Haitao Zhao, Lip Ket Chin, Yuzhi Shi, Kim Truc Nguyen, Patricia Yang Liu, Yi Zhang, Meng Zhang, Jingbo Zhang, Hong Cai, Eric Peng Huat Yap, Wee Ser, Ai-Qun Liu
The emerging single-cell technologies call for novel biological tools that can manipulate target cells in a massive and spatially-arranged manner. Here we report a nanophotonic platform, named WANTS (Waveguide-pair Array-based Nanophotonic Trapping System), for massive trapping and alignment of rod-shaped bacteria. This platform leverages silicon waveguide-pair arrays to engineer an optical lattice pattern and the accompanying optical force field. The rod-shaped bacteria inside the field are trapped and aligned by three motions: the out-of-plane rotation, the in-plane rotation, and the translational motion. Massive shigella are arranged into a closely-seated distribution at a trapping rate of ∼12 shigella/min. As a demonstration, we utilize the platform to investigate the bacterial biophysical property and find that the measured bacterial lengths are 23.65% more accurate than the results measured with free solutions. Subsequently, we study the bacterial viability in situ and find that shigella present high heterogeneity in response to chemical stimuli. The WANTS holds significant promise to integrate with lab-on-a-chip technologies and yield a compact and robust platform for practical biological studies at the single-cell level.
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Cheng-Yu Li, Ya-Feng Kang, Bei Zheng, Chun-Miao Xu, Chong-Yang Song, Dai-Wen Pang, Hong-Wu Tang
We report a new upconversion nanoparticles (UCNPs) based luminescent resonance energy transfer (LRET) analytical platform by making use of optical tweezers technology. The LRET model is designed by simultaneously conjugating Yb3+ and Er3+ co-doped UCNPs (as the donors) and tetramethyl rhodamine (TAMRA) molecules (as the acceptors) on microspheres to fabricate complex microspheres. Upon a single complex microsphere entering the three-dimensional potential well formed with a tightly focused 980 nm Guassian-shaped laser beam, it is optically trapped and concurrently the upconversion emission is excited, whereby the donor signals are transferred to the acceptors. As a proof-of-concept investigation, microRNA-21 sequences are selected as the targets, by which the distance between the two perfectly matched luminophors is controlled to several nanometers via nucleic acid hybridization. Without the involvement of luminescence amplification strategies, the proposed single microsphere based LRET method shows highly competitive sensitivity with a limit of detection down to 114 fM and satisfactory specificity towards microRNAs detection. Moreover, its practical working ability is demonstrated by credibly quantifying the absolute contents of miRNA-21 sequences in three cancer cell lines and even tracing the targets in as few as 100 cancer cells. Thus, this favorable analytical methodology provides an alternative for bioassays and holds certain potential in biomedical applications.
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Di Cao, Cheng-Yu Li, Chu-Bo Qi, Hong-Lei Chen, Dai-Wen Pang, Hong-WuTang
Although suspension bead-based assay technology has been widely used owing to its advantages of high-throughput and microvolume detection, its sensitivity is greatly limited because it detects the fluorescence signal emitted by microbeads for a short time in the flowing fluid. In this work, we present the approach for prostate-specific antigen (PSA) detection of both free PSA (fPSA) and total PSA (tPSA) based on bead-array based fluorescence imaging by combining multiple optical trapping and bead-based bioassays. The polystyrene beads were employed to enrich the targets using the classic sandwich immuno-binding and tagged with fluorescent quantum dots (QDs), and the QDs-tagged beads in suspension were trapped array-by-array using multiple optical tweezers constructed with a diffraction optical element and excited with a 405 nm fiber laser for wide-field fluorescence imaging. The distinctive size information from the image of the trapped beads enabled the sorting of different targets. Moreover, the limits of detection for fPSA and tPSA are 3.8 pg/mL and 2.5 pg/mL respectively with good specificity. More importantly, this strategy was successfully used to detect fPSA and tPSA simultaneously in real serum samples. The high sensitivity, good selectivity, and tiny sample volume make this strategy a promising method for life sciences and clinical applications.
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Jing Zhong, Hengjun Liu, Hisataka Maruyama, Taisuke Masuda, Fumihito Arai
Fast and effective transportation of beads/molecules into living cells with high cell viability is essential for drug development and cell biology. This study presents a new approach of injecting single magnetic nanobeads with low surface temperature into living cells using a continuous-wave laser. Experimental results demonstrate the successful injection of magnetic nanobeads into living cells with high injection rates reaching 100%, short injection times of about 1 sec, and maximal cell survival rates of 100%.
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Hengjun Liu, Hisataka Maruyama, Taisuke Masuda, Fumihito Arai
In this paper, we propose the selective adhesion and rapid injection of a fluorescent sensor into a target cell via the optical control of zeta potential and local vibration stimulus using optical tweezers. A multi-fluorescent sensor, which can respond to both temperature and pH, was encapsulated in anionic lipid layers containing a photochromic material (spiropyran) via the layer-by-layer method. The zeta potential of the lipid layers containing spiropyran was adjusted from negative to positive by photo-isomerization of spiropyran using UV illumination. A single sensor was manipulated by optical tweezers and transferred to a cell surface, thereafter adhering selectively to the cell surface under UV illumination without excess sensor adhesion. We then drove the focal point of the optical tweezers to move up and down circularly near the sensor, mimicking a vibration on the sensor or rapid injection. The surface zeta potential of the liposome layers was measured using a zeta potential analyzer. The fluorescence resonance energy transfer (FRET) method was used to observe the changes in contact area between the adhered sensor and cell membrane before and after vibration. Holographic optical tweezers (HOT) and laser confocal microscopy were used to manipulate the single sensor and to capture fluorescent images. The results showed that the vibration applied on the sensor could push down the sensor, inducing a downward displacement. This displacement caused a corresponding deformation of the cell membrane, which increased the contact area between the sensor and the cell membrane. Without vibration, the sensor was injected into the cytoplasm in 5 h at an injection rate of 40%. By applying the vibration stimulus, we succeeded in the rapid injection of the sensor in 30 min at an injection rate of 80%.
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