Seok Hyun (Andy) Yun

Stimulated Brillouin scattering (SBS) is a valuable technique for studying the mechanical properties of biological samples. We propose a novel scheme utilizing low duty cycle, nanosecond pulses for pump and probe beams. Our approach achieves higher signal-to-noise (SNR) than SBS microscopy and continuous-wave Brillouin microscopy, even with reduced average power exposure. Experimental results demonstrate a shot noise-limited SNR exceeding 1000 with precise mapping of cellular features. The interlaced boxcar method effectively retrieves the SBS signal, while optimizing pulse width and peak power further enhances optical power efficiency. This pulse scheme offers improved precision and reduced laser power exposure compared to spontaneous Brillouin and continuous wave (cw) SBS approaches.

Advances in immunology, immuno-oncology, drug discovery and vaccine development demand improvements in the capabilities of flow cytometry to allow it to measure more protein markers per cell at multiple timepoints. However, the size of panels of fluorophore markers is limited by overlaps in fluorescence-emission spectra, and flow cytometers typically perform cell measurements at one timepoint. Here we describe multi-pass high-dimensional flow cytometry, a method leveraging cellular barcoding via microparticles emitting near-infrared laser light to track and repeatedly measure each cell using more markers and fewer colours. By using live human peripheral blood mononuclear cells, we show that the method enables the time-resolved characterization of the same cells before and after stimulation, their analysis via a 10-marker panel with minimal compensation for spectral spillover and their deep …

2024-01-10 Assigned to NATIONAL INSTITUTES OF HEALTH (NIH), US DEPT. OF HEALTH AND HUMAN SERVICES (DHHS), US GOVERNMENT reassignment NATIONAL INSTITUTES OF HEALTH (NIH), US DEPT. OF HEALTH AND HUMAN SERVICES (DHHS), US GOVERNMENT CONFIRMATORY LICENSE (SEE DOCUMENT FOR DETAILS). Assignors: MASSACHUSETTS GENERAL HOSPITAL

Understanding corneal stiffness is valuable for improving refractive surgery, detecting corneal abnormalities, and assessing intraocular pressure. However, accurately measuring the elastic properties, specifically the tensile and shear moduli that govern mechanical deformation, has been challenging. To tackle this issue, we have developed guided-wave optical coherence elastography that can simultaneously excite and analyze symmetric (S0) and anti-symmetric (A0) elastic waves in the cornea at around 10 kHz frequencies, enabling us to extract tensile and shear properties from measured wave dispersion curves. We verified the technique using elastomer phantoms and ex vivo porcine corneas and investigated the dependence on intraocular pressure using acoustoelastic theory that incorporates corneal tension and a nonlinear constitutive tissue model. In a pilot study involving six healthy human subjects aged …

The prevalence of antibiotic resistance and tolerance in wound infection management poses a serious and growing health threat, necessitating the exploration of alternative approaches. Antimicrobial blue light therapy offers an appealing, non-pharmacological solution. However, its practical application has been hindered by the requirement for high irradiance levels, which particularly raises safety concerns. Here, we introduce a light-bathing strategy that employs prolonged, continuous exposure to blue light at an irradiance range lower by more than an order of magnitude (5 mW/cm2). This method consistently applies bacteriostatic pressure, keeping wound bioburden low, all while minimizing photothermal risks. Leveraging tailor-made, wearable light-emitting patches, we conducted preclinical trials on rat models of wound infection, demonstrating its safety and efficacy for suppressing infections induced by methicillin-resistant S. aureus and multidrug-resistant P. aeruginosa. Our results pave a new way for the application of blue light therapy in wound care.

Antibiotic resistance has posed a grand and rising threat to the global health. Blue light, specifically 400-430 nm range, has been shown as an attractive antimicrobial alternative considering its drug/agent-free nature, broad-spectrum antimicrobial effect, and no reported resistance. However, its clinical applications have been hampered by several major bottlenecks. Here, we present our translational development towards clinical application of blue light for managing wound infections via innovations in establishing a safe, effective treatment regimen built upon bacteriostatic and long-term illumination strategy (with therapeutical window identified between minimum inhibitory irradiance, MII, and maximum permissible irradiance, MPI), a wearable LED array-based device prototype, an in vivo testbed of free-moving rats with skin wound infections, and its integration with standard wound care procedures. These concepts …

Semiconductor-based laser particles (LPs) with an exceptionally narrowband spectral emission have been used in biological systems for cell tagging purposes. The fabrication of these LPs typically requires highly specialized lithography and etching equipment and is typically done in a cleanroom environment, hindering the broad adoption of this exciting new technology. Here, using only easily accessible laboratory equipment, we demonstrate a simple layer-by-layer fabrication strategy that overcomes this obstacle. We start from an indium phosphide substrate with multiple epitaxial indium gallium arsenide phosphide layers that are sequentially processed to yield LPs of various compositions and spectral properties. The LPs isolated from each layer are characterized, exhibiting excellent optical properties with a lasing emission full width at half maximum as narrow as< 0.3 nm and typical thresholds of∼ 6 pJ upon …

Measuring the spatial variation of the cornea has clinical significance for diagnosing corneal ectasia disease and evaluating refractive surgery outcomes. We present spatially-resolved stiffness mapping of the human cornea in vivo using optical coherence elastography.

Stimulated Brillouin scattering is an emerging technique for probing the mechanical properties of biological samples. However, the nonlinear process requires high optical intensities to generate sufficient signal-to-noise ratio (SNR). Here, we show that the SNR of stimulated Brillouin scattering can exceed that of spontaneous Brillouin scattering with the same average power levels suitable for biological samples. We verify the theoretical prediction by developing a novel scheme using low duty cycle, nanosecond pulses for the pump and probe. A shot noise-limited SNR over 1000 was measured with a total average power of 10 mW for 2 ms or 50 mW for 200 µs integration on water samples. High-resolution maps of Brillouin frequency shift, linewidth, and gain amplitude from cells in vitro are obtained with a spectral acquisition time of 20 ms. Our results demonstrate the superior SNR of pulsed stimulated Brillouin …

Here, we demonstrate omnidirectional-emitting laser particles based on the incorporation of nanoscale light scatterers into the microlasers. Transferred into live cells in vitro, omnidirectional laser particles within moving cells could be tracked continuously, holding potential in spectrally-multiplexed large-scale tracking of single cells.

Micro- and nanodisk lasers have emerged as promising optical sources and probes for on-chip and free-space applications. However, the randomness in disk diameter introduced by standard nanofabrication makes it challenging to obtain deterministic wavelengths. To address this, we developed a photoelectrochemical (PEC) etching-based technique that enables us to precisely tune the lasing wavelength with subnanometer accuracy. We examined the PEC mechanism and compound semiconductor etching rate in diluted sulfuric acid solution. Using this technique, we produced microlasers on a chip and isolated particles with distinct lasing wavelengths. These precisely tuned disk lasers were then used to tag cells in culture. Our results demonstrate that this scalable technique can be used to produce groups of lasers with precise emission wavelengths for various nanophotonic and biomedical applications.

Nano-scale lasers harnessing metallic plasmons hold promise across physical sciences and industrial applications. Plasmons are categorized as surface plasmon polaritons (SPP) and localized surface plasmons (LSP). While SPP has gained popularity for nano-lasers by fitting a few cycles of SPP waves into resonators, achieving LSP lasing in single nanoparticles remains an elusive goal. Here, we highlight the equivalence of LSP and SPP within resonant systems and present lasers oscillating in the lowest-order LSP or, equivalently, half-cycle SPP. This diffraction-limited dipolar emitter is realized through strong coupling of plasmonic oscillation in gold and dielectric resonance in high-gain III-V semiconductor in the near infrared away from surface plasmon frequencies. The resulting single-mode stimulated emission peak exhibits linewidth Q factors over 50 at room temperature, with wide tunability spanning from 1190 to 1460 nm determined by resonator sizes ranging from 190 to 280 nm. A semiconductor laser model elucidates the temporal and spectral buildup dynamics under optical pumping. Notably, linewidth Q values surpassing 250 are attained from higher-order, isolated laser particles within live biological cells. These results offer fresh perspectives in nanophotonics and indicate promising opportunities for multiplexed biological applications.

Despite advances in high-dimensional cellular analysis, the molecular profiling of dynamic behaviors of cells in their native environment remains a major challenge. We present a method that allows us to couple the physiological behaviors of cells in an intact murine tissue to deep molecular profiling of individual cells. This method enabled us to establish a novel molecular signature for a striking migratory cellular behavior following injury in murine airways.

Purpose: Understanding scleral collagen remodeling in refractive eye development is essential to new therapeutical approaches for Myopia, and to correlate the structural, metabolical and mechanical changes occurring. We combine fluorescence lifetime measurements, and second harmonic generation (SHG) microscopy to investigate the links between molecular and structural changes following riboflavin mediated scleral crosslinking (SCXL).Methods: Measurements were performed in a porcine eye model (10 porcine eyes, Animal Biotech Industries) in control and treated regions, with riboflavin-UVA light cross-linking (UVX-SCXL)(Dresden protocol, 370nm, 3mW/cm 2, 30min), using a commercial device (Avedro, Glaukos). After SCXL, scleral strips were cut from both treated and non-treated regions and measurements performed in the treated/non-treated riboflavin immersed strips. Porcine eyes were imaged …

Type 1 (T1D) or type 2 diabetes (T2D) are caused by a deficit of functional insulin-producing β cells. Thus, the identification of β cell trophic agents could allow the development of therapeutic strategies to counteract diabetes. The discovery of SerpinB1, an elastase inhibitor that promotes human β cell growth, prompted us to hypothesize that pancreatic elastase (PE) regulates β cell viability. Here, we report that PE is up-regulated in acinar cells and in islets from T2D patients, and negatively impacts β cell viability. Using high-throughput screening assays, we identified telaprevir as a potent PE inhibitor that can increase human and rodent β cell viability in vitro and in vivo and improve glucose tolerance in insulin-resistant mice. Phospho-antibody microarrays and single-cell RNA sequencing analysis identified PAR2 and mechano-signaling pathways as potential mediators of PE. Taken together, our work highlights PE …

A cellular coding construct uniquely codes a cellular entity and includes a laser particle and a structurally coded oligonucleotide. The structurally coded oligonucleotide and the laser particle have a physical association with each other and are configured for physical association with the cellular entity and also configured for distinctive identification of the cellular entity.

We demonstrate single-mode InGaP and InGaAsP nanolasers using disk-on-pillar and disk-on-gold structures (360 nm in diameter). Silica-coated nanolaser particles produce stable sub-nanometer emission across 80 nm bandwidth (635 to 715 nm) from within biological cells.

While photoluminescent graphene quantum dots (GQDs) have long been considered very suitable for bioimaging owing to their protein‐like size, superhigh photostability and in vivo long‐term biosafety, their unique and crucial bioimaging applications in vivo remain unreachable. Herein, planted GQDs are presented as an excellent tool for in vivo fluorescent, sustainable and multimodality tumor bioimaging in various scenarios. The GQDs are in situ planted in the poly(ethylene glycol) (PEG) layer of PEGylated nanoparticles via a bottom‐up molecular approach to obtain the NPs‐GQDs‐PEG nanocomposite. The planted GQDs show more than four times prolonged blood circulation and 7–8 times increased tumor accumulation than typical GQDs in vivo. After accessible specificity modification, the multifunctional NPs‐GQDs‐PEG provides targeted, multimodal molecular imaging for various tumor models in vitro or in …

Surface plasmon polariton (SPP) lasers have so far relied on metallic substrates. Here, we report a three-dimensional (3D) plasmonic particle laser using gold coating on lead halide perovskite crystals as small as 620 nm in size. Upon optical pumping, SPP modes are strongly confined along the particle edges with high Purcell enhancement in room conditions. Lasing of metal-coated plasmonic laser particles in live cells is demonstrated.

Objective The mechanical properties of corneal tissues play a crucial role in determining corneal shape and have significant implications in vision care. This study aimed to address the challenge of obtaining accurate in vivo data for the human cornea. Methods We have developed a high-frequency optical coherence elastography (OCE) technique using shear-like antisymmetric (A0)-mode Lamb waves at frequencies above 10 kHz. Results By incorporating an anisotropic, nonlinear constitutive model and utilizing the acoustoelastic theory, we gained quantitative insights into the influence of corneal tension on wave speeds and elastic moduli. Our study revealed significant spatial variations in the shear modulus of the corneal stroma on healthy subjects for the first time. The central cornea exhibited a shear modulus of 74 kPa, while the corneal periphery showed a decrease to 41 kPa. The limbus demonstrated an increased shear modulus exceeding 100 kPa. We obtained wave displacement profiles that are consistent with highly anisotropic corneal tissues. Conclusion Our approach enabled precise measurement of corneal tissue elastic moduli in situ with high precision (< 7%) and high spatial resolution (< 1 mm). Significance The high-frequency OCE technique holds promise for biomechanical evaluation in clinical settings, providing valuable information for refractive surgeries, degenerative disorder diagnoses, and intraocular pressure assessments.