This PDF file contains the front matter associated with SPIE Proceedings Volume 12395, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Efficient functionalization of the silicon nitride waveguide with bioreceptors, e.g. antibodies, is key to increase antigen binding activity in photonic sensors based on silicon nitride (SiN) waveguides. A bioreceptor coating technique using silica nanoparticles (NPs) to enhance the density of functionalized antibodies, by increasing the surface areas for biomolecule binding, is proposed. The detection of S100 Calcium-Binding Protein A6 (S100A6), a proposed cholangiocarcinoma marker, has been demonstrated using the SiN resonator sensor with 400nm thick waveguide, fabricated by low-cost 500 nm technology. The NPs were synthesized by silica condensation. Antibodies were attached to the NPs by 1-ethyl-3-(3- dimethyl aminopropyl)–carbodiimide (EDC)/ N-hydroxysuccinimide (NHS)-crosslinking. Then the NPs were coated on SiN sensor by N-terminal to N-terminal crosslinkers. It was found that the application of silica NPs coating showed increased sensor sensitivity at approximately 8.8 pm/(ng/ml) in optical resonant wavelength shift compared to 0.36 pm/(ng/ml) by our previous antibody coating technique using (3-Aminopropyl) triethoxysilane (APTES) silanization with EDC/NHS protein crosslink.

Single-molecule localization microscopy (SMLM) strategies based on fluorescence photoactivation permit the imaging of live cells with subdiffraction resolution and the high-throughput tracking of individual biomolecules in their interior. They rely predominantly on genetically-encoded fluorescent proteins to label live cells selectively and allow the sequential single-molecule localization of sparse populations of photoactivated fluorophores. Synthetic counterparts to these photoresponsive proteins are limited to a few remarkable examples at the present stage, mostly because of the daunting challenges in engineering biocompatible molecular constructs with appropriate photochemical and photophysical properties for live-cell SMLM. Our laboratory developed a new family of synthetic photoactivatable fluorophores specifically designed for these imaging applications. They combine a borondipyrromethene (BODIPY) fluorophore and an ortho-nitrobenzyl (ONB) photocage in a single molecular skeleton. The photoinduced ONB cleavage extends electronic delocalization to shift bathochromically the BODIPY absorption and emission bands. As a result, these photochemical transformations can be exploited to switch fluorescence on in a spectral region compatible with bioimaging applications and allow the localization of the photochemical product at the single-molecule level. Furthermore, our compounds can be delivered and operated in the interior of live cells to enable the visualization of organelles with nanometer resolution and the intracellular tracking of single photoactivated molecules.

The design and synthesis of DNA and RNA sensors are critical towards the improvement of early diagnosis of various diseases. In this paper, we discuss our recent efforts to construct a sensor based on upconversion nanoparticles (UCNPs) and graphene oxide (GO) for the detection of synthetic viral oligonucleotide targets.

Colloidal quantum dots are desirable for a broad range of applications from biosensing to in vivo imaging due to their high luminosity and large surface areas available for bioconjugation. QDs are highly effective as fluorescent donors for Förster resonance energy transfer (FRET) and can be conjugated with multiple acceptors to enhance FRET efficiency and increase on/off ratios for sensing applications. We have demonstrated an efficient method for conjugating nucleic acids to QDs using chimeric peptide-peptide nucleic acids (peptide-PNA), and here we have characterized QD-FRET reporters assembled with this technique for use in CRISPR/Cas nuclease assays to identify factors which could limit the sensitivity of such reporters in practice.

Inorganic perovskite nanocrystals (IPNCs) have drawn much attention due to their unique photophysical properties such as high fluorescent quantum yield, narrow- and size-tunable emissions, excellent photostability, and large multiphoton absorption cross-section. IPNCs have been utilized as contrast agents for biomedical imaging, as well as other applications such as photovoltaics, light-emitting diodes, and photodetectors. IPNCs can be synthesized by a variety of different techniques, e.g., hot injection, ligand-assisted reprecipitation, and anion exchange methods, amongst others. These methods produce size controlled IPNCs but require multiple synthesis steps which can affect the reproducibility, i.e., variation in photophysical properties across batches. Here, we present a simple water-assisted one-pot strategy for the synthesis of highly bright IPNCs. This approach involves dissolving precursor salts in nonpolar solvents like toluene and hexane. Recrystallization is induced by the addition of minuscule quantities of water, due to phase separation between solvent and water, which leads to the formation of IPNCs. The fluorescence emission of these IPNCs was tuned by changing the halide ions, e.g., bromide for green-yellow fluorescence and iodide for red fluorescence. The size and shape, which affects the quantum yield, can be easily tuned by changing the reactant concentration and volume of water. These IPNCs were further modified to improve their water stability, by coating them with hydrophobic polymers, like silica, which facilitated their use as contrast agents for labeling cancer cells.

The aim of our work is to develop a heavy metal detection sensor that can be used in the field to easily and accurately test water samples at the range of the strict concentration levels set by international standards. The sensor is based on a gold thin-film electrode on a silicon substrate and a genetically modified bacterial flagellin protein deposited onto the gold thin-film electrode. To ensure that the surface is adequately covered, and the protein is attached to the electrode, additional gold nanoparticles were deposited to the surface. Changes on the sensor surface were investigated by in-situ ellipsometry and cyclic voltammetry. The determination of the exact surface morphology, as well as the validation of the ellipsometric measurements were done by using scanning electron microscope.

Synthesized nanoparticles with strong luminescence in the second near-infrared window show great potential for applications in biomedical imaging and diagnosis. Nanoscale dimensions and tunable optical properties can enable nanoparticles to operate as fluorescent probes in the imaging of tumors and lymphatic tissues. Lanthanide-doped rare-earth fluoride nanoparticles with photoluminescence tuned to the second near-infrared window can circumvent many of the issues currently limiting the clinical utility of fluorescence imaging technology and show promise as tools for the early detection of cancer. We report on the synthesis and characterization of colloidal LiYF₄ nanoparticles doped with erbium. The nanoparticles were synthesized through a coprecipitation method using rare-earth chlorides, LiOHꞏH₂O, and NH₄F as precursors. 1-octadecene was used as a high-temperature solvent, and oleic acid was used as an organic capping agent. The reaction took place under the protection of nitrogen atmosphere. The size, morphology, and colloidal stability of the nanoparticles were determined using data obtained from transmission electron microscopy, dynamic light scattering, and zeta potential techniques. Optical characterization data were collected using NIR absorption spectroscopy and fluorescence spectroscopy. The Er³⁺-doped LiYF₄ nanoparticles show NIR-II emission peaks at 1001 nm, 1490 nm, 1531 nm, and 1558 nm upon NIR-II excitation at 972 nm. The excellent luminescence in the NIR-II range makes them a strong candidate for bioimaging applications.

Periodontal diseases are prevalent worldwide and are linked to numerous other health conditions due to dysbiosis and chronic inflammatory state. Most periodontal diseases are caused by pathogenic bacteria that colonize dental tissues in the form of biofilm. Eradication of bacterial biofilms can be difficult to achieve due to the complex architecture of the teeth and gums which complicates the removal. Orthodontic wires and dental devices introduce additional hurdles to the adequate removal of biofilms by traditional methods since mechanical disruption via direct contact with toothbrush bristles, floss, and abrasive toothpaste is limited. Magnetically activated nanoparticles (NPs), specifically iron oxide nanoparticles (IONPs) that can be functionalized as antimicrobial particles and remotely controlled by magnetic fields, are of interest for oral biofilm eradication. We present data in multi-species bacterial cultures, established biofilms, human gingival keratinocytes, and human gingival fibroblast cells alone and in the presence of multispecies biofilm co-cultures to determine the safest, most efficacious IONP size ranges and treatment concentrations of active magnetic NPs for removal of dental biofilms. We report enhanced efficacy for IONPs coated with alginate vs. dextran, and small sizes (~8 nm vs. >20 nm in size) appear to exhibit enhanced antimicrobial efficacy. Human gingival keratinocyte (TIGK) cells in co-culture with treated and untreated multispecies biofilms in an in-vitro periodontitis model also exhibited a trend of reduced inflammatory markers in wells with IONP-treated biofilms.

Nano/microparticles, being used in diverse fields including biotechnology and imaging, can be fabricated using various processes. Here, a functional surface with bio-polymer nano/microparticles and its fabrication method based on electrospraying are presented. The proposed nano/microparticulate surface can provide various beneficial effects on the cell culture behavior because of its morphological and geometrical properties. We experimentally show that the surface can provide the positive effects on cell attachment and culture with the comparison with the conventional flat surface.

Alzheimer’s Disease (AD) is a severe neurodegenerative disorder, marked by cognitive decline, memory loss, and behavioral skill impairment. Actually, amyloid β-peptide 1-42 (Aβ (1-42)) is one of the main recognized AD biomarkers. The possibility of detect Aβ (1-42) at very low concentration in different biological fluids allow the early-stage diagnosis, which currently represents the most efficacious AD therapy. To date, optical detection techniques have gained rising attention for the development of Aβ (1-42) sensors based on the analyses of liquid samples. In this context, optical metallic nanoconstructs are promising alternative for the development of novel rapid and low-cost methods for the targeting of Aβ (1-42) in fluids. Herein, diagnostic platforms are based on gold citratecapped nanoparticles (AuNPs), whose aggregation can be modulated by the presence of the target biomarker as a function of its concentration and has been smartly used to develop colorimetric assays. The performances of this novel system are validated for specific detection of synthetic ß- amyloid peptide (Aß) in liquid fluids with high selectivity and sensitivity down to the nanomolar.