduce the stickiness and yield strength of printing material. Based on FTIR measurements, FP weakened the hydrogen bond strength of inks, but it was still an important gradient for the formation of the ink suitable for precision 3D printing. The TPA results shown that the addition of FP (0-10 %) remarkably reduced both the stickiness and hardness of the ink. These results shown that compared with the control group, materials with FGG additions possessed higher printing accuracy and self-supporting ability. Ink with 5 % FP content exhibited the best printability and swallowability, while ink with 10 % FP content had the lowest viscosity and hardness, but it was not suitable for 3D printing. 3D printing of objects printed using Ink-C (5%FP and 0.8 %FGG) showed high support characteristic and attractive appearance. According to the international IDDSI testing standards, Ink-C (5%FP and 0.8 %FGG), Ink-E (15%FP and 0.8 %FGG), and Ink-F (20%FP and 0.8 %FGG) were defined as level 5-minced and moist foods.

An investigation into the effects of ink formulations of semi-solid extrusion 3D printing on the performance of printed solid dosage forms

Semi-solid extrusion (SSE) 3D printing has recently attracted increased attention for its pharmaceutical application as a potential method for small-batch manufacturing of personalised solid dosage forms. It has the advantage of allowing ambient temperature printing, which is especially beneficial for the 3D printing of thermosensitive drugs. In this study, the effects of polymeric compositions (single hydroxypropyl methylcellulose (HPMC) system and binary HPMC + polyvinylpyrrolidone (PVP) system), disintegrant (silicon oxide (SiO2)), and active pharmaceutical ingredients (tranexamic acid (TXA) and paracetamol (PAC)) on the printability of semisolid inks and the qualities of SSE printed drug-loaded tablets were investigated. Printability is defined by the suitability of the material for the process in terms of its physical properties during extrusions and post-extrusion, including rheology, solidification time, avoiding slumping, etc. The rheological properties of the inks were investigated as a function of polymeric compositions and drug concentrations and further correlated with the printability of the inks. The SSE 3D printed tablets were subjected to a series of physicochemical properties characterisations and in vitro drug release performance evaluations. The results indicated that an addition of SiO2 would improve 3D printing shape fidelity (e.g., pore area and porosity) by altering the ink rheology. The pores of HPMC + PVP + 5PAC prints completely disappeared after 12 hours of drying (pore area = 0 mm2). An addition of SiO2 significantly improved the pore area of the prints which are 3.5 ± 0.1 mm2. It was noted that the drug release profile of PAC significantly increased (p < 0.05) when additive SiO2 was incorporated in the formulation. This could be due to a significantly higher porosity of HPMC + PVP + SiO2 + PAC (70.3 ± 0.2%) compared to HPMC + PVP + PAC (47.6 ± 2.1%). It was also likely that SiO2 acted as a disintegrant speeding up the drug release process. Besides, the incorporation of APIs with different aqueous solubilities, as well as levels of interaction with the polymeric system showed significant impacts on the structural fidelity and subsequently the drug release performance of 3D printed tablets.

The Process of Sterilizing Tattoo Inks Releases Formaldehyde

INTRODUCTION

Around 12% of Europeans and 20% of Americans have at least one tattoo. Tattoo inks, the substances used to create tattoos on the body, consist of chemicals that contain formaldehyde, which can be harmful to human health. The amount of formaldehyde present in commercially available tattoo inks and its causes are not well understood.

METHODS

We investigated the levels of formaldehyde in tattoo ink products sold in different countries and identified the factors contributing to its production. We also explored methods to reduce formaldehyde generation in tattoo inks. Seven tattoo inks from various brands were tested.

RESULTS

Formaldehyde release was predominantly associated with gamma radiation sterilization. Formaldehyde levels were observed to be higher in compositions containing organic components compared to those with inorganic components, irrespective of sterilization method and container type. Glycerin released over seven times more formaldehyde than other components during gamma-ray sterilization.

CONCLUSION

The results suggest that the presence of hydroxyl groups in carbon organic compounds in tattoo ink leads to photodegradation during gamma-ray radiation sterilization, resulting in increased concentrations of formaldehyde. Further research is needed to examine the chemical reactions occurring during sterilization processes and identify alternative sterilization methods that minimize formaldehyde formation. Additionally, the development of tattoo inks with reduced formaldehyde content and the establishment of strict quality control measures can help ensure the safety of tattooing practices.

Protocol for preparing patterned superlattice structures by printing assembly technology for multi-channel detection

The transformation of superlattice structures into functional devices requires high-quality preparation. Inkjet printing is potentially a cutting-edge technology for nanofabrication. Here, we present a protocol to prepare inks for constructing patterned superlattice structures using print assembly techniques. We describe steps for preparing oleophobic substrates, optimizing ink parameters, and preparing the patterned superlattice array. We then detail procedures for preparing a multichannel surface-enhanced Raman scattering sensor and evaluating its performance. This protocol can potentially facilitate the commercialization of superlattice-related devices. For complete details regarding the use and execution of this protocol, please refer to Zhao et al.1.

Development of a C-reactive protein quantification method based on flow rate measurement of an ink solution pushed out by oxygen gas generated by catalase reaction

A novel determination method for protein biomarkers based on on-chip flow rate measurement was developed using a microchip with organic photodiodes (OPDs). This quantitative method is based on the flow rate measurement of an ink solution pushed out by oxygen gas generated through catalase reaction. The amount of oxygen gas generated in the sample reservoir is dependent on the concentration of the analyte; therefore, the flow rate of the ink solution is also dependent on the concentration of the analyte. The concentration of the analyte can thus be estimated by measurement of the ink solution flow rate. The ink solution flow rate was estimated by measuring the migration time of the ink solution between two points using two OPDs placed below the microchannel. The principle of this method was demonstrated by the measurement of catalase using the microchip. In addition, the developed method was applied to the determination of C-reactive protein (CRP), a biomarker of inflammation, based on a catalase-linked immunosorbent assay (C-LISA). The limit of detection for CRP was 0.20 µg/mL. The method was also applied to the determination of CRP in human serum, and the quantitative values obtained by this method were in excellent agreement with those obtained by the conventional enzyme-linked immunosorbent assay (ELISA) method. The developed method does not require a photodetector with high sensitivity and is thus capable of downsizing; therefore, this will be useful for on-site analyses such as point-of-care testing and field measurements.

Tattoo-Associated Skin Reactions: A Danish Population-Based Survey in 5,914 Tattooed Individuals

BACKGROUND

In Europe, Australia, and the USA, the estimated overall prevalence of tattooing is around 10-20%. Tattoo ink often comprises harmful chemicals and epidemiological studies on adverse effects of tattoos are lacking.

OBJECTIVES

We aimed to estimate the prevalence of tattoo-associated skin reactions in the general Danish population and describe individuals with tattoo-associated skin reactions by socio-demographic factors and tattoo characteristics.

METHODS

The study was based on respondents aged 16 years or older from a population-based 2021 survey entitled "How are you?" conducted in the Central Denmark Region (n = 33,925). Logistic regression was used to characterise individuals with tattoo-associated skin reactions by socio-demographic factors (gender, age, educational level, and ethnic background). Also, the relationship between size, age and colour of the tattoo, and tattoo-associated skin reactions was studied. Model 1 was adjusted for all socio-demographic variables (gender, age, educational level, and ethnic background); model 2, for all socio-demographic variables and tattoo characteristics (size, age, and colour).

RESULTS

In total, 21.1% reported that they had at least one tattoo, 10.2% hereof reported that they had experienced tattoo-associated skin reactions (itching, pain, inflammation, and swelling) beyond the first 3 weeks after the tattoo was made. Lower age (16-44 years) (adjusted odds ratio (AOR) ≥1.75), larger tattoos (AOR ≥1.61) and having had tattoos for more than 10 years (AOR = 2.92, 95% confidence interval 1.45-5.88) increased the odds of tattoo-associated skin reactions. In general, tattooed individuals with colours other than black had higher odds of tattoo-associated skin reactions.

CONCLUSION

Among participants with at least one tattoo, 10.2% had experienced tattoo-associated skin reactions beyond the first 3 weeks after their tattoo was made. This finding highlights the need for safer tattoo inks to prevent the adverse health problems experienced by many individuals with tattoos.

3D Bioprinting of Diatom-Laden Living Materials for Water Quality Assessment

Diatoms have long been used as living biological indicators for the assessment of water quality in lakes and rivers worldwide. While this approach benefits from the great diversity of these unicellular algae, established protocols are time-consuming and require specialized equipment. Here, this work 3D prints diatom-laden hydrogels that can be used as a simple multiplex bio-indicator for water assessment. The hydrogel-based living materials are created with the help of a desktop extrusion-based printer using a suspension of diatoms, cellulose nanocrystals (CNC) and alginate as bio-ink constituents. Rheology and mechanical tests are employed to establish optimum bio-ink formulations, whereas cell culture experiments are utilized to evaluate the proliferation of the entrapped diatoms in the presence of selected water contaminants. Bioprinting of diatom-laden hydrogels is shown to be an enticing approach to generate living materials that can serve as low-cost bio-indicators for water quality assessment.

Recent advances in 3D printed cellulose-based wound dressings: A review on in vitro and in vivo achievements

Chronic wounds, especially diabetic ulcers, pose a significant challenge in regenerative medicine. Cellulose derivatives offer remarkable wound management properties, such as effective absorption and retention of wound exudates, maintaining an optimal moisture environment crucial for successful chronic wound regeneration. However, conventional dressings have limited efficacy in managing and healing these types of skin lesions, driving scientists to explore innovative approaches. The emergence of 3D printing has enabled personalized dressings that meet individual patient needs, improving the healing process and patient comfort. Cellulose derivatives meet the demanding requirements for biocompatibility, printability, and biofabrication necessary for 3D printing of biologically active scaffolds. However, the potential applications of nanocellulose and cellulose derivative-based inks for wound regeneration remain largely unexplored. Thus, this review provides a comprehensive overview of recent advancements in cellulose-based inks for 3D printing of personalized wound dressings. The composition and biofabrication approaches of cellulose-based wound dressings are thoroughly discussed, including the functionalization with bioactive molecules and antibiotics for improved wound regeneration. Similarly, the in vitro and in vivo performance of these dressings is extensively examined. In summary, this review aims to highlight the exceptional advantages and diverse applications of 3D printed cellulose-based dressings in personalized wound care.

An Electroactive and Self-Assembling Bio-Ink, based on Protein-Stabilized Nanoclusters and Graphene, for the Manufacture of Fully Inkjet-Printed Paper-Based Analytical Devices

Hundreds of new electrochemical sensors are reported in literature every year. However, only a few of them makes it to the market. Manufacturability, or rather the lack of it, is the parameter that dictates if new sensing technologies will remain forever in the laboratory in which they are conceived. Inkjet printing is a low-cost and versatile technique that can facilitate the transfer of nanomaterial-based sensors to the market. Herein, an electroactive and self-assembling inkjet-printable ink based on protein-nanomaterial composites and exfoliated graphene is reported. The consensus tetratricopeptide proteins (CTPRs), used to formulate this ink, are engineered to template and coordinate electroactive metallic nanoclusters (NCs), and to self-assemble upon drying, forming stable films. The authors demonstrate that, by incorporating graphene in the ink formulation, it is possible to dramatically improve the electrocatalytic properties of the ink, obtaining an efficient hybrid material for hydrogen peroxide (H2 O2 ) detection. Using this bio-ink, the authors manufactured disposable and environmentally sustainable electrochemical paper-based analytical devices (ePADs) to detect H2 O2 , outperforming commercial screen-printed platforms. Furthermore, it is demonstrated that oxidoreductase enzymes can be included in the formulation, to fully inkjet-print enzymatic amperometric biosensors ready to use.

Inking cell blocks improves scanner detection for diagnosis in pathology

Cell blocks may be hard to be totally automatically detected by the scanner (ADS), generating incomplete whole slide images (WSIs), with areas that are not scanned, leading to possible false negative diagnosis. The aim of this study is to test if inking the cell blocks helps increasing ADS. Test 1: 15 cell blocks were sectioned, one half inked black (1HB) and the other inked green (1HG). Each of the halves was individually processed to generate a WSI stained by the H&E. 1HBs and 1HGs had similar scanning time (median 59 s vs. 65 s, p = .126) and file sizes (median 382 Mb vs. 381 Mb, p = .567). The black ink interfered less in the observation (2.2% vs. 44.4%; p < .001) than in the green one. Test 2: 15 cell blocks were sectioned, one half inked black (2HB) and the other left unstained/null (2HN). Each of the halves was individually processed to generate three WSIs-one HE, one periodic-acid Schiff (PAS), and one immunostained by cytokeratin AE1&AE3 (CKAE1AE3). HE and PAS WSIs from both 2HN and 2HB groups were all totally ADS and had similar scanning times and file sizes. Concerning immunostaining with CKAE1AE3: ADS (46.7% vs. 93.3%; p = .014), median time for scanning (57 s vs. 83 s; p < .001) and file size (178 Mb vs. 338 Mb; p < .001) were reduced significantly in the 2HN group in comparison with the 2HB. Although increasing scanning time and file size, inking the cell blocks helps increasing ADS after immunostaining, improving the safety and efficiency of the digital pathology workflow.

High-Fidelity Extrusion Bioprinting of Low-Printability Polymers Using Carbopol as a Rheology Modifier

Extrusion three-dimensional (3D) bioprinting is a promising technology with many applications in the biomedical and tissue engineering fields. One of the key limitations for the widespread use of this technology is the narrow window of printability that results from the need to have bioinks with rheological properties that allow the extrusion of continuous filaments while maintaining high cell viability within the materials during and after printing. In this work, we use Carbopol (CBP) as rheology modifier for extrusion printing of biomaterials that are typically nonextrudable or present low printability. We show that low concentrations of CBP can introduce the desired rheological properties for a wide range of formulations, allowing the use of polymers with different cross-linking mechanisms and the introduction of additives and cells. To explore the opportunities and limitations of CBP as a rheology modifier, we used ink formulations based on poly(ethylene glycol)diacrylate with extrusion 3D printing to produce soft, yet stable, hydrogels with tunable mechanical properties. Cell-laden constructs made with such inks presented high viability for cells seeded on top of cross-linked materials and cells incorporated within the bioink during printing, showing that the materials are noncytotoxic and the printed structures do not degrade for up to 14 days. To our knowledge, this is the first report of the use of CBP-containing bioinks to 3D-print complex cell-laden structures that are stable for days and present high cell viability. The use of CBP to obtain highly printable inks can accelerate the evolution of extrusion 3D bioprinting by guaranteeing the required rheological properties and expanding the number of materials that can be successfully printed. This will allow researchers to develop and optimize new bioinks focusing on the biochemical, cellular, and mechanical requirements of the targeted applications rather than the rheology needed to achieve good printability.

Advances in volumetric bioprinting

The three-dimensional (3D) bioprinting technologies are suitable for biomedical applications owing to their ability to manufacture complex and high-precision tissue constructs. However, the slow printing speed of current layer-by-layer (bio)printing modality is the major limitation in biofabrication field. To overcome this issue, volumetric bioprinting (VBP) is developed. VBP changes the layer-wise operation of conventional devices, permitting the creation of geometrically complex, centimeter-scale constructs in tens of seconds. VBP is the next step onward from sequential biofabrication methods, opening new avenues for fast additive manufacturing in the fields of tissue engineering, regenerative medicine, personalized drug testing, and soft robotics, etc. Therefore, this review introduces the printing principles and hardware designs of VBP-based techniques; then focuses on the recent advances in VBP-based (bio)inks and their biomedical applications. Lastly, the current limitations of VBP are discussed together with future direction of research.

Fabrication of conductive Ag/AgCl/Ag nanorods ink on Laser-induced graphene electrodes on flexible substrates for non-enzymatic glucose detection

An unusual strategy was designed to fabricate conductive patterns for flexible surfaces, which were utilized for non-enzymatic amperometric glucose sensors. The Ag/AgCl/Ag quasi-reference ink formulation utilized two reducing agents, NaBH[Formula: see text] and ethylene glycol. The parameters of the ink, such as sintering time and temperature, NaBH[Formula: see text] concentration, and layer number of coatings on flexible laser-induced graphene (LIG) electrodes were investigated. The conductive Ag/AgCl/Ag ink was characterized using electrochemical and surface analysis techniques. The electrocatalytic activity of Ag/AgCl/Ag NRs can be attributed to their high surface area, which offer numerous active sites for catalytic reactions. The selectivity and sensitivity of the electrodes for glucose detection were investigated. The XRD analysis showed (200) oriented AgCl on covered Ag NRs, and with the addition of NaBH[Formula: see text], the intensity of the peaks of the Ag NRs increased. The wide linear range of non-enzymatic sensors was attained from 0.003 to 0.18 mM and 0.37 to 5.0 mM, with a low limit of detection of 10 [Formula: see text]M and 20 [Formula: see text]M, respectively.The linear range of enzymatic sensor in real sample was determined from 0.040 to 0.097 mM with a detection limit of 50 [Formula: see text]M. Furthermore, results of the interference studies demonstrated excellent selectivity of the Ag/AgCl/Ag NRs/LIG electrode. The Ag/AgCl/Ag NRs on the flexible LIG electrode exhibited excellent sensitivity,long-time stablity,and reproducibility. The efficient electroactivity were deemed suitable for various electrochemical applications and biosensors.