Biodistribution of iron oxide tattoo pigment: An experimental murine study.

Tattoo pigment is expected to migrate beyond the skin to regional lymph nodes and the liver. Modern tattoo ink commonly contains metals that may pose a clinical problem during MRI examinations. This study aimed to investigate the biodistribution of iron oxide pigment to internal organs in mice. Moreover, when exposed to a static magnetic field, we studied whether any reactions followed in the tattooed skin. Twenty-seven hairless C3.Cg-Hrhr/TifBomTac mice were included; 20 were tattooed with iron oxide ink in a rectangular 3 cm2 pattern; seven were controls. Ten of the tattooed mice were exposed to a 3 T MRI scanner's static magnetic field. Following euthanasia, evaluations of dissected organs involved MRI T2*-mapping, light microscopy (LM) and metal analysis. T2*-mapping measures the relaxation times of hydrogen nuclei in water and fat, which may be affected by neighbouring ferrimagnetic particles, thus enabling the detection of iron oxide particles in organs. Elemental analysis detected a significant level of metals in the tattooed skin compared to controls, but no skin reactions occurred when exposed to a 3 T static magnetic field. No disparity was observed in the liver samples with metal analysis. T2* mapping found no significant difference between the two groups. Only minute clusters of pigment particles were observed in the liver by LM. Our results demonstrate a minimal systemic distribution of the iron oxide pigments to the liver, whereas the kidney and brain were unaffected. The static magnetic field did not trigger skin reactions in magnetic tattoos but may induce image artefacts during MRI.

Micromixer driven by bubble-induced acoustic microstreaming for multi-ink 3D bioprinting.

Recently, the 3D printing of cell-laden hydrogel structures, known as bioprinting, has received increasing attention owing to advances in tissue engineering and drug screening. However, a micromixing technology that efficiently mixes viscous bioinks under mild conditions is needed. Therefore, this study presents a novel method for achieving homogeneous mixing of multiple inks in 3D bioprinting through acoustic stimulation. This technique involves generating an acoustic microstream through bubble oscillations inside a 3D bioprinting nozzle. We determined the optimal hole design for trapping a bubble, hole arrangement, and voltage for efficient mixing, resulting in a four-fold increase in mixing efficiency compared to a single bubble arrangement. Subsequently, we propose a nozzle design for efficient mixing during bioprinting. The proposed nozzle design enabled the successful printing of line structures with a uniform mixture of different viscous bioinks, achieving a mixing efficiency of over 80% for mixing 0.5-1.0 wt% sodium alginate aqueous solutions. Additionally, acoustic stimulation had no adverse effects on cell viability, maintaining a high cell viability of 88% after extrusion. This study presents the first use of a bubble micromixer in 3D bioprinting, demonstrating gentle yet effective multi-ink mixing. We believe this approach will broaden 3D printing applications, particularly for constructing functional structures in 3D bioprinting.

Composite bioink incorporating cell-laden liver decellularized extracellular matrix for bioprinting of scaffolds for bone tissue engineering.

The field of bone tissue engineering (BTE) has witnessed a revolutionary breakthrough with the advent of three-dimensional (3D) bioprinting technology, which is considered an ideal choice for constructing scaffolds for bone regeneration. The key to realizing scaffold biofunctions is the selection and design of an appropriate bioink, and existing bioinks have significant limitations. In this study, a composite bioink based on natural polymers (gelatin and alginate) and liver decellularized extracellular matrix (LdECM) was developed and used to fabricate scaffolds for BTE using 3D bioprinting. Through in vitro studies, the concentration of LdECM incorporated into the bioink was optimized to achieve printability and stability and to improve the proliferation and osteogenic differentiation of loaded rat bone mesenchymal stem cells (rBMSCs). Furthermore, in vivo experiments were conducted using a Sprague Dawley rat model of critical-sized calvarial defects. The proposed rBMSC-laden LdECM-gelatin-alginate scaffold, bioprinted layer-by-layer, was implanted in the rat calvarial defect and the development of new bone growth was studied for four weeks. The findings showed that the proposed bioactive scaffolds facilitated angiogenesis and osteogenesis at the defect site. The findings of this study suggest that the developed rBMSC-laden LdECM-gelatin-alginate bioink has great potential for clinical translation and application in solving bone regeneration problems.

Europium (III)-modified sunflower-derived carbon dots for fluorescent anti-counterfeiting inks and photocatalysis.

A highly water-soluble and fluorescent N,S-doped carbon dots/europium (N,S-CDs/Eu) was successfully synthesized via a secondary hydrothermal method. This involved surface modification of N,S-CDs derived from sunflower stem pith (SSP) with europium ions (Eu3+) doping. When excited within the range of 400-470 nm, N,S-CDs/Eu exhibited a stable and broad optimal emission wavelength ranging from 505 to 540 nm. Notably, the photoluminescence quantum yield (PLQY) of N,S-CDs/Eu is 31.4%, significantly higher than the 19.5% observed for N,S-CDs. Additionally, by dissolving N,S-CDs/Eu into polyvinyl alcohol (PVA), a uniform fluorescent anti-counterfeiting ink can be prepared. The N,S-CDs/Eu/TiO2 composite demonstrates excellent photocatalytic degradation ability towards the organic dye methylene blue (MB). N,S-CDs/Eu has potential in the field of fluorescent inks and photocatalysis due to its simple and efficient preparation and excellent properties.

Single-Component Cellulose Acetate Sulfate Hydrogels for Direct Ink Writing 3D Printing.

Hydrogels, typically favored for 3D printing due to their viscoelasticity, are now trending toward ecofriendly alternatives amid growing environmental concerns. In this study, we crafted cellulose-based hydrogels, specifically employing cellulose acetate sulfate (CAS). By keeping the acetyl group substitution degree (DSacetyl = 1.8) and CAS molecular weight constant, we varied rheological properties by adjusting sulfate group substitution (DSsulfate = 0.4, 0.7, and 1.0) and CAS concentration (2-5 wt %). Rheological characterizations, including shear-thinning, yield stress, and thixotropy, were performed to identify optimal conditions for formulating CAS hydrogel ink in direct ink writing for 3D printing under selected experimental conditions. Based on rheological findings, CAS hydrogels with DSsulfate 0.7 and concentration of 4 wt % was used for 3D printing, with subsequent evaluation of printing metrics. Additionally, the effect of ionic cross-linking using Ca2+ ions on the structural integrity of 3D-printed structures was evaluated, demonstrating effective preservation through reinforced polymer networks. The shrinking and swelling behaviors of the 3D-printed structures were also significantly affected by this ionic cross-linking. Building on these findings, this work could broaden the range of cellulose derivatives available for the preparation of cellulose-based hydrogels for 3D printing.

Cuttlefish ink-derived melanin nanoparticle-embedded tremella fuciformis polysaccharide hydrogels for the treatment of MRSA-infected diabetic wounds.

Diabetic wounds arise great attention as they are difficult to heal and easily suffer from serious bacterial infection. However, the overuse of antibiotics increases the resistance of bacteria and makes common drugs ineffective. Here, we developed a photothermal hydrogel (TFP/NP) composed of tremella fuciformis polysaccharides (TFPs) and cuttlefish ink-derived melanin nanoparticles (NPs). The NPs can produce reliable photothermal effects under near-infrared laser (NIR) irradiation and help to remove the bacteria in the wounds, while TFPs were able to form hydrogel frameworks which possessed anti-inflammatory effects and could be applied to promote wound healing. The TFP/NP hydrogels produced stable thermal effects under NIR irradiation and could continuously kill bacteria. The experiment on a full-layer skin wound sMRSA activity and could improve the healing efficiency. The wounds of the mice could be repaired within 14 days after reasonable treatment. In addition, the hydrogels play significant roles in promoting collagen deposition, anti-inflammation, angiogenesis, and cell proliferation during the therapeutic process. This research provides a simple and effective method for the therapy of bacterial infection wounds through the synergistic effect of TFPs and NPs.

Characterization and application of photocrosslinkable collagen maleate as bioink in extrusion-based 3D bioprinting.

3D bioprinting, a significant advancement in biofabrication, is renowned for its precision in creating tissue constructs. Collagen, despite being a gold standard biomaterial, faces challenges in bioink formulations due to its unique physicochemical properties. This study introduces a novel, neutral-soluble, photocrosslinkable collagen maleate (ColME) that is ideal for 3D bioprinting. ColME was synthesized by chemically modifying bovine type I collagen with maleic anhydride, achieving a high substitution ratio that shifted the isoelectric point to enhance solubility in physiological pH environments. This modification was confirmed to preserve the collagen's triple-helix structure substantially. Bioprinting parameters for ColME were optimized, focusing on adjustments to the bioink concentration, extrusion pressure, nozzle speed, and temperature. Results demonstrated that lower temperatures and smaller nozzle sizes substantially improved the print quality of grid structures. Additionally, the application of intermittent photo-crosslinking facilitated the development of structurally robust 3D multilayered constructs, enabling the stable fabrication of complex tissues. Cell viability assays showed that encapsulated cells within the ColME matrix maintained high viability after printing. When compared to methacrylated gelatin, ColME exhibited superior mechanical strength, resistance to enzymatic digestion, and overall printability, positioning it as an outstanding bioink for the creation of durable, bioactive 3D tissues.

Development of hybrid polyvinylpyrrolidone/carboxymethyl cellulose/collagen incorporated oregano scaffolds via direct ink write printing for potential wound healing applications.

Additive manufacturing can develop regenerative scaffolds for wound healing. 3D printing offers meticulous porosity, mechanical integrity, cell adhesion and cost-effectiveness. Herein, we prepared ink composed of carboxymethyl cellulose (CMC), polyvinylpyrrolidone (PVP), collagen, and oregano extract for the fabrication of tissue constructs. The blend was optimized to form a homogeneous ink and rheological characterization demonstrated shear thinning behavior. The scaffolds were printed using Direct Ink Write (DIW) at a flow speed of 4 mm3/s and a layer height of 0.18 mm. The fabricated scaffolds demonstrated an ultimate tensile strength (UTS) and toughness of 730 KPa and 2.72 MJ/m3, respectively. Scanning Electron Microscopy (SEM) revealed an average pore size of 300 ± 30 µm. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that all materials were present. The contact angle of the composite scaffold was 68° ± 1°. Moreover, the scaffolds presented 82 % mass loss (degradation) in phosphate buffer saline (PBS) over 14 days. The composite scaffold exhibited inhibition zones of 9 mm and 12 mm against Staphylococcus aureus and Escherichia coli, respectively. The PVP/CMC/collagen/oregano 3D printed scaffolds exhibited excellent biocompatibility with the mesenchymal stem cells and humman dermal fibroblast cells, confirmed by water-soluble tetrazolium - 8 (WST-8) assay (test conducted for 7 days). The enhanced angiogenic potential of said scaffold was assesed by release of vascular endothelial growth factor followed by further validation through in-vivo CAM assay. Thus, confirming suitability for the potential wound healing application.

Photo-annealable agarose microgels for jammed microgel printing: Transforming thermogelling hydrogel to a functional bioink.

Three-dimensional (3D) printing of hydrogel structures using jammed microgel inks offer distinct advantages of improved printing functionalities, as these inks are strain-yielding and self-recovering types. However, interparticle binding in granular hydrogel inks is a challenge to overcome the limited integrity and reduced macroscale modulus prevalent in the 3D printed microgel scaffolds. In this study, we prepared chemically annealable agarose microgels through a process of xerogel rehydration, applying a low-cost and high throughput method of spray drying. The crosslinked jammed microgel matrix is found to have superior mechanical properties with a Young's modulus of 2.23 MPa and extensibility up to 7.2%, surpassing those of traditional biopolymer-based and microgel-based inks. Furthermore, this study addresses the complexities encountered in the existing system of printing thermoresponsive agarose bioink using this jammed microgel printing approach. The jammed agarose microgel ink exhibited to be self-recovering, yield stress fluid and validated the temperature-independent printing. Furthermore, the 3D printed jammed microgel scaffold demonstrated good cell responsiveness as evaluated through the viability and morphological study in-vitro with mesenchymal stem cells cultured in it. This unique fabrication approach offers exciting possibilities to expand on microgel printing for varied requirements in tissue engineering.

Vascular tissues bioprinted with smooth muscle cell-only bioinks in support baths mimic features of native coronary arteries.

This study explores the bioprinting of a smooth muscle cell-only bioink into ionically crosslinked oxidized methacrylated alginate (OMA) microgel baths to create self-supporting vascular tissues. The impact of OMA microgel support bath methacrylation degree and cell-only bioink dispensing parameters on tissue formation, remodeling, structure and strength was investigated. We hypothesized that reducing dispensing tip diameter from 27 G (210µm) to 30 G (159µm) for cell-only bioink dispensing would reduce tissue wall thickness and improve the consistency of tissue dimensions while maintaining cell viability. Printing with 30 G tips resulted in decreased mean wall thickness (318.6µm) without compromising mean cell viability (94.8%). Histological analysis of cell-only smooth muscle tissues cultured for 14 d in OMA support baths exhibited decreased wall thickness using 30 G dispensing tips, which correlated with increased collagen deposition and alignment. In addition, a TUNEL assay indicated a decrease in cell death in tissues printed with thinner (30 G) dispensing tips. Mechanical testing demonstrated that tissues printed with a 30 G dispensing tip exhibit an increase in ultimate tensile strength compared to those printed with a 27 G dispensing tip. Overall, these findings highlight the importance of precise control over bioprinting parameters to generate mechanically robust tissues when using cell-only bioinks dispensed and cultured within hydrogel support baths. The ability to control print dimensions using cell-only bioinks may enable bioprinting of more complex soft tissue geometries to generatein vitrotissue models.

Exploiting CO2 laser to boost graphite inks electron transfer for fructose biosensing in biological fluids.

The possibility to print electronics by means of office tools has remarkedly increased the possibility to design affordable and robust point-of-care/need devices. However, conductive inks suffer from low electrochemical and rheological performances limiting their applicability in biosensors. Herein, a fast CO2 laser approach to activate printed carbon inks towards direct enzymatic bioelectrocatalysis (3rd generation) is proposed and exploited to build biosensors for D-fructose analysis in biological fluids. The CO2 laser treatment was compared with two lab-grade printed transducers fabricated with solvent (SB) and water (WB) based carbon inks. The use of the laser revealed significant morpho-chemical variations on the printed inks and was investigated towards enzymatic direct catalysis, using Fructose dehydrogenase (FDH) integrated into entirely lab-produced biosensors. The laser-driven activation of the inks unveils the inks' direct electron transfer (DET) ability between FDH and the electrode surface. Sub-micromolar limits of detection (SB-ink LOD = 0.47 µM; WB-ink LOD = 0.24 µM) and good linear ranges (SB-ink: 5-100 µM; WB-ink: 1-50 µM) were obtained, together with high selectivity due to use of the enzyme and the low applied overpotential (0.15 V vs. pseudo-Ag/AgCl). The laser-activated biosensors were successfully used for D-fructose determination in complex synthetic and real biological fluids (recoveries: 93-112%; RSD ≤8.0%, n = 3); in addition, the biosensor ability for continuous measurement (1.5h) was also demonstrated simulating physiological D-fructose fluctuations in cerebrospinal fluid.

In vitrothree-dimensional volumetric printing of vitreous body models using decellularized extracellular matrix bioink.

Hyalocytes, which are considered to originate from the monocyte/macrophage lineage, play active roles in vitreous collagen and hyaluronic acid synthesis. Obtaining a hyalocyte-compatible bioink during the 3D bioprinting of eye models is challenging. In this study, we investigated the suitability of a cartilage-decellularized extracellular matrix (dECM)-based bioink for printing a vitreous body model. Given that achieving a 3D structure and environment identical to those of the vitreous body necessitates good printability and biocompatibility, we examined the mechanical and biological properties of the developed dECM-based bioink. Furthermore, we proposed a 3D bioprinting strategy for volumetric vitreous body fabrication that supports cell viability, transparency, and self-sustainability. The construction of a 3D structure composed of bioink microfibers resulted in improved transparency and hyalocyte-like macrophage activity in volumetric vitreous mimetics, mimicking real vitreous bodies. The results indicate that our 3D structure could serve as a platform for drug testing in disease models and demonstrate that the proposed printing technology, utilizing a dECM-based bioink and volumetric vitreous body, has the potential to facilitate the development of advanced eye models for future studies on floater formation and visual disorders.

3D printing for constructing biocarriers using sodium alginate/ε-poly-l-lysine ink: Enhancing microbial enrichment for efficient nitrogen removal in wastewater.

The microbial enrichment of traditional biocarriers is limited due to the inadequate consideration of spatial structure and surface charging characteristics. Here, capitalizing on the ability of 3D printing technology to fabricate high-resolution materials, we further designed a positively charged sodium alginate/ε-poly-l-lysine (SA/ε-PL) printing ink, and the 3D printed biocarriers with ideal pore structure and rich positive charge were constructed to enhance the microbial enrichment. The rheological and mechanical tests confirmed that the developed SA/ε-PL ink could simultaneously satisfy the smooth extrusion for printing process and the maintenance of 3D structure. The utilization of the ε-PL secondary cross-linking strategy reinforced the 3D mechanical structure and imparted the requisite physical properties for its application as a biocarrier. Compared with traditional sponge carriers, 3D printed biocarrier had a faster initial attachment rate and a higher biomass of 14.58 ± 1.18 VS/cm3, and the nitrogen removal efficiency increased by 53.9 %. Besides, due to the superior electrochemical properties and biocompatibility, the 3D printed biocarriers effectively enriched the electroactive denitrifying bacteria genus Trichococcus, thus supporting its excellent denitrification performance. This study provided novel insights into the development of new functional biocarriers in the wastewater treatment, thereby providing scientific guidance for practical engineering.

Depletion Flocculation of High Internal Phase Pickering Emulsion Inks: A Colloidal Engineering Approach to Develop 3D Printed Porous Scaffolds with Tunable Bioactive Delivery.

Flocculation is a type of aggregation where the surfaces of approaching droplets are still at distances no closer than a few nanometers while still remaining in close proximity. In a high internal-phase oil-in-water (O/W) emulsion, the state of flocculation affects the bulk flow behavior and viscoelasticity, which can consequently control the three-dimensional (3D)-printing process and printing performance. Herein, we present the assembly of O/W Pickering high-internal-phase emulsions (Pickering-HIPEs) as printing inks and demonstrate how depletion flocculation in such Pickering-HIPE inks can be used as a facile colloidal engineering approach to tailor a porous 3D structure suitable for drug delivery. Pickering-HIPEs were prepared using different levels of cellulose nanocrystals (CNCs), co-stabilized using "raw" submicrometer-sized sustainable particles from a biomass-processing byproduct. In the presence of this sustainable particle, the higher CNC contents facilitated particle-induced depletion flocculation, which led to the formation of a mechanically robust gel-like ink system. Nonetheless, the presence of adsorbed particles on the surface of droplets ensured their stability against coalescence, even in such a highly aggregated system. The gel structures resulting from the depletion phenomenon enabled the creation of high-performance printed objects with tunable porosity, which can be precisely controlled at two distinct levels: first, by introducing voids within the internal structure of filaments, and second, by generating cavities (pore structures) through the elimination of the water phase. In addition to printing efficacy, the HIPEs could be applied for curcumin delivery, and in vitro release kinetics demonstrated that the porous 3D scaffolds engineered for the first time using depletion-flocculated HIPE inks played an important role in 3D scaffold disintegration and curcumin release. Thus, this study offers a unique colloidal engineering approach of using depletion flocculation to template 3D printing of sustainable inks to generate next-generation porous scaffolds for personalized drug deliveries.

Constraint based Bayesian optimization of bioink precursor: a machine learning framework.

Current research practice for optimizing bioink involves exhaustive experimentation with multi-material composition for determining the printability, shape fidelity and biocompatibility. Predicting bioink properties can be beneficial to the research community but is a challenging task due to the non-Newtonian behavior in complex composition. Existing models such as Cross model become inadequate for predicting the viscosity for heterogeneous composition of bioinks. In this paper, we utilize a machine learning framework to accurately predict the viscosity of heterogeneous bioink compositions, aiming to enhance extrusion-based bioprinting techniques. Utilizing Bayesian optimization (BO), our strategy leverages a limited dataset to inform our model. This is a technique especially useful of the typically sparse data in this domain. Moreover, we have also developed a mask technique that can handle complex constraints, informed by domain expertise, to define the feasible parameter space for the components of the bioink and their interactions. Our proposed method is focused on predicting the intrinsic factor (e.g. viscosity) of the bioink precursor which is tied to the extrinsic property (e.g. cell viability) through the mask function. Through the optimization of the hyperparameter, we strike a balance between exploration of new possibilities and exploitation of known data, a balance crucial for refining our acquisition function. This function then guides the selection of subsequent sampling points within the defined viable space and the process continues until convergence is achieved, indicating that the model has sufficiently explored the parameter space and identified the optimal or near-optimal solutions. Employing this AI-guided BO framework, we have developed, tested, and validated a surrogate model for determining the viscosity of heterogeneous bioink compositions. This data-driven approach significantly reduces the experimental workload required to identify bioink compositions conducive to functional tissue growth. It not only streamlines the process of finding the optimal bioink compositions from a vast array of heterogeneous options but also offers a promising avenue for accelerating advancements in tissue engineering by minimizing the need for extensive experimental trials.

Effect of viscosity of gelatin methacryloyl-based bioinks on bone cells.

The viscosity of gelatin methacryloyl (GelMA)-based bioinks generates shear stresses throughout the printing process that can affect cell integrity, reduce cell viability, cause morphological changes, and alter cell functionality. This study systematically investigated the impact of the viscosity of GelMA-gelatin bioinks on osteoblast-like cells in 2D and 3D culture conditions. Three bioinks with low, medium, and high viscosity prepared by supplementing a 5% GelMA solution with different concentrations of gelatin were evaluated. Cell responses were studied in a 2D environment after printing and incubation in non-cross-linked bioinks that caused the gelatin and GelMA to dissolve and release cells for attachment to tissue culture plates. The increased viscosity of the bioinks significantly affected cell area and aspect ratio. Cells printed using the bioink with medium viscosity exhibited greater metabolic activity and proliferation rate than those printed using the high viscosity bioink and even the unprinted control cells. Additionally, cells printed using the bioink with high viscosity demonstrated notably elevated expression levels of alkaline phosphatase and bone morphogenetic protein-2 genes. In the 3D condition, the printed cell-laden hydrogels were photo-cross-linked prior to incubation. The medium viscosity bioink supported greater cell proliferation compared to the high viscosity bioink. However, there were no significant differences in the expression of osteogenic markers between the medium and high viscosity bioinks. Therefore, the choice between medium and high viscosity bioinks should be based on the desired outcomes and objectives of the bone tissue engineering application. Furthermore, the bioprinting procedure with the medium viscosity bioink was used as an automated technique for efficiently seeding cells onto 3D printed porous titanium scaffolds for bone tissue engineering purposes.

Techniques and applications in 3D bioprinting with chitosan bio-inks for drug delivery: A review.

Three-dimensional bioprinting leverages computer-aided design to construct tissues and organs with specialized bioinks. A notable biomaterial for this purpose is chitosan, a natural polysaccharide sourced from crustacean exoskeletons. Chitosan's biocompatibility, biodegradability, non-toxicity, and ability to promote cell adhesion and proliferation make it an excellent component for bioinks. Initially, the rheological properties of chitosan presented challenges for its use in bioprinting. Enhancements in its printability and stability were achieved by integrating it with other natural or synthetic polymers, facilitating its successful application in bioprinting. Chitosan-based bioinks are particularly promising for controlled drug delivery. Incorporating pharmaceuticals directly into the bioink enables the printed structures to serve as localized, sustained-release systems. This approach offers multiple advantages, including precise drug delivery to targeted disease sites, increased therapeutic efficiency, and reduced systemic side effects. Moreover, bioprinting allows for the customization of drug delivery mechanisms to meet individual patient requirements. Although there have been considerable advancements, the use of chitosan-based bioinks in drug delivery is still an emerging field. This review highlights chitosan's essential role in both systemic and localized drug delivery, underscoring its significance and discussing ongoing trends in its application for pharmaceutical purposes.

Detection of anaerobic and aerobic bacteria from commercial tattoo and permanent makeup inks.

Tattooing and use of permanent makeup (PMU) have dramatically increased over the last decade, with a concomitant increase in ink-related infections. Studies have shown evidence that commercial tattoo and PMU inks are frequently contaminated with pathogenic microorganisms. Considering that tattoo inks are placed into the dermal layer of the skin where anaerobic bacteria can thrive and cause infections in low-oxygen environments, the prevalence of anaerobic and aerobic bacteria should be assessed in tattoo and PMU inks. In this study, we tested 75 tattoo and PMU inks using the analytical methods described in the FDA Bacteriological Analytical Manual Chapter 23 for the detection of both aerobic and anaerobic bacterial contamination, followed by 16S rRNA gene sequencing for microbial identification. Of 75 ink samples, we found 26 contaminated samples with 34 bacterial isolates taxonomically classified into 14 genera and 22 species. Among the 34 bacterial isolates, 19 were identified as possibly pathogenic bacterial strains. Two species, namely Cutibacterium acnes (four strains) and Staphylococcus epidermidis (two strains) were isolated under anaerobic conditions. Two possibly pathogenic bacterial strains, Staphylococcus saprophyticus and C. acnes, were isolated together from the same ink samples (n = 2), indicating that tattoo and PMU inks can contain both aerobic (S. saprophyticus) and anaerobic bacteria (C. acnes). No significant association was found between sterility claims on the ink label and the absence of bacterial contamination. The results indicate that tattoo and PMU inks can also contain anaerobic bacteria. IMPORTANCE: The rising popularity of tattooing and permanent makeup (PMU) has led to increased reports of ink-related infections. This study is the first to investigate the presence of both aerobic and anaerobic bacteria in commercial tattoo and PMU inks under aerobic and anaerobic conditions. Our findings reveal that unopened and sealed tattoo inks can harbor anaerobic bacteria, known to thrive in low-oxygen environments, such as the dermal layer of the skin, alongside aerobic bacteria. This suggests that contaminated tattoo inks could be a source of infection from both types of bacteria. The results emphasize the importance of monitoring these products for both aerobic and anaerobic bacteria, including possibly pathogenic microorganisms.

Preparation of thermochromic ink from anthocyanidin-encapsulated alginate nanoparticles for anticounterfeiting applications.

In order to make commercial products less vulnerable to counterfeiting, thermochromic inks have proven to be a viable authentication strategy. Herein, we developed a thermochromic ink for authentication by combining an anthocyanidin (ACYD) extract with alginate (ALG). To increase the anthocyanidin/alginate ink stability, a mordant (ferrous sulfate) was employed to tie up the anthocyanidin biomolecules with alginate. ACYD was extracted from red-cabbage and then immobilized into alginate to serve as an environmentally friendly spectroscopic probe. Thermochromic composite inks (ACYD@ALG) were made by adjusting the content of anthocyanidin. A homogenous blue film (608 nm) was printed on a paper surface and investigated by the CIE Lab coordinate system. The blue color transformed into reddish (477 nm) when heated from 35°C to 65°C. Nanoparticles (NPs) of anthocyanidin/mordant (ACYD/M) were examined for their size and morphology to indicate diameters of 80-90 nm, whereas the ACYD/M-encapsulated alginate nanoparticles showed diameters of 120-150 nm. Multiple analytical techniques were utilized to examine the printed papers. The mechanical and rheological performance of both stamped sheets and ink fluid were explored. The cytotoxicity and antimicrobial efficacy of ink (ACYD@ALG) were investigated.

Aptamer Based on Silver Nanoparticle-Modified Flexible Carbon Ink Printed Electrode for the Electrochemical Detection of Chikungunya Virus.

Medical devices have progressed from their initial bulky forms to smart devices. However, their rigidity hampers their seamless integration into everyday life. The fields of stretchable, textile, and flexible electronics are emerging research areas with the potential to drive significant technological progress. This research presents a laboratory-based technique to produce highly sensitive and flexible biosensors for detecting the chikungunya virus. These biosensors are based on 0D nanomaterials and demonstrate significant advancements in voltammetry. The electrochemical platform was created utilizing the stencil printing (StPE) technique. Adapting the biosensor setup involved the selection of aptamer as the biorecognition element bound with silver nanoparticles (AgNPs). This biosensor was employed in the voltammetric identification of the Chikungunya virus antigen (CHIKV-Ag) within a solution containing 0.5 mM potassium ferro/ferri cyanide, a redox pair. The biosensor was employed to evaluate CHIKV-Ag within a human serum sample. It demonstrated a linear detection span ranging from 0.1 ng/mL to 1 µg/mL, with a detection limit of 0.1 ng/mL for CHIKV-Ag. The proposed approach, due to its flexibility in production and the electrocatalytic attributes displayed by the zero-dimensional nanostructure, presents innovative opportunities for cost-effective and tailored aptamer-based bioelectronics, thereby broadening the scope of this domain.