Surface plasmon resonance imaging as a multidimensional surface characterization instrument--application to biochip genotyping

Dual-Channel Surface Plasmon Resonance for Quantification of ApoE Gene and Genotype Discrimination in Unamplified Genomic DNA Extracts

Identification of gene variation is of great importance for attaining information related to disease susceptibility. A highly sensitive and specific surface plasmon resonance (SPR) method for quantification of the apoE gene and genotype discrimination was demonstrated. The complementary sequences with the specific recognition sites of GCGC bases upon hybridization to the preimmobilized biotinylated probes could be cleaved by the restriction enzyme HhaI, while the existence of the single-base mismatch (GTGC) prevented the cleavage reaction. In both cases, the incorporation of streptavidin increased the sensitivity of the SPR assay, and the detection levels of 10 fM and 50 fM for the complementary and single-base mismatched sequences were attained, respectively. The sensing protocol is simple, label-free, and quantitative, thus avoiding the complicated polymerase chain reaction (PCR) amplification procedures. The proposed method serves as a viable means for facile and sensitive analyses of apoE genes in four unamplified genomic DNA extracts.

Bioanalytical approaches for the detection of single nucleotide polymorphisms by Surface Plasmon Resonance biosensors

The mapping of specific single nucleotide polymorphisms (SNPs) in patients' genome is a main goal in theranostics, aiming to the development of therapies based on personalized medicine. In this review, Surface Plasmon Resonance (SPR) and Surface Plasmon Resonance imaging (SPRi) biosensors applied to the recognition of SNPs were reviewed, since these technologies are emerging in clinical diagnosis as powerful tools thanks to their analytical features, mainly the real-time and label-free monitoring based on array format for parallel analysis. Since the literature is heterogeneous, a critical classification and a systemic comparison of the analytical performances of published methods were here reviewed on the basis of the analytical strategy and the assay design. In particular, the use of helping agents (i.e. proteins, nanoparticles (NPs), intercalating agents) or artificial DNAs, often coupled to SPR to achieve allele discrimination and/or enhanced sensitivity, were here revised and classified. Finally, the real suitability of SPR biosensors to clinical diagnostics for SNPs detection was addressed by comparing their features and performances with those of other biosensors based on other techniques (e.g. electrochemical biosensors).

Surface plasmon resonance applications in clinical analysis

In the last 20 years, surface plasmon resonance (SPR) and its advancement with imaging (SPRi) emerged as a suitable and reliable platform in clinical analysis for label-free, sensitive, and real-time monitoring of biomolecular interactions. Thus, we report in this review the state of the art of clinical target detection with SPR-based biosensors in complex matrices (e.g., serum, saliva, blood, and urine) as well as in standard solution when innovative approaches or advanced instrumentations were employed for improved detection. The principles of SPR-based biosensors are summarized first, focusing on the physical properties of the transducer, on the assays design, on the immobilization chemistry, and on new trends for implementing system analytical performances (e.g., coupling with nanoparticles (NPs). Then we critically review the detection of analytes of interest in molecular diagnostics, such as hormones (relevant also for anti-doping control) and biomarkers of interest in inflammatory, cancer, and heart failure diseases. Antibody detection is reported in relation to immune disorder diagnostics. Subsequently, nucleic acid targets are considered for revealing genetic diseases (e.g., point mutation and single nucleotides polymorphism, SNPs) as well as new emerging clinical markers (microRNA) and for pathogen detection. Finally, examples of pathogen detection by immunosensing were also analyzed. A parallel comparison with the reference methods was duly made, indicating the progress brought about by SPR technologies in clinical routine analysis.

Deep UV nano-microstructuring of substrates for surface plasmon resonance imaging

In this paper, we describe wafer-scale fabrication and characterization of plasmonic chips-containing different sizes and spacings of metallic micro- and nanoline structures-using deep UV lithography. Using a high dose (25 mJ cm( - 2)) and a proper lift-off process, feature sizes as small as 25 nm are obtained. Moreover, we study the dependence of surface plasmon resonance on the angle of incidence and wavelength for different micro- and nanoline size and spacing values, yielding localized to quasi-propagative plasmonic behaviors. Rigorous coupled wave analysis (RCWA) techniques are employed to numerically confirm these experimental observations. Finally, the refractive index of media around the SPRI sensor chips is varied, showing the angulo-spectral regions of higher sensitivity for each type of structure.

Affinity-based biosensors as promising tools for gene doping detection

Innovative bioanalytical approaches can be foreseen as interesting means for solving relevant emerging problems in anti-doping control. Sport authorities fear that the newer form of doping, so-called gene doping, based on a misuse of gene therapy, will be undetectable and thus much less preventable. The World Anti-Doping Agency has already asked scientists to assist in finding ways to prevent and detect this newest kind of doping. In this Opinion article we discuss the main aspects of gene doping, from the putative target analytes to suitable sampling strategies. Moreover, we discuss the potential application of affinity sensing in this field, which so far has been successfully applied to a variety of analytical problems, from clinical diagnostics to food and environmental analysis.

SPR-based biosensors: a tool for biodetection of hormonal compounds

Novel cancer treatments, prevention of postmenopausal disorder, and prescription of oral contraceptives are the main developments in the design of synthetic estrogenic medication. The increasing consumption of these synthetic pharmaceuticals, in addition to human and animal natural estrogenic compound excretion, contribute to their environmental dissemination worldwide. Their assimilation as a result of consumption of food and water perturbs normal endocrine systems and leads to the emergence of human and animal diseases and malformations. These compounds are active in the organism at low concentrations. Accordingly, daily low-level exposure disrupts the natural equilibrium in the endocrine system. A method enabling quantification at such products at low levels (from pg L(-1) to ng L(-1)) is therefore required for these products. Surface plasmon resonance, essentially used for comprehension of molecular mechanisms and in drug discovery, can also be used for environmental pollutant monitoring. This technology has already been used for evaluation of the effects of chemical pollutants on specific nuclear receptors. It has been possible to determine the role of each individual compound on the disruption of the estrogen-activated cellular pathway. Development of SPR screening methods enables application of such an approach for quantification of these compounds in water.