Fábio Ferreira Carlos

Gold Nanoparticles for Diagnostics: Advances towards Points of Care

The remarkable physicochemical properties of gold nanoparticles (AuNPs) have prompted developments in the exploration of biomolecular interactions with AuNP-containing systems, in particular for biomedical applications in diagnostics. These systems show great promise in improving sensitivity, ease of operation and portability. Despite this endeavor, most platforms have yet to reach maturity and make their way into clinics or points of care (POC). Here, we present an overview of emerging and available molecular diagnostics using AuNPs for biomedical sensing that are currently being translated to the clinical setting.

Gold nanoparticle-based theranostics: disease diagnostics and treatment using a single nanomaterial

Nanotheranostics takes advantage of nanotechnology-based systems in order to diagnose and treat a specific disease. This approach is particularly relevant for personalized medicine, allowing the detection of a disease at an early stage, to direct a suitable therapy toward the target tissue based on the molecular profile of the altered phenotype, subsequently facilitating disease monitoring and following treatment. A tailored strategy also enables to reduce the off-target effects associated with universal treatments and improve the safety profile of a given treatment. The unique optical properties of gold nanoparticles, their ease of surface modification, and high surface-to-volume ratio have made them central players in this area. By combining imaging, targeting, and therapeutic agents in a single vehicle, these nanoconjugates are (ought to be) an important tool in the clinics. In this review, the multifunctionality of gold nanoparticles as theranostics agents will be highlighted, as well as the requirements before the translation of these nanoplatforms into routine clinical practice.

Association of FTO and PPARG polymorphisms with obesity in Portuguese women.

Purpose We evaluated the association between risk of obesity in the Portuguese population and two obesity-related single-nucleotide gene polymorphisms: fat-mass and obesity-associated (FTO) rs9939609 and peroxisome proliferator-activated receptor gamma (PPARG) rs1801282. Patients and methods A total of 194 Portuguese premenopausal female Caucasians aged between 18 and 50 years (95 with body mass index [BMI] ≥30 g/m2, 99 controls with BMI 18.5–24.9 kg/m2) participated in this study. The association of the single-nucleotide polymorphisms with obesity was determined by odds ratio calculation with 95% confidence intervals. Results Significant differences in allelic expression of FTO rs9939609 (P<0.05) were found between control and case groups, indicating a 2.5-higher risk for obesity in the presence of both risk alleles when comparing the control group with the entire obese group. A fourfold-higher risk was found for subjects with class III obesity compared to those with classes I and II. No significant differences in BMI were found between the control and case groups for PPARG rs1801282 (P>0.05). Conclusion For the first time, a study involving an adult Portuguese population shows that individuals harboring both risk alleles in the FTO gene locus are at higher risk for obesity, which is in agreement to what has been reported for other European populations.

Characterization of genomic single nucleotide polymorphism via colorimetric detection using a single gold nanoprobe.

Identification of specific nucleic acid sequences mediated by gold nanoparticles derivatized thiol-modified oligonucleotides (Au-nanoprobes) has been proven to be a useful tool in molecular diagnostics. Here, we demonstrate that, on optimization, detection may be simplified via the use of a single Au-nanoprobe to detect a single nucleotide polymorphism (SNP) in homo- or heterozygote condition. We validated this non-cross-linking approach through the analysis of 20 clinical samples using a single specific Au-nanoprobe for an SNP in the FTO (fat mass and obesity-associated) gene against direct DNA sequencing. Sensitivity, specificity, and limit of detection (LOD) were determined, and statistical differences were calculated by one-way analysis of variance (ANOVA) and a post hoc Tukeys test to ascertain whether there were any differences between Au-nanoprobe genotyped groups. For the first time, we show that the use of a single Au-nanoprobe can detect SNP for each genetic status (wild type, heterozygous, or mutant) with high degrees of sensitivity (87.50%) and specificity (91.67%).

One nanoprobe, two pathogens: gold nanoprobes multiplexing for point-of-care

BackgroundGold nanoparticles have been widely employed for biosensing purposes with remarkable efficacy for DNA detection. Amongst the proposed systems, colorimetric strategies based on the remarkable optical properties have provided for simple yet effective sequence discrimination with potential for molecular diagnostics at point of need. These systems may also been used for parallel detection of several targets to provide additional information on diagnostics of pathogens.ResultsFor the first time, we demonstrate that a single Au-nanoprobe may provide for detection of two distinct targets (pathogens) allowing colorimetric multi-target detection. We demonstrate this concept by using one single gold-nanoprobe capable to detect members of the Mycobacterium tuberculosis complex and Plasmodium sp., the etiologic agents of tuberculosis and malaria, respectively. Following characterisation, the developed gold-nanoprobe allowed detection of either target in individual samples or in samples containing both DNA species with the same efficacy.ConclusionsUsing one single probe via the non-cross-linking colorimetric methodology it is possible to identify multiple targets in one sample in one reaction. This proof-of-concept approach may easily be integrated into sensing platforms allowing for fast and simple multiplexing of Au-nanoprobe based detection at point-of-need.

Single nucleotide polymorphism detection using gold nanoprobes and bio‐microfluidic platform with embedded microlenses

The use of microfluidics platforms combined with the optimal optical properties of gold nanoparticles has found plenty of application in molecular biosensing. This paper describes a bio‐microfluidic platform coupled to a non‐cross‐linking colorimetric gold nanoprobe assay to detect a single nucleotide polymorphism associated with increased risk of obesity fat‐mass and obesity‐associated (FTO) rs9939609 (Carlos et al., 2014). The system enabled significant discrimination between positive and negative assays using a target DNA concentration of 5 ng/µL below the limit of detection of the conventionally used microplate reader (i.e., 15 ng/µL) with 10 times lower solution volume (i.e., 3 µL). A set of optimization of our previously reported bio‐microfluidic platform (Bernacka‐Wojcik et al., 2013) resulted in a 160% improvement of colorimetric analysis results. Incorporation of planar microlenses increased 6 times signal‐to‐loss ratio reaching the output optical fiber improving by 34% the colorimetric analysis of gold nanoparticles, while the implementation of an optoelectronic acquisition system yielded increased accuracy and reduced noise. The microfluidic chip was also integrated with a miniature fiber spectrometer to analyze the assays’ colorimetric changes and also the LEDs transmission spectra when illuminating through various solutions. Furthermore, by coupling an optical microscope to a digital camera with a long exposure time (30 s), we could visualise the different scatter intensities of gold nanoparticles within channels following salt addition. These intensities correlate well to the expected difference in aggregation between FTO positive (none to small aggregates) and negative samples (large aggregates). Biotechnol. Bioeng. 2015;112: 1210–1219.

Gold Nanoparticles in Molecular Diagnostics and Molecular Therapeutics

Gold nanoparticles, due to their unique physicochemical properties, are among the most widely used nanoscale-based platforms for molecular diagnostics. The intrinsic chemical stability and apparent lack of toxicity have also prompted for application in therapeutics, e.g., for imaging modalities and as vectorization strategies for molecular modulators, i.e., gene silencing, specific targeting of cellular pathways, etc. Because of their common molecular ground, these approaches have been synergistically coupled together into molecular theranostic systems that allow for radical new in vivo diagnostics modalities with simultaneous tackling of molecular disequilibria leading to disease. Despite this tremendous potential, gold nanoparticle-based systems still have to make their effective translation to the clinics. This chapter focuses on the use of gold nanoparticles for molecular diagnostics and molecular therapeutics and their application in theranostics. Attention is paid to those systems that have moved toward the clinics.

Allele specific LAMP- gold nanoparticle for characterization of single nucleotide polymorphisms

Highlights • Allele-specific isothermal amplification method (AS-LAMP) for SNP characterization.• Use of ssDNA-functionalized gold nanoparticles (AuNPs) for SNP full discrimination.• A simple and low-cost strategy to provide fast results in medium throughput settings.• AS-LAMP amplification products can be easily interpreted in less than 15 min.