Publications

In recent years, metaplasmonic biosensors have emerged as a novel counterpart of well-established plasmonic biosensors based on thin metallic layers. Metaplasmonic biosensors offer high potential for sensor miniaturiza-tion, extreme sensitivity biosensing, and high multiplexing capabilities with detection methods free of coupling optical elements. These capabilities make metaplasmonic biosensors highly attractive for Point-of-Care and handled/portable devices or novel On-Chip devices; as a result, it has increased the number of prototypes and potential applications that emerged during the last years. One of the main challenges to achieving fully operative devices is the achievement of high-throughput biointerfaces for sensitive and selective biodetection in complex media. Despite the superior surface sensitivity achieved by metaplasmonic sensors compared to conventional plasmonic sensors based on metallic thin films, the main limitations to achieving high-throughput and multiplexed biosensing usually are associated with the sensitivity and selectivity of the bioin-terface and, as a consequence, their application to the direct analysis of real complex samples. This graphical review discusses the potential challenges and capabilities of different biofunctionalization strategies, biorecog-nition elements, and antifouling strategies to achieve scalable and high-throughput metaplasmonic biosensing for Point-of-Care devices and bioengineering applications like Organs-On-Chip.

JTD Keywords: Biointerfaces, Biosensing, Biosensors, Cell culture monitoring, Metaplasmonic, Nanoplasmonic, Organ-on-chip, Point-of-care

The in vitro biological characterization of biomaterials is largely based on static cell cultures. However, for highly reactive biomaterials such as calcium-deficient hydroxyapatite (CDHA), this static environment has limitations. Drastic alterations in the ionic composition of the cell culture medium can negatively affect cell behavior, which can lead to misleading results or data that is difficult to interpret. This challenge could be addressed by a microfluidics-based approach (i.e. on-chip), which offers the opportunity to provide a continuous flow of cell culture medium and a potentially more physiologically relevant microenvironment. The aim of this work was to explore microfluidic technology for its potential to characterize CDHA, particularly in the context of inflammation. Two different CDHA substrates (chemically identical, but varying in microstructure) were integrated on-chip and subsequently evaluated. We demonstrated that the on-chip environment can avoid drastic ionic alterations and increase protein sorption, which was reflected in cell studies with RAW 264.7 macrophages. The cells grown on-chip showed a high cell viability and enhanced proliferation compared to cells maintained under static conditions. Whereas no clear differences in the secretion of tumor necrosis factor alpha (TNF-α) were found, variations in cell morphology suggested a more anti-inflammatory environment on-chip. In the second part of this study, the CDHA substrates were loaded with the drug Trolox. We showed that it is possible to characterize drug release on-chip and moreover demonstrated that Trolox affects the TNF-α secretion and morphology of RAW 264.7 ​cells. Overall, these results highlight the potential of microfluidics to evaluate (bioactive) biomaterials, both in pristine form and when drug-loaded. This is of particular interest for the latter case, as it allows the biological characterization and assessment of drug release to take place under the same dynamic in vitro environment.© 2022 The Authors.

JTD Keywords: alpha-tocopherol, antioxidant, biomaterials, calcium phosphate cement, culture, delivery, drug release, in vitro, in-vitro, ion, macrophage, on-chip, release, tool, Biomaterial, Calcium phosphate cement, Calcium-phosphate cements, Drug release, In vitro, Macrophage, On-chip

Tumor vessel-on-a-chip systems have attracted the interest of the cancer research community due to their ability to accurately recapitulate the multiple dynamic events of the metastatic cascade. Vessel-on-a-chip microfluidic platforms have been less utilized for investigating the distinctive features and functional heterogeneities of tumor-derived vascular networks. In particular, vascular tumors are characterized by the massive formation of thrombi and severe bleeding, a rare and life-threatening situation for which there are yet no clear therapeutic guidelines. This is mainly due to the lack of technological platforms capable of reproducing these characteristic traits of the pathology in a simple and well-controlled manner. Herein, we report the fabrication of a versatile tumor vessel-on-a-chip platform to reproduce, investigate, and characterize the massive formation of thrombi and hemorrhage on-chip in a fast and easy manner. Despite its simplicity, this method offers multiple advantages to recapitulate the pathophysiological events of vascular tumors, and therefore, may find useful applications in the field of vascular-related diseases, while at the same time being an alternative to more complex approaches. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

JTD Keywords: in vitro model, microfluidics, organ-on-chip, vascular tumor, vessel, In vitro model, Microfluidics, Organ-on-chip, Vascular tumor, Vessel

Tissue barriers play a crucial role in human physiology by establishing tissue compartmentalization and regulating organ homeostasis. At the interface between the extracellular matrix (ECM) and flowing fluids, epithelial and endothelial barriers are responsible for solute and gas exchange. In the past decade, microfluidic technologies and organ-on-chip devices became popular as in vitro models able to recapitulate these biological barriers. However, in conventional microfluidic devices, cell barriers are primarily grown on hard polymeric membranes within polydimethylsiloxane (PDMS) channels that do not mimic the cell-ECM interactions nor allow the incorporation of other cellular compartments such as stromal tissue or vascular structures. To develop models that accurately account for the different cellular and acellular compartments of tissue barriers, researchers have integrated hydrogels into microfluidic setups for tissue barrier-on-chips, either as cell substrates inside the chip, or as self-contained devices. These biomaterials provide the soft mechanical properties of tissue barriers and allow the embedding of stromal cells. Combining hydrogels with microfluidics technology provides unique opportunities to better recreate in vitro the tissue barrier models including the cellular components and the functionality of the in vivo tissues. Such platforms have the potential of greatly improving the predictive capacities of the in vitro systems in applications such as drug development, or disease modeling. Nevertheless, their development is not without challenges in their microfabrication. In this review, we will discuss the recent advances driving the fabrication of hydrogel microfluidic platforms and their applications in multiple tissue barrier models.

JTD Keywords: hydrogel, microfabrication, microfluidics, organ-on-chip, tissue barrier, Hydrogel, Microfabrication, Microfluidics, Organ-on-chip, Tissue barrier

Human aging is accompanied by a relevant increase in age-associated chronic pathologies, including neurodegenerative and metabolic diseases. The appearance and evolution of numerous neurodegenerative diseases is paralleled by the appearance of intracellular and extracellular accumulation of misfolded proteins in affected brains. In addition, recent evidence suggests that most of these amyloid proteins can behave and propagate among neural cells similarly to infective prions. In order to improve understanding of the seeding and spreading processes of these “prion-like” amyloids, microfluidics and 3D lab-on-chip approaches have been developed as highly valuable tools. These techniques allow us to monitor changes in cellular and molecular processes responsible for amyloid seeding and cell spreading and their parallel effects in neural physiology. Their compatibility with new optical and biochemical techniques and their relative availability have increased interest in them and in their use in numerous laboratories. In addition, recent advances in stem cell research in combination with microfluidic platforms have opened new humanized in vitro models for myriad neurodegenerative diseases affecting different cellular targets of the vascular, muscular, and nervous systems, and glial cells. These new platforms help reduce the use of animal experimentation. They are more reproducible and represent a potential alternative to classical approaches to understanding neurodegeneration. In this review, we summarize recent progress in neurobiological research in “prion-like” protein using microfluidic and 3D lab-on-chip approaches. These approaches are driven by various fields, including chemistry, biochemistry, and cell biology, and they serve to facilitate the development of more precise human brain models for basic mechanistic studies of cell-to-cell interactions and drug discovery.

JTD Keywords: Lab-On-Chip, Amyloid propagation, Microfluidics, Fibril, Seeding, Spreading, Prion-like, Prionoid

Bacteria concentration and detection is time-consuming in regular microbiology procedures aimed to facilitate the detection and analysis of these cells at very low concentrations. Traditional methods are effective but often require several days to complete. This scenario results in low bioanalytical and diagnostic methodologies with associated increased costs and complexity. In recent years, the exploitation of the intrinsic electrical properties of cells has emerged as an appealing alternative approach for concentrating and detecting bacteria. The combination of dielectrophoresis (DEP) and impedance analysis (IA) in microfluidic on-chip platforms could be key to develop rapid, accurate, portable, simple-to-use and cost-effective microfluidic devices with a promising impact in medicine, public health, agricultural, food control and environmental areas. The present document reviews recent DEP and IA combined approaches and the latest relevant improvements focusing on bacteria concentration and detection, including selectivity, sensitivity, detection time, and conductivity variation enhancements. Furthermore, this review analyses future trends and challenges which need to be addressed in order to successfully commercialize these platforms resulting in an adequate social return of public-funded investments.

JTD Keywords: Bacteria, Dielectrophoresis, Impedance, Microfluidics, On-chip

Pharmaceutical drug screening and research into diseases call for significant improvement in the effectiveness of current in vitro models. Better models would reduce the likelihood of costly failures at later drug development stages, while limiting or possibly even avoiding the use of animal models. In this regard, promising advances have recently been made by the so-called "organ-on-chip" (OOC) technology. By combining cell culture with microfluidics, biomedical researchers have started to develop microengineered models of the functional units of human organs. With the capacity to mimic physiological microenvironments and vascular perfusion, OOC devices allow the reproduction of tissue- and organ-level functions. When considering drug testing, nephrotoxicity is a major cause of attrition during pre-clinical, clinical, and post-approval stages. Renal toxicity accounts for 19% of total dropouts during phase III drug evaluation-more than half the drugs abandoned because of safety concerns. Mimicking the functional unit of the kidney, namely the nephron, is therefore a crucial objective. Here we provide an extensive review of the studies focused on the development of a nephron-on-chip device.

JTD Keywords: Disease model, Drug discovery, Kidney, Nephron-on-chip, Organ-on-chip

The continuous flow focussing and manipulation of particles and cells are important factors in microfluidic applications for performing accurate and reproducible procedures downstream. Many particle focussing methods require complex setups or channel designs that can limit the process and its applications. Here, we present diamagnetic repulsion as a simple means of focussing objects in continuous flow, based only on their intrinsic properties without the requirement of any label. Diamagnetic polystyrene particles were suspended in a paramagnetic medium and pumped through a capillary between a pair of permanent magnets, whereupon the particles were repelled by each magnet into the central axis of the capillary, thus achieving focussing. By investigating this effect, we found that the focussing was greatly enhanced with (i) increased magnetic susceptibility of the medium, (ii) reduced flow rate of the suspension, (iii) increased particle size, and (iv) increased residence time in the magnetic field. Furthermore, we applied diamagnetic repulsion to the flow focussing of living, label-free HaCaT cells.

JTD Keywords: Feeble magnetic substances, On-chip, Blood-cells, Microfluidic device, Separation, Field, Levitation, Magnetophoresis, Fractionation, Nanoparticles

In this paper, a multiple-channel extension of a dual-grating Coupler biosensor is presented as a Solution for the problem of resolving different selectivities, Usual when heterogeneous samples are analyzed. Several differently functionalized channels can perform quantitative analysis of competiting recognition events, Suppress shifts due to buffer changes and even monitorize drifts coming from the light Source. Here, the multiple-channel approach is developed and proven for a four-channel configuration, providing a resolution limit of 10(-5) Refractive index Units (RIU) and with an a potentially Unlimited scalability. Finally, a differential HSA recognition event is monitored, at both an IgG functionalized channel and at a blocked one.

JTD Keywords: Optical grating coupler, Multi-channel biorecognition, On-chip reference