Bifunctional fluorescent/Raman nanoprobe for the early detection of amyloid

One of the pathological hallmarks of Alzheimer’s disease (AD) is the abnormal aggregation of amyloid beta (Aβ) peptides. Therefore the detection of Aβ peptides and imaging of amyloid plaques are considered as promising diagnostic methods for AD. Here we report a bifunctional nanoprobe prepared by conjugating gold nanoparticles (AuNPs) with Rose Bengal (RB) dye. RB is chosen due to its unique Raman fingerprints and affinity with Aβ peptides. After the conjugation, Raman signals of RB were significantly enhanced due to the surface-enhanced Raman scattering (SERS) effect. Upon binding with Aβ42 peptides, a spectrum change was detected, and the magnitude of the spectrum changes can be correlated with the concentration of target peptides. The peptide/probe interaction also induced a remarkable enhancement in the probes’ fluorescence emission. This fluorescence enhancement was further utilized to image amyloid plaques in the brain slices from transgenic mice. In this study, the RB-AuNPs were used for both SERS-based detection of Aβ42 peptides and fluorescence-based imaging of amyloid plaques. Compared to monofunctional probes, the multifunctional probe is capable to provide more comprehensive pathophysiological information, and therefore, the implementation of such multifunctional amyloid probes is expected to help the investigation of amyloid aggregation and the early diagnosis of AD.MOE (Min. of Education, S’pore)Published versio

3D/4D multiscale imaging in acute lymphoblastic leukemia cells-visualizing dynamics of cell death

Quantitative phase detection is a new methodology that provides quantitative information on cellular morphology to monitor the cell status, drug response and toxicity. In this paper the morphological changes in acute leukemia cells treated with chitosan were detected using d’Bioimager a robust imaging system. Quantitative phase image of the cells was obtained with numerical analysis. Results show that the average area and optical volume of the chitosan treated cells is significantly reduced when compared with the control cells, which reveals the effect of chitosan on the cancer cells. From the results it can be attributed that d’Bioimager can be used as a non-invasive imaging alternative to measure the morphological changes of the living cells in real time.Published versio

Biomimetic autonomous enzymatic nanowalker of high fuel efficiency

Replicating efficient chemical energy utilization of biological nanomotors is one ultimate goal of nanotechnology and energy technology. Here, we report a rationally designed autonomous bipedal nanowalker made of DNA that achieves a fuel efficiency of less than two fuel molecules decomposed per productive forward step, hence breaking a general threshold for chemically powered machines invented to date. As a genuine enzymatic nanomotor without changing itself nor the track, the walker demonstrates a sustained motion on an extended double-stranded track at a speed comparable to previous burn-bridge motors. Like its biological counterparts, this artificial nanowalker realizes multiple chemomechanical gatings, especially a bias-generating product control unique to chemically powered nanomotors. This study yields rich insights into how pure physical effects facilitate harvest of chemical energy at the single-molecule level and provides a rarely available motor system for future development toward replicating the efficient, repeatable, automatic, and mechanistically sophisticated transportation seen in biomotor-based intracellular transport but beyond the capacity of the current burn-bridge motors

Bessel-Gauss beam light sheet assisted fluorescence imaging of Trabecular meshwork in the Iridocorneal region using long working distance objectives

Glaucoma is one of the leading cause of blindness characterized by increased intra ocular pressure (IOP), visual field defects and irreversible loss of vision. Remedial intervention of glaucoma primarily aims at the reduction of IOP and subsequent examination concerning the related anomalies in the aqueous outflow system (AOS) especially with newer angle procedures. Thus, high resolution imaging of the iridocorneal angle (ICA) region comprising trabecular meshwork (TM) is extremely valuable to clinicians and vision analysts in comprehending the disease state for the efficacious analysis and treatment of glaucoma. Imaging of the AOS inside the eye using the digitally scanned Bessel-Gauss beam light sheet microscopy has been used in this study to obtain high resolution optical sections with minimal phototoxicity and photobleaching. This paper investigates the effect of long working distance objectives in obtaining high resolution TM images while offering non-contact and non-invasive approach in imaging. A series of experiments were conducted to optimize various imaging parameters using porcine eyes as test samples. Investigations carried out by illuminating both the anterior segment region and limbal region resulted in promising results. A delineated network of collagen fibers in a meshwork fashion can be clearly seen in the obtained images of the TM. The optical sectioning capability of this technique is demonstrated and the structural features match well with previous literature reports.Agency for Science, Technology and Research (A*STAR)Accepted versionThe authors acknowledge the financial support received through A*STAR-MIG project (BMRC1619077002) and the facilities and research manpower provided through COLE-EDB funding

Nanosensor detection of synthetic auxins in planta using corona phase molecular recognition

Synthetic auxins such as 1-naphthalene acetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) have been extensively used in plant tissue cultures and as herbicides because they are chemically more stable and potent than most endogenous auxins. A tool for rapid in planta detection of these compounds will enhance our knowledge about hormone distribution and signaling and facilitate more efficient usage of synthetic auxins in agriculture. In this work, we show the development of real-time and nondestructive in planta NAA and 2,4-D nanosensors based on the concept of corona phase molecular recognition (CoPhMoRe), to replace the current state-of-the-art sensing methods that are destructive and laborious. By designing a library of cationic polymers wrapped around single-walled carbon nanotubes with general affinity for chemical moieties displayed on auxins and its derivatives, we developed selective sensors for these synthetic auxins, with a particularly large quenching response to NAA (46%) and a turn-on response to 2,4-D (51%). The NAA and 2,4-D nanosensors are demonstrated in planta across several plant species including spinach, Arabidopsis thaliana (A. thaliana), Brassica rapa subsp. chinensis (pak choi), and Oryza sativa (rice) grown in various media, including soil, hydroponic, and plant tissue culture media. After 5 h of 2,4-D supplementation to the hydroponic medium, 2,4-D is seen to accumulate in susceptible dicotyledon pak choi leaves, while no uptake is observed in tolerant monocotyledon rice leaves. As such, the 2,4-D nanosensor had demonstrated its capability for rapid testing of herbicide susceptibility and could help elucidate the mechanisms of 2,4-D transport and the basis for herbicide resistance in crops. The success of the CoPhMoRe technique for measuring these challenging plant hormones holds tremendous potential to advance the plant biology study.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Singapore-MIT Alliance for Research and Technology (SMART)This research was supported by the National Research Foundation (NRF), Prime Minister's Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) program. The Disruptive & Sustainable Technology for Agricultural Precision (DiSTAP) is an interdisciplinary research group of the Singapore-MIT Alliance for Research and Technology (SMART) Center. T.T.S.L. was supported on a graduate fellowship by the Agency of Science, Research and Technology, Singapore. M.P. is grateful for the support of the Samsung scholarship. A.D. was supported on the Singapore-MIT undergraduate research fellowship

Decoding early stress signaling waves in living plants using nanosensor multiplexing

Abstract Increased exposure to environmental stresses due to climate change have adversely affected plant growth and productivity. Upon stress, plants activate a signaling cascade, involving multiple molecules like H2O2, and plant hormones such as salicylic acid (SA) leading to resistance or stress adaptation. However, the temporal ordering and composition of the resulting cascade remains largely unknown. In this study we developed a nanosensor for SA and multiplexed it with H2O2 nanosensor for simultaneous monitoring of stress-induced H2O2 and SA signals when Brassica rapa subsp. Chinensis (Pak choi) plants were subjected to distinct stress treatments, namely light, heat, pathogen stress and mechanical wounding. Nanosensors reported distinct dynamics and temporal wave characteristics of H2O2 and SA generation for each stress. Based on these temporal insights, we have formulated a biochemical kinetic model that suggests the early H2O2 waveform encodes information specific to each stress type. These results demonstrate that sensor multiplexing can reveal stress signaling mechanisms in plants, aiding in developing climate-resilient crops and pre-symptomatic stress diagnoses