Two-Dimensional Multi-parameter Cytometry Platform for Single-Cell Analysis.

A 2D flow cytometry platform, known as CytoLM Plus, was developed for multi-parameter single-cell analysis. Single particles or cells after hydrodynamic alignment in a microfluidic unit undergo first-dimension fluorescence and side scattering dual-channel optical detection. They were thereafter immediately directed to ICP-MS by connecting the microfluidic unit with a high-efficiency nebulizer to facilitate the second-dimension ICP-MS detection. Flow cytometry measurements of fluorescent microspheres evaluated the performance of CytoLM Plus for optical detection. 6434 fluorescence bursts were observed with a valid signal proportion as high as 99.7%. After signal unification and gating analysis, 6067 sets of single-particle signals were obtained with 6.6 and 6.2% deviations for fluorescence burst area and height, respectively. This is fairly comparable with that achieved by a commercial flow cytometer. Afterward, CytoLM Plus was evaluated by 2D flow cytometry measurement of Ag+-incubated and AO-stained MCF-7 cells. A program for 2D single-cell signal unification was developed based on the algorithm of screening in lag time window. In the present case, a lag time window of -4.2 ± 0.09 s was determined by cross-correlation analysis and two-parameter optimization, which efficiently unified the concurrent single-cell signals from fluorescence, side scattering, and ICP-MS. A total of 495 sets of concurrent 2D signals were screened out, and the statistical analysis of these single-cell signals ensured 2D multi-parameter single-cell analysis and data elucidation.

In situ SERS monitoring of intracellular H2O2 in single living cells based on label-free bifunctional Fe3O4@Ag nanoparticles.

Visualization of signaling molecules in single living cells is crucial for understanding cellular metabolism and physiology, which can provide valuable insights into early diagnoses and treatments of diseases. Highly sensitive in situ monitoring of intracellular analytes released from single living cells by virtue of label-free nanosensors is urgently needed, which can avoid interferences from molecular labeling. Here, we proposed an ultrasensitive strategy for in situ imaging of intracellular H2O2 in single living cancer cells by surface-enhanced Raman scattering (SERS) spectroscopy with the utilization of label-free Fe3O4@Ag core-satellite nanoparticles (NPs). The Fe3O4@Ag NPs can efficiently and selectively catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. Additionally, they exhibit excellent SERS activity that allows for in situ monitoring of intracellular H2O2 in living cells through establishing the correlation between the H2O2 level and the SERS intensity of the catalytic oxidation product of TMB. The H2O2 concentration is revealed through the SERS intensity of oxidized TMB with a good linear response in a wide range from 1 fM to 1 mM. Moreover, the intracellular H2O2 level in live cancer cells and imaging of the distribution of H2O2 inside single cells can be achieved by using such a label-free nanosensor based strategy. Our work demonstrates that the label-free Fe3O4@Ag NP-based SERS imaging and quantification strategy is a promising and powerful approach to assess intracellular H2O2 in living cells and allows us to monitor single-cell signaling molecules with nanoscale resolution.

ICP-MS and Photothermal Dual-Readout Assay for Ultrasensitive and Point-of-Care Detection of Pancreatic Cancer Exosomes.

Pancreatic cancer is known to have a high mortality rate, and its early diagnosis remains challenging due to the occult location of the pancreas. Exosomes derived from pancreatic cancer cells specifically express glypican-1, which may provide a liquid biopsy opportunity for the early diagnosis of pancreatic cancer. Herein, an inductively coupled plasma mass spectrometry (ICP-MS) and photothermal dual-readout platform was proposed for the ultrasensitive and point-of-care analysis of pancreatic cancer exosomes. In our design, exosomes were specifically captured by the sandwich immunoassay, and simultaneously, alkaline phosphatase was introduced in a low-background manner. The alkaline phosphatase triggered the hydrolysis of l-ascorbic acid 2-phosphate to produce ascorbic acid, followed by the etching of Fe3O4@MnO2 nanoflowers. As a result, the Mn2+ generated by etching stripped off the Fe3O4 and was quantified using ICP-MS. Meanwhile, the reduced Fe3O4@MnO2 was applied for the photothermal assay by oxidizing dopamine with MnO2. The protocol exhibits a detection limit down to 19.1 particles mL-1, which is the most sensitive protocol reported so far. To our knowledge, this is the first endeavor for exosome quantification using ICP-MS and photothermal methods. The developed dual-readout platform not only is capable of distinguishing pancreatic cancer patients from healthy people, but also shows excellent discernibility of individual differences at low concentrations of exosomes. This dual-readout assay is a promising platform for the ultrasensitive and point-of-care detection of exosomes in liquid biopsy-based early cancer diagnosis.

Two-Dimensional Cytometry Platform for Single-Particle/Cell Analysis with Laser-Induced Fluorescence and ICP-MS.

A two-dimensional cytometry platform (CytoLM) with high sensitivity and high temporal resolution is developed for single-particle and single-cell sampling and analysis. First, a Dean flow-assisted vortex capillary cell sampling (VCCS) unit confines the sample stream in curved flow and drives to focus and align the particles or cells in a small probe volume. By coupling VCCS to a laser-induced fluorescence (LIF) detector with data acquisition and processing capability, a high-throughput single-particle/cell analysis system (VCCS-LIF) was established. The particle analysis throughput of 119.42/s and a detection recovery of 78.20 ± 1.75% were achieved at a density of 9.16 × 104/mL for fluorescent particles, and the cell analysis throughput is 48.20/s at a density of 1.5 × 105/mL. Second, the CytoLM platform is constructed by hyphenating VCCS-LIF with inductively coupled plasma mass spectrometry (ICP-MS). In the analysis of HepG2 cells by Ag+ incubation and AO staining, 10,760 fluorescence bursts and 3068 MS events were observed in 240 s. Invalid signals due to undispersed cells were controlled at 3.80% for LIF and 1.01% for MS, with a proportion of effective signal of >96.20%. After peak identification and integral processing of the original data, the statistical results including peak area, height, width, and spacing are obtained concurrently and the information on concentration and elemental quantification of single cells is evaluated. CytoLM facilitates high-throughput, multi-dimensional, and multi-parameter characterization of particles and cells, and it may provide vast potential in life science analysis.

Plasmonic Colorimetric Biosensor for Sensitive Exosome Detection via Enzyme-Induced Etching of Gold Nanobipyramid@MnO2 Nanosheet Nanostructures.

Exosomes involved in tumor-specific processes display excellent potential in the early diagnosis of cancer. Herein, a highly sensitive plasmonic colorimetric biosensor was proposed for exosome quantification. The sensing strategy mainly includes two steps: exosome-triggered competitive reaction and etching of gold nanobipyramid@MnO2 nanosheet nanostructures (Au NBP@MnO2 NSs). A competitive reaction between exosomes and placeholder chains induced by exosomes can translate the signal of exosomes into the amount of alkaline phosphatase, which simplifies the experimental process and amplifies the signal. The etching of Au NBP@MnO2 NSs by ascorbic acid generated from the hydrolysis of l-ascorbic acid 2-phosphate by alkaline phosphatase changes the refractive index of Au NBPs, accompanied by the blue shift of the longitudinal localized surface plasmon resonance peak. Profiting from the signal amplification of the competitive reaction and superior refractive index sensitivity of colorimetric substrates, this protocol exhibits high sensitivity toward exosomes within 8.5 × 102 to 8.5 × 104 particles µL-1, along with a detection limit of 1.35 × 102 particles µL-1, which is more sensitive than previously reported colorimetric methods. In addition, a sensitive multicolor visual detection of exosomes was realized by adjusting the aspect ratio of Au NBPs. It is worth mentioning that the Au NBP@MnO2 NSs was synthesized through in situ growth of MnO2 nanosheets on Au NBPs, and the attractive optical properties and ease of etching make Au NBP@MnO2 NSs promising candidates for plasmonic detection.

Inertial-Force-Assisted, High-Throughput, Droplet-Free, Single-Cell Sampling Coupled with ICP-MS for Real-Time Cell Analysis.

Single-cell analysis facilitates perception into the most essential processes in life's mysteries. While it is highly challenging to quantify them at the single-cell level, where precise single-cell sampling is the prerequisite. Herein, a real-time single-cell quantitative platform was established for high-throughput droplet-free single-cell sampling into time-resolved (TRA) ICP-MS and real-time quantification of intracellular target elements. The concentrated cells (2 × 106 cells mL-1) were spontaneously and orderly aligned in a spiral microchannel with 104 periodic dimensional confined micropillars. The quantification is conducted simultaneously by internal standard inducing from another branch channel in the chip. The flow-rate-independent feature of single-cell focusing into an aligned stream within a wide range of fluidic velocities (100-800 µL min-1) facilitates high-throughput, oil-free, single-cell introduction into TRA-ICP-MS. The system was used for real-time exploration of intracellular antagonism of Cu2+ against Cd2+. an obvious antagonistic effect was observed for the MCF-7 cell by culturing for 3, 6, 9, and 12 h with 100 µg L-1 Cd2+ and 100 µg L-1 Cu2+, and a rivalry rate of 12.8% was achieved at 12 h. At identical experimental conditions, however, limited antagonistic effect was encountered for a bEnd3 cell within the same incubation time period, with a rivalry rate of 4.81%. On the contrary, an antagonistic effect was not observed for the HepG2 cell by culturing for 6 h, while an obvious antagonistic effect was found by further culturing to 12 h, with a rivalry rate of 10.43%. For all three cell lines, significant heterogeneity was observed among individual cells.

Multiplexed detection of micro-RNAs based on microfluidic multi-color fluorescence droplets.

In this work, simple, rapid, and low-cost multiplexed detection of tumor-related micro-RNAs (miRNAs) was achieved based on multi-color fluorescence on a microfluidic droplet chip, which simplified the complexity of light path to a half. A four-T-junction structure was fabricated to form uniform nano-volume droplet arrays with customized contents. Multi-color quantum dots (QDs) used as the fluorescence labels were encapsulated into droplets to develop the multi-path fluorescence detection module. We designed an integrated multiplex fluorescence resonance energy transfer system assisted by multiple QDs (four colors) and one quencher to detect four tumor-related miRNAs (miRNA-20a, miRNA-21, miRNA-155, and miRNA-221). The qualitative analysis of miRNAs was realized by the color identification of QDs, while the quantitative detection of miRNAs was achieved based on the linear relationship between the quenching efficiency of QDs and the concentration of miRNAs. The practicability of the multiplex detection device was further confirmed by detecting four tumor-related miRNAs in real human serum samples. The detection limits of four miRNAs ranged from 35 to 39 pmol/L was achieved without any target amplification. And the linear range was from 0.1 nmol/L to 1 µmol/L using 10 nL detection volume (one droplet) under the detection speed of 320 droplets per minute. The multiple detection system for miRNAs is simple, fast, and low-cost and will be a powerful platform for clinical diagnostic analysis. Graphical abstract.

Colloidal photonic crystal array chip based on nanoparticle self-assembly on patterned hydrophobic surface for signal-enhanced fluorescent assay of adenosine.

A controllable approach for preparing a portable colloidal photonic crystal (CPC) array chip is presented. The approach was inspired by the confinement effect of nanoparticle self-assembly on patterned surface. Hydrophobic polydimethylsiloxane substrate with reproducible micro-region array was fabricated by soft-lithography. The substrate was employed as the patterned template for self-assembly of monodisperse polystyrene nanoparticles. The CPC units can be prepared in several minutes, and exhibit consistent reflection wavelength. By adjusting the size of polystyrene nanoparticles and the shape of micro-regions, CPC units with multiple structure, colors and geometries were obtained. The CPC array chip features fluorescence enhancement owing to the optical modulation capability of the periodic nanostructure of the self-assembled CPC. With the reflection wavelength (523 nm) of green CPC units overlapping the emission wavelength (520 nm, with excitation wavelength of 490 nm) of 6-carboxyfluorescein-labeled DNA probe, the fluorescence intensity increased more than 10-fold. For signal-amplified assay of adenosine, the concentration range of linear response was 5.0 × 10-5 mol L-1 to 1.0 × 10-3 mol L-1, and the limit of detection was 1.3 × 10-6 mol L-1. Because of the enhancement effect of photonic crystal, the fluorescence images were more readable from the CPC array chip, compared with those from the planar substrate. The chip has potential applications in multiplex determination with high-throughput via encoding strategy based on the tunable structure, color or geometric shape. Graphical abstractSchematic diagram of signal-enhanced fluorescent detection of adenosine based on the colloidal photonic crystal array chip (PDMS, polydimethylsiloxane; PS NPs, polystyrene nanoparticles; CPC, colloidal photonic crystal; GO, graphene oxide; FAM, 6-carboxyfluorescein).

A Chiral-Label-Free SERS Strategy for the Synchronous Chiral Discrimination and Identification of Small Aromatic Molecules.

A versatile and robust chiral discrimination strategy for small aromatic compounds is of significant importance in multidisciplinary fields. However, most current methods lack either the sufficient sensitivity for recognizing the chirality of the target molecules or their molecular specificity information. We have developed a versatile and chiral-label-free surface-enhanced Raman scattering (SERS)-based chiral discrimination sensing system for small aromatic molecules, where the molecular structural specificity and enantioselectivity can be given synchronously in a single SERS spectrum. More than 10 types of chiral aromatic molecules were successfully identified by using this system. This work has enormous potential for recognizing chiral products effectively in sophisticated systems, especially in the fields of chiral synthesis and chiral catalysis.

A Spiral-Helix (3D) Tubing Array That Ensures Ultrahigh-Throughput Single-Cell Sampling.

ICP-MS is powerful in evaluating elemental species at the single-cell level, where high throughput/efficiency/precision are the keys for achieving statistically significant information based on massive data. We report an ultrahigh-throughput single-cell sampling system, consisting of a 3D spiral-helix tubing array to facilitate single-cell focusing into an orderly flow by inertial lift force and Dean drag force. The spiral-helix array ensures a superb single-cell sampling rate of 40 000 cells min-1 at a favorable temporal-spatial resolution of 41.55 ± 17.46 µm (distance between adjacent cells) or 0.97 ± 0.41 ms (time interval between adjacent cells). With a laboratory-made nebulization device, a cell measurement efficiency up to 42.1 ± 7.2% is achieved in ICP-MS assay. Analysis of Au nanoparticles (AuNPs) in living K562 cells after incubation illustrates obvious diversification of AuNPs among cells. The ultrahigh throughput and cell measurement efficiency generate massive data on single-cell assay, make statistical analysis more comprehensive, and enable interpreting extremely subtle differences among individual cells.

SERS monitoring of the Fenton degradation reaction based on microfluidic droplets and alginate microparticles.

Surface-enhanced Raman scattering (SERS) spectroscopy as a powerful tool has been used to explore different catalysis degradation reactions, whereas some drawbacks caused by ferric ions still exist in the current SERS monitoring of the Fenton reaction process. In this work, microfluidic droplet- and alginate microparticle-based methods were, respectively, applied to realize SERS monitoring of the Fenton degradation process in a relatively stable environment, which benefited from reduction of the loss of ferrous ions and the aggregation of the SERS substrate. As expected, the spectroscopic evidence at the molecular level directly revealed the degradation mechanism of rhodamine dyes, showing that the chemical bonds between xanthene and carboxybenzene broke continuously during the reaction. Afterward, the degradation mechanism determined by SERS was verified via mass spectrometry detection, which confirmed the validity of the SERS-based method. More broadly, the microfluidic droplet- and microparticle-based methods are potentially applicable for SERS monitoring of more Fenton degradation reactions.

Effect of TiO2 on Altering Direction of Interfacial Charge Transfer in a TiO2 -Ag-MPY-FePc System by SERS.

Interfacial charge transfer (CT) is of interest owing to its effect on the performance of molecular photovoltaic (PV) devices. The characteristics and structures of interfacial materials, such as TiO2 nanoparticles (NPs) in some solar cells, are employed to adjust the CT process. In this study, three kinds of interfacial systems, including a solar cell-like TiO2 -Ag- p-mercaptopyridine (MPY)- iron phthalocyanine (FePc) system, are compared to investigate the interfacial CT process using surface-enhanced Raman scattering (SERS) spectroscopy. The SERS results show the significance of TiO2 NPs in the system on altering the direction and path of the interfacial CT, which is closely associated with the CT enhancement contribution to SERS in such an interfacial system. SERS spectroscopy is expected to be a promising technique for the exploration and estimation of the interfacial CT behavior in PV devices, which may further extend the applications of SERS in the field of solar cells.

High-Throughput/High-Precision Sampling of Single Cells into ICP-MS for Elucidating Cellular Nanoparticles.

In single-cell analysis with ICP-MS it is highly important to ensure precise single-cell sampling into ICP. For this purpose, a simple configured pressure-resistant MicroCross interface is developed for high-throughput/high-precision microdroplet generation and single-cell encapsulation. Aqueous cell suspension is ejected and sheared into droplets by tangent-flowing hexanol-continuous phases in the flow-focusing geometry of MicroCross, wherein to precisely trap a single cell into a droplet, with an extremely low probability of <0.005% for a single droplet encapsulating two cells. MicroCross interface is coupled with time-resolved ICP-MS (TRA-ICP-MS) for quantifying nanoparticles in single MCF-7 cells. At the optimal conditions, sufficient temporal-spatial resolution of the microdroplets is achieved facilitating high-throughput sampling of single cells into ICP. For solving the serious carbon deposition on the sampling cone and the unstable plasma torch caused by incomplete oxidation of hexanol phase in ICP, dimethyl carbonate (DMC) is for the first time used as a superb oxygen compensation reagent, which ensures adequate oxidation of hexanol, effectively eliminates the carbon deposition, and maintains a stable plasma. The single-cell analysis results indicated a remarkable discrepancy of the number of nanoparticles among the individual cells, falling into a range of 130-584 per MCF-7 cell in the case of AuNPs.

NiO Nanoparticles for Exceptionally Stable DNA Adsorption and Its Extraction from Biological Fluids.

Selective extraction of a small amount of nucleic acids from complex biological samples containing a high concentration of proteins is critical for bioanalytical chemistry. A number of previously published studies have focused on long, double-stranded DNA such as plasmid DNA. On the other hand, we are interested in short oligonucleotides. Nucleic acids have a negatively charged phosphate backbone that interacts with metal oxides strongly, and this may be used to distinguish them from proteins. In this work, a few metal oxide nanoparticles were screened, including NiO, CoO, ZnO, TiO2, CeO2, and Fe3O4 for DNA recovery. NiO had the highest DNA adsorption efficiency from mixtures containing bovine serum albumin or human blood serum. The adsorption of DNA by NiO was further characterized as a function of the pH, salt concentration, DNA length, and DNA sequence. The adsorption mechanism was studied by adding competing chemicals or denaturing agents. A striking observation was the extremely high adsorption affinity of NiO, much higher than that of the other tested oxides. Polyphosphate was the most effective agent for displacing adsorbed DNA, whereas simple inorganic phosphate was less effective. NiO was able to concentrate DNA from a serum mixture by 33- to 55-fold, depending on the serum concentration. NiO is thus a promising candidate for extracting DNA from biological samples.

In situ self-assembled reduced graphene oxide aerogel embedded with nickel oxide nanoparticles for the high-efficiency separation of ovalbumin.

A three-dimensional reduced graphene oxide aerogel with embedded nickel oxide nanoparticles was prepared by a one-step self-assembly reaction in a short time. The nanoparticles could be captured into the interior of reduced graphene oxide network during the formation of the three-dimensional architecture. The composite exhibited porosity, good biocompatibility, and abundant metal affinity binding sites. The aerogel was used to isolate ovalbumin selectively from egg white, and favorable adsorption was achieved at pH 3. An adsorption efficiency of 90.6% was obtained by using 1 mg of the composite for adsorbing 70 µg/mL of ovalbumin in 1.0 mL of sample solution, and afterwards a recovery of 90.7% was achieved by using an eluent of 1.0 mL Britton-Robinson buffer solution at pH 5. After the adsorption/desorption, ovalbumin showed no change in the conformation. The adsorption behavior of ovalbumin on the reduced graphene oxide composite well fitted to the Langmuir adsorption model, and a corresponding theoretical maximum adsorption capacity was 1695.2 mg/g. A sodium dodecyl sulfate polyacrylamide gel electrophoresis assay demonstrated that the aerogel could selectively isolate ovalbumin from chicken egg white.

Profuse color-evolution based aptasensor for mucin 1 detection utilizing urease-mediated color mixing of the mixed pH indicator.

Mucin 1 is a significant tumor marker, and developing portable and cost-effective methods for its detection is crucial, especially in resource-limited areas. Herein, we developed an innovative approach for mucin 1 detection using a visible multicolor aptasensor. Urease-encapsulated DNA microspheres were used to mediate multicolor change facilitated by the color mixing of the mixed pH indicator, a mixed methyl red and bromocresol green solution. Distinct color changes were exhibited in response to varying mucin 1 concentrations. Notably, the color mixing of the mixed pH indicator was used to display various hues of colors, broadening the range of color variation. And color tonality is much easier to differentiate than color intensity, improving the resolution with naked-eyes. Besides, the variation of color from red to green (a pair of complementary colors) enhanced the color contrast, heightening sensitivity for visual detection. Importantly, the proposed method was successfully applied to detect mucin 1 in real samples, demonstrating a clear differentiation of colors between the samples of healthy individuals and breast cancer patients. The use of a mixed pH indicator as a multichromatic substrate offers the merits of low cost, fast response to pH variation, and plentiful color-evolution. And the incorporation of calcium carbonate microspheres to encapsulate urease ensures stable urease activity and avoids the need for extra urease decoration. The color-mixing dependent strategy opens a new way for multicolor detection of MUC1, characterized by vivid color changes.

Structural engineering of mitochondria-targeted Au-Ag2S photosensitizers for enhanced photodynamic and photothermal therapy.

Much effort has been devoted to designing diverse photosensitizers for efficient photodynamic therapy (PDT) and photothermal therapy (PTT) performance. However, the effect of PS morphology on the PDT and PTT performance needs to be further explored. In this work, a photosensitizer, Au-Ag2S nanoparticles functionalized with indocyanine green, caspase-3 recognition peptides, and mitochondria-targeting peptides (AICM NPs) with different morphologies, including core-shell, eccentric core-shell-I, eccentric core-shell-II, and Janus morphologies, were synthesized to enhance PDT and PTT performance. Among them, AICM Janus NPs with enhanced charge-transfer efficiency and photothermal conversion demonstrate superior PDT and PTT performance compared to those of other morphologies. In addition, AICM NPs exhibit satisfactory surface-enhanced Raman scattering performance for in situ SERS monitoring of caspase-3 during PDT and PTT processes. After PDT and PTT treatment with AICM Janus NPs, the damaged mitochondria released caspase-3. AICM Janus NPs achieved a superior apoptosis rate in tumor cells in vitro. Furthermore, AICM Janus NPs treat the tumors in vivo within only 10 days, which is half the time reported in other work. The AICM NPs demonstrated superior therapeutic safety both in vitro and in vivo. This study investigates the effects of morphology-property-performance of photosensitizers on the PDT and PTT performances, which opens a new pathway toward designing photosensitizers for efficient PDT and PTT.

One-step fabrication of a self-driven point-of-care chip by femtosecond laser direct writing and its application in cancer cell H2O2 detection via semiconductor-based SERS.

Self-driven microfluidic systems have attracted significant attention and demonstrated great potential in the field of point-of-care (POC) testing due to their device simplicity, low power consumption, increased portability, and reduced sample consumption. To develop POC detection chips with diverse characteristics that meet different requirements, there is a strong demand for feasible strategies that enable easy operation and reduce processing time. Here, a one-step processing approach using femtosecond laser direct writing technology was proposed to fabricate a capillary-actuated POC microfluidic chip. The driving force of the chip is highly dependent on its surface wettability, which can be easily adjusted by changing the laser processing parameters. This POC microfluidic chip allowed for the detection of intracellular H2O2 through a catalytic reaction system that incorporated 5-aminosalicylic acid -sensitized colloidal TiO2 nanoparticles and horse radish peroxidase, with integrating semiconductor-based surface-enhanced Raman scattering (SERS) quantitative technique. The concentration of H2O2 was determined by the SERS signal of the catalytic products in the microfluidic chip, resulting in rapid detection with minimal sample consumption. Our method provides a simple, feasible, and alternative strategy for POC testing of H2O2, with a linear range of 10-2∼10-6 M and a limit of detection of 0.55 µM. This approach was successfully applied to rapid detection of intracellular H2O2 in MCF-7 breast cancer cells with high sensitivity and minimal sample consumption. Additionally, this study not only demonstrates the exceptional advantages of femtosecond laser processing technology in fabricating diverse microfluidic chips for various applications, but also presents an efficient POC testing strategy for detecting cell signaling molecules.

Advances of machine learning-assisted small extracellular vesicles detection strategy.

Detection of extracellular vesicles (EVs), particularly small EVs (sEVs), is of great significance in exploring their physiological characteristics and clinical applications. The heterogeneity of sEVs plays a crucial role in distinguishing different types of cells and diseases. Machine learning, with its exceptional data processing capabilities, offers a solution to overcome the limitations of conventional detection methods for accurately classifying sEV subtypes and sources. Principal component analysis, linear discriminant analysis, partial least squares discriminant analysis, XGBoost, support vector machine, k-nearest neighbor, and deep learning, along with some combined methods such as principal component-linear discriminant analysis, have been successfully applied in the detection and identification of sEVs. This review focuses on machine learning-assisted detection strategies for cell identification and disease prediction via sEVs, and summarizes the integration of these strategies with surface-enhanced Raman scattering, electrochemistry, inductively coupled plasma mass spectrometry and fluorescence. The performance of different machine learning-based detection strategies is compared, and the advantages and limitations of various machine learning models are also evaluated. Finally, we discuss the merits and limitations of the current approaches and briefly outline the perspective of potential research directions in the field of sEV analysis based on machine learning.

Shape-memory microfluidic chips for fluid and droplet manipulation.

Fluid manipulation is an important foundation of microfluidic technology. Various methods and devices have been developed for fluid control, such as electrowetting-on-dielectric-based digital microfluidic platforms, microfluidic pumps, and pneumatic valves. These devices enable precise manipulation of small volumes of fluids. However, their complexity and high cost limit the commercialization and widespread adoption of microfluidic technology. Shape memory polymers as smart materials can adjust their shape in response to external stimuli. By integrating shape memory polymers into microfluidic chips, new possibilities for expanding the application areas of microfluidic technology emerge. These shape memory polymers can serve as actuators or regulators to drive or control fluid flow in microfluidic systems, offering innovative approaches for fluid manipulation. Due to their unique properties, shape memory polymers provide a new solution for the construction of intelligent and automated microfluidic systems. Shape memory microfluidic chips are expected to be one of the future directions in the development of microfluidic technology. This article offers a summary of recent research achievements in the field of shape memory microfluidic chips for fluid and droplet manipulation and provides insights into the future development direction of shape memory microfluidic devices.