Advances in In Vitro Blood-Air Barrier Models and the Use of Nanoparticles in COVID-19 Research.

Respiratory infections caused by coronaviruses (CoVs) have become a major public health concern in the past two decades as revealed by the emergence of SARS-CoV in 2002, MERS-CoV in 2012, and SARS-CoV-2 in 2019. The most severe clinical phenotypes commonly arise from exacerbation of immune response following the infection of alveolar epithelial cells localized at the pulmonary blood-air barrier. Preclinical rodent models do not adequately represent the essential genetic properties of the barrier, thus necessitating the use of humanized transgenic models. However, existing monolayer cell culture models have so far been unable to mimic the complex lung microenvironment. In this respect, air-liquid interface models, tissue engineered models, and organ-on-a-chip systems, which aim to better imitate the infection site microenvironment and microphysiology, are being developed to replace the commonly used monolayer cell culture models, and their use is becoming more widespread every day. On the contrary, studies on the development of nanoparticles (NPs) that mimic respiratory viruses, and those NPs used in therapy are progressing rapidly. The first part of this review describes in vitro models that mimic the blood-air barrier, the tissue interface that plays a central role in COVID-19 progression. In the second part of the review, NPs mimicking the virus and/or designed to carry therapeutic agents are explained and exemplified.

Sybodies as Novel Bioreceptors toward Field-Effect Transistor-Based Detection of SARS-CoV-2 Antigens.

The SARS-CoV-2 pandemic has increased the demand for low-cost, portable, and rapid biosensors, driving huge research efforts toward new nanomaterial-based approaches with high sensitivity. Many of them employ antibodies as bioreceptors, which have a costly development process that requires animal facilities. Recently, sybodies emerged as a new alternative class of synthetic binders and receptors with high antigen binding efficiency, improved chemical stability, and lower production costs via animal-free methods. Their smaller size is an important asset to consider in combination with ultrasensitive field-effect transistors (FETs) as transducers, which respond more intensely when biorecognition occurs near their surface. This work demonstrates the immobilization of sybodies against the spike protein of the virus on silicon surfaces, which are often integral parts of the semiconducting channel of FETs. Immobilized sybodies maintain the capability to capture antigens, even at low concentrations in the femtomolar range, as observed by fluorescence microscopy. Finally, the first proof of concept of sybody-modified FET sensing is provided using a nanoscopic silicon net as the sensitive area where the sybodies are immobilized. The future development of further sybodies against other biomarkers and their generalization in biosensors could be critical to decrease the cost of biodetection platforms in future pandemics.

Electrochemical detection of ascorbic acid in artificial sweat using a flexible alginate/CuO-modified electrode.

A flexible sensor is presented for electrochemical detection of ascorbic acid in sweat based on single-step modified gold microelectrodes. The modification consists of electrodeposition of alginate membrane with trapped CuO nanoparticles. The electrodes are fabricated at a thin polyimide support and the soft nature of the membrane can withstand mechanical stress beyond requirements for skin monitoring. After characterization of the membrane via optical and scanning electron microscopy and cyclic voltammetry, the oxidative properties of CuO are exploited toward ascorbic acid for amperometric measurement at micromolar levels in neutral buffer and acidic artificial sweat, at ultralow applied potential (- 5 mV vs. Au pseudo-reference electrode). Alternatively, measurement of the horizontal shift of redox peaks by cyclic voltammetry is also possible. Obtaining a limit of detection of 1.97 µM, sensitivity of 0.103 V log (µM)-1 of peak shift, and linear range of 10-150 µM, the effect of possible interfering species present in sweat is minimized, with no observable cross-reaction, thus maintaining a high degree of selectivity despite the absence of enzymes in the fabrication scheme. With a lateral flow approach for sample delivery, repeated measurements show recovery in few seconds, with relative standard deviation of about 20%, which can serve to detect increased loss or absence of vitamin, and yet be improved in future by optimized device designs. This sensor is envisioned as a promising component of wearable devices for e.g. non-invasive monitoring of micronutrient loss through sweat, comprising features of light weight, low cost, and easy fabrication needed for such application. Graphical Abstract Schematic depiction of the cyclic voltammetry signal change as the sweat flows over the sensor surface.

Nanosensors-Assisted Quantitative Analysis of Biochemical Processes in Droplets.

: Here, we present a miniaturized lab-on-a-chip detecting system for an all-electric and label-free analysis of the emulsion droplets incorporating the nanoscopic silicon nanowires-based field-effect transistors (FETs). We specifically focus on the analysis of ß-galactosidase e.g.activity, which is an important enzyme of the glycolysis metabolic pathway. Furthermore, the efficiency of the synthesis and action of ß-galactosidase can be one of the markers for several diseases, e.g., cancer, hyper/hypoglycemia, cell senescence, or other disruptions in cell functioning. We measure the reaction and reaction kinetics-associated shift of the source-to-drain current Isd in the system, which is caused by the change of the ionic strength of the microenvironment. With these results, we demonstrate that the ion-sensitive FETs are able to sense the interior of the aqueous reactors; thus, the conjunction of miniature nanosensors and droplet-based microfluidic systems conceptually opens a new route toward a sensitive, optics-less analysis of biochemical processes.

Dynamics of cytokines and role of immunocorrection in nosocomial pneumonia.

We have studied the changes in the serum level of the following cytokines during the course of treatment of nosocomial pneumonia (NP): pro-inflammatory--IL-1alpha and IL-6, chemoattractive--IL-8, anti-inflammatory--IL-4 and IL-10, and differentiating-activating--IFN-gamma and TNF-alpha. It has been found that at the time of admission of the patients the clinical severity of their condition was correlated with increased levels of all circulating cytokines except for IFN-gamma, the level of which was low. An adequate ethiotropic therapy helped to clear the clinical symptoms of infection and intoxication in 1-2 weeks. The level of circulating pro- and anti-inflammatory cytokines, IL-8, and TNF-alpha was decreasing, however, the level of IFN-gamma did not change significantly during 15 days. The ratio IFN-gamma/IL-10 did not change much but was slightly low during the treatment of the severe form of NP. Radical positive changes in the cytokine dynamics were achieved after the addition of leukinferon to the ethiotropic therapy.

Immunocorrection Therapy: Drugs and Prospects.

The analysis has been made for the basic immunocorrection drugs, used in clinical practice. By their features, the drugs are divided into 6 groups: immunoactive structures of pathogens, polyelectrolites, inductors of IFN-alpha, thymic hormones and their analogs, bone marrow regulators (myelopeptides) and cytokines. The first 3 groups of drugs are characterized by the inductive mechanism of action, whereas thymic hormones, myelopeptides and cytokines by the substitutive mechanism. The substitutive immunomodulators are preferential drugs at the advanced stages of infection. Immunocorrection should be used by the adequate courses and under the control of clinical dynamics, immunogram or differential blood counts. Transplantation of heterologous tissues and organs, transfusion of blood cell fractions and the first trimester of gestation may be called as contraindications for administration of immunocorrection. The high clinical efficiency of immunocorrection is shown on the usage of leukinferon in an extremely severe human pathology, such as sepsis, complicated by syndrome of polyorgan insufficiency.