This PDF file contains the front matter associated with SPIE Proceedings Volume 12859, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Shortwave infrared (SWIR) imaging capitalizes on the low tissue scattering and low autofluorescence in the near infrared- II (NIR-II) window (1000 nm – 1700 nm) for in vivo imaging with deep imaging penetration and high signal-to-noise contrast. Combining NIR-I excitation and emission in SWIR window, quantitative multiplexed imaging could be applied to study biological structures or physiological phenomenon in a single specimen. This study introduces a set of three high quantum yield lead sulfide/cadmium sulfide (PbS/CdS) core/shell quantum dots (QDs) with distinct SWIR emissions (1100 – 1550 nm). Applying these QDs, we demonstrated detailed lymphatic pathway, lymphatic drainage, and spatially overlapping vascular structures, marking a significant advancement beyond the conventional two-color schemes in SWIR imaging. We further evaluated the effect of surface coatings of the QDs on the pharmacokinetics and biodistribution of QDs in mice. The capacity to differentiate several fluorescent contrast agents through SWIR detection unlocks numerous opportunities for studies of disease progression, drug pharmacokinetics and biodistribution, and cell trafficking dynamics in living organisms.

There remains a gap in understanding the enzyme interactions with the coacervate as a substrate hub. Here, we study how the hydrophobicity nature of coacervate affects the interactions of the embedded substrate with a protease. We design oligopeptide-based coacervates that comprise an anionic Asp-peptide (D₁₀) and a cationic Arg-peptide (R₅R₅) with a proteolytic cleavage site. The coacervates dissolve when exposed to the main protease. We exploit the condensed structure, implement a self-quenching mechanism, and characterize enzyme kinetics with Cy5.5-labeled peptides. The determined specificity constant is 5,817 M^-1 s^-1 and is similar to that of the free substrate. We further show that the enzyme kinetics depend on the amount of dye incorporated into the coacervates. Our work presents a simple design for coacervates with tuned bioactivities and provides insights into the kinetics between the enzyme and coacervates as a substrate hub.

The use of spectroscopy in the field of biomedical science has increased in recent years. Many biological samples such as viruses and bacteria could be detected using FTIR spectroscopy in the MIR range. An important challenge arises when analyzing samples with low concentrations is that they might not be detected or accurately predicted within the capabilities of the instrument’s signal-to-noise ratio. To overcome such challenge, absorption signal enhancement techniques can be used to improve the detectability of the samples. One of such techniques is the use of quantum dots (QDs) that are particles of crystal structure with sizes ranging from a few to tens of nanometers, which exhibit interesting optical properties. In this work, we apply a multi-scale modeling approach to describe the enhancement of QDs starting with an atomistic simulator to extract the absorption lines by solving Schrödinger’s equation. Next, the optical constants of the QDs and biological samples are extracted using Kramer-Kronig’s (KK) relations and Fresnel coefficients, followed by using Maxwell Garnett model in an effective medium approximation. Then, a transfer matrix method (TMM) is used to model layered media containing biological samples mixed with QDs. Using this theoretical description, an enhancement of about 2.5x in a transmission configuration is predicted by simulations for a sample with refractive index representing a saliva sample mixed with mercury telluride (HgTe) QDs. This model can be used to predict the enhancement of different types of QDs with different types of samples, which enhances the detection of various biological samples. Then, the QDs are synthesized experimentally using a two-step injection method. Finally, a practical measurement of the attenuated total reflection (ATR) spectrum in the range of 400-4000 cm^-1 of a dried saliva sample mixed with HgTe QDs is carried showing an absorption enhancement of about 1.3x.

Lanthanide nanoparticles offer potential in nanoscale photonics due to their high lifetime and quantum yield. However, surface quenching degrades these properties, requiring time-consuming experimental optimization. Here, we present a versatile Monte-Carlo approach that accurately predicts the lifetimes and quantum yields of lanthanide nanoparticles. Based on a Bayesian optimization algorithm, we optimize the geometry and doping concentration of nanocrystals resulting in simulated quantum yields of >60% and lifetimes of >30μs. This approach saves 95% time compared to experimental methods and holds promise for applications such as nanoparticle lasers or quantum memories.

The emergence of chiral nanomaterials has opened up exciting new avenues for the evolution of advanced optical materials. We first describe the mechanism for the generation of a quadrupole field chirality by permanent magnets, which enables the meticulous assembly of magnetic nanoparticles into long-range chiral superstructures. Then we discuss the design of stimuli-responsive chiral superstructures by transferring chirality to pH-responsive polyaniline, endowing them with the ability for dynamic regulation of their chiroptical properties, including circular dichroism (CD) and optical rotatory dispersion (ORD). Finally, we present the design of chiroptical switches and reconfigurable information encryption systems using these chiral superstructures as building blocks. Collectively, our findings delineate the transformative potential of magnetic assembly in chiral nanomaterial research, promising for advanced optical and biomedical applications.

One of the cornerstones in nanophotonics research is the miniaturization of optical devices to the nanometer scale. DNA nanotechnology offers a pathway to realize high-speed nanoscale optical devices using DNA as a molecular building block. Its biorecognition and addressability have led to the successful engineering of self-assembled nanostructures. In particular, the DNA origami technique, which involves the bottom-up self-assembly of long single-stranded DNA “scaffold” into predefined 2D and 3D shapes using specifically designed short oligonucleotides “staple strands”, enables the scalable production of intricate nanostructures with high yields. In this talk, I present recent advancements and my perspectives on self-assembled plasmonic nanosystems using DNA origami technology. These systems include plasmonic waveguides, optical nanoantennas, and plasmonic switches, which efficiently manipulate, concentrate, and guide light without being diffraction-limited. Advanced near/far-field optical spectroscopies empower precise characterization of these plasmonic systems with nanometer resolution. The optical spectroscopy results reveal that DNA-assembled plasmonic devices allow sub-micron mode confinement and well-defined surface plasmon resonances within a specific frequency window. These capabilities hold significant potential in nanoscale energy transfer, energy conversion, biosensing, and various biomedical applications.

Erythrocyte-derived optical microparticles containing near infrared (NIR) dyes such as indocyanine green (ICG) present a promising platform for fluorescence imaging and laser treatment of abnormal vasculature, including port wine birthmarks. Herein, we have investigated the effects of blood type utilized in fabricating these microparticles, and the number density of the particles on their circulation time in mice by real-time NIR fluorescence imaging of the dermal vasculature. We find that the emission half-life of microparticles engineered from human O⁺ blood type increases by approximately two-fold as compared to those engineered from B⁺ blood type. Increasing the number density of the microparticles fabricated from O⁺ blood type from ~0.5 millions/μl to 1.6 millions/μl is associated with nearly a fourfold increase in the emission half-life of the particles. These findings emphasize the importance of blood type and number density in engineering erythrocyte-derived particles for clinical applications as treatment of PWBs.

One of the most serious current global threats is the emergence of bacteria that have built resistance to our most powerful available drugs due to drug overuse. As a result, there is an urgency for the discovery of new antimicrobial agents to fight resistance of bacteria. In recent years, various types of nanoparticles and nanoclusters have been researched for this purpose. The advantage of employing nanoparticles in bacteria killing is that the properties of nanoparticles can be customized by altering nanoparticle physicochemical properties, enabling the tuning of mechanisms that bacteria can be killed. In this paper we present our recent findings in our investigation of the antibacterial properties of 5‑mercapto-2-nitrobenzoic acid coated silver nanoclusters against a wide range of pathogenic bacterial species.