High-performance Bloch surface wave biosensor based on a prism-coupled porous silicon composite structure for the detection of hemoglobin

Biosensors have various potential applications in biomedical research and clinical diagnostic, especially in detection of biomolecules in highly diluted solutions. In this study, a high-performance Bloch surface wave biosensor was constructed for the detection of hemoglobin. The procedure consisted of designing a porous silicon-based Kretschmann configuration to ensure excitation of the Bloch surface wave. The performance of the resulting sensor was then optimized by adjusting the buffer layer parameters based on the impedance matching method. The results showed an increase in the quality factor and figure of merit of the biosensor as a function of the decrease in thickness and refractive index of the buffer layer. The combination of the two optimization methods resulted in the quality factor and figure of merit of the optimized biosensor reaching as high as Q = 6967.4 and FOM = 11050RIU^-1, respectively. In sum, the designed biosensor with high performance looks promising for future detection of hemoglobin.

Functional Nanoparticles-driven Self-assembled Diblock Copolymer Hybrid Nano-Patterns

Herein, we report how functional gold nanoparticles can drive the block copolymer BCP thin film morphologies of polystyrene-block-poly(vinylbenzyl-3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)prop-1-yne (PS-b-PVBEG). PS-b-PVBEG was obtained via Nitroxide Mediated Polymerization and two consecutive post-polymerization...

Biosensors and bioassays for determination of matrix metalloproteinases: state of the art and recent advances

Matrix metalloproteinases (MMPs) are closely associated with various physiological and pathological processes, and have been regarded as potential biomarkers for severe diseases including cancer. Accurate determination of MMPs would advance our understanding of their roles in disease progression, and is of great significance for disease diagnosis, treatment and prognosis. In this review, we present a comprehensive overview of the developed bioassays/biosensors for detection of MMPs, and highlight the recent advancement in nanomaterial-based immunoassays for MMP abundance measurements and nanomaterial-based biosensors for MMP activity determination. Enzyme-linked immunosorbent assay (ELISA)-based immunoassays provide information about total levels of MMPs with high specificity and sensitivity, while target-based biosensors measure the amounts of active MMPs, and allow imaging of MMP activities in vivo. For multiplex and high-throughput analysis of MMPs, microfluidics and microarray-based assays are described. Additionally, we put forward the existing challenges and future prospects from our perspective.

A nanopatterned dual reactive surface driven by block copolymer self-assembly

Herein, we report the selective functionalization of nano-domains obtained by the self-assembly of a polystyrene-block-poly(vinyl benzyl azide) PS-b-PVBN₃ copolymer synthesized in three steps. First, a polystyrene macro-initiator was synthesized, and then extended with vinyl benzyl chloride by nitroxide mediated polymerization to form polystyrene-block-poly(vinyl benzyl chloride) PS-b-PVBC. Nucleophilic substitution of vinyl benzyl chloride into a vinyl benzyl azide moiety is finally performed to obtain PS-b-PVBN₃ which self-assembled into nano-domains of vinyl benzyl azide PVBN₃. Click chemistry was then used to bind functional gold nanoparticles and poly(N-isopropylacrylamide) (PNIPAM) on PVBN₃ domains due to the specific anchoring at the surface of the nanopatterned film. Atomic force microscopy (AFM) was used to observe the block copolymer self-assembly and the alignment of the gold nanoparticles at the surface of the PVBN₃ nanodomains. Thorough X-ray photoelectron spectroscopy (XPS) analysis of the functional film showed evidence of the sequential grafting of nanoparticles and PNIPAM. The hybrid surface expresses thermo-responsive properties and serves as a pattern to perfectly align and control the assembly of inorganic particles at the nanoscale.

Hybrid polymer/porous silicon nanofibers for loading and sustained release of synthetic DNA-based responsive devices

Synthetic DNA-based oligonucleotides are loaded into porous silicon nanoparticles (pSiNPs) and incorporated into nanofibers of poly(lactide-co-glycolide) (PLGA), poly-l-lactic acid (PLA), or polycaprolactone (PCL). The resulting hybrid nanofibers are characterized for their ability to release the functional oligonucleotide payload under physiologic conditions. Under temperature and pH conditions mimicking physiological values, the PLGA-based nanofibers release >80% of their DNA cargo within 5 days, whereas the PLA and PCL-based fibers require 15 days to release >80% of their cargo. The quantity of DNA released scales with the quantity of DNA-loaded pSiNPs embedded in the nanofibers; mass loadings of between 2.4 and 9.1% (based on mass of DNA-pSiNP construct relative to mass of polymer composite) are investigated. When a responsive DNA-based nanodevice (i.e. molecular beacon) is used as a payload, it retains its functionality during the release period, independent of the polymer used for the formation of the nanofibers.

Oriented Nanofibrous Polymer Scaffolds Containing Protein-Loaded Porous Silicon Generated by Spray Nebulization

Oriented composite nanofibers consisting of porous silicon nanoparticles (pSiNPs) embedded in a polycaprolactone or poly(lactide-co-glycolide) matrix are prepared by spray nebulization from chloroform solutions using an airbrush. The nanofibers can be oriented by an appropriate positioning of the airbrush nozzle, and they can direct growth of neurites from rat dorsal root ganglion neurons. When loaded with the model protein lysozyme, the pSiNPs allow the generation of nanofiber scaffolds that carry and deliver the protein under physiologic conditions (phosphate-buffered saline (PBS), at 37 °C) for up to 60 d, retaining 75% of the enzymatic activity over this time period. The mass loading of protein in the pSiNPs is 36%, and in the resulting polymer/pSiNP scaffolds it is 3.6%. The use of pSiNPs that display intrinsic photoluminescence (from the quantum-confined Si nanostructure) allows the polymer/pSiNP composites to be definitively identified and tracked by time-gated photoluminescence imaging. The remarkable ability of the pSiNPs to protect the protein payload from denaturation, both during processing and for the duration of the long-term aqueous release study, establishes a model for the generation of biodegradable nanofiber scaffolds that can load and deliver sensitive biologics.

Magnetic Fe3O4@poly(propylene fumarate-co-ethylene glycol) core–shell biomaterials

MagP®-NH₂/(P(PF-co-EG)) core–shell biocomposites show antibacterial activity and magnetic-field tunable mechanical properties, hence they could be used as scaffolds for soft-tissue replacement.

Detection of trace heavy metal ions in water by nanostructured porous Si biosensors

Specific and sensitive detection and quantification of heavy metals in real water using label-free optical biosensors.

Chemical patterning on preformed porous silicon photonic crystals: towards multiplex detection of protease activity at precise positions†Electronic supplementary information (ESI) available: SEM images, XPS result and more optical reflectivity data. See DOI: 10.1039/c4tb00281dClick here for additional data file

Porous silicon rugate filters were chemically patterned with biomolecules and used for multiplex detection of protease activity at precise positions.

Porous silicon (PSi) rugate filters modified with alkyne-terminated monolayers were chemically patterned using a combination of photolithography of photoresist and click chemistry. Two chemical functionalities were obtained by conjugating, via click reactions, ethylene glycol moieties containing two different terminal groups to discrete areas towards the exterior of a PSi rugate filter. The patterning of biological species to the functionalized surface was demonstrated through the conjugation of fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA). Fluorescence microscopy showed selective positioning of FITC-BSA at discretely functionalized areas. Meanwhile, the optical information from precisely defined positions on the patterned surface was monitored by optical reflectivity measurements. The optical measurements revealed successful step-wise chemical functionalization followed by immobilization of gelatin. Multiplex detection of protease activity from different array elements on the patterned surface was demonstrated by monitoring the blue shifts in the reflectivity spectra resulted from the digestion of gelatin by subtilisin. Precise information from both individual elements and average population was acquired. This technique is important for the development of PSi into a microarray platform for highly parallel biosensing applications, especially for cell-based assays.