In this work, we clearly demonstrate the capability of protein nanopatterns of improving the quality factors of immunosensing devices, such as lowering of the limit of detection and increase of ...sensitivity. This beneficial effect is obtained by the formation on the sensor’s surface of bioadhesive domains of nanometric dimensions in a nonadhesive matrix by means of colloidal lithography.
In this work, we compare the immunoreaction efficiency between uniformly functionalized surface and chemically nanopatterned surfaces when applied as platforms for antigen/antibody interactions with ...and without the use of protein A as orienting protein. On the nanopatterned platform, the immunoreaction efficiency is higher than all the other cases with no protein A pretreatment of the surface, providing evidence of the capability of the adhesive/antiadhesive nanopatterned surface to immobilize the molecules in a reactive state, increasing their possibility to form complexes.
Nucleic acid-based biochips represent a promising tool for gene sequence analysis, especially for mutation detection. Surface plasmon resonance imaging (SPRI) technique allows kinetic monitoring of ...molecular interaction, such as DNA–DNA, in real-time and without any prior labelling step. SPRI was applied to developing a DNA sensor for the detection of gene mutations accounting for human cystic fibrosis and specifically some of those localized in exon 10, with the common three-base-pair deletion ΔF508, alongside several single nucleotide polymorphisms (SNPs). The SPRI system enabled us to monitor the hybridisation kinetics of unlabelled DNA targets (short oligonucleotides or a 377
pb PCR product) to a 196 spots matrix of ssDNA probes immobilised onto a bio-functionalised surface, and to detect in real-time the mutations in a DNA fragment.
Thermoresponsive polymer layers offer the possibility of preparing smart surfaces with properties that are switchable through a phase transition, usually close to the lower critical solution ...temperature of the polymer. In particular, poly(N-isopropylacrylamide) (pNIPAM) has gained a great deal of attention because it has such a phase transition in a physiologically interesting temperature range. We have prepared ultrathin thermoresponsive coatings by grafting pNIPAM on a plasma-CVD-deposited, poly(ethylene oxide)-like polymer substrate that was activated in an Ar plasma discharge to initiate the grafting. The presence and integrity of pNIPAM was verified by XPS and ToF-SIMS, and a dramatic change in the wettability during the phase transition was identified by temperature-dependent contact angle measurements. The transition from the hydrated to the collapsed conformation was analyzed by temperature-dependent QCM measurements and by AFM. An unusual, reversible behavior of the viscoelastic properties was seen directly at the phase transition from the swollen to the collapsed state. The phase transition leads to a switching from protein repulsion to a state that allows the adsorption of proteins.
Droplet formation during adsorption of the protein lactoferrin from an aqueous solution on a surface functionalized by plasma deposited poly(acrylic acid) is studied using quartz crystal microbalance ...and atomic force microscopy. The formation of protein droplets is particularly favored at pH values close to the isoelectric point of lactoferrin, where the molecules carry little excess charge and intermolecular attraction exceeds the molecule−surface interaction. By combining topographic data with information on the system dynamics, it is possible to describe the viscoelastic properties of the adsorbate within a quantitative model for nonhomogeneous layers.
Bulk acoustic waves have been applied as affinity sensors. In particular, a nucleic acid sensor for hybridization studies has been developed and applied for detecting DNA target sequences in ...solution. A DNA probe is immobilized on the sensor surface while the target sequence is free in solution; the interaction between the two complementary strands (hybridization) is followed in real-time, without the use of any label. The system has been applied to analytical problems, i.e., genetically modified organisms (GMOs) detection. The probe was complementary to characteristic DNA sequences present in GMOs. The probe sequences were internal to the sequence of 35S promoter and Nos terminator that are inserted sequences in the genome of the GMO regulating the transgene expression. Two different probe immobilization procedures were characterized to improve the performances of a piezoelectric crystal DNA sensor for GMOs detection: 1) thiol-dextran-streptavidin-biotin procedure and 2) thiol-derivatized probe and blocking thiol procedure. The system has been optimized using synthetic oligonucleotides. The probe immobilization step was monitored by a surface plasmon resonance system.
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•The Langmuir–Blodgett technique offers a two-degree control for nanoparticle layers.•Tunable plasmonic substrates can be easily obtained with gold nanoparticle monolayers.•Optimizing ...the lateral packing or hotspot size reveals a resonance in SERS intensity.
Nanoparticle self-assembly is a robust and versatile strategy for the development of functional nanostructured materials, offering low-cost and scalable methods that can be fine-tuned for many different specific application. In this work, we demonstrate a pathway for the fabrication of tailorable quasi-two-dimensional lattices of gold nanoparticles to be used in Surface Enhanced Raman Scattering (SERS) detection of biomolecules. As a first step, nanoparticles are spread as a monolayer at the water/air interface, compressed to a target lateral density in a Langmuir–Blodgett technique, and transferred to a properly functionalized substrate surface. Once firmly adhered to the substrate, the lattice of nanoparticles can be directly used or be further processed using electroless gold deposition to let the nanoparticle grow thus tuning the plasmonic response and SERS enhancement. Compared to direct deposition or self-assembly methods, our protocol enables to obtain consistent results and much higher coverage of Au nanoparticles thanks to the active control of the surface pressure of the spread monolayer.
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