Quantitative detection of urinary bladder cancer antigen via peptide-immobilized magnetic bead-based SERS probe.

Antibody pairing is a difficult step in developing all immune-sandwich assay for antigen detection. Urinary bladder cancer (UBC) antigen is a typical bladder cancer biomarker for the early diagnosis of bladder cancer. Based on peptide-antibody pairing, a surface-enhanced Raman scattering platform for the ultrasensitive detection of UBC is presented. The phage display tech was used to screen and obtain a 12-peptide ligand against UBC (KD = 4.84 × 10-7 M). Twelve-peptide-conjugate magnetic beads (MNs@12-peptide) and antibody-conjugate silver nanoparticles (AgNPs@Ab) were prepared for SERS measurements. AgNPs@Ab can be linked onto the surface of MNs@12-peptide through ligand/antibody recognition to assess a sandwich-shape complex, which turns on the SERS signal of 4-ABP. Furthermore, the second SERS signal amplification is from the magnetic field-induced spontaneous collection effect. The above design enhances the SERS signal to achieve the limit of detection as 6.25 ng/mL, the clinical threshold of 10 ng/mL. Six clinical urine samples from bladder cancer patients and healthy volunteers were also successfully detected using the dual enhancement SERS measurement. The proposed method provides the future direction of fully automated and ultrasensitive assays.

Hermetic Welding of an Optical Fiber Fabry-Pérot Cavity for a Diaphragm-Based Pressure Sensor Using CO2 Laser.

A diaphragm-based hermetic optical fiber Fabry-Pérot (FP) cavity is proposed and demonstrated for pressure sensing. The FP cavity is hermetically sealed using one-step CO2 laser welding with a cavity length from 30 to 100 µm. A thin diaphragm is formed by polishing the hermetic FP cavity for pressure sensing. The fabricated FP cavity has a fringe contrast larger than 15 dB. The experimental results show that the fabricated device has a linear response to the change in pressure, with a sensitivity of -2.02 nm/MPa in the range of 0 to 4 MPa. The results demonstrate that the proposed fabrication technique can be used for fabricating optical fiber microcavities for sensing applications.

Dislocation nucleation facilitated by atomic segregation.

Surface segregation-the enrichment of one element at the surface, relative to the bulk-is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

Local electronic descriptors for solute-defect interactions in bcc refractory metals.

The interactions between solute atoms and crystalline defects such as vacancies, dislocations, and grain boundaries are essential in determining alloy properties. Here we present a general linear correlation between two descriptors of local electronic structures and the solute-defect interaction energies in binary alloys of body-centered-cubic (bcc) refractory metals (such as W and Ta) with transition-metal substitutional solutes. One electronic descriptor is the bimodality of the d-orbital local density of states for a matrix atom at the substitutional site, and the other is related to the hybridization strength between the valance sp- and d-bands for the same matrix atom. For a particular pair of solute-matrix elements, this linear correlation is valid independent of types of defects and the locations of substitutional sites. These results provide the possibility to apply local electronic descriptors for quantitative and efficient predictions on the solute-defect interactions and defect properties in alloys.