Surface-engineered quantum dots/electrospun nanofibers as a networked fluorescence aptasensing platform toward biomarkers

Highly fluorescent hybrid nanofibers as potential nanofibrous scaffolds for studying cell-fiber interactions

In this study, we report on the fabrication of hybrid nanofibers for labeling and bioimaging applications. Our approach is involved for developing highly fluorescent nanofibers using a blend of polylactic acid, polyethyleneglycol, and perylenediimide dyes, through the solution blow spinning technique. The nanofibers are exhibited diameters ranging from 330 nm to 420 nm. Nanofibers showed excellent red and near-infrared fluorescence emissive properties in fluorescent spectroscopy. Moreover, the strong two-photon absorption phenomenon was observed for nanofibers under confocal microscopy. To assess the applicability of these fluorescent nanofibers in bioimaging settings, we employ two types of mammalian cells B16F1 melanoma cells and J774.A1 macrophages. Both cell types exhibit negligible cytotoxicity after 24 h incubation with the nanofibers, indicating the suitability of nanofibers for cell-based experiments. We also observe strong interactions between the nanofibers and cells, as evidenced by two major events: a) the acquisition of an elongated cellular morphology with the major cellular axis parallel to the nanofibers and b) the accumulation of actin filaments along the points of contact of the cells with the fibers. Our findings demonstrate the suitability of these newly developed fluorescent nanofibers in cell-based applications for guiding cellular behavior. We expect that these fluorescent nanofibers have the potential to serve as scaffold materials for long-time tracking of cell-fiber interactions in fluorescence microscopy.

Magnetically Controlled Photothermal, Colorimetric, and Fluorescence Trimode Assay for Gastric Cancer Exosomes Based on Acid-Induced Decomposition of CP/Mn-PBA DSNBs

The accurate quantification of cancer-derived exosomes, which are emerging as promising noninvasive biomarkers for liquid biopsies in the early diagnosis of cancer, is becoming increasingly imperative. In our work, we developed a magnetically controlled photothermal, colorimetric, and fluorescence trimode aptasensor for human gastric cancer cell (SGC-7901)-derived exosomes. This sensor relied on CP/Mn-PBA DSNBs nanocomposites, created by decorating copper peroxide (CP) nanodots on polyethyleneimine-modified manganese-containing Prussian blue analogues double-shelled nanoboxes (PEI-Mn-PBA DSNBs). Through self-assembly, we attached CD63 aptamer-labeled CP/Mn-PBA DSNBs (Apt-CP/Mn-PBA DSNBs) to complementary DNA-labeled magnetic beads (cDNA-MB). During exosome incubation, these aptamers preferentially formed complexes with exosomes, and we efficiently removed the released CP/Mn-PBA DSNBs by using magnetic separation. The CP/Mn-PBA DSNBs exhibited high photoreactivity and photothermal conversion efficiency under near-infrared (NIR) light, leading to temperature variations under 808 nm irradiation, correlating with different exosome concentrations. Additionally, colorimetric detection was achieved by monitoring the color change in a 3,3',5,5'-tetramethylbenzidine (TMB) system, facilitated by PEI modification, NIR-enhanced peroxidase-like activity of CP/Mn-PBA DSNBs and their capacity to generate Cu2+ and H2O2 under acidic conditions. Moreover, in the presence of Cu2+ and ascorbic acid (AA), DNA sequences could form dsDNA-templated copper nanoparticles (CuNPs), which emitted strong fluorescence at around 575 nm. Increasing exosome concentrations correlated with decreases in temperature, absorbance, and fluorescence intensity. This trimode biosensor demonstrated satisfactory ability in differentiating gastric cancer patients from healthy individuals using human serum samples.

Nanoplasmonic biosensors for multicolor visual analysis of acetylcholinesterase activity and drug inhibitor screening in point-of-care testing

The monitoring of acetylcholinesterase (AChE) activity and the screening of its inhibitors are significance of the diagnosis and drug therapy of nervous diseases. A metal ions-mediated signal amplification strategy was developed for the highly sensitive and multicolor assay of AChE activity and visually screening its drug inhibitors. After the specific reaction between AChE and acetylthiocholine (ATCh), the hydrolysis product thiocholine (TCh) can directly and decompose the α-FeOOH nanorods (NRs) to release amounts of Fe2+, which was regarded as Fenton reagent to efficiently catalyze H2O2 to produce ·OH. Then, the as-formed ·OH can further largely shorten the gold nanobipyramids (Au NBPs), generating a series of palpable color variations. The linear range for AChE activity was 0.01-500.0 U/L with the limit of detection as low as 0.0074 U/L. The vivid visual effects could be easily distinguished for the multicolor assay of AChE activity by naked eye in visible light. To achieve the point-of-care testing, Au NBPs were further assembled on polymeric electrospun nanofibrous films (ENFs) surface as test strips for the easy-to-use test of AChE activity by RGB values with a smartphone. Fascinatingly, this proposed strategy can be used for the visual screening AChE inhibitors or non-inhibitors. Comparing with the clinical drugs (rivastigmine tartrate, and donepezil), some natural alkaloids such as evodiamine, caffeine, camptothecin, and berberine hydrochloride were selected as inhibitor modes to confirm the drug screening capability of this method. This proposed strategy may have great potential in the other disease-related enzymatic biomarkers assay and the rapid screening of drug therapy.

Biomolecule-functionalized nanoformulations for prostate cancer theranostics

BACKGROUND

Even with the advancement in the areas of cancer nanotechnology, prostate cancer still poses a major threat to men's health. Nanomaterials and nanomaterial-derived theranostic systems have been explored for diagnosis, imaging, and therapy for different types of cancer still, for prostate cancer they have not delivered at full potential because of the limitations like in vivo biocompatibility, immune responses, precise targetability, and therapeutic outcome associated with the nanostructured system.

AIM OF REVIEW

Functionalizing nanomaterials with different biomolecules and bioactive agents provides advantages like specificity towards cancerous tumors, improved circulation time, and modulation of the immune response leading to early diagnosis and targeted delivery of cargo at the site of action.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we have emphasized the classification and comparison of various nanomaterials based on biofunctionalization strategy and source of biomolecules such that it can be used for possible translation in clinical settings and future developments. This review highlighted the opportunities for embedding highly specific biological targeting moieties (antibody, aptamer, oligonucleotides, biopolymer, peptides, etc.) on nanoparticles which can improve the detection of prostate cancer-associated biomarkers at a very low limit of detection, direct visualization of prostate tumors and lastly for its therapy. Lastly, special emphasis was given to biomimetic nanomaterials which include functionalization with extracellular vesicles, exosomes and viral particles and their application for prostate cancer early detection and drug delivery. The present review paves a new pathway for next-generation biofunctionalized nanomaterials for prostate cancer theranostic application and their possibility in clinical translation.

Recent Development of Polymer Nanofibers in the Field of Optical Sensing

In recent years, owing to the continuous development of polymer nanofiber manufacturing technology, various nanofibers with different structural characteristics have emerged, allowing their application in the field of sensing to continually expand. Integrating polymer nanofibers with optical sensors takes advantage of the high sensitivity, fast response, and strong immunity to electromagnetic interference of optical sensors, enabling widespread use in biomedical science, environmental monitoring, food safety, and other fields. This paper summarizes the research progress of polymer nanofibers in optical sensors, classifies and analyzes polymer nanofiber optical sensors according to different functions (fluorescence, Raman, polarization, surface plasmon resonance, and photoelectrochemistry), and introduces the principles, structures, and properties of each type of sensor and application examples in different fields. This paper also looks forward to the future development directions and challenges of polymer nanofiber optical sensors, and provides a reference for in-depth research of sensors and industrial applications of polymer nanofibers.

Sensitive determination of prostate-specific antigen with graphene quantum dot-based fluorescence aptasensor using few-layer V2CTx MXene as quencher

A novel fluorescence aptasensor of prostate-specific antigen (PSA) was established using few-layer vanadium carbide (FL-V₂CT_x) nanosheet as a quencher. First, FL-V₂CT_x was prepared by the delamination of multi-layer V₂CT_x (ML-V₂CT_x) with tetramethylammonium hydroxide. The aptamer-carboxyl graphene quantum dots (CGQDs) probe was prepared by combining the aminated PSA aptamer and CGQDs. Then, the aptamer-CGQDs were absorbed onto the surface of FL-V₂CT_x by hydrogen bond interaction, which led to the decrease in fluorescence of aptamer-CGQDs due to photoinduced energy transfer. After addition of PSA, PSA-aptamer-CGQDs complex was released from FL-V₂CT_x. The fluorescence intensity of aptamer-CGQDs-FL-V₂CT_x with PSA was higher than that without PSA. The FL-V₂CT_x-based fluorescence aptasensor provided a PSA detection linear range from 0.1 to 20 ng mL^-1 with detection limit of 0.03 ng mL^-1. The ΔF value of fluorescence intensities for aptamer-CGQDs-FL-V₂CT_x with and without PSA was 5.6, 3.7, 7.7, and 5.4 times of ML-V₂CT_x, few-layer titanium carbide (FL-Ti₃C₂T_x), ML-Ti₃C₂T_x and graphene oxide aptasensors, respectively, indicating the advantage of FL-V₂CT_x. The aptasensor had high selectivity for PSA detection compared with some proteins and tumor markers. This proposed method had convenience and high sensitivity for PSA determination. The determination results of PSA in human serum samples using the aptasensor were consistent with those by chemiluminescent immunoanalysis. The fluorescence aptasensor can be successfully applied for PSA determination in serum samples of prostate cancer patients.

High-Luminescence Electrospun Polymeric Microfibers In Situ Embedded with CdSe Quantum Dots with Excellent Environmental Stability for Heat and Humidity Wearable Sensors

In this paper, hydrophobic luminescent CdSe quantum dots are successfully dispersed in a mixture of styrene and methyl methacrylate through the oleic to methacrylic acid ligand exchange. Further in situ solution polymerization of the quantum dots in a mixture of styrene and methyl methacrylate followed by electrospinning allowed us to prepare luminescence hybrid styrene-co-methyl methacrylate fibers embedded with quantum dots. CdSe@P(S+MMA) hybrid fibers with 27% quantum yield showed excellent moisture, heat and salt resistance with a photoluminescence output below 120 °C. When dry heated, the hybrid fibers of the fluorescence signals decreased with temperature to 79%, 40%, 28%, 20% and 13% at 120 °C, 140 °C, 160 °C, 180 °C and 200 °C, respectively, due the to the chemical degradation of CdSe QDs. Such hybrid fibers show the potential to manufacture wearable moisture- and heat-sensing protective clothing in a 120–200 °C range due to the thermal-induced quenching of quantum dot photoluminescence.

Sensitive and selective "signal-off" electrochemiluminescence sensing of prostate-specific antigen based on an aptamer and molecularly imprinted polymer

Specific and sensitive determination of prostate-specific antigen (PSA) in complex real samples holds significant importance as it is an effective molecular biomarker for the clinical diagnosis of prostate cancer. Herein, we constructed a dual-recognition electrochemiluminescence (ECL) sensor based on both the recognition elements of an aptamer and molecularly imprinted polymers (MIP) for the selective and ultrasensitive determination of PSA. The aptamer was self-assembled on gold nanoparticle (AuNP) modified electrodes through Au-S bonds. Subsequently, a layer of MIP membrane was synthesized by electropolymerization of dopamine (DA) to fabricate an aptamer-MIP sensor. After the rebinding of PSA onto imprinted cavities, the ECL response of luminol in the solution decreased. This "signal-off" strategy was employed for PSA detection with a wide linear range and a low limit of detection of 5 pg mL^-1-50 ng mL^-1 and 3.0 pg mL^-1, respectively. Compared with individual aptamer sensors, the dual-recognition sensor showed higher specific recognition ability for the determination of PSA. Meanwhile, the good stability, reproducibility, and regenerability endowed the dual recognition sensor with favorable application value in early clinical diagnosis.

A single nucleotide polymorphism electrochemical sensor based on DNA-functionalized Cd-MOFs-74 as cascade signal amplification probes

An ultrasensitive electrochemical sensor has been constructed for the detection of single nucleotide polymorphisms (SNPs) based on DNA-functionalized Cd-MOFs-74 as cascade signal amplification probe under enzyme-free conditions. Interestingly, the introduction of an auxiliary probe did not disturb the detection of SNP targets, but could bind more Cd-MOFs-74 signal elements to enhance the different pulse voltammetry electrochemical signal 2~3 times as compared to sensing system without auxiliary probe, which obviously improves the sensitivity of the proposed sensor. Experimental results taking p53 tumor suppressor gene as SNP model demonstrated that the proposed method can be employed to sensitively and selectively detect target p53 gene fragment with a linear response ranging from 0.01 to 30 pmol/L (detection limit of 6.3 fmol/L) under enzyme-free conditions. Utilizing this strategy, the ultrasensitive SNP electrochemical sensor is a promising tool for the determination  of SNPs in biomedicine. Graphical Abstract.

Aptamer-based fluorescent sensors for the detection of cancer biomarkers

Aptamers are short single-stranded RNA or DNA molecules that can recognize a series of targets with high affinity and specificity. Known as "chemical antibodies", aptamers have many unique merits, including ease of chemical synthesis, high chemical stability, low molecular weight, lack of immunogenicity, and ease of modification and manipulation compared to their protein counterparts. Using aptamers as the recognition groups, fluorescent aptasensors provide exciting opportunities for sensitive detection and quantification of analytes. Herein, we give an overview on the recent development of aptamer-based fluorescent sensors for the detection of cancer biomarkers. Based on various nanostructured sensor designs, we extended our discussions on sensitivity, specificity and the potential applications of aptamer-based fluorescent sensors in early diagnosis, treatment and prognosis of cancers.

A Comprehensive Review of the Covalent Immobilization of Biomolecules onto Electrospun Nanofibers

Biomolecule immobilization has attracted the attention of various fields such as fine chemistry and biomedicine for their use in several applications such as wastewater, immunosensors, biofuels, et cetera. The performance of immobilized biomolecules depends on the substrate and the immobilization method utilized. Electrospun nanofibers act as an excellent substrate for immobilization due to their large surface area to volume ratio and interconnectivity. While biomolecules can be immobilized using adsorption and encapsulation, covalent immobilization offers a way to permanently fix the material to the fiber surface resulting in high efficiency, good specificity, and excellent stability. This review aims to highlight the various covalent immobilization techniques being utilized and their benefits and drawbacks. These methods typically fall into two categories: (1) direct immobilization and (2) use of crosslinkers. Direct immobilization techniques are usually simple and utilize the strong electrophilic functional groups on the nanofiber. While crosslinkers are used as an intermediary between the nanofiber substrate and the biomolecule, with some crosslinkers being present in the final product and others simply facilitating the reactions. We aim to provide an explanation of each immobilization technique, biomolecules commonly paired with said technique and the benefit of immobilization over the free biomolecule.

Lab-on-Membrane Platform Coupled with Paper Spray Ionization for Analysis of Prostate-Specific Antigen in Clinical Settings

The analysis of protein antigens as biomarkers in clinical samples is particularly helpful for the early diagnosis of diseases. However, this is difficult to accomplish owing to the presence of the antigens in trace amounts as well as the complexity of the matrixes in clinical samples. In this study, a lab-on-membrane platform that can be combined with paper spray ionization mass spectrometry was developed for the in situ high-throughput sensitive detection of the prostate-specific antigen (PSA). The sensitivity of the proposed platform was enhanced via two strategies: (1) the synthesis of a biotin-streptavidin scaffold caused an increase in the capturing efficiency of PSA by a factor of 5 and (2) the immobilization of a large number of mass tag molecules on the gold nanoparticles allowed for the amplification of the mass spectrometry signals. The limit of detection was approximately 3.0 pg mL^-1. The selectivity to PSA was guaranteed by using an antibody-aptamer pairing sandwich immunoassay, and PSA detection was unaffected even when other protein antigens (carcinoembryonic antigen and carbohydrate antigen 125) were present. The modified membranes maintained their performance for at least 30 days when stored at 4 °C. Finally, analysis of human serum samples confirmed that the PSA concentration as determined using the proposed platform was consistent with that determined with a conventional chemiluminescent immunoassay. Thus, this PSA analyzing platform is suitable for prostate cancer diagnosis in clinical settings.

Recent advances in optical aptasensor technology for amplification strategies in cancer diagnostics

Aptamers are chemically synthetic single-stranded DNA or RNA molecules selected by molecular evolution. They have been widely used as attractive tools in biosensing and bioimaging because they can bind to a large variety of targets with high sensitivity and high affinity and specificity. As recognition elements, aptamers contribute in particular to cancer diagnostics by recognizing different cancer biomarkers, while they can also facilitate ultrasensitive detection by further employing signal amplification elements. Optical techniques have been widely used for direct and real-time monitoring of cancer-related biomolecules and bioprocesses due to the high sensitivity, quick response, and simple operation, which has greatly benefited cancer diagnostics. In this review, we highlight recent advances in optical platform-based sensing strategies for cancer diagnostics aided by aptamers. Limitations and current challenges are also discussed.

A promising approach toward efficient isolation of the exosomes by core-shell PCL-gelatin electrospun nanofibers

Exosomes as cell-derived vesicles are promising biomarkers for noninvasive and early detection of different types of cancer. However, a straightforward and cost-effective technique for isolation of exosomes in routine clinical settings is still challenging. Herein, we present for the first time, a novel coaxial nanofiber structure for the exosome isolation from body fluids with high efficiency. Coaxial nanofiber structure is composed of polycaprolactone polymer as core and a thin layer of gelatin (below 10 nm) as the shell. The thermo-sensitive thin layer of gelatin can efficiently release the captured exosome by specific antibody namely, CD63, whenever its temperature raised to the physiological temperature of 37 °C. Moreover, the thin layer of gelatin induces less contamination to separated exosomes. The interconnected micro-pores of electrospun nanofibrous membrane insurances large surface area for immobilization of specific antibody for efficient exosome capturing. The efficacy of exosome isolation is determined by direct ELISA and compared with ultracentrifugation technique. For the exosome isolation, it was observed that over 87% of exosomes existed in the culture medium can be effectively isolated by coaxial electrospun nanofibers with the average thickness of 50 µm. Therefore, this promising technique can be substituted for the traditional techniques for exosome isolation which are mostly suffering from low efficacy, high cost, and troublesome process.

Carbon dots and AuNCs co-doped electrospun membranes for ratiometric fluorescent determination of cyanide

Due to the extremely toxic nature of cyanide, the World Health Organization (WHO) has set 1.9 μM as the maximum acceptable level in drinking water. Therefore, methods for facile screening and on-site detection of cyanide is urgently needed. In this work, a ratiometric fluorescent method for cyanide detection was developed based on blue-emitting carbon dots (CDs) and red-emitting AuNCs. To suit an on-site detection, the two fluorophores were incorporated into a nanofibrous membrane through electrospinning, yielding the core-shell structure of CDs/AuNCs-PVA@CA. Upon reaction with cyanide, the red fluorescence of AuNCs was quenched but the blue fluorescence of CDs was retained, resulting in ratiometric fluorescence change. Besides, both CDs and AuNCs can be excited with a handheld UV lamp (365 nm), and the resultant visible fluorescence color change could be visualized with naked eye. The proposed ratiometric method provided a limit of detection (LOD) 0.15 μM for cyanide, which was far lower than 1.9 μM. The membrane was further employed for screening analysis of cyanide in tap water samples. After collection of 500 analytical results, only 5.6% of the results located outside the X¯±2s criteria, while for the X¯±3s criteria, there is no outlier. The statistical results indicated that the proposed method may be potentially useful for screening analysis of cyanide in water samples.

Noble Metal Nanostructured Materials for Chemical and Biosensing Systems

Nanomaterials with unique physical and chemical properties have attracted extensive attention of scientific research and will play an increasingly important role in the future development of science and technology. With the gradual deepening of research, noble metal nanomaterials have been applied in the fields of new energy materials, photoelectric information storage, and nano-enhanced catalysis due to their unique optical, electrical and catalytic properties. Nanostructured materials formed by noble metal elements (Au, Ag, etc.) exhibit remarkable photoelectric properties, good stability and low biotoxicity, which received extensive attention in chemical and biological sensing field and achieved significant research progress. In this paper, the research on the synthesis, modification and sensing application of the existing noble metal nanomaterials is reviewed in detail, which provides a theoretical guidance for further research on the functional properties of such nanostructured materials and their applications of other nanofields.

Electrochemical detection of C-reactive protein using functionalized iridium nanoparticles/graphene oxide as a tag

C-reactive protein (CRP) has become a recognized indicator of inflammation. CRP concentration in serum is an important indicator for monitoring early heart damage, and it is also a newly discovered coronary heart disease-associated inflammatory factor. A conductive nano-hybrid material composed of Au NPs and ionic liquid functionalized molybdenum disulfide (Au NPs/IL-MoS₂) was prepared and utilized to immobilize primary CRP antibodies. Subsequently, 1,5-diaminonaphthalene (DN) was adsorbed onto graphene oxide (GO) through π–π stacking, which was used to load iridium nanoparticles (Ir NPs) as a tag to label secondary CRP antibodies. The large surface area of Au NPs/IL-MoS₂ and the excellent electrocatalytic properties of Ir NPs/GO-DN toward the reduction of H₂O₂ resulted in a highly sensitive assay for CRP antigens. This immunosensor exhibited wide linear ranges from 0.01 to 100 ng mL⁻¹ and a lower detection of limit of 3.3 pg mL⁻¹ (S/N = 3). This CRP immunosensor can be applied in real serum sample analysis with satisfactory results, indicating that the immunosensor has potential applications in biomedical detection.

Ir NPs@GO-DN was used as a tag to label CRP antibody to construct a sandwich CRP immunosensor.

One-step sensitive thrombin detection based on a nanofibrous sensing platform

Convenient and time-saving one-step strategies for detecting ultralow concentrations of protein biomarkers play key roles in rapid disease diagnosis. In this study, we report a one-step detection method based on a nanofibrous sensing platform via the combination of proximity-induced DNA strand displacement (PiDSD), catalytic hairpin assembly (CHA) amplification and thioflavin T (ThT) binding. The interface behaviors on the nanofibrous membrane were studied to promote interface reaction kinetics and thermodynamics. Thrombin was used as a model biomarker, and the nanofibrous sensing platform achieved a limit of detection as low as 1.0 pM, a wide linear range of 50 pM to 5 nM, excellent specificity and good long-term stability. Compared with previous one-step thrombin detection methods, our one-step detection method is label-free, convenient and much more sensitive; it has potential applications for protein detection in point-to-care testing (POCT) and early diagnosis.

Application of various optical and electrochemical aptasensors for detection of human prostate specific antigen: A review

Early stage detection of prostate cancer, one of the main causes of mortality among men, is of great importance for better treatment of the patients. Prostate specific antigen (PSA) is a glycoprotein which has been considered as the most potential serological biomarker for the detection of prostate cancer. Among the various techniques employed for PSA detection, aptamer-based biosensors (aptasensors) have achieved notable attention because of their unique features and great potentials as diagnostic tools. A variety of strategies such as integration of nanomaterials (NMs) into the structure of aptasensors have also been applied for enhancing the sensitivity of PSA detection. This article reviews recent advances in various optical and electrochemical aptasensors used for PSA detection.

Fluorometric nanoprobes for simultaneous aptamer-based detection of carcinoembryonic antigen and prostate specific antigen

A "turn-on" fluorometric assay based on the combined effects of fluorescence resonance energy transfer (FRET) and internal filter effect (IFE) is described for the rapid and ultrasensitive detection of both carcinoembryonic antigen (CEA) and prostate specific antigen (PSA). Their unique porous structures and high specific surface enable mesoporous silica nanoparticles (MSNs) to load a large number of CdTe quantum dots (QDs). These amplify the fluorescence signal and provide a platform to fabricate more distinctly fluorescent MSNs (QD-MSNs). Two kinds of QD-MSNs with the maximum emission wavelengths at 590 nm (orange) and 731 nm (dark red) were fabricated and served as two types of fluorescent probes for the dual detection. Two aptamers were covalently connected to fluorescent MSNs as the recognition unit to warrant the selectivity of assay. The fluorescence of QD-MSNs can be quenched by molybdenum disulfide nanosheets (MoS₂) due to FRET mechanism, IFE also contributed to the the reduction of fluorescence intensity. The fluorescence of QD-MSNs was further recovered in the presence of CEA and PSA attributing to the excellent specificity of aptamers. A "turn-on" fluorescent two-channel nanoprobe is introduced for simultaneous quantification of CEA and PSA. The respective limits of detection (at S/N = 3) are 0.7 fg•mL^-1 for CEA and 0.9 fg•mL^-1 for PSA. Graphical abstract Schematic presentation of the turn-on fluorescent nanoprobes for simultaneous detection of CEA and PSA.

Nanofiber-integrated miniaturized systems: an intelligent platform for cancer diagnosis

Cancer diagnostic tools enabling screening, diagnosis, and effective disease management are essential elements to increase the survival rate of diagnosed patients. Low abundance of cancer markers present in large amounts of interferences remains the major issue. Moreover, current diagnostic technologies are restricted to high-resourced settings only. Integrating nanofibers into miniaturized analytical systems holds a significant promise to address these challenges as demonstrated by recent publications. A large surface area, three-dimensional porous network, and diverse range of functional chemistries make nanofibers an excellent candidate as immobilization support and/or transduction elements, enabling high capture yield and ultrasensitive detection in miniaturized devices. Functional nanofibers have thus been used to isolate and detect various cancer-related biomarkers with a high degree of success in both on-chip and off-chip platforms. In fact, the chemical and functional adaptability of nanofibers has been exploited to address the technical challenges unique to each of the cancer markers in body fluids, where circulating tumor cells are prominently investigated among others (proteins, nucleic acids, and exosomes). So far, none of the work has exploited the nanofibers for cancer-derived exosomes, opening an avenue for further research effort. The trend and future prospects signal possibilities to strengthen the implementation of nanofiber-miniaturized system hybrid for a next generation of cancer diagnostic platforms both in clinical and point-of-care testing.

Ag/CdO NP-Engineered Magnetic Electrochemical Aptasensor for Prostatic Specific Antigen Detection

A simple magnetic electrochemical aptasensor was established for the detection of prostatic specific antigen (PSA). Ag/CdO nanoparticles (NPs) were fabricated and exhibited strong electroreduction peaks at -1.07 V, attributing to the electron transfer from Cd²⁺ to Cd⁰ and the superior electron transportation of Ag. Aptamer-modified Ag/CdO NPs were assembled on the surface of superparamagnetic Fe₃O₄/graphene oxide nanosheets (GO/Fe₃O₄ NSs) through the hydrophobic and π-π stacking interaction of aptamers and GO NSs. These assemblies possessed superior electroactive properties, efficient electron transfer, and superparamagnetic response and could serve as sensing units for PSA detection with the aid of a magnetic electrode. With increasing concentrations of PSA, the high affinity of aptamers to PSA enabled the dissociation of Ag/CdO NPs from GO/Fe₃O₄ NSs, decreasing the intensity of electroreduction peaks. The Ag/CdO NP-engineered magnetic electrochemical aptasensor achieved sensitive and accurate detection of PSA in the range of 50 pg/mL to 50 ng/mL. The limit of detection (LOD) was as low as 28 pg/mL. This developed protocol can be extended to a large set of strong electroactive labels for reliable tumor biomarker detection with high sensitivity and specificity.

Hybridization induced fluorescence enhanced DNA-Ag nanocluster/aptamer probe for detection of prostate-specific antigen

In this work, a label-free Ag nanocluster (AgNC)-based fluorescent probe is proposed to detect tumor marker, prostate-specific antigen (PSA). In the experiments, DNA sequences containing segments complemented to different parts of PSA aptamer were used to synthesize DNA-Ag nanoclusters (DNA-AgNC). Some of the obtained specific DNA-AgNC exhibited significant fluorescence increase after hybridization with PSA aptamer. Based on this, a simple DNA-AgNC/aptamer hybridization probe was fabricated for PSA detection using fluorescence quenching, because competitively specific binding between PSA and its aptamer inhibited the fluorescence enhancement effect of PSA aptamer on DNA-AgNC. The sequence of template DNA, pH and salt concentration of binding buffer, and the concentration of aptamer were optimized. Under optimum conditions, the concentration of PSA within the range of 2-150 ng mL^-1 with the detection limit of 1.14 ng mL^-1 was detected (3σ; n = 7). This approach was also successfully applied to determine PSA in spiked serum samples. As is well known, this was the first report to realize PSA detection using fluorescent AgNC-based probe. This work would provide reference for construction of AgNC-based probes for detecting other proteins.

Graphitic C3N4 nanosheet and hemin/G-quadruplex DNAzyme-based label-free chemiluminescence aptasensing for biomarkers

Here we first reported that graphitic carbon nitride nanosheet (g-C₃N₄ NS) could effectively quench the chemiluminescence (CL) of luminol-hydrogen peroxide (H₂O₂) system. According to the new discovery, a label-free and homogeneous CL aptasensing platform was designed for sensitive detecting of biomarkers. In the absence of target, DNA probe containing hemin/G-quadruplex DNAzyme structure was adsorbed on the surface of g-C₃N₄ NS, causing the CL quenching of luminol through an electron transfer process. However, in the presence of the target, a DNA-DNA duplex was formed due to DNA hybridization reaction and target recognition effect, which could not be adsorbed onto the g-C₃N₄ NS surface because of its weak affinity. Thus, the electron transfer was blocked and the CL emission of luminol could be enhanced. The proposed CL aptasensor could detect carcinoembryonic antigen (CEA) with a detection limit of 63.0 pg/mL and it can also be used as a general detecting strategy for adenosinetriphosphate (ATP) detection. This aptasensing platform exhibited high sensitivity toward biomarkers and the probe need not be labeled, showing great promise for disease diagnosis.

Highly Selective, Naked-Eye, and Trace Discrimination between Perfect-Match and Mismatch Sequences Using a Plasmonic Nanoplatform

A plasmonic nanoplatform to perform an enzyme-free, naked-eye, and trace discrimination of single-base mutation from fully matched sequence is reported. The nanoplatform showed great potential to enhance catalytic hairpin assembly (CHA) amplification efficiency and biocatalytic activity of hemin/G-quadruplex (DNAzyme). When human immunodeficiency virus (HIV) DNA biomarker was used as the model analyst, a naked-eye detection with high selectivity and high sensitivity down to 10^-17 M in whole serum was achieved by observing red-to-blue color change. Single-base mismatch and two-base mismatch were detected at the low concentrations of 10^-11 and 10^-8 M, respectively. The naked-eye detection based on the enzyme-free plasmonic nanoplatform is expected to have potential applications ranging from quick detection and early diagnostics to point-of-care research.

Engineered Healing of Avascular Meniscus Tears by Stem Cell Recruitment

Meniscus injuries are extremely common with approximately one million patients undergoing surgical treatment annually in the U.S. alone. Upon injury, the outer zone of the meniscus can be repaired and expected to functionally heal but tears in the inner avascular region are unlikely to heal. To date, no regenerative therapy has been proven successful for consistently promoting healing in inner-zone meniscus tears. Here, we show that controlled applications of connective tissue growth factor (CTGF) and transforming growth factor beta 3 (TGFβ3) can induce seamless healing of avascular meniscus tears by inducing recruitment and step-wise differentiation of synovial mesenchymal stem/progenitor cells (syMSCs). A short-term release of CTGF, a selected chemotactic and profibrogenic cue, successfully recruited syMSCs into the incision site and formed an integrated fibrous matrix. Sustain-released TGFβ3 then led to a remodeling of the intermediate fibrous matrix into fibrocartilaginous matrix, fully integrating incised meniscal tissues with improved functional properties. Our data may represent a novel clinically relevant strategy to improve healing of avascular meniscus tears by recruiting endogenous stem/progenitor cells.