Smartphone-based hand-held polarized light microscope for on-site pharmaceutical crystallinity characterization.

Polarized light microscopy (PLM) is a common but critical method for pharmaceutical crystallinity characterization, which has been widely introduced for research purposes or drug testing and is recommended by many pharmacopeias around the world. To date, crystallinity characterization of pharmaceutical solids is restricted to laboratories due to the relatively bulky design of the conventional PLM system, while little attention has been paid to on-site, portable, and low-cost applications. Herein, we developed a smartphone-based polarized microscope with an ultra-miniaturization design ("hand-held" scale) for these purposes. The compact system consists of an optical lens, two polarizers, and a tailor-made platform to hold the smartphone. Analytical performance parameters including resolution, imaging quality of interference color, and imaging reproducibility were measured. In a first approach, we illustrated the suitability of the device for pharmaceutical crystallinity characterization and obtained high-quality birefringence images comparable to a conventional PLM system, and we also showed the great promise of the device for on-site characterization with high flexibility. In a second approach, we employed the device as a proof of concept for a wider application ranging from liquid crystal to environmental pollutants or tissues from plants. As such, this smartphone-based hand-held polarized light microscope shows great potential in helping pharmacists both for research purposes and on-site drug testing, not to mention its broad application prospects in many other fields.

Nano/Micromotors for Cancer Diagnosis and Therapy: Innovative Designs to Improve Biocompatibility.

Nano/micromotors are artificial robots at the nano/microscale that are capable of transforming energy into mechanical movement. In cancer diagnosis or therapy, such "tiny robots" show great promise for targeted drug delivery, cell removal/killing, and even related biomarker sensing. Yet biocompatibility is still the most critical challenge that restricts such techniques from transitioning from the laboratory to clinical applications. In this review, we emphasize the biocompatibility aspect of nano/micromotors to show the great efforts made by researchers to promote their clinical application, mainly including non-toxic fuel propulsion (inorganic catalysts, enzyme, etc.), bio-hybrid designs, ultrasound propulsion, light-triggered propulsion, magnetic propulsion, dual propulsion, and, in particular, the cooperative swarm-based strategy for increasing therapeutic effects. Future challenges in translating nano/micromotors into real applications and the potential directions for increasing biocompatibility are also described.

Nanomaterials meet surface-enhanced Raman scattering towards enhanced clinical diagnosis: a review.

Surface-enhanced Raman scattering (SERS) is a very promising tool for the direct detection of biomarkers for the diagnosis of i.e., cancer and pathogens. Yet, current SERS strategies are hampered by non-specific interactions with co-existing substances in the biological matrices and the difficulties of obtaining molecular fingerprint information from the complex vibrational spectrum. Raman signal enhancement is necessary, along with convenient surface modification and machine-based learning to address the former issues. This review aims to describe recent advances and prospects in SERS-based approaches for cancer and pathogens diagnosis. First, direct SERS strategies for key biomarker sensing, including the use of substrates such as plasmonic, semiconductor structures, and 3D order nanostructures for signal enhancement will be discussed. Secondly, we will illustrate recent advances for indirect diagnosis using active nanomaterials, Raman reporters, and specific capture elements as SERS tags. Thirdly, critical challenges for translating the potential of the SERS sensing techniques into clinical applications via machine learning and portable instrumentation will be described. The unique nature and integrated sensing capabilities of SERS provide great promise for early cancer diagnosis or fast pathogens detection, reducing sanitary costs but most importantly allowing disease prevention and decreasing mortality rates.

On-board smartphone micromotor-based fluorescence assays.

Herein, we describe the design of a portable device integrated with micromotors for real-time fluorescence sensing of (bio)markers. The system comprises a universal 3D printed platform to hold a commercial smartphone, which is equipped with an external magnification optical lens (20-400×) and tailor-made emission filters directly attached to the camera, an adjustable sample holder to accommodate a glass slide and laser excitation sources. On a first approach, we illustrate the suitability of the platform using magnetic Janus micromotors modified with fluorescent ZnS@CdxSe1-x quantum dots for real-time ON-OFF mercury detection. On a second approach, graphdiyne tubular catalytic micromotors modified with a rhodamine labelled affinity peptide are used for the OFF-ON detection of cholera toxin B. The micromotor-based smartphone for fluorescence sensing approach was compared to a high-performance optical microscope, and similar analytical features were obtained. This versatility allows for easy integration of micromotor fluorescence sensing strategies based on different propulsion mechanisms, allowing for its future use with a myriad of biomarkers and even multiplexed schemes.

Smartphone-Based Janus Micromotors Strategy for Motion-Based Detection of Glutathione.

Herein, we describe a Janus micromotor smartphone platform for the motion-based detection of glutathione. The system compromises a universal three-dimensional (3D)-printed platform to hold a commercial smartphone, which is equipped with an external magnification optical lens (20-400×) directly attached to the camera, an adjustable sample holder to accommodate a glass slide, and a light-emitting diode (LED) source. The presence of glutathione in peroxide-rich sample media results in the decrease in the speed of 20 µm graphene-wrapped/PtNPs Janus micromotors due to poisoning of the catalytic layer by a thiol bond formation. The speed can be correlated with the concentration of glutathione, achieving a limit of detection of 0.90 µM, with percent recoveries and excellent selectivity under the presence of interfering amino acids and proteins. Naked-eye visualization of the speed decrease allows for the design of a test strip for fast glutathione detection (30 s), avoiding previous amplification strategies or sample preparation steps. The concept can be extended to other micromotor approaches relying on fluorescence or colorimetric detection for future multiplexed schemes.

Real-time monitoring of aristolochic acid I reduction process using surface-enhanced Raman Spectroscopy with DFT simulation.

With the increasing number of reports on aristolochic acid I (AAI), more and more toxic and side effects have been discovered successively. The main recognized carcinogenic mechanism is that AAI is metabolized into aristololactam I (AAT) in the body by nitroreductases, ultimately forming AAT-DNA adducts that cause disease. However, the carcinogenic mechanism is still not well understood by currently reported indirect method, there has always been a great demand to develop a direct method for real-time monitoring such process. In this work, surface-enhanced Raman spectroscopy (SERS) was used for the first time to monitor the process of AAI under the action of reducing agent sodium borohydride and catalyst Raney nickel to form AAT. We first found the abundant intermediate product-amino derivative of AAI, which was never reported before by other methods. The AAT was then obtained by a one-step dehydration reaction from the amino derivative of AAI under such reduction conditions. The product of amino derivative of AAI and AAT were further verified by thin-layer chromatography, H nuclear magnetic resonance spectra, mass spectrometry, and ultra-high performance liquid chromatography. Furthermore, a density functional theory-supported in-depth vibrational characterization of AAI and AAT was performed. The monitoring of the AAI reduction process by SERS can be of great significance for further exploration of its pathogenic mechanism, prevention, and monitoring of "nephropathy" and other diseases caused by AAI.

Dual-Propelled Lanbiotic Based Janus Micromotors for Selective Inactivation of Bacterial Biofilms.

Graphene oxide/PtNPs/Fe2 O3 "dual-propelled" catalytic and fuel-free rotary actuated magnetic Janus micromotors modified with the lanbiotic Nisin are used for highly selective capture/inactivation of gram-positive bacteria units and biofilms. Specific interaction of Nisin with the Lipid II unit of Staphylococcus Aureus bacteria in connection with the enhanced micromotor movement and generated fluid flow result in a 2-fold increase of the capture/killing ability (both in bubble and magnetic propulsion modes) as compared with free peptide and static counterparts. The high stability of Nisin along with the high towing force of the micromotors allow for efficient operation in untreated raw media (tap water, juice and serum) and even in blood and in flowing blood in magnetic mode. The high selectivity of the approach is illustrated by the dramatically lower interaction with gram-negative bacteria (Escherichia Coli). The double-propulsion (catalytic or fuel-free magnetic) mode of the micromotors and the high biocompatibility holds considerable promise to design micromotors with tailored lanbiotics that can response to the changes that make the bacteria resistant in a myriad of clinical, environmental remediation or food safety applications.

Janus Micromotors Coated with 2D Nanomaterials as Dynamic Interfaces for (Bio)-Sensing.

In this work, we study the interaction of graphdiyne oxide (GDYO)-, graphene oxide (GO)-, or black phosphorous (BP)-wrapped Janus micromotors using a model system relying on a fluorescence-labeled affinity peptide, which is released upon specific interaction with a target Cholera Toxin B. Such ON-OFF-ON system allows mimicking similar processes occurring at (bio)-interfaces and to study the related sorption and desorption kinetics. The distinct surface properties of each nanomaterial play a critical role in the loading/release capacity of the peptide, greatly influencing the release profiles. Sorption obeys a second-order kinetic model using the two-dimensional (2D) nanomaterials in connection with micromotors, indicating a strong influence of chemisorption process for BP micromotors. Yet, release kinetics are faster for GDYO and GO nanomaterials, indicating a contribution of π and hydrophobic interactions in the probe sorption (Cholera Toxin B affinity peptide) and target probe release (in the presence of Cholera Toxin B). Micromotor movement also plays a critical role in such processes, allowing for efficient operation in low raw sample volumes, where the high protein content can diminish probe loading/release, affecting the overall performance. The loading/release capacity and feasibility of the (bio)-sensing protocol are illustrated in Vibrio cholerae and Vibrio parahaemolyticus bacteria cultures as realistic domains. The new concept described here holds considerable promise to understand the interaction of micromotor with biological counterparts in a myriad of biomedical and other practical applications, including the design of novel micromotor-based sensors.

Light-driven nanomotors and micromotors: envisioning new analytical possibilities for bio-sensing.

The aim of this conceptual review is to cover recent developments of light-propelled micromotors for analytical (bio)-sensing. Challenges of self-propelled light-driven micromotors in complex (biological) media and potential solutions from material aspects and propulsion mechanism to achieve final analytical detection for in vivo and in vitro applications will be comprehensively covered. Graphical abstract.

Graphdiyne Micromotors in Living Biomedia.

Graphdiyne (GDY), a new kind of two-dimensional (2D) material, was combined with micromotor technology for "on-the-fly" operations in complex biomedia. Microtubular structures were prepared by template deposition on membrane templates, resulting in functional structures rich in sp and sp2 carbons with highly conjugated π networks. This resulted in a highly increased surface area for a higher loading of anticancer drugs or enhanced quenching ability over other 2D based micromotors, such as graphene oxide (GO) or smooth tubular micromotors. High biocompatibility with almost 100 % cell viability was observed in cytotoxicity assays with moving micromotors in the presence of HeLa cells. On a first example, GDY micromotors loaded with doxorubicin (DOX) were used for pH responsive release and HeLa cancer cells killing. The use of affinity peptide engineered GDY micromotors was also illustrated for highly sensitive and selective fluorescent OFF-ON detection of cholera toxin B through specific recognition of the subunit B region of the target toxin. The new developments illustrated here offer considerable promise for the use of GDY as part of micromotors in living biosystems.

Nano/Micromotors for Diagnosis and Therapy of Cancer and Infectious Diseases.

Micromotors are man-made nano/microscale devices capable of transforming energy into mechanical motion. The accessibility and force offered by micromotors hold great promise to solve complex biomedical challenges. This Review highlights current progress and prospects in the use of nano and micromotors for diagnosis and treatment of infectious diseases and cancer. Motion-based sensing and fluorescence switching detection strategies along with therapeutic approaches based on direct cell capture; killing by direct contact or specific drug delivery to the affected site, will be comprehensively covered. Future challenges to translate the potential of nano/micromotors into practical applications will be described in the conclusions.

Correction: Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood.

[This corrects the article DOI: 10.1039/C8SC04637A.].

Strongly fluorescent cysteamine-coated copper nanoclusters as a fluorescent probe for determination of picric acid.

This paper describes the synthesis of fluorescent copper nanoclusters (CuNC) with a fluorescence quantum yield as high as 2.3% after modification with cysteamine. The modified CuNC are shown to be viable probes for the determination of picric acid (PA). Fluorescence drops with increasing concentration of PA which can be detected fluorometrically with a 0.14 µM limit of detection. This is much lower than required by the People's Republic of China Surface Water Environmental Quality Standard (2.2 µM). The probe was successfully applied to the determination of PA in spiked tap water, lake water and river water. Graphical abstract Copper nanoclusters (CuNC) have weak fluorescence but after the modification with cysteamine, the fluorescence of CuNC is strongly enhanced. The fluorescence of such cysteamine-coated copper nanoclusters (CuNC-CA) is reduced upon the addition of picric acid (PA) through an inner filter effect (IFE).

Self-Assembly of Au@Ag Nanoparticles on Mussel Shell To Form Large-Scale 3D Supercrystals as Natural SERS Substrates for the Detection of Pathogenic Bacteria.

Herein, we developed a natural surface-enhanced Raman scattering (SERS) substrate based on size-tunable Au@Ag nanoparticle-coated mussel shell to form large-scale three-dimensional (3D) supercrystals (up to 10 cm2) that exhibit surface-laminated structures and crossed nanoplates and nanochannels. The high content of CaCO3 in the mussel shell results in superior hydrophobicity for analyte enrichment, and the crossed nanoplates and nanochannels provided rich SERS hot spots, which together lead to high sensitivity. Finite-difference time-domain simulations showed that nanoparticles in the channels exhibit apparently a higher electromagnetic field enhancement than nanoparticles on the platelets. Thus, under optimized conditions (using Au@AgNPs with 5 nm shell thickness), highly sensitive SERS detection with a detection limit as low as 10-9 M for rhodamine 6G was obtained. Moreover, the maximum electromagnetic field enhancement of different types of 3D supercrystals shows no apparent difference, and Au@AgNPs were uniformly distributed such that reproducible SERS measurements with a 6.5% variation (613 cm-1 peak) over 20 spectra were achieved. More importantly, the as-prepared SERS substrates can be utilized for the fast discrimination of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa by discriminant analysis. This novel Au@Ag self-assembled mussel shell template holds considerable promise as low-cost, durable, sensitive, and reproducible substrates for future SERS-based biosensors.

Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood.

In this study, a new biosensor based on a sandwich structure has been developed for the isolation and detection of multiple bacterial pathogens via magnetic separation and SERS tags. This novel assay relies on antimicrobial peptide (AMP) functionalized magnetic nanoparticles as "capturing" probes for bacteria isolation and gold coated silver decorated graphene oxide (Au@Ag-GO) nanocomposites modified with 4-mercaptophenylboronic acid (4-MPBA) as SERS tags. When different kinds of bacterial pathogens are combined with the SERS tags, the "fingerprints" of 4-MPBA show corresponding changes due to the recognition interaction between 4-MPBA and different kinds of bacterial cell wall. Compared with the label-free SERS detection of bacteria, 4-MPBA here can be used as an internal standard (IS) to correct the SERS intensities with high reproducibility, as well as a Raman signal reporter to enhance the sensitivity and amplify the differences among the bacterial "fingerprints". Thus, three bacterial pathogens (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) were successfully isolated and detected, with the lowest concentration for each of the strains detected at just 101 colony forming units per mL (CFU mL-1). According to the changes in the "fingerprints" of 4-MPBA, three bacterial strains were successfully discriminated using discriminant analysis (DA). In addition, the AMP modified Fe3O4NPs feature high antibacterial activities, and can act as antibacterial agents with low cellular toxicology in the long-term storage of blood for future safe blood transfusion applications. More importantly, this novel method can be applied in the detection of bacteria from clinical patients who are infected with bacteria. In the validation analysis, 97.3% of the real blood samples (39 patients) could be classified effectively (only one patient infected with E. coli was misclassified). The multifunctional biosensor presented here allows for the simultaneous isolation, discrimination and killing of bacteria, suggesting its high potential for clinical diagnosis and safe blood transfusions.

Chip-based molecularly imprinted monolithic capillary array columns coated GO/SiO2 for selective extraction and sensitive determination of rhodamine B in chili powder.

A novel solid-phase extraction chip embedded with array columns of molecularly imprinted polymer-coated silanized graphene oxide (GO/SiO2-MISPE) was established to detect trace rhodamine B (RB) in chili powder. GO/SiO2-MISPE monolithic columns for RB detection were prepared by optimizing the supporting substrate, template, and polymerizing monomer under mild water bath conditions. Adsorption capacity and specificity, which are critical properties for the application of the GO/SiO2-MISPE monolithic column, were investigated. GO/SiO2-MIP was examined by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy. The recovery and the intraday and interday relative standard deviations for RB ranged from 83.7% to 88.4% and 2.5% to 4.0% and the enrichment factors were higher than 110-fold. The chip-based array columns effectively eliminated impurities in chili powder, indicating that the chip-based GO/SiO2-MISPE method was reliable for RB detection in food samples using high-performance liquid chromatography. Accordingly, this method has direct applications for monitoring potentially harmful dyes in processed food.

Chip-based dual-molecularly imprinted monolithic capillary array columns coated Ag/GO for selective extraction and simultaneous determination of bisphenol A and nonyl phenol in fish samples.

An analytical technique for selective, simultaneous determination of bisphenol A (BPA) and nonyl phenol (NP) in fish samples was established by a solid-phase extraction chip integrated with array columns of dual-molecularly imprinted polymer-coated silver-modified graphene oxide (Ag/GO-dual-MISPE-chip). Ag/GO dual-molecularly imprinted polymers (Ag/GO-dual-MIPs) were synthesized by in situ polymerization using Ag/GO as the supporting matrix which extracted templates easily. The affinity and specificity on the Ag/GO-dual-MISPE monolithic column were also investigated. The array extraction chip showed high binding capacity and selectivity to BPA and NP, with the imprinting factors of BPA and NP reaching 2.6 and 2.9, respectively. Ag/GO-dual-MIPs were characterized by scanning electron microscopy and Fourier transform-infrared (FT-IR) spectroscopy. As Low as 2.4ngL-1 BPA and 4.7ngL-1 NP were detected by high performance liquid chromatography coupled with fluorescence detection. The enrichment factor was 113-fold for BPA and 92-fold for NP. Therefore, the chip-based array columns are feasibly applicable to facile extraction of BPA and NP and effective clean-up of impurities in fish samples.

A simple and compact fluorescence detection system for capillary electrophoresis and its application to food analysis.

A novel fluorescence detection system for CE was described and evaluated. Two miniature laser pointers were used as the excitation source. A Y-style optical fiber was used to transmit the excitation light and a four-branch optical fiber was used to collect the fluorescence. The optical fiber and optical filter were imported into a photomultiplier tube without any extra fixing device. A simplified PDMS detection cell was designed with guide channels through which the optical fibers were easily aligned to the detection window of separation capillary. According to different requirements, laser pointers and different filters were selected by simple switching and replacement. The fluorescence from four different directions was collected at the same detecting point. Thus, the sensitivity was enhanced without peak broadening. The fluorescence detection system was simple, compact, low-cost, and highly sensitive, with its functionality demonstrated by the separation and determination of red dyes and fluorescent whitening agents. The detection limit of rhodamine 6G was 7.7 nM (S/N = 3). The system was further applied to determine illegal food dyes. The CE system is potentially eligible for food safety analysis.

Molecularly imprinted coated graphene oxide solid-phase extraction monolithic capillary column for selective extraction and sensitive determination of phloxine B in coffee bean.

A method was developed to sensitively determine phloxine B in coffee bean by molecularly imprinted polymers (MIPs) coated graphene oxide (GO) solid-phase extraction (GO-MISPE) coupled with high-performance liquid chromatography and laser-induced fluorescence detection (HPLC-LIF). The GO-MISPE capillary monolithic column was prepared by water-bath in situ polymerization, using GO as supporting material, phloxine B, methacrylic acid (MAA), and ethylene dimethacrylate (EDMA) as template, functional monomer, and cross-linker, respectively. The properties of the homemade GO-MISPE capillary monolithic column, including capacity and specificity, were investigated under optimized conditions. The GO-MIPs were characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FT-IR). The mean recoveries of phloxine B in coffee bean ranged from 89.5% to 91.4% and the intra-day and inter-day relative standard deviation (RSD) values all ranged from 3.6% to 4.7%. Good linearity was obtained over 0.001-2.0 µg mL(-1) (r=0.9995) with the detection limit (S/N=3) of 0.075 ng mL(-1). Under the selected conditions, enrichment factors of over 90-fold were obtained and extraction on the monolithic column effectively cleaned up the coffee bean matrix. The results demonstrated that the proposed GO-MISPE HPLC-LIF method can be applied to sensitively determine phloxine B in coffee bean.