Nanophotonics has become a key enabling technology in biomedicine with great promises in early diagnosis and less invasive therapies. In this context, the unique capability of plasmonic noble metal nanoparticles to concentrate light on the nanometer scale has widely contributed to biosensing and enhanced spectroscopy. Recently, high-refractive index dielectric nanostructures featuring low loss resonances have been proposed as a promising alternative to nanoplasmonics, potentially offering better sensing performances along with full compatibility with the microelectronics industry. In this letter we report the first demonstration of biosensing with silicon nanoresonators integrated in state-of-the-art microfluidics. Our lab-on-a-chip platform enables detecting Prostate Specific Antigen (PSA) cancer marker in human serum with a sensitivity that meets clinical needs. These performances are directly compared with its plasmonic counterpart based on gold nanorods. Our work opens new opportunities in the development of future point-of-care devices toward a more personalized healthcare.

Label-free biosensing based on metallic nanoparticles supporting localized surface plasmon resonances (LSPR) has recently received growing interest (Anker, J. N., et al. Nat. Mater. 2008, 7, 442−453). Besides its competitive sensitivity (Yonzon, C. R., et al. J. Am. Chem. Soc. 2004, 126, 12669−12676; Svendendahl, M., et al. Nano Lett. 2009, 9, 4428−4433) when compared to the surface plasmon resonance (SPR) approach based on extended metal films, LSPR biosensing features a high-end miniaturization potential and a significant reduction of the interrogation device bulkiness, positioning itself as a promising candidate for point-of-care diagnostic and field applications. Here, we present the first, paralleled LSPR lab-on-a-chip realization that goes well beyond the state-of-the-art, by uniting the latest advances in plasmonics, nanofabrication, microfluidics, and surface chemistry. Our system offers parallel, real-time inspection of 32 sensing sites distributed across 8 independent microfluidic channels with very high reproducibility/repeatability. This enables us to test various sensing strategies for the detection of biomolecules. In particular we demonstrate the fast detection of relevant cancer biomarkers (human alpha-feto-protein and prostate specific antigen) down to concentrations of 500 pg/mL in a complex matrix consisting of 50% human serum. KEYWORDS: Plasmonics, LSPR, parallel, biosensing, lab-on-a-chip, cancer T he biosensing community has long been striving for an idealistic device consisting of high sensitivity, specificity, selectivity, and parallel real-time detection, coupled with low production and operational costs. In addition this device should be both environmentally and user-friendly and be portable, robust, and resistant to a wide range of external conditions (temperature, electromagnetic (EM) radiation, humidity), among other things. On the road toward this biosensing "Holy Grail", contemporary technology has been able to deliver numerous classes of biosensors that are focused on a particular application or niche in the biosensing market; however, no such device currently exists that delivers all or most of these requirements. Among these, optical biosensors operating in a label-free format have positioned themselves as very promising candidates owing to the inherent properties of light. Speed, inertness to external interferences, and almost unlimited bandwidth for data transfer has made light a preferred choice of transduction. With the advent of nanotechnology, especially in the field of plasmonics, surface plasmon resonance (SPR) technology revolutionized the biosensing field in the last two decades. The gold standard status of SPR is owed largely to its highly sensitive transducing mechanism. Namely, surface propagating EM waves called surface plasmon polaritons (SPPs) exhibit extraordinary sensitivity to the refractive index interfacial changes at the boundary between metal and dielectric. However, the activation of this transducing mechanism requires rather complex supporti...

Over the past decade, the capability of double-stranded RNAs to interfere with gene expression has driven new therapeutic approaches. Since small interfering RNA (siRNAs, 21 base pair double-stranded RNA) was shown to be able to elicit RNA interference (RNAi), efforts were directed toward the development of efficient delivery systems to preserve siRNA bioactivity throughout the delivery route, from the administration site to the target cell. Here we provide evidence of RNAi triggering, specifically silencing c-myc protooncogene, via the synthesis of a library of novel multifunctional gold nanoparticles (AuNPs). The efficiency of the AuNPs is demonstrated using a hierarchical approach including three biological systems of increasing complexity: in vitro cultured human cells, in vivo invertebrate (freshwater polyp, Hydra ), and in vivo vertebrate (mouse) models. Our synthetic methodology involved fine-tuning of multiple structural and functional moieties. Selection of the most active functionalities was assisted step-by-step through functional testing that adopted this hierarchical strategy. Merging these chemical and biological approaches led to a safe, nonpathogenic, self-tracking, and universally valid nanocarrier that could be exploited for therapeutic RNAi.

The need for point-of-care devices able to detect diseases early and monitor their status, out of a lab environment, has stimulated the development of compact biosensing configurations. Whereas localized surface plasmon resonance (LSPR) sensing integrated into a state-of-the-art microfluidic chip stands as a promising approach to meet this demand, its implementation into an operating sensing platform capable of quantitatively detecting a set of molecular biomarkers in an unknown biological sample is only in its infancy. Here, we present an on-chip LSPR sensor capable of performing automatic, quantitative, and multiplexed screening of biomarkers. We demonstrate its versatility by programming it to detect and quantify in human serum four relevant human serum protein markers associated with breast cancer.

Semipermanently polarized hydroxyapatite, named SP/HAp­(w), is obtained by applying a constant dc electric field of 1–10 kV/cm at 300–850 °C to the samples previously sintered in water vapor, while permanently polarized hydroxyapatite, PP/HAp­(a), is produced by applying a dc electric field of 3 kV/cm at 1000 °C to the samples sintered in air. SP/HAp­(w) has been used for biomedical applications, while PP/HAp­(a) has been proved to be a valuable catalyst for N2 and CO2 fixation. In this work, structural differences between SP/HAp­(w) and PP/HAp­(a) have been ascertained using Raman microscopy, wide-angle X-ray diffraction, scanning electronic microscopy, high-resolution transmission electron microscopy, and grazing incidence X-ray diffraction. Results prove the existence of crystal distortion in the form of amorphous calcium phosphate and β-tricalcium phosphate (β-TCP) phases close to the surface because of the atmosphere used in the sintering process. The existence of an amorphous layer in the surface and the phase transition through β-TCP of SP/HAp­(w) are the structural factors responsible for the differences with respect to PP/HAp­(a). Moreover, a superstructure has been identified in PP/HAp­(a) samples, which could be another structural factor associated with enhanced conductivity, permanent polarization, and catalytic activity of this material.

The insertion of an implant in the body of a patient raises the risk of a posterior infection and formation of a biofilm, which can have critical consequences on the patient’s health and be associated with a high sanitary cost. While antibacterial agents can be used to prevent the infection, such a strategy is time-limited and causes bacteria resistance. As an alternative to biochemical approaches, we propose here to use light-induced local hyperthermia with plasmonic nanoparticles. This strategy is implemented on surgical meshes, extensively used in the context of hernia repairing, one of the most common general surgeries. Surgical meshes were homogeneously coated with gold nanorods designed to efficiently convert near-infrared light into heat. The modified mesh was exposed to a biofilm of Staphylococcus aureus (S. aureus) bacteria before being treated with a train of light pulses. We systematically study how the illumination parameters, namely fluence, peak intensity and pulse length, influence the elimination of attached bacteria. Additionally, fluorescence confocal microscopy provides us some insight on the mechanism involved in the degradation of the biofilm. This proof-of-principle study opens a new set of opportunities for the development of novel disinfection approaches combining light and nanotechnology.

No abstract

Biosensing based on optical micro-and nanoresonators integrated in a microfluidic environment is a promising approach to lab-on-a-chip platforms capable of detecting low concentrations of analytes from small sample volumes. While sensitivity has reached the single molecule level, in practice, the applicability to real-life settings is limited by Brownian diffusion of the analyte to the sensor surface, which dictates the total duration of the sensing assay. Here, we use the electrothermoplasmonic (ETP) effect to overcome this limit through opto-electrical fluid convective flow generation. To this end, we designed a Localized Surface Plasmon Resonance (LSPR) sensing chip that integrates ETP operation into state-ofthe-art microfluidics. First, we optimize and characterize the ETP dynamics inside the microfluidic chamber, showing high fluid velocities. Then, we perform proof-of-concept experiments on model immunoglobulin G detection to demonstrate ETPenhanced biosensing. Our results demonstrate the synergetic effect of temperature and electric field proving that ETP-LSPR has improved performances over standard LSPR.