ABSTRACT
In this study, we demonstrate a three-dimensional surface-modified origami-paper-based analytical device (3D-soPAD) for immunoassay applications. The platform enables the sequential steps of immunoassays to be easily performed using a folded, sliding paper design featuring multiple pre-stored reagents, allowing us to take advantage of the vertical diffusion of the analyte through the different paper layers. The cellulose substrate is composed of carboxymethyl cellulose modified with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide, which provide covalent bonding sites for bio-recognition molecules. After the optimization of the operation parameters, we determined the detection limit of the 3D-soPAD for human immunoglobulin G (HIgG) which can be as low as 0.01 ng mL-1, with a total turnaround time of 7 min. In order to study the long-term storage of the platform, anti-HIgG horseradish peroxidase (aHIgG-HRP) conjugates were stored by freeze-drying in sugar matrices composed of 10% sucrose/10% trehalose (w/w%) on the paper device, retaining 80% of their activity after 75 days of storage at 4 °C. To evaluate the performance of the paper device using real samples, we demonstrated the detection of protein A (a biomarker for Staphylococcus aureus infection) in highly viscous human synovial fluid. These results show that the proposed 3D-soPAD platform can provide sensitive, high-throughput, and on-site prognosis of infection in resource-limited settings.
Subject(s)
Immunoassay , Microfluidic Analytical Techniques , Paper , Staphylococcal Protein A/analysis , Biomarkers/analysis , Humans , Immunoassay/instrumentation , Microfluidic Analytical Techniques/instrumentation , Particle Size , Staphylococcal Infections/diagnosis , Surface Properties , Synovial Fluid/chemistry , Synovial Fluid/microbiologyABSTRACT
A confocal micro X-ray fluorescence thickness gauge based on a polycapillary focusing X-ray lens, a polycapillary parallel X-ray lens and a laboratory X-ray source was designed in order to analyze nondestructively the thickness of thin film and cladding material. The performances of this confocal thickness gauge were studied. Two Ni films with a thickness of about 25 and 15 microm respectively were measured. The relative errors corresponding to them were 3.5% and 7.1%, respectively. The thickness uniformity of a Ni films with a thickness of about 10 microm was analyzed. This confocal technology for measuring the thickness was both spatially resolved and elemental sensitive, and therefore, it could be used to measure the thickness of the multilayer sample and analyze the thickness uniformity of the sample. This confocal thickness gauge had potential applications in analyzing the thickness of sample.
ABSTRACT
The confocal micro X-ray fluorescence (XRF) based on polycapillary X-ray lens and conventional X-ray source was used to carry out the scanning analysis of the distribution of the elements in a single hair. The elemental distribution in the single hair was obtained. In the confocal micro XRF technology, the output focal spot of the polycapillary focusing X-ray lens and the input focal spot of the polycapillary parallel X-ray lens were adjusted confocally. The detector could only detect the X-rays from the overlapping foci. This confocal structure decreased the effects of the background on the X-ray spectra, and was accordingly helpful for improving the accuracy of this XRF technology. A polycapillary focusing X-ray lens with a high gain in power density was used to decrease the requirement of power of the X-ray source used in this confocal technology, and made it possible to perform such confocal micro XRF analysis by using the conventional X-ray source with low cost. Experimental results indicated that the confocal micro X-ray fluorescence based on polycapillary X-ray lens had potential applications in analyzing the elemental distribution of individual hairs.
