The activity of alkaline phosphatase in breast cancer exosomes simplifies the biosensing design

A novel, portable, and cost-effective turbidimetric sensor for sensitive alkaline phosphatase activity assay

The development of enzyme activity analysis methods is critical for precise and rapid assessments of enzyme activity levels within biological systems, facilitating a more profound comprehension of physiological functions and disease mechanisms. Alkaline phosphatase (ALP) participates in various physiological processes involving phosphate ester hydrolysis. Altered ALP activity levels are often indicative of different diseases, underscoring the necessity for accurate ALP activity determination in medical diagnostics. This study innovatively applies turbidity as a physical variable, proposing a turbidimetric sensor based on an enhanced ammonium molybdate reagent for phosphate analysis. By integrating this with the ALP substrate p-nitrophenyl phosphate, a turbidimetric sensor was devised and employed for ALP activity analysis. The proposed turbidimetric sensor demonstrated high sensitivity both for phosphate (0.18 μmol/L) and ALP activity (0.03 mU/mL) assay. In practical applications, this turbidimetric sensor has been effectively employed to detect ALP activity in mouse feces, showcasing its potential for auxiliary diagnosis of inflammatory bowel disease. Significantly, this novel turbidity-based approach offers not only swift and straightforward procedures but also remarkable portability and cost-efficiency. Requiring solely a handheld turbidimeter and eliminating the need for bulky instruments, this approach holds significant potential for point-of-care testing applications.

Silver ion-regulated reliable and rapid detection technique for alkaline phosphatase based on surface-enhanced Raman spectroscopy

The primary characteristics of a clinical assay are its accuracy and speed. For alkaline phosphatase (ALP) monitoring in medical treatment, a rapid, reliable surface-enhanced Raman scattering (SERS) detection technique was designed based on the controlled "hot spot" effect caused by the mediation of silver ions (Ag+). Consisting of functionalized Au nanoparticles (NPs), Ag+, and the enzyme substrate 2-phospho-L-ascorbic acid triso-dium salt (AAP), the fabricated detection technique can achieve a reliable clinical assay for ALP detection in human serum within several minutes. Herein, due to the coordination interaction of Ag+ and the cyano group (-CN), Ag+ can coordinate with p-mercaptobenzonitrile (MBN) modified on the surface of Au NPs, leading to the connection of adjacent Au NPs in a controllable manner to form a chain structure, in which the SERS signal of MBN at 2228 cm-1 in the Raman silent region would be highly amplified. Under the enzymatic biocatalysis of ALP, AAP was converted into ascorbic acid (AA). AA triggered the reduction of Ag+ into Ag0, resulting in a decrease in the concentration of Ag+. Meanwhile, the decrease in the SERS intensity of MBN was well-controlled and was recognized with the increased amounts of ALP. Based on this, the SERS detection technique for ALP was established. The limit of detection (LOD) for the detection of ALP was as low as 1.23 pg mL-1 (0.005 U L-1). Because of all these characteristics and its ultrahigh stability, this SERS detection technique is an important point-of-care candidate for the reliable, efficacious, and highly sensitive detection of ALP.

Peptide-based biosensing approaches for targeting breast cancer-derived exosomes

Exosomes are nanovesicles present in all the biological fluids, making them attractive as non-invasive biomarkers for diseases like cancer, among many others. However, exosomes are complex to separate and detect, requiring comprehensive molecular characterization for their routine use in diagnostics. This study explores the use of peptides as cost-effective and stable alternatives to antibodies for exosome binding. To achieve that, phage display technology was employed to select peptides with high specificity for target molecules in exosomes. Specifically, a selected peptide was evaluated for its ability to selectively bind breast cancer-derived exosomes. Proteomic analysis identified 38 protein candidates targeted by the peptide on exosome membranes. The binding of the peptide to breast cancer-derived exosomes was successfully demonstrated by flow cytometry and magneto-actuated immunoassays. Furthermore, an electrochemical biosensor was also tested for breast cancer-derived exosome detection and quantification. The peptide demonstrated effective binding to exosomes from aggressive cancer cell lines, offering promising results in terms of specificity and recovery. This research shows potential for developing rapid, accessible diagnostic tools for breast cancer, especially in low-resource healthcare settings.

Nanoarchitectonics-based electrochemical aptasensors for highly efficient exosome detection

Exosomes, a type of extracellular vesicles, have attracted considerable attention due to their ability to provide valuable insights into the pathophysiological microenvironment of the cells from which they originate. This characteristic implicates their potential use as diagnostic disease biomarkers clinically, including cancer, infectious diseases, neurodegenerative disorders, and cardiovascular diseases. Aptasensors, which are electrochemical aptamers based biosensing devices, have emerged as a new class of powerful detection technology to conventional methods like ELISA and Western analysis, primarily because of their capability for high-performance bioanalysis. This review covers the current research landscape on the detection of exosomes utilizing nanoarchitectonics strategy for the development of electrochemical aptasensors. Strategies involving signal amplification and biofouling prevention are discussed, with an emphasis on nanoarchitectonics-based bio-interfaces, showcasing their potential to enhance sensitivity and selectivity through optimal conduction and mass transport properties. The ongoing challenges to broaden the clinical applications of these biosensors are also highlighted.

Weak Value Amplification-Based Biochip for Highly Sensitive Detection and Identification of Breast Cancer Exosomes

Exosomes constitute an emerging biomarker for cancer diagnosis because they carry multiple proteins that reflect the origins of the parent cell. The highly sensitive detection of exosomes is a crucial prerequisite for the diagnosis of cancer. In this study, we report an exosome detection system based on quantum weak value amplification (WVA). The WVA detection system consists of a reflection detection light path and a Zr-ionized biochip. Zr-ionized biochips effectively capture exosomes through the specific interaction between zirconium dioxide and the phosphate groups on the lipid bilayer of exosomes. Aptamer-modified gold nanoparticles (Au NPs) are then used to specifically recognize proteins on exosomes to enhance the detection signal. The sensitivity and resolution of the detection system are 2944.07 nm/RIU and 1.22 × 10-5 RIU, respectively. The concentration of exosomes can be directly quantified by the WVA system, ranging from 105-107 particles/mL with the detection limit of 3 × 104 particles/mL. The use of Au NPs-EpCAM for the specific enhancement of breast cancer MDA-MB-231 exosomes is demonstrated. The results indicate that the WVA detection system can be a promising candidate for the detection of exosomes as tumor markers.

Construction of single-molecule counting-based biosensors for DNA-modifying enzymes: A review

DNA-modifying enzymes act as critical regulators in a wide range of genetic functions (e.g., DNA damage & repair, DNA replication), and their aberrant expression may interfere with regular genetic functions and induce various malignant diseases including cancers. DNA-modifying enzymes have emerged as the potential biomarkers in early diagnosis of diseases and new therapeutic targets in genomic research. Consequently, the development of highly specific and sensitive biosensors for the detection of DNA-modifying enzymes is of great importance for basic biomedical research, disease diagnosis, and drug discovery. Single-molecule fluorescence detection has been widely implemented in the field of molecular diagnosis due to its simplicity, high sensitivity, visualization capability, and low sample consumption. In this paper, we summarize the recent advances in single-molecule counting-based biosensors for DNA-modifying enzyme (i.e, alkaline phosphatase, DNA methyltransferase, DNA glycosylase, flap endonuclease 1, and telomerase) assays in the past four years (2019 - 2023). We highlight the principles and applications of these biosensors, and give new insight into the future challenges and perspectives in the development of single-molecule counting-based biosensors.

Probiotics Influence Gut Microbiota and Tumor Immune Microenvironment to Enhance Anti-Tumor Efficacy of Doxorubicin

Probiotics have been reported to influence the gut microbiota and immune system in various diseases. Now, the potential impacts of probiotics on tumor treatment still need to be investigated. In this study, three strains of probiotics, Bifidobacterium breve BBr60 (BBr60), Pediococcus pentosaceus PP06 (PP06), and Bifidobacterium longum subsp. longum BL21 (BL21) were investigated for their combination with chemotherapeutic drugs doxorubicin (DOX). Our study showed that PP06 and BL21 have good performance in gastric acid, bile salt, and intestinal fluid tolerance, antimicrobial activity to pathogenic Staphylococcus aureus, and adhesion to Caco-2 cells. Besides, the probiotics all exhibited antioxidant effect, especially BL21. In vitro cytotoxicity and in vivo animal studies revealed that probiotics used alone could not directly induce anti-tumor effects, but the combination of PP06/BL21 and DOX exhibits a higher inhibition rate than DOX alone, via recruitment and infiltration of immune cells in the tumor region. After 16S rRNA analysis of fecal samples from animal models, it was found that BL21 could increase the abundance of Akkermansia, which may also play a role in regulating the tumor microenvironment to improve immune response. In conclusion, BL21 and PP06 in this study could enhance the anti-tumor efficacy by influencing the gut microbiota and tumor immune microenvironment.

Methylene Blue-Stained Single-Stranded DNA Aptamers as a Highly Efficient Electronic Switch for Quasi-Reagentless Exosomes Detection: An Old Dog with New Tricks

Improving the convenience, sensitivity, and cost-effectiveness of electrochemical biosensors is crucial for advancing their clinical diagnostic applications. Herein, we presented an elegant approach to construct electrochemical aptasensors for tumor-derived exosome detection by harnessing the alterable interaction between methylene blue (MB) and DNA aptamer. In detail, the anti-EpCAM aptamer, named SYL3C, was found to exhibit a strong affinity toward MB due to the specific interaction between MB and unbound guanine bases. Thereby, SYL3C could be stained with MB to arouse a strong electrochemical signal on a gold electrode (AuE). Upon binding to EpCAM-positive exosomes, SYL3C underwent a conformational transformation. The resulting conformation, or exosomes-SYL3C complex, not only reduced the accumulation of MB on SYL3C by obstructing the accessibility of guanines to MB but also impeded the transfer of electrons from the bound MB to AuE, leading to a notable decrease in the electrochemical signal. Using MB-stained SYL3C as an electronic switch, an electrochemical aptasensor was readily established for the detection of EpCAM-positive exosome detection. Without the need for signal amplification strategies, expensive auxiliary reagents, and complex operation, this unique signal transduction mechanism alone could endow the aptasensor with ultrahigh sensitivity. A limit of detection (LOD) of 234 particles mL-1 was achieved, surpassing the performance of most reported methods. As a proof of concept, the aptasensor was applied to analyze clinical serum samples and effectively distinguish non-small-cell lung cancer (NSCLC) patients from healthy individuals. As EpCAM exhibits broad expression in exosomes derived from different tumor sources, the developed aptasensor holds promise for diagnosing other tumor types.

Distinguishable Colorimetric Biosensor for Diagnosis of Prostate Cancer Bone Metastases

Castration-resistant prostate cancer (PCa) causes severe bone metastasis (BM), which significantly increases mortality in men with PCa. Imaging tests and radiometric scanning require long analysis times, expensive equipment, specialized personnel, and a slow turnaround. New visualization technologies are expected to solve the above problems. Nonetheless, existing visualization techniques barely meet the urgency for precise diagnosis because the human eyes cannot recognize and capture even slight variations in visual information. By using dye differentiated superposition enhancement colorimetric biosensors, an effective method to diagnose prostate cancer bone metastases (PCa-BM) with excellent accuracy for naked-eye quantitative detection of alkaline phosphatase (ALP) is developed. The biomarker ALP specific hydrolytic product ascorbic acid can be detected by rhodamine derivatives (Rd) as gold nanobipyramids (Au NBPs) are deposited and grown. Color-recombining enhancement effects between Rd and Au NBPs significantly improved abundance. The 150 U L-1 threshold between normal and abnormal can be identified by color. And with color enhancement effect and double signal response, the ALP index is visually measured to diagnose PCa-BM and provide handy treatment recommendations. Additionally, the proposed colorimetric sensing strategy can be used to diagnose other diseases.

Application of Biosensors in Detecting Breast Cancer Metastasis

Breast cancer has garnered global attention due to its high incidence worldwide, and even more noteworthy is that approximately 90% deaths due to breast cancer are attributed to cancer metastasis. Therefore, the early diagnosis of breast cancer metastasis holds significant importance for reducing mortality outcomes. Biosensors play a crucial role in the early detection of metastatic breast cancer due to their advantages, such as ease of use, portability, and real-time analysis capabilities. This review primarily described various types of sensors for detecting breast cancer metastasis based on biomarkers and cell characteristics, including electrochemical, optical, and microfluidic chips. We offered detailed descriptions of the performance of these various biosensors and made comparisons between them. Furthermore, we described the pathology of breast cancer and summarized commonly used biomarkers for metastatic breast cancer. Finally, we discussed the advantages of current-stage biosensors and the challenges that need to be addressed, as well as prospects for their future development.

The diagnostic effectiveness of serum sialic acid predicts both qualitative and quantitative prostate cancer in patients with prostate-specific antigen between 4 and 20 ng/mL

Introduction

This study aimed to evaluate the predictive value of the serum biochemical index, including alkaline phosphatase (AKP), lactate dehydrogenase (LDH), α-L-fucosidase (AFU), serum sialic acid (SA), and fibrinogen (FIB), for prostate cancer (PCa) and clinically significant prostate cancer (CSPCa) in patients with a prostate-specific antigen (PSA) value between 4 and 20 ng/mL.

Patients and methods

This study retrospectively examined the clinical data of 408 eligible patients who underwent prostate biopsies in our hospital between March 2015 and July 2022. CSPCa was defined as a "Gleason grade group of≥2". For analyzing the association between PCa/CSPCa and serum biochemical index, univariable logistic regression and multivariable logistic regression were conducted. Based on the multivariable logistic regression model, we constructed models and compared the area under the curve (AUC). We generated the nomogram, the ROC curve, the DCA curve, and the calibration curve for PCa.

Results

Overall, we studied 271 patients with PCa (including 155 patients with CSPCa) and 137 non-PCa patients. Patients with PCa were more likely to consume alcohol, have higher total PSA (TPSA) values, and have lower free PSA (FPSA) and free/total PSA (f/T) values. There were higher TPSA values and lower f/T values in the CSPCa group when compared with the non-CSPCa group. The univariate logistic regression analyses did not show significant results. However, AKP, AFU, SA, TPSA, and FPSA all retain significant significance when all factors are included in multifactor logistic regression analysis. This finding suggests that the exposure factor exhibited an independent effect on the outcome after controlling for other factors, including the potential confounding effects that may have been underestimated. Through ROC curves, we found that SA and TPSA levels are more powerful predictors. In contrast, there is a lack of excellent predictive value for PCA and CSPCa using Age, AFU, FIB, and FPSA.

Conclusion

In our study, serum biochemical index is a potential prediction tool for PCa and CSPCa for patients with PSA values between 4 and 20 ng/mL. Additionally, the new serum biochemical index SA is also useful when diagnosing PCa and CSPCa, as we conclude in our study.

Mussel-inspired polydopamine decorated silane modified-electroconductive gelatin-PEDOT:PSS scaffolds for bone regeneration

This study seeks to simulate both the chemistry and piezoelectricity of bone by synthesizing electroconductive silane-modified gelatin-poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) scaffolds using the freeze drying technique. In order to enhance hydrophilicity, cell interaction, and biomineralization, the scaffolds were functionalized with polydopamine (PDA) inspired by mussels. Physicochemical, electrical, and mechanical analyses were conducted on the scaffolds, as well as in vitro evaluations using the osteosarcoma cell line MG-63. It was found that scaffolds had interconnected porous structures, so the PDA layer formation reduced the size of pores while maintaining scaffold uniformity. PDA functionalization reduced the electrical resistance of the constructs while improving their hydrophilicity, compressive strength, and modulus. As a result of the PDA functionalization and the use of silane coupling agents, higher stability and durability were achieved as well as an improvement in biomineralization capability after being soaked in SBF solution for a month. Additionally, the PDA coating enabled the constructs to enhance viability, adhesion, and proliferation of MG-63 cells, as well as to express alkaline phosphatase and deposit HA, indicating that scaffolds can be used for bone regeneration. Therefore, the PDA-coated scaffolds developed in this study and the non-toxic performance of PEDOT:PSS present a promising approach for further in vitro and in vivo studies.

Pd(II)-based coordination polymer nanosheets for ratiometric colorimetric and photothermal dual-mode assay of serum alkaline phosphatase

Fabrication of a multi-signal readout assay with high sensitivity and selectivity is highly desirable for clinical and biochemical analysis, but remains a challenge due to laborious procedures, large-scale instruments, and inadequate accuracy. Herein, a straightforward, rapid, and portable detection platform based on palladium(II) methylene blue (MB) coordination polymer nanosheets (PdMBCP NSs) was unveiled for the ratiometric dual-mode detection of alkaline phosphatase (ALP) with temperature and colorimetric signal readout properties. The sensing mechanism is the ALP-catalyzed generation of ascorbic acid for competitive binding and etching PdMBCP NSs to release free MB in a quantitive means for detection. Specifically, ALP addition led to the decrease of temperature signal readout from the decomposed PdMBCP NSs under 808 nm laser excitation, and simultaneous increase of the temperature from the generated MB with a 660 nm laser, together with the corresponding absorbance changes at both wavelengths. Notably, this ratiometric nanosensor exhibited a detection limit of 0.013 U/L (colorimetric) and 0.095 U/L (photothermal) within 10 min, respectively. The reliability and satisfactory sensing performance of the developed method were further confirmed by clinic serum samples. Therefore, this study provides a new insight for the development of dual-signal sensing platforms for convenient, universal, and accurate detection of ALP.

The Applications of Electrochemical Immunosensors in the Detection of Disease Biomarkers: A Review

Disease-related biomarkers may serve as indicators of human disease. The clinical diagnosis of diseases may largely benefit from timely and accurate detection of biomarkers, which has been the subject of extensive investigations. Due to the specificity of antibody and antigen recognition, electrochemical immunosensors can accurately detect multiple disease biomarkers, including proteins, antigens, and enzymes. This review deals with the fundamentals and types of electrochemical immunosensors. The electrochemical immunosensors are developed using three different catalysts: redox couples, typical biological enzymes, and nanomimetic enzymes. This review also focuses on the applications of those immunosensors in the detection of cancer, Alzheimer's disease, novel coronavirus pneumonia and other diseases. Finally, the future trends in electrochemical immunosensors are addressed in terms of achieving lower detection limits, improving electrode modification capabilities and developing composite functional materials.

A Comprehensive Review on Electrochemical Nano Biosensors for Precise Detection of Blood-Based Oncomarkers in Breast Cancer

Breast cancer (BC), one of the most common and life-threatening cancers, has the highest incidence rate among women. Early diagnosis of BC oncomarkers is considered the most effective strategy for detecting and treating BC. Finding the type and stage of BC in women as soon as possible is one of the greatest ways to stop its incidence and negative effects on medical treatment. The development of biosensors for early, sensitive, and selective detection of oncomarkers has recently attracted much attention. An electrochemical nano biosensor (EN) is a very suitable option for a powerful tool for cancer diagnosis. This comprehensive review provides information about the prevalence and pathobiology of BC, recent advances in clinically available BC oncomarkers, and the most common electrochemical nano biosensors for point-of-care (POC) detection of various BC oncomarkers using nanomaterial-based signal amplification techniques.

Ratiometric electrochemical OR gate assay for NSCLC-derived exosomes

Non-small cell lung cancer (NSCLC) is the most common pathological type of LC and ranks as the leading cause of cancer deaths. Circulating exosomes have emerged as a valuable biomarker for the diagnosis of NSCLC, while the performance of current electrochemical assays for exosome detection is constrained by unsatisfactory sensitivity and specificity. Here we integrated a ratiometric biosensor with an OR logic gate to form an assay for surface protein profiling of exosomes from clinical serum samples. By using the specific aptamers for recognition of clinically validated biomarkers (EpCAM and CEA), the assay enabled ultrasensitive detection of trace levels of NSCLC-derived exosomes in complex serum samples (15.1 particles μL^-1 within a linear range of 10²-10⁸ particles μL^-1). The assay outperformed the analysis of six serum biomarkers for the accurate diagnosis, staging, and prognosis of NSCLC, displaying a diagnostic sensitivity of 93.3% even at an early stage (Stage I). The assay provides an advanced tool for exosome quantification and facilitates exosome-based liquid biopsies for cancer management in clinics.

Highly Effective Detection of Exosomal miRNAs in Plasma Using Liposome-Mediated Transfection CRISPR/Cas13a

Exosomal miRNAs play a critical role in cancer biology and could be potential biomarkers for cancer diagnosis. However, due to the low abundance of miRNAs in the exosomes, recognizing and detecting disease-associated exosomal miRNAs in an easy-to-operate way remain a challenge. Herein, we used a liposome-mediated membrane fusion strategy (MFS) to transfect CRISPR/Cas13a into exosomes, termed MFS-CRISPR, directly measuring exosomal miRNAs in plasma. Using the MFS-CRISPR platform for detection of the exosomal miR-21, we achieve a linear range spanning four orders of magnitude (10⁴-10⁸ particles/mL) and the method is able to detect the exosomal miR-21 in as low as 1.2 × 10³ particles/mL. The liposome-mediated MFS could confine fluorescent signals in fused vesicles, which can be used for exosome heterogeneity analysis. Moreover, MFS-CRISPR assay was evaluated by measuring clinical samples, and the difference of miR-21 expression of breast cancer patients and healthy donors was significant. Because of high sensitivity and simplicity, the proposed method could have promising clinical potential for cancer diagnosis and treatment monitoring.

Electrochemical Genosensing of Overexpressed GAPDH Transcripts in Breast Cancer Exosomes

Exosomes are receiving highlighted attention as new biomarkers for the detection of cancer since they are profusely released by tumor cells in different biological fluids. In this paper, the exosomes are preconcentrated from the serum by immunomagnetic separation (IMS) based on a CD326 receptor as a specific epithelial cancer-related biomarker and detected by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) transcripts. Following the lysis of the captured exosomes, the released GAPDH transcripts are amplified by reverse transcription polymerase chain reaction (RT-PCR) with a double-tagging set of primers on poly(dT)-modified-MPs to increase the sensitivity. The double-tagged amplicon is then quantified by electrochemical genosensing. The IMS/double-tagging RT-PCR/electrochemical genosensing approach is first demonstrated for the sensitive detection of exosomes derived from MCF7 breast cancer cells and compared with CTCs in terms of the analytical performance, showing an LOD of 4 × 102 exosomes μL-1. The genosensor was applied to human samples by immunocapturing the exosomes directly from serum from breast cancer patients and showed a higher electrochemical signal (3.3-fold, p < 0.05), when compared with healthy controls, suggesting an overexpression of GAPDH on serum-derived exosomes from breast cancer patients. The detection of GAPDH transcripts is performed from only 1.0 mL of human serum using specific magnetic particles, improving the analytical simplification and avoiding ultracentrifugation steps, demonstrating to be a promising strategy for minimal invasive liquid biopsy.

Practical tips and new trends in electrochemical biosensing of cancer-related extracellular vesicles

To tackle cancer and provide prompt diagnoses and prognoses, the constantly evolving biosensing field is continuously on the lookout for novel markers that can be non-invasively analysed. Extracellular vesicles (EVs) may represent a promising biomarker that also works as a source of biomarkers. The augmented cellular activity of cancerous cells leads to the production of higher numbers of EVs, which can give direct information on the disease due to the presence of general and cancer-specific surface-tethered molecules. Moreover, the intravesicular space is enriched with other molecules that can considerably help in the early detection of neoplasia. Even though EV-targeted research has indubitably received broad attention lately, there still is a wide lack of practical and effective quantitative procedures due to difficulties in pre-analytical and analytical phases. This review aims at providing an exhaustive outline of the recent progress in EV detection using electrochemical and photoelectrochemical biosensors, with a focus on handling approaches and trends in the selection of bioreceptors and molecular targets related to EVs that might guide researchers that are approaching such an unstandardised field.

Magnetic Separation of Cell-Secreted Vesicles with Tailored Magnetic Particles and Downstream Applications

The analysis of the receptors on the surface of the cell-secreted vesicles provides valuable information of the cell signature and may also offer diagnosis and/or prognosis of a wide range of diseases, including cancer.Due to their low concentration, conventional procedures for extracellular vesicle (EV) detection usually require relatively large sample volumes, involving preliminary purification or preconcentration steps from complex specimens. Here, we describe the separation and preconcentration in magnetic particles of extracellular vesicles obtained from cell culture supernatants from MCF7, MDA-MB-231, and SKBR3 breast cancer cell lines, human fetal osteoblastic cell line (hFOB), and human neuroblastoma SH-SY5Y cell line, as well as exosomes from human serum. The first approach involves the covalent immobilization for the exosomes directly on micro (4.5 μm)-sized magnetic particles. The second approach is based on tailored magnetic particles modified with antibodies for further immunomagnetic separation of the exosomes. In these instances, micro (4.5 μm)-sized magnetic particles are modified with different commercial antibodies against selected receptors, including the general tetraspanins CD9, CD63, and CD81 and the specific receptors (CD24, CD44, CD54, CD326, CD340, and CD171). The magnetic separation can be easily coupled with downstream characterization and quantification methods, including molecular biology techniques such as immunoassays, confocal microscopy, or flow cytometry.

Inner filter effect-based red-shift and fluorescence dual-sensor platforms with sulfur quantum dots for detection and bioimaging of alkaline phosphatase

Alkaline phosphatase (ALP), one of the vital biomarkers in several diseases, plays a role in indicating disease presence or severity in early diagnosis. Here, a simple H₂O₂ assisted top-down method was used to synthesize sulfur quantum dots (SQDs) with excitation and emission at 355 nm and 440 nm. Adding ALP into p-nitrophenyl phosphate (p-NPP) and SQDs was found to exhibit a red shift in the emission wavelength and fluorescence intensity quenching of SQDs, respectively, allowing us to propose dual-sensor platforms of red shift of emission wavelength (RSEW) and fluorescence quenching of SQDs. These dual-sensor platforms were highly sensitive and selective in ALP detection, with a linear response to ALP in the concentration range of 0.25 to 100 U L^-1 and detection limits of 0.08 and 0.10 U L^-1, respectively. The absorption of p-NP at 400 nm showed a good overlap with the excitation and emission of SQDs, leading to inner filter effect-based RSEW and fluorescence quenching of SQDs. This sensor platform was successfully applied in ALP sensing of serum samples as well as monitoring of ALP in cells. More importantly, this platform can serve as an example of using RSEW to detect ALP.

Nickel-Doped Microfluidic Chip for Rapid and Efficient Immunomagnetic Separation and Detection of Breast Cancer Cell-Derived Exosomes

Breast cancer cell-derived exosomes have high potential as biomarkers for continuous biopsies and longitudinal monitoring in breast cancer. However, it is extremely difficult to separate exosomes with high recovery and high purity from complex media, such as urine, plasma, saliva and cell culture supernatants. Here, we designed a flexible and simple microfluidic chip for exosome separation. The capture zone of the chip is a three-dimensional structure of interlaced cylinders doped with nickel powder. Exosomes were separated from cell culture supernatant by the immunomagnetic separation method in continuous flow mode and were detected by fluorescence imaging with high sensitivity. The chip achieved a high exosome recovery rate (> 74%) and purity (> 67%) at an injection rate of 3.6 mL/h. Thus, this chip was demonstrated to be a cutting-edge platform for the separation and detection of exosomes. It could also be applied to separate and detect other types of exosomes, microbubbles and cells.

Advances in exosome analysis

There is growing demand for novel biomarkers that detect early stage disease as well as monitor clinical management and therapeutic strategies. Exosome analysis could provide the next advance in attaining that goal. Exosomes are membrane encapsulated biologic nanometric-sized particles of endocytic origin which are released by all cell types. Unfortunately, exosomes are exceptionally challenging to characterize with current technologies. Exosomes are between 30 and 200nm in diameter, a size that makes them out of the sensitivity range to most cell-oriented sorting or analysis platforms, i.e., traditional flow cytometers. The most common methods for targeting exosomes to date typically involve purification followed by the characterization and the specific determination of their cargo. The whole procedure is time consuming, requiring thus skilled personnel as well as laboratory facilities and benchtop instrumentation. The most relevant methodology for exosome isolation, characterization and quantification is addressed in this chapter, including the most up-to-date approaches to explore the potential usefulness of exosomes as biomarkers in liquid biopsies and in advanced nanomedicine.

Ratiometric detection and imaging of endogenous alkaline phosphatase activity by fluorescein-coumarin-based fluorescence probe

Alkaline phosphatase (ALP) is a type of enzyme that widely exists in various tissues of the human body; it plays an important role in regulating many cell functions. The development of a sensitive and accurate tool to detect the changes of ALP activity in organisms can contribute to research in the fields of biochemistry, cytology, clinical medicine, etc. In this paper, a small organic molecule-based ratiometric fluorescent probe (FCP) was designed based on the hydroxyl electron-donating group in fluorescein-coumarin protected by the phosphate group. ALP can trigger the fluorescence change through the enzyme-catalyzed cleavage of phosphoryl ester groups, and the ratio of ALP can be measured at wavelengths of 465 nm and 530 nm. The probe had high selectivity and sensitivity to ALP, and the detection limit measured under the optimal conditions in an aqueous medium reached 0.006 mU/mL. The ALP activity of human serum samples was determined using the probe and found to be in good agreement with that measured using commercial ALP kits. Finally, the probe was also successfully applied to image ALP in living hepatocytes with good selectivity and sensitivity.

Electrochemical nano-sensing interface for exosomes analysis and cancer diagnosis

Exosomes are a class of the nanosized extracellular vesicles, which have emerged as representative liquid biopsy biomarkers. To date, the electrochemical nanosensors are of great significance in the exosome detection with the advantages of easy operation, high accuracy and reliable repeatability. Especially, the growing field of nano interface has provided the electrochemical sensing platforms for the accurate exosomes analysis. The incorporation of multiple nanomaterials can take advantages and synergistic properties of functional units. So, based on the integration of with nanomaterial-based signal transduction and specific biorecognition, the nano-sensing interface provides excellent electrochemical features owing to rapid mass transport and excellent conductivity. The nano-sensing interface with a wide variety of morphologies and structure also provides the large active surface area for the immobilization of bio-capturing agents. Furthermore, through the design of nanostructured electrode array, the efficiency of transducer can be greatly improved. It should be noticed that the elaboration of a proper sensor requires the profound knowledge of the nano-sensing interface. Therefore, this article presents a review of the recent advance in exosomes detection based on the electrochemical nano-sensing interface, including electrochemical analysis principles, exosome sensing mechanisms, nano-interface construction strategies, as well as the typical diagnosis application. In particular, the article is focused on the exploration of the various electrochemical sensing performance of nano-interface in the exosome detection. We have also prospected the future trend and challenge of the electrochemical nano-sensing interface for exosomes analysis in clinical cancer diagnosis.

Gold-Nanoparticle-Coated Magnetic Beads for ALP-Enzyme-Based Electrochemical Immunosensing in Human Plasma

A simple and sensitive AuNP-coated magnetic beads (AMB)-based electrochemical biosensor platform was fabricated for bioassay. In this study, AuNP-conjugated magnetic particles were successfully prepared using biotin-streptavidin conjugation. The morphology and structure of the nanocomplex were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX) and UV-visible spectroscopy. Moreover, cyclic voltammetry (CV) was used to investigate the effect of AuNP-MB on alkaline phosphatase (ALP) for electrochemical signal enhancement. An ALP-based electrochemical (EC) immunoassay was performed on the developed AuNP-MB complex with indium tin oxide (ITO) electrodes. Subsequently, the concentration of capture antibodies was well-optimized on the AMB complex via biotin-avidin conjugation. Lastly, the developed AuNP-MB immunoassay platform was verified with extracellular vesicle (EV) detection via immune response by showing the existence of EGFR proteins on glioblastoma multiforme (GBM)-derived EVs (10⁸ particle/mL) spiked in human plasma. Therefore, the signal-enhanced ALP-based EC biosensor on AuNP-MB was favorably utilized as an immunoassay platform, revealing the potential application of biosensors in immunoassays in biological environments.

Design, Synthesis, and Biological Evaluation of Novel Dihydropyridine and Pyridine Analogs as Potent Human Tissue Nonspecific Alkaline Phosphatase Inhibitors with Anticancer Activity: ROS and DNA Damage-Induced Apoptosis

Small molecules with nitrogen-containing scaffolds have gained much attention due to their biological importance in the development of new anticancer agents. The present paper reports the synthesis of a library of new dihydropyridine and pyridine analogs with diverse pharmacophores. All compounds were tested against the human tissue nonspecific alkaline phosphatase (h-TNAP) enzyme. Most of the compounds showed excellent enzyme inhibition against h-TNAP, having IC₅₀ values ranging from 0.49 ± 0.025 to 8.8 ± 0.53 µM, which is multi-fold higher than that of the standard inhibitor (levamisole = 22.65 ± 1.60 µM) of the h-TNAP enzyme. Furthermore, an MTT assay was carried out to evaluate cytotoxicity against the HeLa and MCF-7 cancer cell lines. Among the analogs, the most potent dihydropyridine-based compound 4d was selected to investigate pro-apoptotic behavior. The further analysis demonstrated that compound 4d played a significant role in inducing apoptosis through multiple mechanisms, including overproduction of reactive oxygen species, mitochondrial dysfunction, DNA damaging, and arrest of the cell cycle at the G1 phase by inhibiting CDK4/6. The apoptosis-inducing effect of compound 4d was studied through staining agents, microscopic, and flow cytometry techniques. Detailed structure–activity relationship (SAR) and molecular docking studies were carried out to identify the core structural features responsible for inhibiting the enzymatic activity of the h-TNAP enzyme. Moreover, fluorescence emission studies corroborated the binding interaction of compound 4d with DNA through a fluorescence titration experiment.

A ratiometric fluorescence method based on nitrogen-doped carbon quantum dots for the determination of the activity of alkaline phosphatase

Herein, a simple and sensitive ratiometric fluorescence sensing platform to detect alkaline phosphatase (ALP) activity is developed on the basis of yellow fluorescent nitrogen-doped carbon quantum dots (YNCDs). The hydrolysis of ascorbic acid 2-phosphate (AAP) into ascorbic acid (AA) is catalyzed by ALP. Then, AA will react with o-phenylenediamine (OPD) to form 3-(1,2-dihydroxyethyl)furo[3,4b]-quinoxaline (QXD) which is a blue fluorescent quinoxaline derivative with emission at 435 nm in the presence of Cu²⁺. YNCDs have yellow fluorescence emission at 555 nm, and can maintain stable in QXD reaction system. Therefore, by utilizing the fluorescence of YNCDs at 555 nm as reference signal and the fluorescence of QXD at 435 nm as report signal, we can detect the ALP activity by monitoring the fluorescence ratio (F₄₃₅/F₅₅₅). The linear range is 0.5-5 U/L, and the limit of detection is 0.14 U/L. An application of this method for the analysis of ALP in human serum has given satisfactory results. A ratiometric fluorescent nanoprobe for ascorbic acid and alkaline phosphatase detection with excellent biocompatible and high sensitivity was successfully constructed based on YNCDs and QXD.

Metabolic Features of Saliva in Breast Cancer Patients

The aim of the work was to study the metabolic characteristics of saliva in breast cancer and the subsequent assessment of the potential information content of its individual biochemical indicators. The study included 487 patients of the Omsk Clinical Oncology Center with morphologically verified breast cancer and 298 volunteers without breast pathologies. Saliva samples were obtained from all patients before the start of treatment, and the values of 34 biochemical indicators were determined. It has been shown that concentration of total protein, urea, uric acid (UA), the total content of α-amino acids and lipid peroxidation products, and the activity of metabolic and antioxidant enzymes (in particular catalase—CAT) of saliva changed significantly in breast cancer. Biochemical indicators characterizing early breast cancer have been identified, which can be used for timely diagnosis in addition to existing methods. The coefficients UA/Urea and UA·CAT/Urea are proposed, for which the maximum deviation from the norm was observed in the early stages of the disease. It was shown that for ductal breast cancer, changes in the activity of metabolic enzymes of saliva were more pronounced, while, for lobular breast cancer, the indicators of enzymatic and non-enzymatic components of antioxidant protection changed. The results confirmed the potential importance of saliva in the diagnosis of breast cancer.