Journal of Innovative Optical Health Sciences

Single-cell volumetric imaging is essential for researching individual characteristics of cells. As a nonscanning imaging technique, light field microscopy (LFM) is a critical tool to achieve real-time three-dimensional imaging with the advantage of single-shot. To address the inherent limits including nonuniform resolution and block-wise artifacts, various modified LFM strategies have been developed to provide new insights into the structural and functional information of cells. This review will introduce the principle and development of LFM, discuss the improved approaches based on hardware designs and 3D reconstruction algorithms, and present the applications in single-cell imaging.

Benefiting from the developments of advanced optical microscopy techniques, the mysteries of biological functions at the cellular and subcellular levels have been continuously revealed. Stimulated Raman scattering (SRS) microscopy is a rapidly growing technique that has attracted broad attentions and become a powerful tool for biology and biomedicine, largely thanks to its chemical specificity, high sensitivity and fast image speed. This review paper introduces the principles of SRS, discusses the technical developments and implementations of SRS microscopy, then highlights and summarizes its applications on biological cellular machinery and finally shares our visions of potential breakthroughs in the future.

As an emerging hybrid imaging modality, microwave-induced thermoacoustic imaging (MTAI), using microwaves as the excitation source and ultrasonic signals as the information carrier for combining the characteristics of high contrast of electromagnetic imaging and high resolution of ultrasound imaging, has shown broad prospects in biomedical and clinical applications. The imaging contrast depends on the microwave-absorption coefficient of the endogenous imaged tissue and the injected MTAI contrast agents. With systemically introduced functional nanoparticles, MTAI contrast and sensitivity can be further improved, and enables visualization of biological processes in vivo. In recent years, functional nanoparticles for MTAI have been developed to improve the performance and application range of MTAI in biomedical applications. This paper reviews the recent progress of functional nanoparticles for MTAI and their biomedical applications. The challenges and future directions of microwave thermoacoustic imaging with functional nanoparticles in the field of translational medicine are discussed.

Because the breast cancer is an important factor that threatens women’s lives and health, early diagnosis is helpful for disease screening and a good prognosis. Exosomes are nanovesicles, secreted from cells and other body fluids, which can reflect the genetic and phenotypic status of parental cells. Compared with other methods for early diagnosis of cancer (such as circulating tumor cells (CTCs) and circulating tumor DNA), exosomes have a richer number and stronger biological stability, and have great potential in early diagnosis. Thus, it has been proposed as promising biomarkers for diagnosis of early-stage cancer. However, distinguishing different exosomes remain is a major biomedical challenge. In this paper, we used predictive Convolutional Neural model to detect and analyze exosomes of normal and cancer cells with surface-enhanced Raman scattering (SERS). As a result, it can be seen from the SERS spectra that the exosomes of MCF-7, MDA-MB-231 and MCF-10A cells have similar peaks (939, 1145 and 1380 cm${}^{-1}$). Based on this dataset, the predictive model can achieve 95% accuracy. Compared with principal component analysis (PCA), the trained CNN can classify exosomes from different breast cancer cells with a superior performance. The results indicate that using the sensitivity of Raman detection and exosomes stable presence in the incubation period of cancer cells, SERS detection combined with CNN screening may be used for the early diagnosis of breast cancer in the future.

Physiotherapeutic effects of infrared lasers have been proved in clinic. These infrared-based regulations of the bioelectrical activities can roughly be classified into enhancement and suppression of action potential (AP), which are described by sodium (Na) and potassium (K) transmembrane current equations, named as Hodgkin and Huxley (HH)-model. The enhancement effect is able to evoke or strengthen the AP when infrared light is applied. Its corresponding mechanism is commonly ascribed to the changes of the cell membrane capacitance, which is transiently increased in response to the infrared radiation. The distinctive feature of the suppression effect is to inhibit or reduce the AP by the designed protocols of infrared radiation. However, its mechanism presents more complexity than that in enhancement cases. HH-model describes how the Na current determines the initial phase of AP. So, the enhancement and suppression of AP can be also ascribed to the regulations of the corresponding Na currents. Here, a continuous infrared light at the wavelength of 980nm (CIS-980) was employed to stimulate a freshly isolated hippocampal neuron in vitro and a suppression effect on the Na currents of the neuron cell was observed. Both Na and K currents, which are named as whole cell currents, were simultaneously recorded with the cell membrane capacitance current by using a patch clamp combined with infrared irradiation. The results demonstrated that the CIS-980 was able to reversibly increase the capacitance currents, completely suppressed Na currents, but little changed K currents, which forms the steady outward whole cell currents and plays a major role on the AP repolarization. A confirmation experiment was designed and carried out by synchronizing tens of milliseconds of infrared stimulation on the same kinds of hippocampal neuron cells. After the blocked K channel, a reduction of Na current amplitude was still recorded. This proved that infrared suppression of Na current was irrelevant to K channel. A membrane capacitance mediation process was preliminarily proposed to explain the Na channel suppression process.

The automatic and accurate identification of apoptosis facilitates large-scale cell analysis. Most identification approaches using nucleus fluorescence imaging are based on specific morphological parameters. However, these parameters cannot completely describe nuclear morphology, thus limiting the identification accuracy of models. This paper proposes a new feature extraction method to improve the performance of the model for apoptosis identification. The proposed method uses a histogram of oriented gradient (HOG) of high-frequency wavelet coefficients to extract internal and edge texture information. The HOG vectors are classified using support vector machine. The experimental results demonstrate that the proposed feature extraction method well performs apoptosis identification, attaining $95.7\%$ accuracy with low cost in terms of time. We confirmed that our method has potential applications to cell biology research.

To determine the effects of microwave radiation at the molecular level as well as on the germination, growth and morphology of dry spores at the single-cell level. Dry Bacillus aryabhattai MCCC 1K02966 spores were microwave-treated at different powers and characterized using single-cell optical technology. As determined by laser tweezers Raman spectroscopy, the Ca${}^{2+}$-dipicolinic acid content increased and nucleic acid denaturation occurred in response to microwave treatment. Live-cell microscopy revealed that the germination and growth rates decreased as the microwave power increased. With respect to morphology, atomic force microscopy (AFM) demonstrated that spores became wrinkled and rough after microwave treatment. Furthermore, spores became smaller as the microwave power increased. Microwave treatment can damage DNA, and high-power microwaves can inhibit the germination of spores and reduce spore volumes. These results provide a new perspective on the responses of living single cells to microwave radiation and demonstrate the application of various new techniques for analyses of microorganisms at the single-cell level.

Actin cytoskeleton plays crucial roles in various cellular functions. Extracellular matrix (ECM) can modulate cell morphology by remodeling the internal cytoskeleton. To define how geometry of ECM regulates the organization of actin cytoskeleton, we plated individual NIH 3T3 cells on micropatterned substrates with distinct shapes and sizes. It was found that the stress fibers could form along the nonadhesive edges of T-shaped pattern, but were absent from the opening edge of V-shaped pattern, indicating that the organization of actin cytoskeleton was dependent on the mechanical environment. Furthermore, a secondary actin ring was observed on 50$\mu$m circular pattern while did not appear on 30$\mu$m and 40$\mu$m pattern, showing a size-dependent organization of actin cytoskeleton. Finally, osteoblasts, MDCK and A549 cells exhibited distinct organization of actin cytoskeleton on T-shaped pattern, suggesting a cell-type specificity in arrangement of actin cytoskeleton. Together, our findings brought novel insight into the organization of actin cytoskeleton on micropatterned environments.