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.

Correction: Integrated biosensors for monitoring microphysiological systems.

Correction for 'Integrated biosensors for monitoring microphysiological systems' by Lei Mou et al., Lab Chip, 2022, 22, 3801-3816, https://doi.org/10.1039/D2LC00262K.

Engineered organoids for biomedical applications.

As miniaturized and simplified stem cell-derived 3D organ-like structures, organoids are rapidly emerging as powerful tools for biomedical applications. With their potential for personalized therapeutic interventions and high-throughput drug screening, organoids have gained significant attention recently. In this review, we discuss the latest developments in engineering organoids and using materials engineering, biochemical modifications, and advanced manufacturing technologies to improve organoid culture and replicate vital anatomical structures and functions of human tissues. We then explore the diverse biomedical applications of organoids, including drug development and disease modeling, and highlight the tools and analytical techniques used to investigate organoids and their microenvironments. We also examine the latest clinical trials and patents related to organoids that show promise for future clinical translation. Finally, we discuss the challenges and future perspectives of using organoids to advance biomedical research and potentially transform personalized medicine.

Rapid integration of screen-printed electrodes into thermoplastic organ-on-a-chip devices for real-time monitoring of trans-endothelial electrical resistance.

Trans-endothelial electrical resistance (TEER) is one of the most widely used indicators to quantify the barrier integrity of endothelial layers. Over the last decade, the integration of TEER sensors into organ-on-a-chip (OOC) platforms has gained increasing interest for its efficient and effective measurement of TEER in OOCs. To date, microfabricated electrodes or direct insertion of wires has been used to integrate TEER sensors into OOCs, with each method having advantages and disadvantages. In this study, we developed a TEER-SPE chip consisting of carbon-based screen-printed electrodes (SPEs) embedded in a poly(methyl methacrylate) (PMMA)-based multi-layered microfluidic device with a porous poly(ethylene terephthalate) membrane in-between. As proof of concept, we demonstrated the successful cultures of hCMEC/D3 cells and the formation of confluent monolayers in the TEER-SPE chip and obtained TEER measurements for 4 days. Additionally, the TEER-SPE chip could detect changes in the barrier integrity due to shear stress or an inflammatory cytokine (i.e., tumor necrosis factor-α). The novel approach enables a low-cost and facile fabrication of carbon-based SPEs on PMMA substrates and the subsequent assembly of PMMA layers for rapid prototyping. Being cost-effective and cleanroom-free, our method lowers the existing logistical and technical barriers presenting itself as another step forward to the broader adoption of OOCs with TEER measurement capability.

Malignant choroidal melanoma with vitreous seeds: supported by histopathology and field emission scanning electron microscopy study.

Aim: To report an exceptionally rare case of malignant choroidal melanoma with vitreous seeding, supported by histopathological and field emission scanning electron microscopic (FESEM) studies. Case report: A 58-year-old male with painless diminution of vision in his left eye for past 1 month was found to have a brown retrolental mass lesion on slit lamp examination in the left eye. Detailed fundus examination revealed choroidal melanoma in the left eye with pigmented seeds extending into the vitreous cavity and associated exudative retinal detachment. Ocular imaging was consistent with the diagnosis. Results: The eyeball was enucleated and the tumor was considered as stage IIB (AJCC 8th edition classification). Metastatic workup of the patient was negative. One half of the eyeball was subjected to field emission scanning electron microscopy to further study the nature and appearance of vitreous seeds. Discussion: Vitreous seeding in choroidal melanoma has been reported only in a handful of cases in literature. Histopathological confirmation of vitreous seeds was done in our case and morphological detailing was performed using FESEM study. Conclusions: Treatment naïve choroidal melanoma can very rarely have vitreous seeds. Early enucleation in such cases carries a favorable prognosis.

Vascularized adipose tissue engineering: moving towards soft tissue reconstruction.

Soft tissue defects are a common clinical challenge mostly caused by trauma, congenital anomalies and oncological surgery. Current soft tissue reconstruction options include synthetic materials (fillers and implants) and autologous adipose tissue transplantation through flap surgery and/or lipotransfer. Both reconstructive options hold important disadvantages to which vascularized adipose tissue engineering (VATE) strategies could offer solutions. In this review, we first summarized pivotal characteristics of functional adipose tissue such as the structure, function, cell types, development and extracellular matrix (ECM). Next, we discussed relevant cell sources and how they are applied in different state-of-the-art VATE techniques. Herein, biomaterial scaffolds and hydrogels, ECMs, spheroids, organoids, cell sheets, three dimensional printing and microfluidics are overviewed. Also, we included extracellular vesicles and emphasized their potential role in VATE. Lastly, current challenges and future perspectives in VATE are pointed out to help to pave the road towards clinical applications.

Engineered Vasculature for Cancer Research and Regenerative Medicine.

Engineered human tissues created by three-dimensional cell culture of human cells in a hydrogel are becoming emerging model systems for cancer drug discovery and regenerative medicine. Complex functional engineered tissues can also assist in the regeneration, repair, or replacement of human tissues. However, one of the main hurdles for tissue engineering, three-dimensional cell culture, and regenerative medicine is the capability of delivering nutrients and oxygen to cells through the vasculatures. Several studies have investigated different strategies to create a functional vascular system in engineered tissues and organ-on-a-chips. Engineered vasculatures have been used for the studies of angiogenesis, vasculogenesis, as well as drug and cell transports across the endothelium. Moreover, vascular engineering allows the creation of large functional vascular conduits for regenerative medicine purposes. However, there are still many challenges in the creation of vascularized tissue constructs and their biological applications. This review will summarize the latest efforts to create vasculatures and vascularized tissues for cancer research and regenerative medicine.

Recent advances in biopolymer-based hemostatic materials.

Hemorrhage is the leading cause of trauma-related deaths, in hospital and prehospital settings. Hemostasis is a complex mechanism that involves a cascade of clotting factors and proteins that result in the formation of a strong clot. In certain surgical and emergency situations, hemostatic agents are needed to achieve faster blood coagulation to prevent the patient from experiencing a severe hemorrhagic shock. Therefore, it is critical to consider appropriate materials and designs for hemostatic agents. Many materials have been fabricated as hemostatic agents, including synthetic and naturally derived polymers. Compared to synthetic polymers, natural polymers or biopolymers, which include polysaccharides and polypeptides, have greater biocompatibility, biodegradability and processibility. Thus, in this review, we focus on biopolymer-based hemostatic agents of different forms, such as powder, particles, sponges and hydrogels. Finally, we discuss biopolymer-based hemostatic materials currently in clinical trials and offer insight into next-generation hemostats for clinical translation.

Integrated biosensors for monitoring microphysiological systems.

Microphysiological systems (MPSs), also known as organ-on-a-chip models, aim to recapitulate the functional components of human tissues or organs in vitro. Over the last decade, with the advances in biomaterials, 3D bioprinting, and microfluidics, numerous MPSs have emerged with applications to study diseased and healthy tissue models. Various organs have been modeled using MPS technology, such as the heart, liver, lung, and blood-brain barrier. An important aspect of in vitro modeling is the accurate phenotypical and functional characterization of the modeled organ. However, most conventional characterization methods are invasive and destructive and do not allow continuous monitoring of the cells in culture. On the other hand, microfluidic biosensors enable in-line, real-time sensing of target molecules with an excellent limit of detection and in a non-invasive manner, thereby effectively overcoming the limitation of the traditional techniques. Consequently, microfluidic biosensors have been increasingly integrated into MPSs and used for in-line target detection. This review discusses the state-of-the-art microfluidic biosensors by providing specific examples, detailing their main advantages in monitoring MPSs, and highlighting current developments in this field. Finally, we describe the remaining challenges and potential future developments to advance the current state-of-the-art in integrated microfluidic biosensors.

Organ-On-A-Chip Models of the Blood-Brain Barrier: Recent Advances and Future Prospects.

The human brain and central nervous system (CNS) present unique challenges in drug development for neurological diseases. One major obstacle is the blood-brain barrier (BBB), which hampers the effective delivery of therapeutic molecules into the brain while protecting it from blood-born neurotoxic substances and maintaining CNS homeostasis. For BBB research, traditional in vitro models rely upon Petri dishes or Transwell systems. However, these static models lack essential microenvironmental factors such as shear stress and proper cell-cell interactions. To this end, organ-on-a-chip (OoC) technology has emerged as a new in vitro modeling approach to better recapitulate the highly dynamic in vivo human brain microenvironment so-called the neural vascular unit (NVU). Such BBB-on-a-chip models have made substantial progress over the last decade, and concurrently there has been increasing interest in modeling various neurological diseases such as Alzheimer's disease and Parkinson's disease using OoC technology. In addition, with recent advances in other scientific technologies, several new opportunities to improve the BBB-on-a-chip platform via multidisciplinary approaches are available. In this review, an overview of the NVU and OoC technology is provided, recent progress and applications of BBB-on-a-chip for personalized medicine and drug discovery are discussed, and current challenges and future directions are delineated.

Pathologic evidence of retinoblastoma seeds supported by field emission scanning electron microscopy and Raman spectroscopy.

PURPOSE: The aim of this study was to examine the pathology of retinoblastoma (RB) seeds with supportive evidence by field emission scanning electron microscopy and Raman spectroscopy. METHODS: This study was a laboratory-based observational study. Enucleated eyeballs received in the ocular pathology department of a tertiary eye care center in northeast India were included in the cohort after obtaining written informed consent during the surgery. The study was carried out for 6 years (2015-2020). Most of the eyeballs were Group-E RBs. Standard eyeballs sectioning were done by bread loaf techniques. Gross documentations included RB seeds seen in the smallest calotte done with utmost care. Seeds were documented also in permanent sections. Scanning electron microscopy and Raman spectroscopy were carried out in an index case. RESULTS: Out of the total 59 cases, 35 RB cases had different seedings. The mean age at enucleation was 2.9 years. RB seeds were seen in vitreous (n = 19), subretinal plus vitreous (n = 7), anterior chamber (n = 1), over crystalline lens (n = 3), retinal surface (n = 1), retinal pigment epithelium (RPE; n = 2), subretinal (n = 1), calcified seeds (n = 2). Other characteristics were dusts (n = 7), clouds (n = 11), spheres (n = 4), and unspecified type (n = 13). Histopathological high-risk factors showed significant choroidal (n = 22) and optic nerve (n = 15) involvement. Few cases had extraocular spread. Undifferentiated tumor (n = 24) was seen with higher evidence of necrosis (n = 23). Raman spectra differentiated the seeds from the normal tissue on the basis of lipid and protein content. CONCLUSION: This study highlights the different types of RB seeds with high-risk factors. The morphology of those seeds showed the difference between vitreous and subretinal seeds under advanced microscopic observations.

Real-time transport kinetics of drug encapsulated nanoparticles into apoptotic cancer cells inside microchannels.

Development of nanocomposites as drug delivery vectors is a burgeoning field of research. However, the usage of such newly invented nanomatrices are often limited by the shortcomings associated with the testing of their real-life efficacy. Many drugs fail because a monolayer framework ofin vitrocell line screening method does not adequately mimic thein vivothree-dimensional microenvironments. In this direction, the study unveils the development of a continuous flow microreactor wherein the cellulose acetate nanoparticles (CANPs) with varying sizes are prepared before encapsulating them with an anticancer drug-doxorubicin (DOX). Subsequently, anin vitromicrofluidic drug delivery model has been introduced in which the HeLa cells specific to cervical cancer is treated with the DOX encapsulated CANPs-DOX@CANPs. Thereafter, the transport of the drugs from the fluidic to cellular environment, their transport inside the cell, and the real-time kinetics of the cancer cell apoptosis have been analyzed systematically to uncover the real-time efficacy and cytotoxic effects of the nanocomposite. Interestingly, experiments reveal, (i) ∼89.4% DOX loading on the nanocomposite owing to a facile electrostatic interaction, (ii) a pH-dependent controlled release of drug during the transport with the cancer cells, and (iii) cell apoptosis after the diffused inoculation of the drug. A mathematical model has been developed to emulate the drug transport from the surrounding fluid to the cancer cells. Experiments together with the mathematical model uncover that the kinetics of cancer cell death is limited by the reaction at the cell-nucleus. The microfluidic model has shown significant potential to be translated as a useful tool for the real-time and on-demandin vitroscreening of the cancer drugs.

Multifunctional liquid marbles to stabilize and transport reactive fluids.

The self-organized transport and delivery of reactive liquids without spillage or loss of activity have been among the most daunting challenges for a long time. In this direction, we employ the concept of forming "liquid marbles" (LMs) to encapsulate and transport reactive hydrogen peroxide (H2O2) coated with functional microparticles. For example, peroxide marbles coated with a toner ink display remote-controlled magnetotactic movement inside a fluidic medium, thus overcoming the weaknesses associated with use of the bare droplets. Interestingly, in such a scenario, the coating of the marbles could also be removed or reformed by bringing the magnet towards or away from the marble. In this way, this process could ensure an on-demand remotely guided coating on the peroxide droplet or its removal. The liquid marbles carrying peroxide solutions are found to preserve the activity of the peroxide and exhibit a low evaporation rate compared with the uncoated peroxide fuel. Interestingly, oil droplets floating on the water could be recovered by introducing the armoured LMs into water under magnetic guidance. Further, the functionalized marbles could be employed as suicide bags for the on-demand delivery of reactive materials in targeted locations. Preliminary research on the antibacterial activity of such liquid marbles has proven to be effective in bacterial killing, which may create new avenues for emerging antibacterial and antibiofilm applications. Finally, such functionalized LMs have been employed to investigate the effects of surface charge on attachment of recombinant Escherichia coli bacteria expressing green fluorescent protein and monitoring the real-time imaging of bacterial death attached to the marble surface.

Self-Organized Implanting of Micro/Nanofiltration Membranes in Advanced Flow µ-Reactors.

A low-cost, simple, and one-step synthesis of cellulose acetate nanoparticles (CANPs) has been invented using a continuous-flow advanced microfluidic reactor. For this purpose, the CANPs are self-organized inside a cross-junction microchannel by flowing cellulose acetate (CA) dissolved in N,N-dimethylformamide (DMF) through the axial inlet and the antisolvent water through the pair of side inlets. The preferential solubility (insolubility) of DMF (CA) to antisolvent water stimulates the in situ synthesis of CANPs at the DMF/water miscible interface following a phase-inversion process. Subsequently, nanofiltration, ultrafiltration, and microfiltration membranes of different porosities and permeabilities have been prepared from freshly synthesized CANPs. The porosity, thickness, transparency, and wettability of the membranes are tuned by varying the thickness of the membranes, size of the nanoparticles, and the porosity of the membranes. The as-synthesized CANPs show enhanced bactericidal properties with and without loading an external drug, curcumin, which has been validated against the Gram-negative Pseudomonas aeruginosa species. Importantly, enabling a pulsatile flow during the synthesis, the CANPs are embedded as nanofiltration membranes inside the microfluidic channel. Such microfluidic devices have been used to separate a corrosive dye from water. Concisely, the proposed in situ synthesis of CANPs in the continuous-flow microfluidic reactors, their usage for fabricating membranes with tunable wettability and transparency, and their subsequent integration into the microfluidic channel show the potential of the invention for a host of applications related to health care and environmental remediation.

Self-organization of random copolymers to nanopatterns by localized e-beam dosing.

Strategic electron beam (e-beam) irradiation on the surface of an ultrathin (<100 nm) film of polystyrene-poly(methyl methacrylate) (PS-PMMA) random copolymer followed by solvent annealing stimulates a special variety of dewetting, leading to large-area hierarchical nanoscale patterns. For this purpose, initially, a negative (positive) tone of resist PS (PMMA) under weak e-beam exposure is exploited to produce an array of sites composed of cross-linked PS (chain-scissioned PMMA). Subsequently, annealing with the help of a developer solvent engenders dewetted patterns in the exposed zones where PMMA blocks are confined by the blocks of cross-linked PS. The e-beam dosage was systematically varied from 180µC cm-2to 10 000µC cm-2to explore the tone reversal behavior of PMMA on the dewetted patterns. Remarkably, at relatively higher e-beam dosing, both PMMA and PS blocks act as negative tones in the exposed zone. In contrast, the chain scission of PMMA in the periphery of the exposed regions due to scattered secondary electrons caused confined dewetting upon solvent annealing. Such occurrences eventually lead to pattern miniaturization an order of magnitude greater than with conventional thermal or solvent vapor annealed dewetting. Selective removal of PMMA blocks of RCP using a suitable solvent provided an additional 50% reduction in the size of the dewetted features.

Magnetotactic T-Budbots to Kill-n-Clean Biofilms.

Treatment of persistent biofilm infections has turned out to be a formidable challenge even with broad-spectrum antibiotic therapies. In this direction, intelligent micromachines may serve as active mechanical means to dislodge such deleterious bacterial communities. Herein, we have designed biocompatible micromotors from tea buds, namely, T-Budbots, which shows the capacity to be magnetically driven on a biofilm matrix and remove or fragment biofilms with precision, as a part of the proposed non-invasive "Kill-n-Clean" strategy. In a way, we present a bactericidal robotic platform decorated with magnetite nanoparticles aimed at clearing in vitro biofilms present on the surfaces. We have also shown that the smart porous T-Budbots can integrate antibiotic ciprofloxacin due to electrostatic interaction on their surface to increase their antibacterial efficacy against dreadful pathogenic bacterial communities of Pseudomonas aeruginosa and Staphylococcus aureus. It is noteworthy that the release of this drug can be controlled by tuning the surrounding pH of the T-Budbots. For example, while the acidic environment of the biofilm facilitates the release of antibiotics from the porous T-Budbots, the drug release was rather minimal at higher pH. The work represents a first step in the involvement of a plant-based microbot exhibiting magneto-robotic therapeutic properties, providing a non-invasive and safe approach to dismantle harmful biofilm infections.

Multimodal chemo-/magneto-/phototaxis of 3G CNT-bots to power fuel cells.

We report the development of a 3G microswimmer, namely, CNT-bot, capable of undergoing acid-, alkali-, magneto- and phototaxis inside acidic or alkaline baths of peroxide fuel and/or water. The use of carboxyl-functionalised multi-walled carbon nanotubes (MWCNTs) facilitated the propulsion of CNT-bots in an alkaline-water solution by ejecting carbon-dioxide bubbles. Furthermore, doping of magnetite nanoparticles (FeONPs), ferrous ions (Fe2+) and titanium dioxide nanoparticles (TiONPs) induces magnetic, chemical and photonic modes of propulsion. While FeONPs stimulated magnetotaxis at a rate of up to ~10 body lengths per second under the influence of a bar magnet, chemotaxis of a similar speed in a peroxide fuel was achieved by bubble-propulsion of oxygen gas originating from the Fenton reaction. In addition, the light-stimulated photo-Fenton reaction led to phototaxis of CNT-bots. A thin coating of magnesium imparted a half-faced Janus appearance to the CNT-bots, which facilitated motion in normal or acidic water media through the ejection of hydrogen gas bubbles. This chemotaxis could be transformed into pH-stimulated directional motion by establishing an acid or alkali concentration gradient across the peroxide and/or water baths. The capacity of CNT-bots to produce oxygen (hydrogen) bubbles in peroxide (acidic water) fuel was exploited to power a PEM fuel cell to generate electricity. The pure oxygen and hydrogen gases generated by CNT-bots in separate chambers were fed directly into the fuel cell in which the incessant motions of the particle facilitated the creation and release of the pure gases to achieve on-demand electricity generation. The motor could also induce dye degradation through advanced oxidation owing to the production of intermediate hydroxyl radicals during the Fenton reaction.

Electric field assisted multicomponent reaction in a microfluidic reactor for superior conversion and yield.

We explore the improvements in yield and conversion of a chemical reaction inside a two-phase microfluidic reactor when subjected to an externally applied alternating current (AC) electric field. A computational fluid dynamic (CFD) framework has been developed to incorporate the descriptions of the two-phase flow, multicomponent transport and reaction, and the Maxwell's stresses generated at oil-water interface owing to the presence of the externally applied electric field. The CFD model ensures that the reactants are flown into a microchannel together with the oil and water phases before the reaction takes place at the interface and products diffuse back to the bulk phases. The study unveils that the variation in the intensity of the AC field helps in converting a two-phase stratified flow into an oil-in-water microemulsion composed of oil slugs, plugs, or droplets. Importantly, the results also suggest that harnessing the vortices inside or outside these flow patterns helps in the improvement in mass transfer across the interface, which can be employed to improve the yield and conversion of a reaction. We have shown an example case of a pseudo-first order reaction for which the variation in frequency and intensity of AC field is found to form higher surface-to-volume-ratio flow patterns having a higher throughput. The convective recirculation in and around these miniaturized flow morphologies increase the rate of mass transfer, mixing of reactant and products, conversion of reactant, and yield of products. The results reported can be of significance in the design and development of future advanced-flow rector technologies.