Fluorescence Immunoassay System via Enzyme-Enabled in Situ Synthesis of Fluorescent Silicon Nanoparticles.

The emergence of fluorescent nanomaterials with excellent performances has triggered the development of fluorescence analysis technique, which possesses several advantages in the research and clinical applications. However, current strategies for fluorescence immunoassay usually involve the routine fluorophore-labeled antibody and/or awkward signal generation procedure that may not be available in conventional enzyme-linked immunosorbent assay (ELISA) systems. Herein, we circumvent this problem by imparting an exquisite signal generation mechanism to commercially available alkaline phosphatase (ALP)-based ELISA platform and putting forward a conceptual fluorescent ELISA system based on an original ALP-enabled in situ synthesis of fluorescent nanomaterials. After adding target antigen, the presence of ALP labeled on antibody catalyzes the transformation of the substrate ascorbic acid 2-phosphate into ascorbic acid. Then the resultant ascorbic acid (i.e., ascorbate) interacts with amine-containing silane molecules (no fluorescence) to produce intense cyan fluorescent silicon nanoparticles. For the proof-of-concept, alpha-fetoprotein and human immunoglobulin G are chosen as the model antigen targets, and our proposed immunoassay (designated as the nanoparticles generation-based fluorescent ELISA) enables the detection with either fluorescence spectroscopy or naked-eye readout under the ultraviolet lamp. The convincing recognition mechanism and assay performance ensure fluorescent ELISA to quantitatively evaluate the alpha-fetoprotein level in serologic test and potentially apply in the clinic diagnosis of hepatocellular carcinoma.

Cascaded nano-porous silicon for high sensitive biosensing and functional group distinguishing by Mid-IR spectra.

We present a chemical-biosensor in the Mid-IR range and based on cascaded porous silicon made on p- and n-type (100) silicon substrates of resistivities between 0.001Ωcm and 0.005Ωcm. The stacked porous layers of various porosities (20-80%) and thicknesses (5-9µm) are formed by successive electrochemical etchings with different current densities. Working with FTIR technique that possesses fast response, high sensitivity, and capability of detecting and identifying functional groups, the cascaded porous structures provided enhanced refractive index sensitivities and reduced detection limits in chemical and biodetection. The largest wavenumber shifts were 50cm(-1)/mM obtained for d-(+)-glucose and 96cm(-1)/µg/mL for Cy5-conjungated Rabbit Anti-Mouse IgG. The lowest detectable concentration of glucose was 80µM (1.4mg/mL) with PS porosity of 40% and thickness of about 9µm while it was 40ng/mL for Cy5-conjugated Rabbit Anti-Mouse IgG which is 2.5×10(5) folds better than those in literature.

Porous silicon antibody microarrays for quantitative analysis: measurement of free and total PSA in clinical plasma samples.

The antibody microarrays have become widespread, but their use for quantitative analyses in clinical samples has not yet been established. We investigated an immunoassay based on nanoporous silicon antibody microarrays for quantification of total prostate-specific-antigen (PSA) in 80 clinical plasma samples, and provide quantitative data from a duplex microarray assay that simultaneously quantifies free and total PSA in plasma. To further develop the assay the porous silicon chips was placed into a standard 96-well microtiter plate for higher throughput analysis. The samples analyzed by this quantitative microarray were 80 plasma samples obtained from men undergoing clinical PSA testing (dynamic range: 0.14-44 ng/ml, LOD: 0.14 ng/ml). The second dataset, measuring free PSA (dynamic range: 0.40-74.9 ng/ml, LOD: 0.47 ng/ml) and total PSA (dynamic range: 0.87-295 ng/ml, LOD: 0.76 ng/ml), was also obtained from the clinical routine. The reference for the quantification was a commercially available assay, the ProStatus PSA Free/Total DELFIA. In an analysis of 80 plasma samples the microarray platform performs well across the range of total PSA levels. This assay might have the potential to substitute for the large-scale microtiter plate format in diagnostic applications. The duplex assay paves the way for a future quantitative multiplex assay, which analyzes several prostate cancer biomarkers simultaneously.

Preparation and validation of a skin model for the evaluation of intradermal powder injection devices.

A very promising novel needle-free application method is epidermal powder immunisation, a method delivering particulate vaccines into the viable epidermis of human skin where a dense network of immunocompetent cells resides. These antigen-presenting cells (Langerhans cells) are able to recognise antigens, process them and present them to naïve T-cells and induce effective immune responses. Powder injection devices are being developed, and their evaluation is essential before applying them on live animals and individuals. An appropriate skin model will accelerate the development of such injection devices. Different films made from gelatin, silicon and agar were prepared and investigated as skin model candidates for the evaluation of powder injection devices. The mechanical properties of the skin model candidates were measured with an indentation method using a texture analyser, and the results were compared to the properties of human skin and pig skin. The indentation behaviour of the model films and the biological skin samples suggest that gelatin films plasticised with glycerol are very well suitable for a skin model. The mechanical properties of gelatin based films can be tailored by changing the glycerol content in the film making it even possible to simulate human skin with different mechanical properties as the mechanical properties depend on the individual, age, sex and site of injection. The stability of the gelatin films was also investigated under long-term storage. In addition, confocal laser scanning microscopy was used as a novel tool to determine the depths and size of fluorescently labelled particles in the gelatin model.

Toward a comparison of microelectrodes for acute and chronic recordings.

Several variations of microelectrode arrays are used to record and stimulate intracortical neuronal activity. Bypassing the immune response to maintain a stable recording interface remains a challenge. Companies and researchers are continuously altering the material compositions and geometries of the arrays in order to discover a combination that allows for a chronic and stable electrode-tissue interface. From this interface, they wish to obtain consistent quality recordings and a stable, low impedance pathway for charge injection over extended periods of time. Despite numerous efforts, no microelectrode array design has managed to evade the host immune response and remain fully functional. This study is an initial effort comparing several microelectrode arrays with fundamentally different configurations for use in an implantable epilepsy prosthesis. Specifically, NeuroNexus (Michigan) probes, Cyberkinetics (Utah) Silicon and Iridium Oxide arrays, ceramic-based thin-film microelectrode arrays (Drexel), and Tucker-Davis Technologies (TDT) microwire arrays are evaluated over a 31-day period in an animal model. Microelectrodes are compared in implanted rats through impedance, charge capacity, signal-to-noise ratio, recording stability, and elicited immune response. Results suggest significant variability within and between microelectrode types with no clear superior array. Some applications for the microelectrode arrays are suggested based on data collected throughout the longitudinal study. Additionally, specific limitations of assaying biological phenomena and comparing fundamentally different microelectrode arrays in a highly variable system are discussed with suggestions on how to improve the reliability of observed results and steps needed to develop a more standardized microelectrode design.

In vivo delivery of a peptide, ghrelin antagonist, with mesoporous silicon microparticles.

Peptides may represent potential treatment options for many severe illnesses. However, they need an effective delivery system to overcome rapid degradation after their administration. One possible way to prolong peptide action is to use particulate drug delivery systems. In the present study, thermally hydrocarbonized mesoporous silicon (THCPSi) microparticles (38-53 microm) were studied as a peptide delivery system in vivo. D-lys-GHRP6 (ghrelin antagonist, GhA) was used as a model peptide. The effects of GhA-loaded THCPSi microparticles on food intake (s.c., GhA dose 14 mg/kg) and on blood pressure (s.c., GhA dose 4 mg/kg) were examined in mice and rats, respectively. In addition, the effects of THCPSi microparticles (2 mg) on cytokine secretion in mice after single s.c. administration were examined by determining several cytokine plasma concentrations. The present results demonstrate that GhA can be loaded into THCPSi microparticles with a high loading degree (20% w/w). GhA loaded THCPSi microparticles inhibited food intake for a prolonged time, and increased blood pressure more slowly than encountered with a GhA solution. Furthermore, THCPSi microparticles did not increase cytokine activity. The present results suggest that THCPSi might be used as a drug delivery system for peptides.

Pathogenetic and diagnostic aspects of siliconosis.

Silicones have an adverse effect on human health well beyond that suggested by the recent superficial public controversy. The evidence for immune responses to injected/implanted silicones is extensive, detailed, often very specific, and not at all new. Comprehending the immunopathogenicity, realized and potential, of silicone has grown as our general understanding of the immune system has developed. Several major issues in furthering this comprehension pertain to the nature of the essential epitope, special risk of silicones to women, and definition of the chronic disease complex so evident clinically, one defying classification within currently traditional disease categories and states. The commentary presented here emphasizes the immunopathic evidence, explores the question of the essential epitope, estimates the minimal threshold of silicone load for immune reactivity, presents a profile of autoantibodies for siliconosis, and calls attention to specific silicone-based female contraceptive modalities. The silicone content of personal care products, not always revealed by retail package labeling, is explored as a potential sensitizing factor in the environment.

Risk of connective-tissue disease in men with testicular or penile prostheses: a preliminary study.

AIM: To help clarifying the possibility of connective-tissue diseases in men with penile or testicular prostheses. METHODS: Eight patients underwent inflatable penile prostheses and 15, testicular prostheses consented to the study. Their medical records were reviewed and a follow-up interview and physical and serological examinations were performed. RESULTS: In patients with penile prostheses, there was no abnormal antinuclear antibody (ANA) or IgM elevation. The serum levels of the rheumatoid factor (RF), C4, IgA and IgG were abnormal in one patient, and the levels of erythrocyte sedimentation rate (ESR) and C3, abnormal in two. Four had elevated IgE. In patients with testicular prostheses, there was no abnormal RF, ANA or IgM. The serum levels of ESR and IgA were abnormal in two, and three had abnormal C4, ten abnormal C3, and eleven decreased IgG. All had increased IgE. Men with penile prostheses had higher serum levels of IgG and IgM than those with testicular prostheses (P=0.001, P=0.016, respectively). The rates of abnormal values of IgE and IgG were higher in men with testicular prostheses than in men with penile prostheses (P=0.008, P=0.009, respectively). Physical examination was normal in all patients and nobody had documented symptoms pertinent to connective-tissue diseases. CONCLUSION: Our findings suggest that the risk of connective-tissue diseases is not higher in patients wearing prostheses as the ANA is negative and there is no apparent manifestation suggestive of connective-tissue diseases.

Biocompatibility testing of a new silver-impregnated catheter in vivo.

The purpose of this investigation was to compare the local effects of polyurethane (Tecothane) and silicone tubes with or without silver impregnation in rats. Bacterial colonization or infection of the exit site and/or tunnel were documented and interpreted. All tubes were placed subcutaneously or percutaneously in the neck of 41 Sprague-Dawley rats and guided beneath the dorsal muscles into the peritoneal cavity. The incidence of bacterial abscesses along the implanted tubes was evaluated daily. After 90 days, or earlier if sepsis developed, the animals were killed painlessly and various organs and tissues from the entry site and the catheter tunnel examined histologically. In the group where polyurethane tubes were placed percutaneously, there was no difference in the frequency of abscesses between silver-impregnated and non-impregnated tubes (5/6 with and 5/7 without silver). The only difference noted was in the group with percutaneously placed silicone tubes between those with and without silver. Abscesses only occurred in 2/4 animals in the silver group and in 5/5 animals in the control group. Histological examination showed no difference in either group between infectious and foreign body reactions. Silver particles in subcutaneous, muscle and peritoneal tissue could not be demonstrated.

The immunopathology of siliconosis. History, clinical presentation, and relation to silicosis and the chemistry of silicon and silicone.

Recent evidence confirms the fundamental involvement of the human immune system in the reaction to implantation of silicone-based medical devices. An as yet-to-be particularized epitope of many complex substances sharing siloxane structures is presented through the MHC-II apparatus with development and retention of T cell memory. This memory can be tested for in practical terms using one or more forms of silica, which links the immuno-histopathology and autoimmune attributes of "silicosis" with those of "siliconosis." The lesions of siliconosis are typical of those for persistent antigens and delayed, cell mediated hypersensitivity. The basic descriptive pathology of the reaction to silicone has been known since soon after introduction of silicones in medical procedures, with the exception of some details related to the more recent discoveries on the role of cytokines in the immunopathic process. The clinical consequences of siliconosis are common and can be severe in some individuals implanted with silicone devices.

Immunotoxicity of medical devices. Symposium overview.

Determination of the ability of a medical device to interact with the immune system currently involves assessment of the immunogenic potential and biocompatibility of the device or an extract of the device. However, implants are often in the body for extended periods of time and/or are placed by a surgical procedure that in and of itself will generate an acute inflammatory response. This symposium discussed studies that have been performed to evaluate the immunogenicity of various devices consisting of several different compositions (i.e., silicone, metals, and latex) in contact with different anatomical sites, the ability of a device to modulate an inflammatory response generated by a surgical procedure or trauma, and the response of the body to a material left in place for extended periods of time. This symposium brought together scientists from many different disciplines to begin to identify and fill in the gaps in this area.

Silicone-specific blood lymphocyte response in women with silicone breast implants.

A blinded cross-sectional study was carried out with 99 women, 44 of whom had silicone breast implants. Group I consisted of 55 healthy volunteer women without breast implants; group II comprised 13 volunteer women with breast implants or explants who felt healthy; group III comprised 21 volunteer women with breast implants who had chronic fatigue, musculoskeletal symptoms, and skin disorders; and group IV comprised 10 women who had their prostheses explanted but still presented with clinical symptoms similar to those of the women in group III. Proliferative responses of peripheral blood mononuclear cells from all 99 women were measured by [3H]thymidine uptake after exposure to SiO2 silicon, or silicone gel. The levels of proliferative responses were expressed as stimulation indices, which were obtained by dividing the counts per minute of stimulated cells by the counts per minute of unstimulated cells. Abnormal responses to SiO2, silicon, or silicone gel were defined as a stimulation index of > 2.8, > 2.1, or > 2.4, respectively. Abnormal responses were observed in 0% of group I, 15% of group II, 29% of group III, and 30% of group IV (P < 0.0005 for group I versus groups II and IV). Thirty-one percent of symptomatic women with silicone gel breast implants had elevated serum silicon levels ( > 0.18 mg/liter); however, there was no significant correlation between abnormal cellular responses and silicon levels in blood serum, type of implant, time since first implantation, prosthesis explantation, number of implants, or report of implant leakage or rupture.(ABSTRACT TRUNCATED AT 250 WORDS)

[Contact allergy reactions to Silodent impression material]. / Kontakt allergiás reakciók Silodent lenyomatanyag alkalmazása után.

The silicon based impression materials are often used in dental practice. Recently, we have observed two cases of contact allergic reaction after using Silodent (Ferrokémia) impression material. Epicutaneous test has shown that the allergic reaction is provoked by the catalisator. This hypersensitivity reaction is due to a previous sensibilization (e.g. previous impression taking or environmental hazards). No epicutaneous reaction to the other types of silicon based impression materials was found.

Enhancement of allergic encephalomyelitis by particulate adjuvants inoculated long before antigen.

Carbonyl iron and several other particulate materials have been reported to enhance the development of experimental allergic encephalomyelitis when injected with neural antigen. In the present work, silicon and silica powders have been added to the list of particulate adjuvants. In addition, several particulate materials, but not carbonyl iron, were effective adjuvants when inoculated four weeks or even six months before the neural antigen. It was necessary for adjuvant and antigen to be injected in the same region, but both intraperitoneal and subcutaneous routes were effective. The long-lasting adjuvanticity of certain particulates in the tissues is probably related to their bland and unabsorbable nature. The reasons for restrictions in the range of adjuvants and antigens that are effective in this system and the possibility of a similar occurrence in nature remain to be investigated.