Mannosyl electrochemical impedance cytosensor for label-free MDA-MB-231 cancer cell detection

Visual Detection of LPS at the Femtomolar Level Based on Click Chemistry-Induced Gold Nanoparticles Electrokinetic Accumulation

Lipopolysaccharide (LPS) presents a significant threat to human health. Herein, a novel method for detecting LPS was developed by coupling hybridization chain reaction (HCR), gold nanoparticles (AuNPs) agglutination (AA) triggered by a Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry (CuAAC), and electrokinetic accumulation (EA) in a microfluidic chip, termed the HCR-AA-EA method. Thereinto, the LPS-binding aptamer (LBA) was coupled with the AuNP-coated Fe3O4 nanoparticle, which was connected with the polymer of H1 capped on CuO (H1-CuO) and H2-CuO. Upon LPS recognition by LBA, the polymers of H1- and H2-CuO were released into the solution, creating a "one LPS-multiple CuO" effect. Under ascorbic acid reduction, CuAAC was initiated between the alkyne and azide groups on the AuNPs' surface; then, the product was observed visually in the microchannel by EA. Finally, LPS was quantified by the integrated density of AuNP aggregates. The limit of detections were 29.9 and 127.2 fM for water samples and serum samples, respectively. The levels of LPS in the injections and serum samples by our method had a good correlation with those from the limulus amebocyte lysate test (r = 0.99), indicating high accuracy. Remarkably, to popularize our method, a low-cost, wall-power-free portable device was developed, enabling point-of-care testing.

Surface-Controlled Sialoside-Based Biosensing of Viral and Bacterial Neuraminidases

Neuraminidases (NA) are sialic acid-cleaving enzymes that are used by both bacteria and viruses. These enzymes have sialoside structure-related binding and cleaving preferences. Differentiating between these enzymes requires using a large array of hard-to-access sialosides. In this work, we used electrochemical impedimetric biosensing to differentiate among several pathogene-related NAs. We used a limited set of sialosides and tailored the surface properties. Various sialosides were grafted on two different surfaces with unique properties. Electrografting on glassy carbon electrodes provided low-density sialoside-functionalized surfaces with a hydrophobic submonolayer. A two-step assembly on gold electrodes provided a denser sialoside layer on a negatively charged submonolayer. The synthesis of each sialoside required dozens of laborious steps. Utilizing the unique protein-electrode interaction modes resulted in richer biodata without increasing the synthetic load. These principles allowed for profiling NAs and determining the efficacy of various antiviral inhibitors.

Synthesis of a Multifunctional Glyco-Block Copolymer through Reversible Addition-Fragmentation Chain Transfer Polymerization and Click Chemistry for Enzyme and Drug Loading into MDA-MB-231 Cells

Reversible addition-fragmentation chain transfer polymerization has been used in various applications such as preparing nanoparticles, stimulus-responsive polymers, and hydrogels. In this study, the combination of this polymerization method and Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry was used to prepare the multifunctional glyco-diblock copolymer P(PEG-co-AM)-b-PF, which is composed of mannosides for cell targeting, poly(ethylene glycol) (PEG) for biocompatibility, and aryl-aldehyde moieties for enzyme immobilization. The alkyne group in the polymer structure enables the alternation for other azide-conjugated monomers. The stepwise synthesis of the polymers was fully characterized. P(PEG-co-AM)-b-PF was self-assembled into polymeric nanoparticles (BDOX-GOx@NPs) for glucose oxidase immobilization through Schiff base formation and for encapsulating the prodrug of arylboronate-linked doxorubicin (BA-DOX) under optimal conditions. Glucose oxidase in BDOX-GOx@NPs catalyzes glucose oxidation to produce gluconic acid and H2O2, which cause oxidative stress. Glucose oxidase also consumes glucose, causing starvation in cancer cells. The produced H2O2 can selectively activate the anticancer prodrug BA-DOX for chemotherapy. In vitro data indicate that GOx and the prodrug BA-DOX present inside BDOX-GOx@NPs exhibit higher stability than free glucose oxidase with a favorable active DOX release profile. MDA-MB-231 cells, which express mannose receptors, were used to establish a model in this study. The bioactivity of the nanoplatform in the two- and three-dimensional models of MDA-MB-231 cancer cells was investigated to ascertain its antitumor efficacy.

Fabrication of a reusable electrochemical platform based on acid-responsive host-guest interaction with β- cyclodextrin

A reusable electrochemical glassy carbon electrode (GCE) platform based on the acid-responsive host-guest interaction between β-cyclodextrin (β-CD) and benzimidazole (BM) derivatives was developed. The β-CD can specifically recognize the BM derivative through the acid -responsive host-guest interaction. The electrode was first modified by eletrografting to immobilize a diamine linker (Boc-EDA), resulting in GCEBoc-EDA in which one amine was used for covalent immobilization to the electrode and another Boc protected amine was used to solid-phase synthesis on following step-by-step modifications on the electrode. After deprotection of the Boc group on the GCEBoc-EDA, carbonyldiimidazole (CDI)-activated β-CD was coupled with -NH2 on the electrode to result in GCEβ-CD. Due to the nonspecific interaction, we further improved the GCEβ-CD electrode by introducing immobilized poly(ethylene glycol) methyl ether (PEG-Me) to result in GCEβ-CD/PEG-Me, along with optimized procedures. CV, DPV, and EIS methods were applied for recording the electrochemistry signals. We utilized GCEβ-CD/PEG-Me to investigate the host-guest interaction and found the electrochemical signal exhibited dynamic behavior. The GCEβ-CD/PEG-Me was able to regenerate the β-CD surface more than 20 times after HCl acidic washes. We further investigated the interaction of carbendazim (CBZ), a commonly used fungicide in the agriculture and food industry, and observed a positive electrochemical response. The sensor design has potential applications in ensuring food safety.

Induced ultrasensitive electrochemical biosensor for target MDA-MB-231 cell cytoplasmic protein detection based on RNA-cleavage DNAzyme catalytic reaction

Herein, we implemented RNA-cleaving DNAzymes specific for the endogenous protein of breast cancer cells (MDA-MB -231) and programmed for electrochemical detection. Thionine-modified gold nanoparticles and modified magnetic nanoparticles are attached to the two ends of the DNAzyme molecule. The prepared probe is pulled to the surface of the electrode with the help of a magnetic field, and the signal caused by the electrochemical activity of thionine is observed on the surface of the electrode. The presence of a covalent gold nanoparticle-thionine hybrid as a highly electroactive/enhanced electrochemical label ensures a strong detection signal. After addition of the enzyme activator cofactor (MDA-MB -231 cytoplasmic cell protein), it reacts with the catalytic core of the enzyme sequence in the DNAzyme molecule and triggers the cleavage reaction in the substrate sequence of the DNAzyme molecule. During this process, the gold nanoparticle-thionine labels are detached from the probe and released into the solution. Inductive removal of gold nanoparticles leads to a decrease in the current related to the reduction of thionine on the electrode surface. The results show that this biosensor can detect this protein marker in the linear range of (1.0E-06 to 1.0E+01) pg/ml, with a detection limit (1.0129E-07 pg/ml), using differential pulse voltammetry as a measuring technique. As well as, electrochemical impedance spectroscopy (EIS).

Biocatalysis versus Molecular Recognition in Sialoside-Selective Neuraminidase Biosensing

Sialic acid recognition and hydrolysis are essential parts of cellular function and pathogen infectivity. Neuraminidases are enzymes that detach sialic acid from sialosides, and their inhibition is a prime target for viral infection treatment. The connectivity and type of sialic acid influence the recognition and hydrolysis activity of the many different neuraminidases. The common strategies to evaluate neuraminidase activity, recognition, and inhibition rely on extensive labeling and require a large amount of sialylated glycans. The above limitations make the effort of finding viral inhibitors extremely difficult. We used synthetic sialylated glycans and developed a label-free electrochemical method to show that sialoside structural features lead to selective neuraminidase biosensing. We compared Neu5Ac to Neu5Gc sialosides to evaluate the organism-dependent neuraminidase selectivity-sensitivity relationship. We demonstrated that the type of surface and the glycan monolayer density direct the response to either binding or enzymatic activity. We proved that while the hydrophobic glassy carbon surface increases the interaction with the enzyme hydrophobic interface, the negatively charged interface of the lipoic acid monolayer on gold repels the protein and enables biocatalysis. We showed that the sialoside monolayers can serve as tools to evaluate the inhibition of neuraminidases both by biocatalysis and molecular recognition.

A novel highly sensitive compilation-detachment fluorescence sensing strategy based on RNA-cleavage DNAzyme for MDA-MB-231 breast cancer biomarker determination

Herein, we designed a novel and highly sensitive fluorescence multicomponent detachable platform for MDA-MB-231 breast cancer cell detection as a model. The RNA cleavage DNAzyme was used as a central operator of the multicomponent probe through which compilation and induced detachment of probe was done. During the compilation step, the dsDNA-Sybr green 1 complexes on gold nanoparticles (GNP@dsDNA@SG1) were assembled. The intercalated Sybr green in the DNA structure has been used as an amplified signal generator on one site of DNAzyme and magnetic nanoparticles (MNP) act as a biological carrier and probe collector on the opposite side. The enzyme activator co-factor (MDA-MB-231 cell cytoplasmic protein) provokes the activation of the catalytic core of enzyme sequence in the DNAzyme molecule, followed by cleavage reaction in the substrate sequence and releasing GNP@ dsDNA@SG1 into the solution. The results indicate that the Sybr green emission fluorescence (520 nm) increases with the increment of MDA-MB-231 protein concentration in the linear dynamic range of 8.10 × 10^-2 to 1.95 ng ml^-1 (0.77 × 10^-3-0.019 cell ml^-1) with a detection limit (LOD) of 1/72 × 10^-2 pg ml^-1 under optimal conditions. The proposed immunosensor has great potential in developing ultrasensitive and rapid diagnostic platforms.

AuAg nanocomposites suppress biofilm-induced inflammation in human osteoblasts

Staphylococcus aureus (S. aureus)forms biofilm that causes periprosthetic joint infections and osteomyelitis (OM) which are the intractable health problems in clinics. The silver-containing nanoparticles (AgNPs) are antibacterial nanomaterials with less cytotoxicity than the classic Ag compounds. Likewise, gold nanoparticles (AuNPs) have also been demonstrated as excellent nanomaterials for medical applications. Previous studies have showed that both AgNPs and AuNPs have anti-microbial or anti-inflammatory properties. We have developed a novel green chemistry that could generate the AuAg nanocomposites, through the reduction of tannic acid (TNA). The bioactivity of the nanocomposites was investigated inS. aureusbiofilm-exposed human osteoblast cells (hFOB1.19). The current synthesis method is a simple, low-cost, eco-friendly, and green chemistry approach. Our results showed that the AuAg nanocomposites were biocompatible with low cell toxicity, and did not induce cell apoptosis nor necrosis in hFOB1.19 cells. Moreover, AuAg nanocomposites could effectively inhibited the accumulation of reactive oxygen species (ROS) in mitochondria and in rest of cellular compartments after exposing to bacterial biofilm (by reducing 0.78, 0.77-fold in the cell and mitochondria, respectively). AuAg nanocomposites also suppressed ROS-triggered inflammatory protein expression via MAPKs and Akt pathways. The current data suggest that AuAg nanocomposites have the potential to be a good therapeutic agent in treating inflammation in bacteria-infected bone diseases.

Hierarchal polyaniline-folic acid nanostructures act as a platform for electrochemical detection of tumor cells

The fabrication of electrochemical sensing platforms for cancer monitoring by quantifying circulating tumor cells (CTCs) in blood holds promise for providing a low-cost, rapid, feasible, and safe approach for cancer diagnosis. Here, we isolate cancer cells using CoFe₂O₄ nanoparticles functionalized with folic acid and chitosan as an inexpensive magnetic nanoprobe. This electrochemical cytosensing platform was realized using polyaniline-folic acid nanohybrids with a three-dimensional hierarchical structure that presents abundant affinity sites toward overexpressed folate bioreceptors on cancer cells, in addition to retaining satisfied conductivity. Furthermore, 3D modeling and simulation of the polyaniline-folic acid structures were conducted to investigate the stable complex between aniline and folate, and the interaction between the polyaniline-folate complex and folate receptor alpha1, a bioreceptor on MCF-7 was revealed for the first time. The limit of detection was calculated to be 4 cells mL^-1 with a linear range from 50 to 10⁶ cells mL^-1.

Profiling Heparan Sulfate-Heavy Metal Ions Interaction Using Electrochemical Techniques

Heparan sulfate glycosaminoglycans provides extracellular matrix defense against heavy metals cytotoxicity. Identifying the precise glycan sequences that bind a particular heavy metal ion is a key for understanding those interactions. Here, electrochemical and surface characterization techniques were used to elucidate the relation between the glycans structural motifs, uronic acid stereochemistry, and sulfation regiochemistry to heavy metal ions binding. A divergent strategy was employed to access a small library of structurally well-defined tetrasaccharides analogs with different sulfation patterns and uronic acid compositions. These tetrasaccharides were electrochemically grafted onto glassy carbon electrodes and their response to heavy metal ions was monitored by electrochemical impedance spectroscopy. Key differences in the binding of Hg(II), Cd(II), and Pb(II) were associated with a combination of the uronic acid type and the sulfation pattern.

Label-free detection and enumeration of rare circulating tumor cells by bright-field image cytometry and multi-frame image correlation analysis

Identification and enumeration of circulating tumor cells (CTCs) in peripheral blood are proved to correlate with the progress of metastatic cancer and can provide valuable information for diagnosis and monitoring of cancer. Here, we introduce a bright-field image cytometry (BFIC) technique, assisted by a multi-frame image correlation (MFIC) algorithm, as a label-free approach for tumor cell detection in peripheral blood. For this method, images of flowing cells in a wide channel were continuously recorded and cell types were determined simultaneously using a deep neural network of YOLO-V4 with an average precision (AP) of 98.63%, 99.04%, and 98.95% for cancer cell lines HT29, A549, and KYSE30, respectively. The use of the wide microfluidic channel (400 μm width) allowed for a high throughput of 50 000 cells per min without clogging. Then erroneous or missed cell classifications caused by imaging angle differences or accidental misinterpretations in single frames were corrected by the multi-frame correlation analysis. This further improved the AP to 99.40%, 99.52%, and 99.47% for HT29, A549, and KYSE30, respectively. Meanwhile, cell counting was also accomplished in this dynamic process. Moreover, our imaging cytometry method can readily detect as few as 10 tumor cells from 100 000 white blood cells and was unaffected by the EMT process. Furthermore, CTCs from 8 advanced-stage cancer clinical samples were also successfully detected, while none for 6 healthy control subjects. Although this method is implemented for CTCs, it can also be used for the detection of other rare cells.

Structural characterization and bioimaging of Zn2+ using meta-benziporphodimethene analogue

"Prevention is better than cure, especially when something has no cure." Cancer, in most patients is detected at the stage beyond which it becomes non-curative. Thus, the early detection of cancer cells can play a crucial role in enhancing the chances of a patient's survival. In this light, we present a non-fluorescent receptor employed for the detection of Zn²⁺ ion in MDA-MB-231 carcinoma cells that exhibits fluorescence turn-on behaviour upon binding with the metal ion. In this work, the synthesis of 11,16-bis(2,6-difluorobenzene)-6,6,21,21-tetramethyl-meta-benziporpho-6,21-dimethene and its Zn²⁺ chloride complex have been reported. The compounds were fully characterized using UV-Visible, NMR, IR and mass spectrometry. Furthermore, the X-ray polymorphs of meta-benziporphodimethene analogue have been added. The study of its bioimaging applications in MDA-MB-231 breast cancer cells for the detection of Zn²⁺ ions have been reported.

Ulex Europaeus Agglutinin-I-Based Magnetic Isolation for the Efficient and Specific Capture of SW480 Circulating Colorectal Tumor Cells

The efficient and specific capture of circulating tumor cells (CTCs) from patients' peripheral blood is of significant value in precise cancer diagnosis and cancer therapy. As fine targeting molecules, lectins can recognize cancer cells specifically due to the abnormal glycosylation of molecules on the cancer cell membrane and the specific binding of lectin with glycoconjugates. Herein, a Ulex europaeus agglutinin-I (UEA-I)-based magnetic isolation strategy was developed to efficiently and specifically capture α-1,2-fucose overexpression CTCs from colorectal cancer (CRC) patients' peripheral blood. Using UEA-I-modified Fe₃O₄ magnetic beads (termed MB-UEA-I), up to 94 and 89% of target cells (i.e., SW480 CRC cells) were captured from the cell spiking complete cell culture medium and whole blood, respectively. More than 90% of captured cells show good viability and proliferation ability without detaching from MB-UEA-I. In combination with three-color immunocytochemistry (ICC) identification, MB-UEA-I has been successfully used to capture CTCs from CRC patients' peripheral blood. The experimental results indicate a correlation between CTC characterization and tumor metastasis. Specifically, MB-UEA-I can be applied to screen early CRC by capturing CTCs when served as a liquid biopsy. The presented work offers a new insight into developing cost-effective lectin-functionalized methods for biomedical applications.

D-mannose functionalized MgAl-LDH/Fe-MOF nanocomposite as a new intelligent nanoplatform for MTX and DOX co-drug delivery

Commonly the directly administered chemotherapy drugs lack targeting in tumor treatment. Thus, trying to improve cancer treatment efficiency led us to design a new intelligent system for cancer treatment. Considering these, in the current work, at first, the 2-aminoterephthalic acid (NH₂-BDC) intercalated layered double hydroxides (MgAl-(NH₂-BDC) LDH) were synthesized simply. Afterward, the in situ growth of the iron-based metal-organic frameworks in the presence of MgAl-(NH₂-BDC) LDH occurred (MgAl-LDH/Fe-MOF). In the end, the reaction of MgAl-LDH/Fe-MOF with D-mannose (D-Man) achieved the MgAl-LDH/Fe-MOF/D-Man ternary hybrid nanostructure. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis confirmed the formation of the monodisperse Fe-MOF with nanosize in the presence of MgAl-LDH. Importantly, methotrexate (MTX) and doxorubicin (DOX) entrapment efficiency reached respectively about 28 wt% and 21% for MgAl-LDH/Fe-MOF/D-Man. The in vitro drug release experiments revealed a higher drug release at pH 5.0 in comparison with pH 7.4 which revealed its promising potential for anticancer drug delivery applications. Bioassay results revealed that the co-drug-loaded MgAl-LDH/Fe-MOF/D-Man has higher cytotoxicity on MDA-MB 231 cells. At last, fluorescence microscopy and flow cytometric analysis confirmed the successful uptake of MgAl-LDH/Fe-MOF/D-Man into MDA-MB 231 cell lines, as well as its bioimaging potential. A survey in the published literature approved that this work is the first report on the evaluation of the MgAl-LDH/Fe-MOF/D-Man for targeted co-delivery of both MTX and DOX. Finally, results collectively demonstrate the importance of the biocompatible MgAl-LDH/Fe-MOF/D-Man as a hopeful candidate for biomedicinal applications from the targeted co-drug delivery and bioimaging potential viewpoints.

Mannosylated poly(acrylic acid)-coated mesoporous silica nanoparticles for anticancer therapy

Although mesoporous silica nanoparticles (MSNs) are widely used as anticancer drug carriers, unmodified MSNs induce off-target effects and at high doses, there are adverse effects of hemolysis because of the interaction with the silanol group on the surface and cells. In this study, we developed doxorubicin (DOX)-loaded MSNs coated with mannose grafted poly (acrylic acid) copolymer (DOX@MSNs-man-g-PAA) to enhance the hemocompatibility and target efficacy to cancer cells. This uniform nanosized DOX@MSNs-man-g-PAA showed sustained and pH-dependent drug release with improved hemocompatibility over the bare MSNs. The uptake of the DOX@MSN-man-g-PAA in breast cancer cells was significantly improved by mannose receptor-mediated endocytosis, which showed significant increasing intracellular ROS and changes in mitochondrial membrane potential. This formulation exhibited superior tumor-suppressing activity in the MDA-MB-231 cells inoculated mice. Overall, the present study suggested the possibility of the copolymer-coated MSNs as drug carriers for cancer therapy.

A highly sensitive electrochemical cytosensor based on a triple signal amplification strategy using both nanozyme and DNAzyme

The development of a sensitive cytosensor is beneficial for the early diagnosis and treatment of cancer. Herein, highly sensitive cytosensing was achieved by applying triple signal amplification strategies with Fe₃O₄@Au nanozymes and DNAzyme hybrids as electrochemical nanoprobes and toluidine blue (Tb) as the electron transfer medium. The Fe₃O₄@Au nanocomposites not only acted as nanozymes with excellent catalytic performance towards H₂O₂ reduction but also served as promising scaffolds to carry massive electroactive substances and DNA probes. The dual-functional DNA probes were designed with the sequence of hemin/G-quadruplex to serve as the DNAzyme and the sequence of aptamer to recognize cancer cells. Furthermore, Tb was also conjugated to the surface of the Fe₃O₄@Au nanohybrids, working as the electron transport medium to magnify the electrochemical response. With the above design, the Fe₃O₄@Au nanozymes and hemin/G-quadruplex DNAzyme efficiently co-catalyzed the reduction of H₂O₂ to accelerate the electron transfer of Tb, which realized triple signal amplification and finally improved the performance of the electrochemical cytosensor. The proposed cytosensor achieved a sensitive detection of HepG2 cells with a low detection limit of 20 cells mL^-1, and could be potentially used as an effective analysis tool in early cancer diagnosis in the future.

Preparation of Notch-4 Receptor Containing Quartz Crystal Microbalance Biosensor for MDA MB 231 Cancer Cell Detection

Quartz crystal microbalance (QCM) is a highly sensitive system that is used as a biosensor for biomolecules and cells. Detection and characterization of cancer cells in circulation or biopsy samples is of crucial importance for cancer diagnosis. Here, we introduce approaches for breast cancer cell detection via their surface molecules. The sensor system is based on preliminary coating of QCM chip with polymeric nanoparticles to increase the surface area and allow for the attachment of proteins to the chip surface. This is followed by the attachment of a specific protein in order to functionalize the chip. Breast cancer cells and fibroblast cells as control are cultured and applied to this chip. The functionalized QCM system can detect breast cancer cells with high affinity and selectivity. Here, we present the preparation methods of QCM-based sensors for selective detection of MDA MB 231 cancer cells. Selectivity of QCM-based sensor is carried out in the presence of L929 mouse fibroblast cells.

A Cell-Culture Technique to Encode Glyco-Nanoparticles Selectivity

Nanoparticles (NPs) embedded with bioactive ligands such as carbohydrates, peptides, and nucleic acid have emerged as a potential tool to target biological processes. Traditional in vitro assays performed under statistic conditions may result in non-specific outcome sometimes, mainly because of the sedimentation and self-assembly nature of NPs. Inverted cell-culture assay allows for flexible and accurate detection of the receptor-mediated uptake and cytotoxicity of NPs. By combining this technique with glyco-gold nanoparticles, cellular internalization and cytotoxicity were investigated. Regioselective glycosylation patterns and shapes of the NPs could tune the receptors' binding affinity, resulting in precise cellular uptake of gold nanoparticles (AuNPs). Two cell lines HepG2 and HeLa were probed with galactosamine-embedded fluorescent AuNPs, revealing significant differences in cytotoxicity and uptake mechanism in upright and invert in vitro cell-culture assay, high-specificity toward uptake, and allowing for a rapid screening and optimization technique.

Lectin-Triggered Aggregation of Glyco-Gold Nanoprobes for Activity-based Sensing of Hydrogen Peroxide by the Naked Eye

The purpose of this study was to develop a colorimetric assay for detecting hydrogen peroxide (H₂ O₂ ) through a combination of using an aryl boronate (AB) derivative and gold nanoparticles (AuNPs). The unique optical property of AuNPs is applied to design a detection probe. The aggregation of AuNPs could be directly observed as a color change by the naked eye. A mannoside-boronate-sulfide (MBS) ligand was designed that contains an arylboronate (AB), a mannoside, and a thiol group. The thiol group bonds covalently with the surface of AuNPs to obtain MBS@AuNPs. The mannoside moiety recognizes concanavalin A (Con A), a lectin with four carbohydrate recognition sites that can specifically recognize the non-reducing end of an α-D-mannoside or α-D-glucoside structure. The AB structure on MBS first reacts with H₂ O₂ and then inserts an oxygen atom in the B-H bond, which triggers intramolecular electron rearrangement to cleave the covalent bond, resulting in a MBSt mixture. The MBS or MBSt is then modified to citrate-coated AuNPs (c-AuNPs) to have MBS@AuNPs or MBSt@AuNPs. When the MBS@AuNPs are incubated with Con A, the Con A recognizes multiple mannosides on the surface of the MBS@AuNPs. Subsequently, the MBS@AuNPs aggregate and the solution's color changes from red to purple, but this color change does not occur in the case of MBSt@AuNPs. The phenomenon can be observed by the naked eye.

NIR II Light-Response Au Nanoframes: Amplification of a Pressure- and Temperature-Sensing Strategy for Portable Detection and Photothermal Therapy of Cancer Cells

Quantitative detection of cancer cells using portable devices is promising for the development of simple, fast, and point-of-care cancer diagnostic techniques. However, how to further amplify the detection signal to improve the sensitivity and accuracy of detecting cancer cells by portable devices remains a challenge. To solve the problem, we, for the first time, synthesized folic-acid-conjugated Au nanoframes (FA-Au NFs) with amplification of pressure and temperature signals for highly sensitive and accurate detection of cancer cells by portable pressure meters and thermometers. The resulting Au NFs exhibit excellent near-infrared (NIR) photothermal performance and catalase activity, which can promote the decomposition of NH₄HCO₃ and H₂O₂ to generate corresponding gases (CO₂, NH₃, and O₂), thereby synergistically amplifying pressure signals in a closed reaction vessel. At the same time, Au NFs with excellent peroxidase-like activity can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce TMB oxide (oxTMB) with a strong photothermal effect, thereby cooperating with Au NFs to amplify the photothermal signal. In the presence of cancer cells with overexpressing folate receptors (FRs), the molecular recognition signals between FA and FR can be converted into amplified pressure and temperature signals, which can be easily read by portable pressure meters and thermometers, respectively. The detection limits for cancer cells using pressure meters and thermometers are 6 and 5 cells/mL, respectively, which are better than other reported methods. Moreover, such Au NFs can improve tumor hypoxia by catalyzing the decomposition of H₂O₂ to produce O₂ and perform photothermal therapy of cancer. Together, our work provides new insight into the application of Au NFs to develop a dual-signal sensing platform with amplification of pressure and temperature signals for portable and ultrasensitive detection of cancer cells as well as personalized cancer therapy.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.

Quartz Crystal Microbalance (QCM) Based Biosensor Functionalized by HER2/neu Antibody for Breast Cancer Cell Detection

The heterogeneity and metastatic features of cancer cells lead to a great number of casualties in the world. Additionally, its diagnosis as well as its treatment is highly expensive. Therefore, development of simple but effective diagnostic systems which detect the molecular markers of cancer is of great importance. The molecular changes on cancer cell membranes serve as targets, such as HER2/neu receptor which is detected on the surface of highly metastatic breast cancer cells. We have aimed to develop a specific and simple quartz crystal microbalance (QCM)-based system to identify HER2/neu expressing breast cancer cells via a receptor-specific monoclonal antibody. First, the QCM chip was coated with polymeric nanoparticles composed of hydroxyethylmethacrylate (HEMA) and ethylene glycol dimethacrylate (EDMA). The nanoparticle coated QCM chip was then functionalized by binding of HER2/neu antibody. The breast cancer cells with/without HER2/neu receptor expression, namely, SKBR3, MDA-MB 231 and also mouse fibroblasts were passed over the chip at a rate of 10–500 cells/mL and the mass changes (Δm) on cell/cm2 unit surface of sensor were detected in real-time. The detection limit of the system was 10 cells/mL. Thus, this QCM-based HER2/neu receptor antibody functionalized system might be used effectively in the detection of HER2/neu expressing SKBR3 breast cancer cells.

Recent Advances in Electrochemical Sensors for the Detection of Biomolecules and Whole Cells

Electrochemical sensors are considered an auspicious tool to detect biomolecules (e.g., DNA, proteins, and lipids), which are valuable sources for the early diagnosis of diseases and disorders. Advances in electrochemical sensing platforms have enabled the development of a new type of biosensor, enabling label-free, non-destructive detection of viability, function, and the genetic signature of whole cells. Numerous studies have attempted to enhance both the sensitivity and selectivity of electrochemical sensors, which are the most critical parameters for assessing sensor performance. Various nanomaterials, including metal nanoparticles, carbon nanotubes, graphene and its derivatives, and metal oxide nanoparticles, have been used to improve the electrical conductivity and electrocatalytic properties of working electrodes, increasing sensor sensitivity. Further modifications have been implemented to advance sensor platform selectivity and biocompatibility using biomaterials such as antibodies, aptamers, extracellular matrix (ECM) proteins, and peptide composites. This paper summarizes recent electrochemical sensors designed to detect target biomolecules and animal cells (cancer cells and stem cells). We hope that this review will inspire researchers to increase their efforts to accelerate biosensor progress-enabling a prosperous future in regenerative medicine and the biomedical industry.

Photoelectrochemical aptasensor with low background noise

In photoelectrochemical (PEC) detection, enhancing the PEC signal and depressing the blank signal are conducive to improve the sensitivity. Because the carbon nanotube (CNT) effectively transfers photogenerated electrons from SnSe to the electrode, the composite nanomaterial CNTs/SnSe generates a strong PEC signal. Methionine (Met), AuNPs, and probe DNA are woven together forming a nanoprobe which is used as a quencher to quench the PEC signal of CNTs/SnSe. When the nanoprobe and CNTs/SnSe are modified onto the electrode, there is a low blank signal. In the presence of metastatic breast cancer cells, the cells interact with the aptamer of dsDNA; concomitantly, cDNA is released to trigger catalytic hairpin assembly (CHA). As a result, a new dsDNA which has an overhang is formed. The nanoprobe on the surface of the electrode hybridizes with the newly formed dsDNA. Subsequently, the nanoprobe is released from the surface of the electrode and the quenching effect between the nanoprobe and the CNTs/SnSe disappears. The PEC aptasensor is linear in the concentration range of 300-5,000 cells/mL, and the detection limit is 180 cells/mL under optimized conditions. The relative standard deviation (RSD) is 3.6% at 10,000 cells/mL. This work demonstrates a promising strategy using CNTs/SnSe as the photoactive material and Met-AuNPs as the quencher to establish a PEC aptasensor with a high PEC response and low blank signal. It can be used to detect bioactive substances at ultralow levels prospectively. Graphical abstract.

Tumor-cell detection, labeling and phenotyping with an electron-doped bifunctional signal-amplifier

Cancer cell enumeration and phenotyping can predict the prognosis and the therapy efficacy in patients, yet it remains challenging to detect the rare tumor cells. Herein, we report an octopus-inspired, bifunctional aptamer signal amplifier-based cytosensor (OApt-cytosensor) for sensitive cell analysis. By assembling high-affinity antibodies on an electrode surface, the target cells could be specifically captured and thus been sandwiched by the cell surface marker-specific DNA aptamers. These on-cell aptamers function as electrochemical signal amplifiers by base-selective electronic doping with methylene blue. Such a sandwich configuration enables highly sensitive cell detection down to 10 cells/mL (equal to ~1-2 cells at a sampling volume of 150 μL), even in a large excess of nontarget blood cells. This approach also reveals the cell-surface markers and tracks the cellular epithelial-to-mesenchymal transition induced by signaling regulators. Furthermore, the electron-doped aptamer shows remarkable cell fluorescent labeling that guides the release of the captured cells from electrode surface via electrochemistry. These features make OApt-cytosensor a promising tool in revealing the heterogeneous cancer cells and anticancer drug screening at the single-cell level.

Size Preferences Uptake of Glycosilica Nanoparticles to MDA-MB-231 Cell

Recently, studies on the development and investigation of carbohydrate-functionalized silica nanoparticles (NPs) and their biomedicine applications such as cell-specific targeting and bioimaging has been carried out extensively. Since the number of breast cancer patients has been growing in recent years, potential NPs were being studied in this project for targeting breast cancer cells. Mannose receptors can be found on the surface of MDA-MB-231, which is a kind of human breast cancer cell line. Therefore, we decorated a cyanine 3 fluorescent dye (Cy3) and mannosides on the surface of silica NPs for the purpose of imaging and targeting. Galactoside was also introduced onto the surface of silica NPs acting as a control sample. Various sizes of silica NPs were synthesized by using different amounts of ammonium to investigate the effect of the size of NPs on the cellular uptake rate. The physical properties of these NPs were characterized by scanning electron microscope, dynamic light scattering, and their zeta potential. Cellular experiments demonstrated that mannoside-modified NPs can be uptaken by MDA-MB-231. From the experiment, we found out that the best cellular uptake rate of nanoparticle size is about 250 nm. The MTT assay showed that Man@Cy3SiO₂NPs are not cytotoxic, indicating they may have the potential for biomedical applications.

Mannoside-Modified Branched Gold Nanoparticles for Photothermal Therapy to MDA-MB-231 Cells

Recently, gold nanoparticles (Au NPs) have been used to study the treatment of malignant tumors due to their higher biocompatibility and lesser toxicity. In addition, they can be excited through a specific wavelength to produce oscillating plasmonic photothermal therapy (PPTT) on the basis of the localized surface plasma resonance (LSPR) effect. Au NPs can be heated to kill cancer cells in specific parts of the body in a noninvasive manner. In this study, branched gold nanoparticles (BAu NPs) were prepared by mixing HAuCl₄ in a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution in a molar ratio of 1:2000. The UV–vis absorption peak was detected in the range of 700–1000 nm. Subsequently, BAu NPs were chemically linked to a thiol-modified mannoside molecule via a stable sulfur–Au covalent bond (Man@BAu NPs). Due to the presence of abundant mannose receptors on human-breast-cancer cells, MDA-MB-231, Man@BAu NPs were found to be abundant inside cancer cells. After irradiating the Man@BAu NP-laden MDA-MB231 switch with a near-infrared (NIR) laser at 808 nm wavelength, the photothermal-conversion effect raised the surface temperature of Man@BAu NPs, thus inducing cell death. Our experiment results demonstrated the advantages of applying Man@BAu NPs in inducing cell death in MDA-MB-231.

Fabrication of a cell-recognition/electron-transfer/cross-linker, peptide-immobilized electrode for the sensing of K562 cells

We designed an electrode that has the ability to sense a target cell. This new electrode is intended for use in cell recognition via electron-transfer and cross-linker peptide immobilization. Myelopeptide-4 (MP-4:FRPRIMTP) is a marrow-origin peptide that interacts with receptors of the human leukemia cell line (K562 cells), and allows their differentiation. The YYYYC electron-transfer peptide improves the electron-transfer accessibility from an electroactive compound to an electrode. Oligoalanine plays the role of a cross-linker that immobilizes a peptide series (Ac-FRPRIMTPYYYYCAAAAA) to collagen, which then allows it to be cast onto an electrode. Use of the electrode with a peptide increased the peak currents of [Fe(CN)₆]^4-/3- and also improved the reversibility of redox. These improvements are due to the interaction between [Fe(CN)₆]^4-/3- and the peptide. When electrochemical impedance spectroscopy (EIS) measurements were carried out using a collagen/peptide probe-immobilized electrode, the electron transfer resisitance was lower than that without the peptide. The detection of K562 cells was based on an increase in resistance, because MP-4 was bound to the receptors on the cell surface. The responses were linear and ranged in number from 27 to 2,000 cells/mLwith a detection limit of 8 cells/mL. Recoveries of 50 and 1,000 cells/mL in human serum were accomplished at rates of 98 and 101%, respectively. Consequently, the proposed procedure is a powerful new concept for cytosensing.

Application of electrochemical biosensors in tumor cell detection

Conventional methods for detecting tumors, such as immunological methods and histopathological diagnostic techniques, often request high analytical costs, complex operation, long turnaround time, experienced personnel and high false-positive rates. In addition, these assays are difficult to obtain an early diagnosis and prognosis quickly for malignant tumors. Compared with traditional technology, electrochemical technology has realized the study of interface charge transfer behavior at the atomic and molecular levels, which has become an important analytical and detection tool in contemporary analytical science. Electrochemical technique has the advantages of rapid detection, high sensitivity (single cell) and specificity in the detection of tumor cells, which has not only been successful in differentiating tumor cells from normal cells, but has also achieved targeted detection of localized tumor cells and circulating tumor cells. Electrochemical biosensors provide powerful tools for early diagnosis, staging and prognosis of tumors in clinical medicine. Therefore, this review mainly discusses the development and application of electrochemical biosensors in tumor cell detection in recent years.

Electrochemical cytosensors for detection of breast cancer cells

Breast cancer is one of lethal cancers among women with its metastasis leading to cancer-related morbidity and mortality. Circulating tumor cells (CTCs) derived from a primary tumor can be detected in the venous blood of cancer patients. Monitoring CTCs in blood samples has increased exponentially over the past decades and holds great promise in the diagnosis and treatment of metastatic breast cancer. Electrochemical cytosensors, classified as a class of electrochemical biosensors for sensitive detection and enumeration of targeted cells with minimally invasive methods, have the advantages of electrochemical biosensors, such as simplicity, low cost, and low limit of detection. Here, we review recent progress in the detection of CTCs from breast cancer with a focus on electrochemical cytosensors. This review describes platforms benefiting from these cytosensors to identify cancerous breast cells. Furthermore, strategies for signal amplification and also generation of reusable electrochemical cytosensors are introduced. In addition, breast cancer markers and biorecognition elements for cell capturing are reviewed.

A two-dimensional immunomagnetic nano-net for the efficient isolation of circulating tumor cells in whole blood

An immunomagnetic "nano-net" was designed and synthesized for specifically capturing rare cells of interest from mixtures. The nano-net, Ab@Lipo-MNP-GO, consists of conjugated antibody molecules on a lipid coated magnetic nanoparticle-graphene oxide sheet complex. The magnetism, chemical composition, and the morphology of the construct and its precursors were characterized by SQUID, FTIR, TGA, DLS and SEM, to confirm the feasibility of the synthetic steps and the resulting properties suitable for solution phase immuno-recognition for cell capture. When applied to capturing circulating tumor cells (CTCs) in oral, colon and lung cancer clinical patients' blood samples, the nano-net construct exhibited far superior ability whereas conventional immunomagnetic beads in some cases were unable to capture any CTCs, even by increasing the bead concentration. Confocal images showed that the nano-net wrapped around the CTCs while the immunomagnetic beads attached them with point contacts. A stable, patch-like multivalent matrix nano-net was demonstrated to tackle the shortcomings of single point contact of immunomagnetic beads to the target cell. This strategy is universal for any cell separation in complex fluids.

An electrochemical signal-on apta-cyto-sensor for quantitation of circulating human MDA-MB-231 breast cancer cells by transduction of electro-deposited non-spherical nanoparticles of gold

A highly simple, sensitive, specific and low-cost electrochemical apta-cyto-sensor for determination of circulating human MDA-MB-231 breast cancer cells was fabricated. Non-spherical nanoparticles of gold were electro-deposited in the presence of ethosuximide as a shape directing and size controlling agent. The nanoparticles had dimensions ranging 50-150 nm, and covered the underlying surface with a roughness factor of 8.03. The Non-spherical nanoparticles were then employed as the apta-cyto-sensor transducer. A 83-mer DNA aptamer that is specific to capturing the cell surface proteins was immobilized on the transducer surface, and binding with the cells was followed using the ferro/ferricyanide redox marker. The aptamer was immobilized within ∼200 min on the transducer surface. The cells were quantified with an equation of regression of ΔIp(μA) = (1.028 ± 0.027) log (C (cell mL^-1)) + (0.2199 ± 0.0944), a sensitivity of 1.028 μA (log (concentration / cell mL^-1))^-1 and a quantitation limit of 2 cell mL^-1, in a concentration range of 5 to 2 × 10⁶ cell mL^-1. The apta-cyto-sensor selectivity was also evaluated toward AsPC-1, Calu-6, HeLa, MCF-7 and melanoma B16/F10 cell lines. The apta-cyto-sensor had a fabrication reproducibility of 4.2%, regeneration capability of 5.1%, a stability of 35 days, and a potential application for the detection of MDA-MB-231 cells in the spiked blood serum samples with a sensitivity of 0.8975 μA (log (concentration / cell mL^-1))^-1 and a quantitation limit of 5 cell mL^-1, in a concentration range of 10 to 1 × 10³ cell mL^-1. The apta-cyto-sensor would be applicable for breast cancer diagnosis at early stage.

Self-Assembled 2D Glycoclusters for the Targeted Delivery of Theranostic Agents to Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) is a devastating disease worldwide, for which targeted imaging and therapeutic agents remain elusive. There has been growing awareness that carbohydrates are valuable as drug candidates and targeting agents for a variety of human diseases, including cancers that overexpress carbohydrate receptors on the cell surface. Here, we develop a two-dimensional (2D) glycocluster by means of simple, stepwise self-assembly for the targeted delivery of theranostic agents to TNBC cells that express mannose receptors (MRs) on the cell surface. Human serum albumin, which contains a variety of hydrophobic pockets capable of accommodating small molecules, was used to simultaneously encapsulate a mannose-based glycoprobe and a commercial photosensitizer (i.e., Ce6). The multicomponent "neoglycoprotein" formed was used to self-assemble with 2D MnO₂, producing 2D glycoclusters, which could be selectively internalized by a TNBC cell line (MDA-MB-231) as facilitated by binding to the transmembrane MR. The intracellular degradation of the 2D MnO₂ backbone by biothiols then released Ce6 for cell imaging and, subsequently, photodynamic therapy. This study provides insights into the development of carbohydrate-based materials for targeted, stimuli-responsive theranostics of TNBC.