Measurement of urinary N-telopeptides and serum C-telopeptides from type I collagen using a lateral flow-based immunoassay.

Measuring bone turnover markers could detect early stages of osteoporosis and early responses to anti-osteoporotic treatments. Currently, commonly used bone turnover markers, N-telopeptides (NTx) and C-telopeptides (CTx), are measured using ELISA tests, which demands time and increases cost. Bone turnover markers need to be measured more easily for general use. Lateral flow-based immunoassay would be an appropriate method for this context. This study was performed to investigate the precision of a newly developed lateral flow-based immunoassay for measuring the urinary NTx and serum CTx, and their correlations with ELISA measurements. Urine NTx and serum CTx concentrations were determined by photoscan of newly developed strips, using a lateral flow-based immunoassay for 36 subjects (mean age 66.2 years, SD 7.5 years; four males and 32 females). Repeated measurement of urinary NTx and serum CTx were performed three times, using this technology for a precision test. The correlation of the lateral flow-based immunoassay with the ELISA measurements was analyzed. Precision of the newly developed lateral flow based immunoassay was 0.974 (ICC, 95% confidence interval, 0.955 to 0.986) and 0.995 (ICC, 95% confidence interval, 0.991 to 0.997) for urinary NTx and serum CTx, respectively. The correlation of lateral flow based immunoassay with ELISA was 0.913 for urinary NTx and 0.872 for serum CTx. These results suggest that measuring the urinary NTx and serum CTx, using a lateral flow-based immunoassay, is a relevant method for point-of-care testing and screening of bone resorption markers.

Measurement of urinary N-telopeptides from type I collagen using a colloidal gold-based immunoassay.

This study aimed to investigate precision of a newly developed gold nanoparticle-based immunoassay for measuring urinary N-telopeptides (NTx) and its correlation with ELISA measurement. NTx concentrations were determined by absorption changes using spectroscopy at 535 nm, which were measured three times with an interval of two hours for precision test, using urine samples of 60 subjects (32 males and 28 females; mean age 30.4 years, SD 21.9 years). The correlation of the immunoassay with the measurement of ELISA kit was also analyzed. Precision of the immunoassay and its correlation with ELISA were 0.924 (ICC, 95% confidence interval, 0.661-0.971) and 0.90 (p<0.001). Our findings suggested that this immunoassay of urinary NTx could be used as a means of screening for bone resorption and point-of-care testing.

Measurements of serum C-reactive protein levels in patients with gastric cancer and quantification using silicon nanowire arrays.

We examined the levels of serum alpha-fetoprotein, carcinoembryonic antigen, and carbohydrate antigen in 83 of 400 patients who had undergone surgery for gastric cancer and correlated these markers with stages of the disease. In addition, we measured C-reactive protein (CRP) concentrations in the sera of gastric cancer patients with silicon nanowire field-effect transistors (SiNW FETs) to determine whether SiNW FETs could be used to accurately sense CRP, a marker of inflammation and possible indicator of future progression of the cancer. We designed and fabricated SiNWs to be responsive to CRP. Of the 83 patients examined, six who showed marked elevation of CRP (>3 to 10 mg/dL, according to hospital laboratory measurements) were selected and subjected to measurement with the SiNW FETs. Our findings showed that SiNW-based sensors could be highly sensitive and specific in measuring CRP in the sera of postoperative patients and thus could represent a simple and quick method of prognostic evaluation in patients. FROM THE CLINICAL EDITOR: In this study, silicon nanowire field effect transistors were fabricated to be responsive to C-reactive protein. The new technology resulted in highly sensitive and specific CRP sensors, which may greatly simplify this serum test for a variety of conditions where rapid, accurate and easily repeatable CRP measurements are needed.

Quantitative measurements of C-reactive protein using silicon nanowire arrays.

A silicon nanowire-based sensor for biological application showed highly desirable electrical responses to either pH changes or receptor-ligand interactions such as protein disease markers, viruses, and DNA hybridization. Furthermore, because the silicon nanowire can display results in real-time, it may possess superior characteristics for biosensing than those demonstrated in previously studied methods. However, despite its promising potential and advantages, certain process-related limitations of the device, due to its size and material characteristics, need to be addressed. In this article, we suggest possible solutions. We fabricated silicon nanowire using a top-down and low cost micromachining method, and evaluate the sensing of molecules after transfer and surface modifications. Our newly designed method can be used to attach highly ordered nanowires to various substrates, to form a nanowire array device, which needs to follow a series of repetitive steps in conventional fabrication technology based on a vapor-liquid-solid (VLS) method. For evaluation, we demonstrated that our newly fabricated silicon nanowire arrays could detect pH changes as well as streptavidin-biotin binding events. As well as the initial proof-of-principle studies, C-reactive protein binding was measured: electrical signals were changed in a linear fashion with the concentration (1 fM to 1 nM) in PBS containing 1.37 mM of salts. Finally, to address the effects of Debye length, silicon nanowires coupled with antigen proteins underwent electrical signal changes as the salt concentration changed.

Fabrication of suspended silicon nanowire arrays.

A method to fabricate suspended silicon nanowires that are applicable to electronic and electromechanical nanowire devices is reported. The method allows for the wafer-level production of suspended silicon nanowires using anisotropic etching and thermal oxidation of single-crystal silicon. The deviation in width of the silicon nanowire bridges produced using the proposed method is evaluated. The NW field-effect transistor (FET) properties of the device obtained by transferring suspended nanowires are shown to be practical for useful functions.