An overview of electrochemical biosensors used for COVID-19 detection.

This short review presents the latest advances in the field of electrochemical biosensors, focusing particularly on impedimetric biosensors for the direct measurement of analytes. As a source of study we have chosen to describe these advances in the latest global health crisis originated from the COVID-19 pandemic, initiated by the SARS-CoV-2 virus. In this period, the necessity for swift and precise detection methods has grown rapidly due to an imminent need for the development of an analytical method to identify and isolate infected patients as an attempt to control the spreading of the disease. Traditional approaches such as the enzyme-linked immunosorbent assay (ELISA), were extensively used during the SARS-CoV-2 pandemic, but their drawbacks, including slow response time, became evident. In this context, the potential of electrochemical biosensors as an alternative for COVID-19 detection was emphasized. These biosensors merge electrochemical technology with bioreceptors, offering benefits such as rapidity, accuracy, portability, and real-time result provision. Additionally, we present instances of electrochemical biosensors modified with conductive polymers, eliminating the necessity for an electrochemical probe. The adaptability of the developed materials and devices facilitated the prompt production of electrochemical biosensors during the pandemic, creating opportunities for broader applications in infectious disease diagnosis.

pH stimulus-responsive hybrid nanoparticles: A system designed for follicular delivery of brazilian plant-derived 5-alpha-reductase enzyme inhibitors.

The 5-alpha-reductase enzyme, present in pilosebaceous units, plays a crucial role in the appearance of cutaneous hyperandrogenism manifestations (hirsutism, acne, and androgenetic alopecia). Its inhibition is an excellent strategy to reverse these conditions. Given the limitations of existing treatments, with transient effects and delayed therapeutic response, as well as the possibility of causing undesirable side effects, this study sought to develop new drug delivery systems to overcome these limitations. In other words, innovative stimuli-responsive hybrid nanoparticles were synthesized using silica/natural polysaccharides, encapsulating 5-alpha-reductase enzyme inhibitors derived from the plant Stryphnodendron adstringens (Mart.) Coville (commonly known as 'Barbatimão'). Silica core was synthesized by the modified Stöber method. The pH responsive polysaccharides used to coat the porous silica cores were chitosan, and sodium alginate, this coating was carried out using the Layer-by-Layer technique. The hybrid nanoparticles were characterized at molecular and physical-chemical levels. Furthermore, encapsulation efficiency, pH-dependent release behavior, and cytotoxicity were evaluated. Amorphous mesoporous structure with adequate size for follicular delivery (between 300 and 600 nm) in addition to effective phytocompound loading capacity, above 80 % was obtained. Based on the release studies, it was possible to observe pH responsiveness. The ethyl acetate fraction (EAF) obtained from "Barbatimão" bark extract was released in a controlled and more efficient manner by the alginate-coated nanoparticle (SNP_EAF_SA) at pH 7.4, which corresponds to the pH at the deepest area of hair follicles. Furthermore, SNP_EAF_SA proved to be less cytotoxic compared to EAF and chitosan-coated hybrid nanoparticles (SNP_EAF_CH). Characterization, release, and cytotoxicity results indicate that SNP_EAF_SA is a promising system for on-demand follicular delivery of antiandrogenic actives contained in EAF.

Molecular weight-dependent antitumor effects of prunes-derived type I arabinogalactan on human and murine triple wild-type melanomas.

The regulation of metastasis-related cellular aspects of two structurally similar AGIs from prunes tea infusion, with different molar masses, was studied in vitro against Triple Wild-Type metastatic melanoma (TWM) from murine and human origin. The higher molar mass AGI (AGI-78KDa) induced TWMs cells death and, in murine cell line, it decreased some metastasis-related cellular processes: invasiveness capacity, cell-extracellular matrix interaction, and colonies sizes. The lower molar mass AGI (AGI-12KDa) did not induce cell death but decreased TWMs proliferation rate and, in murine cell line, it decreased cell adhesion and colonies sizes. Both AGIs alter the clonogenic capacity of human cell line. In spite to understand why we saw so many differences between AGIs effects on murine and human cell lines we performed in silico analysis that demonstrated differential gene expression profiles between them. Complementary network topological predictions suggested that AGIs can modulate multiple pathways in a specie-dependent manner, which explain differential results obtained in vitro between cell lines. Our results pointed to therapeutic potential of AGIs from prunes tea against TWMs and showed that molecular weight of AGIs may influence their antitumor effects.

Temperature influence on NiFeMo nanoparticles magnetic properties and their viability in biomedical applications.

NiFeMo alloy nanoparticles were synthesized by co-precipitation in the presence of organic additives. Nanoparticles thermal evolution shows that there is a significant increase in the average size (from 28 to 60 nm), consolidating a crystalline structure of the same type as the Ni3 Fe phase but with lattice parameter a = 0.362 nm. Measurements of magnetic properties follow this morphological and structural evolution increasing saturation magnetization (Ms) by 578% and reducing remanence magnetization (Mr) by 29%. Cell viability assays on as-synthesized revealed that nanoparticles (NPs) are not cytotoxic up to a concentration of 0.4 µg/mL for both non-tumorigenic (fibroblasts and macrophages) and tumor cells (melanoma).

Preparation and Investigation of Thermally Annealed Zein-Propolis Electrospun Nanofibers for Biomedical Applications.

Zein, a corn-derived protein, has a variety of applications ranging from drug delivery to tissue engineering and wound healing. This work aims to develop a biocompatible scaffold for dermal applications based on thermally annealed electrospun propolis-loaded zein nanofibers. Pristine fibers' biocompatibility is determined in vitro. Next, propolis from Melipona quadrifasciata is added to the fibers at different concentrations (5% to 25%), and the scaffolds are studied. The physicochemical properties of zein/propolis precursor dispersions are evaluated and the results are correlated to the fibers' properties. Due to zein's and propolis' very favorable interactions, which are responsible for the increase in the dispersions surface tension, nanometric size ribbon-like fibers ranging from 420 to 575 nm are obtained. The fiber's hydrophobicity is not dependent on propolis concentration and increases with the annealing procedure. Propolis inhibitory concentration (IC50 ) is determined as 61.78 µg mL-1 . When loaded into fibers, propolis is gradually delivered to cells as Balb/3T3 fibroblasts and are able to adhere, grow, and interact with pristine and propolis-loaded fibers, and cytotoxicity is not observed. Therefore, the zein-propolis nanofibers are considered biocompatible and safe. The results are promising and provide prospects for the development of wound-healing nanofiber patches-one of propolis' main applications.

Electrospun polyvinyl-alcohol/gum arabic nanofibers: Biomimetic platform for in vitro cell growth and cancer nanomedicine delivery.

The design of powerful in vitro cell culture platforms to support precision medicine can contribute to predict therapeutic success of cancer patients. Electrospun nanofibers applied to cell culture can mimic extracellular matrix and improve in vitro cell behavior. Here, we describe biocompatible blended polyvinyl-alcohol (PVA)/gum arabic (GA) extracellular matrix (ECM)-like nanofibers for in vitro cell cultures capable of delivering nanocomposite for desired biomedical application. Therefore, PVA/GA ECM-like electrospun nanofibers were developed and characterized. Heat treatment was used to crosslink the nanofibers and biocompatibility was evaluated, which demonstrated the ability of developed platform to provide a cell culture-friendly environment. Previous work demonstrated that GA-gold nanoparticles (GA-AuNPs) in non-cytotoxic concentrations can reduce key metastatic cellular events such as invasion and colony formation of metastatic melanoma cells. Thus, crosslinked nanofibers were functionalized with GA-AuNPs and its cellular delivery was evaluated. GA-AuNPs were efficiently adsorbed onto the PVA/GA nanofibers surface and the system effectively delivered the nanocomposites to metastatic melanoma cells. In conclusion, the described biocompatible system could be prospected as a valuable in vitro tool for precision medicine.

In vitro biocompatibility screening of a colloidal gum Arabic-polyaniline conducting nanocomposite.

Although polyaniline (PANI) is a widely investigated conductive polymer for biological applications, studies addressing the biocompatibility of colloidal PANI dispersions are scarcely found in the literature of the area. Therefore, PANI nanoparticles stabilized by the natural polysaccharide gum Arabic (GA) were screened for their biocompatibility. The GA successfully stabilized the colloidal PANI-GA dispersions when exposed to a protein-rich medium, showing compatibility with the biological environment. The results obtained from a series of in vitro assays showed that, after up to 48 h of exposure to a range of PANI-GA concentrations (1-50 µg/mL), both mouse BALB/3T3 fibroblasts and RAW 264.7 macrophages showed no evidence of change in cellular proliferation, viability and metabolic activity. An increase in macrophage granularity poses as evidence of phagocytic uptake of PANI-GA, without resulting activation of this cell type. Additionally, the PANI-GA nanoparticles modulated the cell morphology changes induced on fibroblasts by GA in a concentration-dependent manner. Thus, this unprecedented biocompatibility study of PANI nanoparticles stabilized by a plant gum exudate polysaccharide showed promising results. This simple biomaterial might be further developed into colloidal formulations for biological and biomedical applications, taking advantage of its versatility, biocompatibility, and conductive properties.

Differential effects of Zincum metallicum on cell models.

INTRODUCTION: Zinc is an essential trace element necessary for life. Traditional and complementary medicines use zinc-based formulations to treat different classes of diseases. Basic research on homeopathic preparations of zinc are rare and there are a few published clinical cases describing its effects on patients. The use of cell-based models in drug screening is a reliable source of evidence. METHODS: We sought to investigate experimental end-points using cell-based models to determine the effects of dilutions of Zincum metallicum prepared according to the Brazilian Homeopathic Pharmacopoeia. Murine RAW 264.7 macrophages and melanoma B16-F10 cell lines were cultured according to standard procedures. Cells were treated with either 5c, 6c or 30c Zincum metallicum and control cells with its respective vehicle (5c, 6c, or 30c Lactose). Macrophage activation by CD54 immunolabeling and intracellular reactive oxygen species (ROS) using DCFH-DA (2,7-dichlorodihydrofluorescein diacetate) were detected by flow cytometry. Phagocytic capacity (endocytic index) was quantified by light microscopy. Features of melanoma cells were analyzed by colorimetric assays to determine melanin content and cell proliferation rate. All obtained data were submitted to normality test followed by statistical analysis. RESULTS: Zincum metallicum 6c shifted high ROS-producing macrophages to a low ROS-producing phenotype. Macrophage CD54 expression was increased by Zincum metallicum 5c. No changes in endocytic index were observed. Melanoma cells were not affected by any treatment we tested. CONCLUSIONS: Differing responses and non-linearity were found on macrophages challenged with Zincum metallicum at high dilutions. No changes in melanoma cells were observed. Customised assays using target cells can be useful to investigate high-dilution effects. Other cell types and conditions should be explored.

Antibacterial activity, inflammatory response, coagulation and cytotoxicity effects of silver nanoparticles.

The incorporation of nanoparticles (NPs) in industrial and biomedical applications has increased significantly in recent years, yet their hazardous and toxic effects have not been studied extensively. Here, we studied the effects of 24 nm silver NPs (AgNPs) on a panel of bacteria isolated from medical devices used in a hospital intensive care unit. The cytotoxic effects were evaluated in macrophages and the expression of the inflammatory cytokines IL-6, IL-10 and TNF-α were quantified. The effects of NPs on coagulation were tested in vitro in plasma-based assays. We demonstrated that 24 nm AgNPs were effective in suppressing the growth of clinically relevant bacteria with moderate to high levels of antibiotic resistance. The NPs had a moderate inhibitory effect when coagulation was initiated through the intrinsic pathway. However, these NPs are cytotoxic to macrophages and are able to elicit an inflammatory response. Thus, beneficial and potential harmful effects of 24 nm AgNPs on biomedical devices must be weighed in further studies in vivo. From the Clinical Editor: The authors of this study demonstrate that gallic acid reduced 24 nm Ag NPs are effective in suppressing growth of clinically relevant antibiotic resistant bacteria. However, these NPs also exhibit cytotoxic properties to macrophages and may trigger an inflammatory response. Thus, the balance of beneficial and potential harmful effects must be weighed carefully in further studies.

Mercurius solubilis: actions on macrophages.

BACKGROUND: Macrophages play central roles in homeostasis as well as host defence in innate and acquired immunity, auto-immunity and immunopathology. Our research group has demonstrated the effects of highly diluted toxic substances in macrophages. AIM: To investigate if highly diluted Mercurius solubilis (Merc sol), can activate or modulate macrophage functions. METHODS: We evaluated the effects of Merc sol in the 6, 12, 30 and 200 centesimal high dilutions (CH) potencies on mice peritoneal macrophages (in vitro and in vivo). Merc sol was added to mice's drinking water for 7 days (in vivo treatment) and animals were euthanised and cells were collected. In vitro treatment was performed on macrophages and bone-marrow cell cultures. RESULTS: Macrophages showed activated morphology, both when Merc sol was added directly to the cell culture and to drinking water. The in vitro experiments showed enhanced morphological activation, increased interferon (IFN)γ release in the supernatant at lower dilutions and interleukin (IL)-4 production at higher dilutions. Increase in nitric oxide and decrease in superoxide (O(2)(-)) and hydrogen peroxide (H(2)O(2)) were also observed. In vivo treatment caused a decrease in O(2)(-) and increase in H(2)O(2) production by macrophages. DISCUSSION: Taken together, the results allow us to conclude that highly diluted Merc sol modulates reactive oxygen species (ROS), reactive nitrogen species (RNS) and cytokine secretion, which are central mediators of the immune system, wound healing and body homeostasis.

An exosome-based secretion pathway is responsible for protein export from Leishmania and communication with macrophages.

Specialized secretion systems are used by numerous bacterial pathogens to export virulence factors into host target cells. Leishmania and other eukaryotic intracellular pathogens also deliver effector proteins into host cells; however, the mechanisms involved have remained elusive. In this report, we identify exosome-based secretion as a general mechanism for protein secretion by Leishmania, and show that exosomes are involved in the delivery of proteins into host target cells. Comparative quantitative proteomics unambiguously identified 329 proteins in Leishmania exosomes, accounting for >52% of global protein secretion from these organisms. Our findings demonstrate that infection-like stressors (37 degrees C +/- pH 5.5) upregulated exosome release more than twofold and also modified exosome protein composition. Leishmania exosomes and exosomal proteins were detected in the cytosolic compartment of infected macrophages and incubation of macrophages with exosomes selectively induced secretion of IL-8, but not TNF-alpha. We thus provide evidence for an apparently broad-based mechanism of protein export by Leishmania. Moreover, we describe a mechanism for the direct delivery of Leishmania molecules into macrophages. These findings suggest that, like mammalian exosomes, Leishmania exosomes function in long-range communication and immune modulation.

Gene expression profiling of macrophages following mice treatment with an immunomodulator medication.

Canova (CA) is a complex homeopathic medication used in diseases where the immune system is depressed. Previous studies demonstrated that it is neither toxic nor mutagenic and activates macrophages. We now evaluate CA effects on cytokine production and gene expression from mice macrophages. The global view of changes in expression of genes with known functions can provide a vivid picture of the way in which cell adapts to a changing environment or a challenge. We found a decrease in IL-2 and IL-4 production and a differential expression in 147 genes from CA group. These genes are mainly involved in transcription/translation, cell structure and dynamics, immune response, cytoprotection, enzymatic process, and receptors/ligands. With gene expression analysis we state that this medication provokes a reaction that involves alterations in gene expression profile mainly in the ones involved with macrophages activation, corroborating the laboratorial research and the clinical data.

Activation of bone marrow cells treated with Canova in vitro.

Canova is a Brazilian complex homeopathic medication produced from Aconitum, Thuya, Bryonia, Lachesis and Arsenicum. Previous studies demonstrated that Canova induces up-regulation in numbers of leukocytes. The bone marrow microenvironment is composed of growth factors, stromal cells, extracellular matrix, and progenitor cells that differentiate into mature blood cells. As it is the major site of blood cell formation, we studied in vitro Canova effects on bone marrow cells of mice. Swiss mouse femurs were dissected, cleaned, and the marrow was flushed. The cells were plated, treated or not, incubated for different times and processed for light, scanning electron, and confocal microscopy, and also flow cytometry. The treatment did not modify the expression of the analyzed surface markers or cytokine production. All microscopy techniques showed that a monocytic lineage (CD11b(+)) and stromal cells (adherent cells) were activated by treatment. Canova also increased cell clusters over adherent cells, suggesting proliferation areas.