High-accuracy noninvasive continuous glucose monitoring using OCT angiography-purified blood scattering signals in human skin.

The accuracy of noninvasive continuous glucose monitoring (CGM) through near-infrared scattering is challenged by mixed scattering signals from different compartments, where glucose has a positive correlation with a blood scattering coefficient but a negative correlation with a tissue scattering coefficient. In this study, we developed a high-accuracy noninvasive CGM based on OCT angiography (OCTA)-purified blood scattering signals. The blood optical scattering coefficient (BOC) was initially extracted from the depth attenuation of backscattered light in OCT and then purified by eliminating the scattering signals from the surrounding tissues under the guidance of a 3D OCTA vascular map in human skin. The purified BOC was used to estimate the optical blood glucose concentration (BGC) through a linear calibration. The optical and reference BGC measurements were highly correlated (R = 0.94) without apparent time delay. The mean absolute relative difference was 6.09%. All optical BGC measurements were within the clinically acceptable Zones A + B, with 96.69% falling in Zone A on Parke's error grids. The blood glucose response during OGTT was mapped with a high spatiotemporal resolution of the single vessel and 5 seconds. This noninvasive OCTA-based CGM shows promising accuracy for clinical use. Future research will involve larger sample sizes and diabetic participants to confirm these preliminary findings.

Acute and continuous exposure of airborne fine particulate matter (PM2.5): diverse outer blood-retinal barrier damages and disease susceptibilities.

BACKGROUND: The association between air pollution and retinal diseases such as age-related macular degeneration (AMD) has been demonstrated, but the pathogenic correlation is unknown. Damage to the outer blood-retinal barrier (oBRB), which consists of the retinal pigment epithelium (RPE) and choriocapillaris, is crucial in the development of fundus diseases. OBJECTIVES: To describe the effects of airborne fine particulate matter (PM2.5) on the oBRB and disease susceptibilities. METHODS: A PM2.5-exposed mice model was established through the administration of eye drops containing PM2.5. Optical coherence tomography angiography, transmission electron microscope, RPE immunofluorescence staining and Western blotting were applied to study the oBRB changes. A co-culture model of ARPE-19 cells with stretching vascular endothelial cells was established to identify the role of choroidal vasodilatation in PM2.5-associated RPE damage. RESULTS: Acute exposure to PM2.5 resulted in choroidal vasodilatation, RPE tight junctions impairment, and ultimately an increased risk of retinal edema in mice. These manifestations are very similar to the pachychoroid disease represented by central serous chorioretinopathy (CSC). After continuous PM2.5 exposure, the damage to the RPE was gradually repaired, but AMD-related early retinal degenerative changes appeared under continuous choroidal inflammation. CONCLUSION: This study reveals oBRB pathological changes under different exposure durations, providing a valuable reference for the prevention of PM2.5-related fundus diseases and public health policy formulation.

Functional OCT angiography reveals early retinal neurovascular dysfunction in diabetes with capillary resolution.

Altered retinal neurovascular coupling may contribute to the development and progression of diabetic retinopathy (DR) but remains highly challenging to measure due to limited resolution and field of view of the existing functional hyperemia imaging. Here, we present a novel modality of functional OCT angiography (fOCTA) that allows a 3D imaging of retinal functional hyperemia across the entire vascular tree with single-capillary resolution. In fOCTA, functional hyperemia was evoked by a flicker light stimulation, recorded by a synchronized time-lapse OCTA (i.e., 4D), and extracted precisely from each capillary segment (space) and stimulation period (time) in the OCTA time series. The high-resolution fOCTA revealed that the retinal capillaries, particularly the intermediate capillary plexus, exhibited apparent hyperemic response in normal mice, and significant functional hyperemia loss (P < 0.001) at an early stage of DR with few overt signs of retinopathy and visible restoration after aminoguanidine treatment (P < 0.05). Retinal capillary functional hyperemia has strong potential to provide sensitive biomarkers of early DR, and retinal fOCTA would provide new insights into the pathophysiology, screening and treatment of early DR.

Airborne fine particulate matter (PM2.5) damages the inner blood-retinal barrier by inducing inflammation and ferroptosis in retinal vascular endothelial cells.

This study was the first to explore the effect of airborne fine particulate matter (PM2.5) exposure on the inner blood-retinal barrier (iBRB). In this study, retinal vascular permeability and diameter were enhanced in the PM2.5-exposed animal model (1 mg/mL PM2.5, 10 µL per eye, 4 times per day, 3 days), together with observable retinal edema and increased inflammation level in retina. PM2.5-induced cell damage in human retinal microvascular endothelial cells (HRMECs) occurred in a time- and dose-dependent manner. Decreased cell viability, proliferation, migration, and angiogenesis, as well as increased apoptosis and inflammation, were observed. Iron overload and excessive lipid oxidation were also discovered after PM2.5 exposure (25, 50, and 100 µg/mL PM2.5 for 24 h), along with significantly altered expression of ferroptosis-related genes, such as prostaglandin-endoperoxide synthase 2, glutathione peroxidase 4, and ferritin heavy chain 1. Moreover, Ferrostatin-1, an inhibitor of ferroptosis, evidently alleviated the PM2.5-induced cytotoxicity of HRMECs. The present study investigated the in vivo effects of PM2.5 on retinas, revealing that PM2.5 exposure induced retinal inflammation, vascular dilatation, and caused damage to the iBRB. The crucial role of ferroptosis was discovered during PM2.5-induced HRMEC cytotoxicity and dysfunction, indicating a potential precautionary target in air pollution-associated retinal vascular diseases.

Phase Modulation of Photonic Band Gap Signal.

We first investigate the probe transmission signal (PTS) and the four wave mixing band gap signal (FWM BGS) modulated simultaneously by the relative phase and the nonlinear phase shift in the photonic band gap (PBG) structure. The switch between the absorption enhancement of PTS and the transmission enhancement of PTS with the help of changing the relative phase and the nonlinear phase shift is obtained in inverted Y-type four level atomic system experimentally and theoretically. The corresponding switch in PTS can be used to realize all optical switches. On other hand, the relative phase and the nonlinear phase shift also play the vital role to modulate the intensity of FWM BGS reflected from the PBG structure. And it can be potentially used to realize the optical amplifier.

Analogy of transistor function with modulating photonic band gap in electromagnetically induced grating.

Optical transistor is a device used to amplify and switch optical signals. Many researchers focus on replacing current computer components with optical equivalents, resulting in an optical digital computer system processing binary data. Electronic transistor is the fundamental building block of modern electronic devices. To replace electronic components with optical ones, an equivalent optical transistor is required. Here we compare the behavior of an optical transistor with the reflection from a photonic band gap structure in an electromagnetically induced transparency medium. A control signal is used to modulate the photonic band gap structure. Power variation of the control signal is used to provide an analogy between the reflection behavior caused by modulating the photonic band gap structure and the shifting of Q-point (Operation point) as well as amplification function of optical transistor. By means of the control signal, the switching function of optical transistor has also been realized. Such experimental schemes could have potential applications in making optical diode and optical transistor used in quantum information processing.

Interplay between six wave mixing photonic band gap signal and second-order nonlinear signal in electromagnetically induced grating.

For the first time, we experimentally and theoretically research about the second-order nonlinear signal (SNS) including electromagnetically induced absorbing (EIA) and electromagnetically induced gain (EIG), six wave mixing band gap signal (SWM BGS) resulting from photonic band gap structure in an inverted Y-type four level system with the electromagnetically induced grating. The interplay between the SNS and SWM BGS is illustrated clearly for the first time. When we change the frequency detuning to make the SWM BGS and SNS overlap, the SWM BGS is suppressed and the intensity of SNS is strongest near the resonance point. We can control the intensity of the SWM BGS and EIG caused by the classic effect through changing the power of coupling field. And the changes on the EIA generated by the quantum effect are obtained by changing the power of dressing field. Since the SWM BGS is the enhancement of the four wave mixing band gap signal (FWM BGS), when we set FWM BGS as the input and SNS as the modulation role to control the amplification amplitude for the FWM BGS in our scheme, the adjustable optical amplifier can be obtained.

Observation of the four wave mixing photonic band gap signal in electromagnetically induced grating.

For the first time, we experimentally and theoretically research about the probe transmission signal (PTS), the reflected four wave mixing band gap signal(FWM BGS) and fluorescence signal (FLS) under the double dressing effect in an inverted Y-type four level system. FWM BGS results from photonic band gap structure. We demonstrate that the characteristics of PTS, FWM BGS and FLS can be controlled by power, phase and the frequency detuning of the dressing beams. It is observed in our experiment that FWM BGS switches from suppression to enhancement, corresponding to the switch from transmission enhancement to absorption enhancement in the PTS with changing the relative phase. We also observe the relation among the three signals, which satisfy the law of conservation of energy. Such scheme could have potential applications in optical diodes, amplifiers and quantum information processing.