Bimetallic ZrHf-based metal-organic framework embedded with carbon dots: Ultra-sensitive platform for early diagnosis of HER2 and HER2-overexpressed living cancer cells

Recent Advances on the Metal-Organic Frameworks-Based Biosensing Methods for Cancer Biomarkers Detection

Sensitive and selective detection of cancer biomarkers is crucial for early diagnosis and treatment of cancer, one of the most dangerous diseases in the world. Metal-organic frameworks (MOFs), a class of hybrid porous materials fabricated through the assembly of metal ions/clusters and organic ligands, have attracted increasing attention in the sensing of cancer biomarkers, due to the advantages of adjustable size, high porosity, large surface area and ease of modification. MOFs have been utilized to not only fabricate active sensing interfaces but also arouse a variety of measurable signals. Several representative analytical technologies have been applied in MOF-based biosensing strategies to ensure high detection sensitivity toward cancer biomarkers, such as fluorescence, electrochemistry, electrochemiluminescence, photochemistry and colorimetric methods. In this review, we summarized recent advances on MOFs-based biosensing strategies for the detection of cancer biomarkers in recent three years based on the categories of metal nodes, and aimed to provide valuable references for the development of innovative biosensing platform for the purpose of clinical diagnosis.

Dual amplification for PEC ultrasensitive aptasensing of biomarker HER-2 based on Z-scheme UiO-66/CdIn2S4 heterojunction and flower-like PtPdCu nanozyme

As an important prognostic indicator in breast cancer, human epithelial growth factor receptor-2 (HER-2) is of importance for assessing prognosis of breast cancer patients, whose accurate and facile analysis are imperative in clinical diagnosis and treatment. Herein, photoactive Z-scheme UiO-66/CdIn2S4 heterojunction was constructed by a hydrothermal method, whose optical property and photoactivity were critically investigated by a range of techniques, combined by elucidating the interfacial charge transfer mechanism. Meanwhile, PtPdCu nanoflowers (NFs) were fabricated by a simple aqueous wet-chemical method, whose peroxidase (POD)-mimicking catalytic activity was scrutinized by representative tetramethylbenzidine (TMB) oxidation in H2O2 system. Taken together, the UiO-66/CdIn2S4 based photoelectrochemical (PEC) aptasensor was established for quantitative analysis of HER-2, where the detection signals were further magnified through catalytic precipitation reaction towards 4-chloro-1-naphthol (4-CN) oxidation (assisted by the PtPdCu NFs nanozyme). The PEC aptasensor presented a broader linear range within 0.1 pg mL-1-0.1 μg mL-1 and a lower limit of detection of 0.07 pg mL-1. This work developed a new PEC aptasensor for ultrasensitive determination of HER-2, holding substantial promise for clinical diagnostics.

Metal-organic framework (MOF)/C-dots and covalent organic framework (COF)/C-dots hybrid nanocomposites: Fabrications and applications in sensing, medical, environmental, and energy sectors

Developing new hybrid materials is critical for addressing the current needs of the world in various fields, such as energy, sensing, health, hygiene, and others. C-dots are a member of the carbon nanomaterial family with numerous applications. Aggregation is one of the barriers to the performance of C-dots, which causes luminescence quenching, surface area decreases, etc. To improve the performance of C-dots, numerous matrices including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and polymers have been composited with C-dots. The porous crystalline structures, which are constituents of metal nodes and organic linkers (MOFs) or covalently attached organic units (COFs) provide privileged features such as high specific surface area, tunable structures, and pore diameters, modifiable surface, high thermal, mechanical, and chemical stabilities. Also, the MOFs and COFs protect the C-dots from the environment. Therefore, MOF/C-dots and COF/C-dots composites combine their features while retaining topological properties and improving performances. In this review, we first compare MOFs with COFs as matrices for C-dots. Then, the recent progress in developing hybrid MOFs/C-dots and COFs/C-dots composites has been discussed and their applications in various fields have been explained briefly.

Sea Anemone-Inspired Conducting Polymer Sensing Platform for Integrated Detection of Tumor Protein Marker and Circulating Tumor Cell

Combining the detection of tumor protein markers with the capture of circulating tumor cells (CTCs) represents an ultra-promising approach for early tumor detection. However, current methodologies have not yet achieved the necessary low detection limits and efficient capture. Here, a novel polypyrrole nanotentacles sensing platform featuring anemone-like structures capable of simultaneously detecting protein biomarkers and capturing CTCs is introduced. The incorporation of nanotentacles significantly enhances the electrode surface area, providing abundant active sites for antibody binding. This enhancement allows detecting nucleus matrix protein22 and bladder tumor antigen with 2.39 and 3.12 pg mL-1 detection limit, respectively. Furthermore, the developed sensing platform effectively captures MCF-7 cells in blood samples with a detection limit of fewer than 10 cells mL-1, attributed to the synergistic multivalent binding facilitated by the specific recognition antibodies and the positive charge on the nanotentacles surface. This sensing platform demonstrates excellent detection capabilities and outstanding capture efficiency, offering a simple, accurate, and efficient strategy for early tumor detection.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Biomedical application of metal-organic frameworks (MOFs) in cancer therapy: Stimuli-responsive and biomimetic nanocomposites in targeted delivery, phototherapy and diagnosis

The nanotechnology is an interdisciplinary field that has become a hot topic in cancer therapy. Metal-organic frameworks (MOFs) are porous materials and hybrid composites consisted of organic linkers and metal cations. Despite the wide application of MOFs in other fields, the potential of MOFs for purpose of cancer therapy has been revealed by the recent studies. High surface area and porosity, significant drug loading and encapsulation efficiency are among the benefits of using MOFs in drug delivery. MOFs can deliver genes/drugs with selective targeting of tumor cells that can be achieved through functionalization with ligands. The photosensitizers and photo-responsive nanostructures including carbon dots and gold nanoparticles can be loaded in/on MOFs to cause phototherapy-mediated tumor ablation. The immunogenic cell death induction and increased infiltration of cytotoxic CD8+ and CD4+ T cells can be accelerated by MOF platforms in providing immunotherapy of tumor cells. The stimuli-responsive MOF platforms responsive to pH, redox, enzyme and ion can accelerate release of therapeutics in tumor site. Moreover, MOF nanocomposites can be modified ligands and green polymers to improve their selectivity and biocompatibility for cancer therapy. The application of MOFs for the detection of cancer-related biomarkers can participate in the early diagnosis of patients.

Bimetallic Coordination Polymers: Synthesis and Applications in Biosensing and Biomedicine

Bimetallic coordination polymers (CPs) have two different metal ions as connecting nodes in their polymer structure. The synthesis methods of bimetallic CPs are mainly categorized into the one-pot method and post-synthesis modifications according to various needs. Compared with monometallic CPs, bimetallic CPs have synergistic effects and excellent properties, such as higher gas adsorption rate, more efficient catalytic properties, stronger luminescent properties, and more stable loading platforms, which have been widely applied in the fields of gas adsorption, catalysis, energy storage as well as conversion, and biosensing. In recent years, the study of bimetallic CPs synergized with cancer drugs and functional nanomaterials for the therapy of cancer has increasingly attracted the attention of scientists. This review presents the research progress of bimetallic CPs in biosensing and biomedicine in the last five years and provides a perspective for their future development.

MOF-based nanocomposites as transduction matrices for optical and electrochemical sensing

Metal Organic Frameworks (MOFs), a class of crystalline microporous materials have been into research limelight lately due to their commendable physio-chemical properties and easy fabrication methods. They have enormous surface area which can be a working ground for innumerable molecule adhesions and site for potential sensor matrices. Their biocompatibility makes them valuable for in vitro detection systems but a compromised conductivity requires a lot of surface engineering of these molecules for their usage in electrochemical biosensors. However, they are not just restricted to a single type of transduction system rather can also be modified to achieve feat as optical (colorimetry, luminescence) and electro-luminescent biosensors. This review emphasizes on recent advancements in the area of MOF-based biosensors with focus on various MOF synthesis methods and their general properties along with selective attention to electrochemical, optical and opto-electrochemical hybrid biosensors. It also summarizes MOF-based biosensors for monitoring free radicals, metal ions, small molecules, macromolecules and cells in a wide range of real matrices. Extensive tables have been included for understanding recent trends in the field of MOF-composite probe fabrication. The article sums up the future scope of these materials in the field of biosensors and enlightens the reader with recent trends for future research scope.

Microswimmer-Assisted Dual-Signal Sensor for Multiple Targets in Whole Blood

Accurate detection of biomarkers in whole blood is an important aspect of diagnostic testing but remains a challenge due to various interferences. However, using a self-calibrating two-signal strategy offers a solution that can overcome interference caused by experimental and environmental factors. Here, we proposed a novel microswimmer {methylene blue (MB)@ZIF-90@aptamer-HER2/3,3',5,5'-tetramethylbenzidine (TMB)@ZIF-90@aptamer-ER}-dual-signal (electrochemical and fluorescence) homogeneous sensor based on functionalized ZIF nanomaterials for one-step simultaneous detection of human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) in whole blood. The proposed one-step ZIF-90 synthesis encapsulates TMB and MB with dual-signal properties. HER2 and ER aptamers adsorbed on MB@ZIF-90/TMB@ZIF-90 function as the gate switches. The microswimmer targets the HER2 and ER with adenosine triphosphate (ATP)-driven motion. When targets are present, aptamers dissociate and reduce the microswimmer's surface negative charge. The microswimmer undergoes attack and decomposition by swimming ATP due to the strong coordination force between ATP and Zn2+, leading to the release of MB and TMB. The negative charges on the surface of indium tin oxide enrich MB and TMB with positive charges, thereby increasing the intensities of electrochemical and fluorescence signals. The detection process was completed within 40 min, and the detection limits for ER and HER2 were 8.1 and 5.7 fg/mL respectively, with a linear range of 0.25-20 pg/mL.

TPN-COF@Fe-MIL-100 composite used as an electrochemical aptasensor for detection of trace tetracycline residues

In this work, a metal-organic framework@covalent organic framework composite (TPN-COF@Fe-MIL-100) was prepared and used as a sensing material to construct an aptasensor for trace detection of tetracycline (TET). The TPN-COF@Fe-MIL-100 integrates a large surface area, porous structure, excellent electrochemical activity, rich chemical functionality, and strong bioaffinity for aptamers, providing abundant active sites to effectively anchor aptamer strands. As a result, the TPN-COF@Fe-MIL-100-based aptasensor shows high sensitivity for detecting TET via specific recognition between aptamer and TET to form G-quadruplex. An ultralow detection limit of 1.227 fg mL-1 is deduced from the electrochemical impedance spectroscopy within a wide linear range of 0.01-10000 pg mL-1 for TET. The TPN-COF@Fe-MIL-100-based aptasensor also exhibits good selectivity, reproducibility, stability, regenerability, and applicability for a real milk sample. Therefore, the TPN-COF@Fe-MIL-100-based aptasensor will be promising for detecting trace harmful antibiotics residues for food safety.

Fabrication of a bi-metallic metal organic framework nanocomposite for selective and sensitive detection of triclosan

Transition metal-ion based nanocomposites are widely used owing to their ease of synthesis and cost-effectiveness in the sensor development. In this study, we have synthesized bi-metallic (iron and zinc) metal organic framework (MOF) nanorods-nanoparticles (denoted as Fe₂Zn-MIL-88B) with a well-defined structure and characterized them. The bimetallic material nanocomposite (Fe₂Zn-MIL-88B, nafion (Nf), and multiwalled carbon nanotube (MWCNT)) was fabricated on the electrode (glassy carbon electrode (GCE) or screen printed carbon electrode (SPCE)) surface within 10 min at room temperature. The Fe₂Zn-MIL-88B/Nf/MWCNT@GCE showed an excellent electron transfer mechanism compared to a bare GCE and bare SPCE. The Fe₂Zn-MIL-88B based nanocomposite electrode triggers the oxidation of the environmental carcinogenic molecule triclosan (TCS). Under optimized conditions, the sensor has a limit of detection of 0.31 nM and high selectivity to TCS in the presence of other interfering agents. The sensor has a good day-to-day TCS detection reproducibility. Fe₂Zn-MIL-88B was stable even after 11 months of synthesis and detected TCS with similar sensitivity. The fabrication of the Fe₂Zn-MIL-88B/Nf/MWCNT nanocomposite was successfully translated from the GCE to SPCE. TCS was detected in human plasma and commercial products such as soaps, skin care products, shampoos, and tooth pastes.

Electrochemical aptasensor based on the engineered core-shell MOF nanostructures for the detection of tumor antigens

It is essential to develop ultrasensitive biosensors for cancer detection and treatment monitoring. In the development of sensing platforms, metal-organic frameworks (MOFs) have received considerable attention as potential porous crystalline nanostructures. Core-shell MOF nanoparticles (NPs) have shown different diversities, complexities, and biological functionalities, as well as significant electrochemical (EC) properties and potential bio-affinity to aptamers. As a result, the developed core-shell MOF-based aptasensors serve as highly sensitive platforms for sensing cancer biomarkers with an extremely low limit of detection (LOD). This paper aimed to provide an overview of different strategies for improving selectivity, sensitivity, and signal strength of MOF nanostructures. Then, aptamers and aptamers-modified core-shell MOFs were reviewed to address their functionalization and application in biosensing platforms. Additionally, the application of core-shell MOF-assisted EC aptasensors for detection of several tumor antigens such as prostate-specific antigen (PSA), carbohydrate antigen 15-3 (CA15-3), carcinoembryonic antigen (CEA), human epidermal growth factor receptor-2 (HER2), cancer antigen 125 (CA-125), cytokeratin 19 fragment (CYFRA21-1), and other tumor markers were discussed. In conclusion, the present article reviews the advancement of potential biosensing platforms toward the detection of specific cancer biomarkers through the development of core-shell MOFs-based EC aptasensors.

Carbon-dots-referenced metal-organic frameworks for chemical sensing of tumor/mood biomarker 5-hydroxyindoleacetic acid in human urine: Covalent grafting blue-emitting carbon dots onto red-emitting MOF

5-HIAA (5-hydroxyindoleacetic acid) is a metabolite for 5-hydroxytryptamine which is excreted in urine and reflects human homeostatic sate. Thus, its monitoring is of great important for clinical diagnosis. In this work, blue-emitting carbon dots (BCD) were firstly synthesize and then covalently grafted onto red-emitting MOF (EuBTC), resulting in a composite sensing platform (BCD@EuBTC) with two emission bands (blue emission peaking at 441 nm and red emission peaking at 616 nm). This composite structure was characterized by means of XRD, IR, TGA, N₂ adsorption/desorption, and SEM/TEM. It was found that BCD was grafted on EuBTC surface, not loaded in its micropores, with doping level of 5.02 wt%. 5-HIAA replaced and released the BCD in BCD@EuBTC. The released BCD showed strong blue emission. In the meanwhile, EuBTC red emission was quenched by 5-HIAA thermal relaxation. As a consequence, a ratiometric sensing signal was observed for 5-HIAA. A linear working calibration curve was fitted as F/F₀ = 0.588 + 1.598*[5-HIAA], R² = 0.999, with detection of limit (LOD) determined as 0.3 μM, working region of 0.3-70 μM, and good selectivity. The practical sensing performance of BCD@EuBTC for 5-HIAA in human urine was confirmed, with recovery of 103%.

Combined Ultrasensitive Detection of Renal Cancer Proteins and Cells Using an Optical Microfiber Functionalized with Ti3C2 MXene and Gold Nanorod-Nanosensitized Interfaces

The ultrasensitive and quantitative detection of renal cancer protein biomarkers present at ultralow concentrations for early-stage cancer diagnosis requires a biosensing probe possessing ultrahigh detection sensitivity and remarkable biosensing selectivity. Here, we report an optical microfiber integrated with Ti₃C₂-supported gold nanorod hybrid nanointerfaces for implementation in ultrasensitive sensing of the carbonic anhydrase IX (CAIX) protein and renal cancer cells. Because the evanescent field of the fiber is strongly coupled with nanointerfaces in the near-infrared region, the proposed optical microfiber biosensor achieves ultrahigh-sensitivity detection of the CAIX protein biomarker with ultralow limits of detection (LODs) of 13.8 zM in pure buffer solution and 0.19 aM in 30% serum solution. In addition, the proposed sensor also successfully and specifically recognizes living renal cancer cells in cell culture media with a LOD of 180 cells/mL. This strategy may serves as a powerful biosensing platform that combines the quantification of protein biomarkers and cancer cells, resulting in a higher accuracy of early-stage renal cancer diagnosis and screenings.

Metal-Organic Frameworks Applications in Synergistic Cancer Photo-Immunotherapy

Conventional cancer therapies, such as radiotherapy and chemotherapy, can have long-term side effects. Phototherapy has significant potential as a non-invasive alternative treatment with excellent selectivity. Nevertheless, its applicability is restricted by the availability of effective photosensitizers and photothermal agents, and its low efficacy when it comes to avoiding metastasis and tumor recurrence. Immunotherapy can promote systemic antitumoral immune responses, acting against metastasis and recurrence; however, it lacks the selectivity displayed by phototherapy, sometimes leading to adverse immune events. The use of metal-organic frameworks (MOFs) in the biomedical field has grown significantly in recent years. Due to their distinct properties, including their porous structure, large surface area, and inherent photo-responsive properties, MOFs can be particularly useful in the fields of cancer phototherapy and immunotherapy. MOF nanoplatforms have successfully demonstrated their ability to address several drawbacks associated with cancer phototherapy and immunotherapy, enabling an effective and low-side-effect combinatorial synergistical treatment for cancer. In the coming years, new advancements in MOFs, particularly regarding the development of highly stable multi-function MOF nanocomposites, may revolutionize the field of oncology.

MoS2-Carbon Nanodots as a New Electrochemiluminescence Platform for Breast Cancer Biomarker Detection

In this work, we present the combination of two different types of nanomaterials, 2D molybdenum disulfide nanosheets (MoS₂-NS) and zero-dimensional carbon nanodots (CDs), for the development of a new electrochemiluminescence (ECL) platform for the early detection and quantification of the biomarker human epidermal growth factor receptor 2 (HER2), whose overexpression is associated with breast cancer. MoS₂-NS are used as an immobilization platform for the thiolated aptamer, which can recognize the HER2 epitope peptide with high affinity, and CDs act as coreactants of the anodic oxidation of the luminophore [Ru(bpy)₃]²⁺. The HER2 biomarker is detected by changes in the ECL signal of the [Ru(bpy)₃]²⁺/CD system, with a low detection limit of 1.84 fg/mL and a wide linear range. The proposed method has been successfully applied to detect the HER2 biomarker in human serum samples.

Carbon-based biosensors from graphene family to carbon dots: A viewpoint in cancer detection

According to the latest report by International Agency for Research on Cancer, 19.3 million new cancer cases and 10 million cancer deaths were globally reported in 2020. Early diagnosis can reduce these numbers significantly, and biosensors have appeared to be a solution to this problem as, unlike the traditional methods, they have low cost, rapid process, and do not need experts present on site for use. These devices have been incorporated to detect many cancer biomarkers and measure cancer drug delivery. To design these biosensors, a researcher must know about their different types, properties of nanomaterials, and cancer biomarkers. Among all types of biosensors, electrochemical and optical biosensors are the most sensitive and promising sensors for detecting complicated diseases like cancer. The carbon-based nanomaterial family has attracted lots of attention due to their low cost, easy preparation, biocompatibility, and significant electrochemical and optical properties. In this review, we have discussed the application of graphene and its derivatives, carbon nanotubes (CNTs), carbon dots (CDs), and fullerene (C60), for designing different electrochemical and optical cancer-detecting biosensors. Furthermore, the application of these carbon-based biosensors for detecting seven widely studied cancer biomarkers (HER2, CEA, CA125, VEGF, PSA, Alpha-fetoprotein, and miRNA21) is reviewed. Finally, various fabricated carbon-based biosensors for detecting cancer biomarkers and anticancer drugs are comprehensively summarized as well.

Construction of MOF@COF composite-based electrochemical aptasensor for detection of Staphylococcus aureus

In this work, a biological metal-organic framework@conductive covalent organic framework composite (bio-MOF@con-COF, denoted as Zn-Glu@PTBD-COF, here, Glu indicates L-glutamic acid, PT indicates 1,10-phenanthroline-2,9-dicarbaldehyde, and BD indicates benzene-1,4-diamine) was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). The Zn-Glu@PTBD-COF integrates the mesoporous structure and abundant defects of the MOF framework, the excellent conductivity of the COF framework, and high stability of the composite, providing abundant active sites to effectively anchor aptamers. As a result, the Zn-Glu@PTBD-COF-based aptasensor shows high sensitivity to detect SA via specific recognition between aptamer and SA, as well as the formation of aptamer-SA complex. Low detection limits of 2.0 and 1.0 CFU·mL^-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-10⁸ CFU·mL^-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples. Therefore, the Zn-Glu@PTBD-COF-based aptasensor will be promising for fast screening of foodborne bacteria in food service industry. Zn-Glu@PTBD-COF composite was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). Low detection limits of 2.0 and 1.0 CFU·mL^-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-10⁸ CFU·mL^-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples.

A versatile platform for colorimetric, fluorescence and photothermal multi-mode glyphosate sensing by carbon dots anchoring ferrocene metal-organic framework nanosheet

Concerns regarding pesticide residues have driven attempts to exploit accurate, prompt and straightforward approaches for food safety pre-warning. Herein, a nanozyme-mediated versatile platform with multiplex signal response (colorimetric, fluorescence and temperature) was proposed for visual, sensitive and portable detection of glyphosate (GLP). The platform was constructed based on a N-CDs/FMOF-Zr nanosensor that prepared by in situ anchoring nitrogen-doped carbon dots onto zirconium-based ferrocene metal-organic framework nanosheets. The N-CDs/FMOF-Zr possessed excellent peroxidase (POD)-like activity and thus could oxide colorless 3, 3', 5, 5'-tetramethylbenzidine (TMB) into a blue oxidized TMB (oxTMB) in presence of H₂O₂. Intriguingly, owing to the blocking effect triggered by multiple interaction between GLP and N-CDs/FMOF-Zr, its POD-like activity of the latter was remarkably suppressed, which can modulate the transformation of TMB into oxTMB, generating tri-signal responses of fluorescence enhancement, absorbance and temperature decrease. More significantly, the temperature mode can be facilely realized by a portable home-made mini-photothermal device and handheld thermometers. The proposed multimodal sensing was capable of providing sensitive results by fluorescence mode and simultaneously realized visual/portable testing by colorimetric and photothermal channels. Consequently, it exhibited more adaptability for practical applications, which can satisfy different testing requirements according to sensitivity and available instruments/meters, presenting a new horizon for exploiting multifunctional sensors.

Recent Advances of Anticancer Studies Based on Nano-Fluorescent Metal-Organic Frameworks

Nano-fluorescent metal-organic frameworks (NF-MOFs), a kind of newly emerged nano-scaled platform, can provide visual, rapid, and highly sensitive optical imaging of cancer lesions both in vitro and in vivo. Meanwhile, the excellent porosity, structural tunability, and chemical modifiability also enable NF-MOFs to achieve simultaneous loading of targeted molecules and therapeutic agents. These NF-MOFs not only possess excellent targeted imaging ability, but also can guide the carried cargos to perform precise therapy, drawing considerable attention in current framework of anticancer drug design. In this review, we outline the fluorescence types and response mechanisms of NF-MOFs, and highlight their applications in cancer diagnosis and therapy in recent years. Based on this panorama, we also discuss current issues and future trends of NF-MOFs in biomedical fields, attempting to clarify the potential value of fluorescence imaging guided anticancer investigations.

Current Update on Biomarkers for Detection of Cancer: Comprehensive Analysis

Early and effective diagnosis of cancer is decisive for its proper management. In this context biomarker-based cancer diagnosis is budding as one of the promising ways for early detection, disease progression monitoring, and effective cancer therapy. Integration of Biosensing devices with different metallic/nonmetallic nanoparticles offers amplification and multiplexing capabilities for simultaneous detection of cancer biomarkers (CB's). This study provides a comprehensive analysis of the most recent designs and fabrication methodologies designed for developing electrochemical biosensors (EB) for early detection of cancers. The role of biomarkers in cancer therapeutics is also discussed.

Applications of carbon dots and its modified carbon dots in bone defect repair

Bone defect repair is a continual and complicated process driven by a variety of variables. Because of its bright multicolor luminescence, superior biocompatibility, water dispersibility, and simplicity of synthesis from diverse carbon sources, carbon dots (CDs) have received a lot of interest. It has a broad variety of potential biological uses, including bone defect repair, spinal cord injury, and wound healing. Materials including CDs as the matrix or major component have shown considerable benefits in enabling bone defect healing in recent years. By altering the carbon dots or mixing them with other wound healing-promoting agents or materials, the repair effect may be boosted even further. The report also shows and discusses the use of CDs to heal bone abnormalities. The study first presents the fundamental features of CDs in bone defect healing, then provides CDs manufacturing techniques that should be employed in bone defect repair, and lastly examines their development in the area of bioengineering, particularly in bone defect repair. In this work, we look at how carbon dots and their alteration products may help with bone defect healing by being antibacterial, anti-infective, osteogenic differentiation-promoting, and gene-regulating.

Sensing performance and mechanism of carbon dots encapsulated into metal-organic frameworks

Metal-organic frameworks (MOFs) can be combined with nanomaterials and the combined composites have excellent optical properties. Carbon dots (CDs) with tiny particle size, non-toxic and rich surface functional groups are novel fluorescent materials. Carbon dots@metal-organic frameworks (CDs@MOFs) are synthesized by encapsulating CDs into MOFs. CDs@MOFs are promising composites for the preparation of a new generation of fluorescence sensors, which combine the hybrid properties of MOFs and the special optical properties of CDs. Urged as such, we are encouraged to categorize according to the sensing mechanisms. These include fluorescence resonance energy transfer (FRET), aggregation-caused quenching (ACQ), static quenching, dynamic quenching, photo-induced electron transfer (PET), inner filter effect (IFE) and so on. Based on the above mechanisms, CDs@MOFs can specifically interact with target analytes to generate fluorescence quenching. This review covers the research progress of CDs@MOFs in recent five years (with 103 refs), synthetic design of CDs@MOFs and introduces the sensing mechanism. The current challenges and future research directions are discussed briefly. The sensing mechanism and applications of CDs@MOFs.

Recent Advances in the Application and Mechanism of Carbon Dots/Metal-Organic Frameworks Hybrids in Photocatalysis and the Detection of Environmental Pollutants

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with simple synthesis conditions, large specific surface area, structural diversity, and a wide range of interesting properties. The integration of MOFs with other materials can provide new multifunctional composites that exhibit both component properties and new characteristics. In recent years, the integration of carbon dots (CDs) into MOFs to form composites has shown improved optical properties and fascinating new characteristics. This review focuses on the design and synthesis strategies of CDs@MOFs composites (including pore-confined synthesis, in situ encapsulation, post-synthesis modification and impregnation method) and their recent research progress in photocatalysis and detection of environmental pollutants. Both the achievements and problems are evaluated and proposed, and the opportunities and challenges of CDs@MOF composite are discussed.

Biorecognition Engineering Technologies for Cancer Diagnosis: A Systematic Literature Review of Non-Conventional and Plausible Sensor Development Methods

Cancer is the second cause of mortality worldwide. Early diagnosis of this multifactorial disease is challenging, especially in populations with limited access to healthcare services. A vast repertoire of cancer biomarkers has been studied to facilitate early diagnosis; particularly, the use of antibodies against these biomarkers has been of interest to detect them through biorecognition. However, there are certain limitations to this approach. Emerging biorecognition engineering technologies are alternative methods to generate molecules and molecule-based scaffolds with similar properties to those presented by antibodies. Molecularly imprinted polymers, recombinant antibodies, and antibody mimetic molecules are three novel technologies commonly used in scientific studies. This review aimed to present the fundamentals of these technologies and address questions about how they are implemented for cancer detection in recent scientific studies. A systematic analysis of the scientific peer-reviewed literature regarding the use of these technologies on cancer detection was carried out starting from the year 2000 up to 2021 to answer these questions. In total, 131 scientific articles indexed in the Web of Science from the last three years were included in this analysis. The results showed that antibody mimetic molecules technology was the biorecognition technology with the highest number of reports. The most studied cancer types were: multiple, breast, leukemia, colorectal, and lung. Electrochemical and optical detection methods were the most frequently used. Finally, the most analyzed biomarkers and cancer entities in the studies were carcinoembryonic antigen, MCF-7 cells, and exosomes. These technologies are emerging tools with adequate performance for developing biosensors useful in cancer detection, which can be used to improve cancer diagnosis in developing countries.

Recent advances in biosensor devices for HER-2 cancer biomarker detection

The human epidermal growth factor receptor 2 (HER-2) protein is a member of the epidermal growth factor receptor (EGFR or ErbB) family and is a transmembrane tyrosine kinase receptor. HER-2 is highly regulated in ovarian, lung, gastric, oral, and breast cancers. The low specificity, complexity, expensiveness and the lack of sensitivity are essential restrictions in traditional diagnosis methods such as FISH, immunohistochemistry and PCR and these disadvantages led to the need for more studies on alternative methods. Biosensor technology has greatly affected the quality of human life owing to its features including, sensitivity, specificity, and rapid diagnosis and monitoring of different patient diseases. In this review article, we examine various biosensors, considering that they have been categorized based on the transducers used including piezoelectric biosensors, optical sensors such as fluorescence and surface plasmon resonance, and electrochemical types for the diagnosis of HER-2 and the effectiveness of some drugs against that. Attention to developing some types of biosensor devices such as colorimetric biosensors for HER-2 detection can be an important point in future studies.

A high-performance electrochemical aptasensor based on graphene-decorated rhodium nanoparticles to detect HER2-ECD oncomarker in liquid biopsy

Evaluation of extracellular domain of human epidermal growth factor receptor-2 (HER2-ECD) oncomarker status is an impressive factor in screening, diagnosing and monitoring early-stage breast cancer (BC). Electrochemical aptamer-based nanobiosensor with high sensitivity and selectivity for quantitative and qualitative measurement of HER2-ECD oncomarker was developed. In this study, the nanocomposite made by distinct materials included reduced graphene oxide nano-sheets (rGONs) and rhodium nanoparticles (Rh-NPs) on the graphite electrode (GE) surface. This structure resulted in amplified electrochemical activity, high surface area, stability, and bio-compatibility. Each of the steps of preparing nanomaterials and setting up biosensor were carefully examined by analytical and electrochemical techniques. Various modified electrodes were constructed and analyzed in terms of electrochemical performance, morphology, size, and shape of nanomaterials. The GE-based aptasensor had a noteworthy and conducive results against HER2-ECD with a wide dynamic range of 10.0-500.0 ng/mL, a low limit of detection (LOD) of 0.667 ng/mL (significantly less than the clinical cut-off), and a low limit of quantification (LOQ) of 2.01 ng/mL. The benefits provided by this aptasensor such as broad dynamic range, high sensitivity, selectivity, stability, reproducibility, and low cost suggest tremendous potential for non-invasive detection and monitoring of the HER2-ECD levels of BC care and clinical diagnosis.

A Review of Biosensors for Detecting Tumor Markers in Breast Cancer

Breast cancer has the highest cancer incidence rate in women. Early screening of breast cancer can effectively improve the treatment effect of patients. However, the main diagnostic techniques available for the detection of breast cancer require the corresponding equipment, professional practitioners, and expert analysis, and the detection cost is high. Tumor markers are a kind of active substance that can indicate the existence and growth of the tumor. The detection of tumor markers can effectively assist the diagnosis and treatment of breast cancer. The conventional detection methods of tumor markers have some shortcomings, such as insufficient sensitivity, expensive equipment, and complicated operations. Compared with these methods, biosensors have the advantages of high sensitivity, simple operation, low equipment cost, and can quantitatively detect all kinds of tumor markers. This review summarizes the biosensors (2013-2021) for the detection of breast cancer biomarkers. Firstly, the various reported tumor markers of breast cancer are introduced. Then, the development of biosensors designed for the sensitive, stable, and selective recognition of breast cancer biomarkers was systematically discussed, with special attention to the main clinical biomarkers, such as human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER). Finally, the opportunities and challenges of developing efficient biosensors in breast cancer diagnosis and treatment are discussed.

Fabricated Metal-Organic Frameworks (MOFs) as luminescent and electrochemical biosensors for cancer biomarkers detection

In the health domain, a major challenge is the detection of diseases using rapid and cost-effective techniques. Most of the existing cancer detection methods show poor sensitivity and selectivity and are time consuming with high cost. To overcome this challenge, we analyzed porous fabricated metal-organic frameworks (MOFs) that have better structures and porosities for enhanced biomarker sensing. Here, we summarize the use of fabricated MOF luminescence and electrochemical sensors in devices for cancer biomarker detection. Various strategies of fabrication and the role of fabricated materials in sensing cancer biomarkers have been studied and described. The structural properties, sensing mechanisms, roles of noncovalent interactions, limits of detection, modeling, advantages, and limitations of MOF sensors have been well-discussed. The study presents an innovative technique to detect the cancer biomarkers by the use of luminescence and electrochemical MOF sensors. In addition, the potential association studies have been opening the way for personalized patient treatments and the development of new cancer-detecting devices.

Recent Advances in Metal-Organic Framework-Based Electrochemical Biosensing Applications

In the face of complex environments, considerable effort has been made to accomplish sensitive, accurate and highly-effective detection of target analytes. Given the versatility of metal clusters and ligands, high porosity and large specific surface area, metal–organic framework (MOF) provides researchers with prospective solutions for the construction of biosensing platforms. Combined with the benefits of electrochemistry method such as fast response, low cost and simple operation, the untapped applications of MOF for biosensors are worthy to be exploited. Therefore, this review briefly summarizes the preparation methods of electroactive MOF, including synthesize with electroactive ligands/metal ions, functionalization of MOF with biomolecules and modification for MOF composites. Moreover, recent biosensing applications are highlighted in terms of small biomolecules, biomacromolecules, and pathogenic cells. We conclude with a discussion of future challenges and prospects in the field. It aims to offer researchers inspiration to address the issues appropriately in further investigations.

Metal-organic frameworks based hybrid nanocomposites as state-of-the-art analytical tools for electrochemical sensing applications

Metal-organic frameworks (MOFs) are remarkably porous materials that have sparked a lot of interest in recent years because of their fascinating architectures and variety of potential applications. This paper systematically summarizes recent breakthroughs in MOFs and their derivatives with different materials such as, carbon nanotubes, graphene oxides, carbon fibers, enzymes, antibodies and aptamers etc. for enhanced electrochemical sensing applications. Furthermore, an overview part is highlighted, which provides some insights into the future prospects and directions of MOFs and their derivatives in electrochemical sensing, with the goal of overcoming present limitations by pursuing more inventive ways. This overview can perhaps provide some creative ideas for future research on MOF-based materials in this rapidly expanding field.

Recent Advances in Functional Carbon Quantum Dots for Antitumour

Carbon quantum dots (CQDs) are an emerging class of quasi-zero-dimensional photoluminescent nanomaterials with particle sizes less than 10 nm. Owing to their favourable water dispersion, strong chemical inertia, stable optical performance, and good biocompatibility, CQDs have become prominent in biomedical fields. CQDs can be fabricated by “top-down” and “bottom-up” methods, both of which involve oxidation, carbonization, pyrolysis and polymerization. The functions of CQDs include biological imaging, biosensing, drug delivery, gene carrying, antimicrobial performance, photothermal ablation and so on, which enable them to be utilized in antitumour applications. The purpose of this review is to summarize the research progress of CQDs in antitumour applications from preparation and characterization to application prospects. Furthermore, the challenges and opportunities of CQDs are discussed along with future perspectives for precise individual therapy of tumours.

Recent advances in metal/covalent organic framework-based electrochemical aptasensors for biosensing applications

The booming development of novel porous materials, metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) has been attracting a lot of attention due to their designabilities, diversities, and extensive applications. MOFs and COFs provide a new potential opportunity and platform to fabricate electrochemical aptasensors for biosensing applications. Compared to other traditional materials, MOF/COF-based electrochemical biosensors can appreciably amplify the electrochemical response signals to improve the sensing performance. Herein, we provide a comprehensive overview of MOF/COF-based electrochemical aptasensors for monitoring different ultra-trace analytes (e.g. antibiotics, pesticides, and cancer markers). This review systematically discusses the classification of electrochemical aptasensors based on various functional materials, including pure MOFs, MOF/conductive composites, metal nanoparticle/MOF composites, pure COFs, COFs/conductive composites, and other hybrid materials. Furthermore, some typical MOF/COF-based electrochemical aptasensors in the recognition of specific targets are described in detail to improve and guide further research for biosensing applications.

Applications of scaffold-based advanced materials in biomedical sensing

There have been many efforts to synthesize advanced materials that are capable of real-time specific recognition of a molecular target, and allow the quantification of a variety of biomolecules. Scaffold materials have a porous structure, with a high surface area and their intrinsic nanocavities can accommodate cells and macromolecules. The three-dimensional structure (3D) of scaffolds serves not only as a fibrous structure for cell adhesion and growth in tissue engineering, but can also provide the controlled release of drugs and other molecules for biomedical applications. There has been a limited number of reports on the use of scaffold materials in biomedical sensing applications. This review highlights the potential of scaffold materials in the improvement of sensing platforms and summarizes the progress in the application of novel scaffold-based materials as sensor, and discusses their advantages and limitations. Furthermore, the influence of the scaffold materials on the monitoring of infectious diseases such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and bacterial infections, was reviewed.

Nanotechnology in Colorectal Cancer for Precision Diagnosis and Therapy

Colorectal cancer (CRC) is the third most frequently occurring tumor in the human population. CRCs are usually adenocarcinomatous and originate as a polyp on the inner wall of the colon or rectum which may become malignant in the due course of time. Although the therapeutic options of CRC are limited, the early diagnosis of CRC may play an important role in preventive and therapeutic interventions to decrease the mortality rate. The CRC-affected tissues exhibit several molecular markers that may be exploited as the novel strategy to develop newer approaches for the treatment of the disease. Nanotechnology consists of a wide array of innovative and astonishing nanomaterials with both diagnostics and therapeutic potential. Several nanomaterials and nano formulations such as Carbon nanotubes, Dendrimer, Liposomes, Silica Nanoparticles, Gold nanoparticles, Metal-organic frameworks, Core-shell polymeric nano-formulations, Nano-emulsion System, etc can be used to targeted anticancer drug delivery and diagnostic purposes in CRC. The light-sensitive photosensitizer drugs loaded gold and silica nanoparticles can be used to diagnose as well as the killing of CRC cells by the targeted delivery of anticancer drugs to cancer cells. This review is focused on the recent advancement of nanotechnology in the diagnosis and treatment of CRC.

Reversible capturing and voltammetric determination of circulating tumor cells using two-dimensional nanozyme based on PdMo decorated with gold nanoparticles and aptamer

A novel cytosensor was constructed for the ultrasensitive detection and nondestructive release of circulating tumor cells (CTCs) by combining Au nanoparticles-loaded two-dimensional bimetallic PdMo (2D Au@PdMo) nanozymes and electrochemical reductive desorption. The 2D Au@PdMo nanozymes possessed high-efficiency peroxidase-like activity and were assembled with an aptamer composed of a thiol-modified epithelial specific cell adhesion molecule (EpCAM) to strengthen CTCs adhesion. Moreover, the electrode surface was decorated with highly fractal Au nanostructures (HFAuNSs) composites due to the similarity in fractal nanostructure with the CTCs membrane to enhance the CTCs anchoring efficiency and release capability. The captured CTCs could be further efficiently dissociated and nondestructively released from the modified electrodes upon electrochemical reductive desorption. The designed cytosensor showed an excellent analytical performance, with a wide linear range from 2 to 1 × 10⁵ cells mL^-1 and low limit of detection (LOD) of 2 cells mL^-1 (S/N = 3) at the working potential in the range  -0.6 to 0.2 V. A satisfactory CTCs release reaching a range of 93.7-97.4% with acceptable RSD from 3.55 to 6.41% and good cell viability was obtained. Thus, the developed cytosensor might provide a potential alternative to perform CTC-based liquid biopsies, with promising applications in early diagnosis of tumors. Preparation and mechanism of desorption of the cytosensor based on 2D Au@PdMo nanozymes and electrochemical reductive desorption for the detection and release of CTCs. A Preparation procedure of the Apt/Au@PbMo bioconjugates. B Fabrication process of the sandwich-type cytosensor. C Electrochemical signal produced by the Au@PdMo nanozymes. D Mechanism of electrochemical reductive desorption for CTCs release.

Recent advances in nanomaterials-based electrochemical immunosensors and aptasensors for HER2 assessment in breast cancer

Human epidermal growth factor receptor 2 (HER2) is one of the key molecular targets in breast cancer pathogenesis. Overexpression and/or amplification of HER2 in approximately 15-20% of breast cancer patients is associated with high mortality and poor prognosis. Accumulating evidence shows that accurate and sensitive detection of HER2 improves the survival outcomes for HER2-positive breast cancer patients from targeted therapies. The current methods of clinical determination of HER2 expression levels are based on slide-based assays that rely on invasively collected primary tumours. Alternatively, ELISA-based detection of the shredded HER2 extracellular domain (HER2-ECD) of has been suggested as a surrogate method for monitoring disease progress and treatment response in breast cancer patients. In the past decade, biosensors have emerged as an alternative modality for the detection of circulating HER2-ECD in human serum samples. In particular, electrochemical biosensors based on nanomaterials and antibodies and aptamers have been increasingly developed as promising tools for rapid, sensitive, and cost-effective detection of HER2-ECD. These biosensors harness the high affinity and specificity of antibodies and aptamers, and unique conductive properties, biocompatibility, large surface area, and chemical stability of nanomaterials for selective and sensitive assessment of the HER2. This review provides an overview of the recent advances in the application of nanomaterials-based immunosensors and aptasensors for detection of circulating HER2-ECD. In particular, various electrochemical techniques, detection approaches, and nanomaterials are discussed. Further, analytical figures of merit of various HER2 immunosensors and aptasensors are compared. Finally, possible challenges and potential opportunities for biosensor-based detection of HER2-ECD are discussed.

Synthesis and modification of carbon dots for advanced biosensing application

There has been an explosion of interest in the use of nanomaterials for biosensing applications, and carbonaceous nanomaterials in particular are at the forefront of this explosion. Carbon dots (CDs), a new type of carbon material, have attracted extensive attention due to their fascinating properties, such as small particle size, tunable optical properties, good conductivity, low cytotoxicity, and good biocompatibility. These properties have enabled them to be highly promising candidates for the fabrication of various high-performance biosensors. In this review, we summarize the top-down and bottom-up synthesis routes of CDs, highlight their modification strategies, and discuss their applications in the fields of photoluminescence biosensors, electrochemiluminescence biosensors, chemiluminescence biosensors, electrochemical biosensors and fluorescence biosensors. In addition, the challenges and future prospects of the application of CDs for biosensors are also proposed.

Electrochemical Sensing in 3D Cell Culture Models: New Tools for Developing Better Cancer Diagnostics and Treatments

Currently, conventional pre-clinical in vitro studies are primarily based on two-dimensional (2D) cell culture models, which are usually limited in mimicking the real three-dimensional (3D) physiological conditions, cell heterogeneity, cell to cell interaction, and extracellular matrix (ECM) present in living tissues. Traditionally, animal models are used to mimic the 3D environment of tissues and organs, but they suffer from high costs, are time consuming, bring up ethical concerns, and still present many differences when compared to the human body. The applications of microfluidic-based 3D cell culture models are advantageous and useful as they include 3D multicellular model systems (MCMS). These models have demonstrated potential to simulate the in vivo 3D microenvironment with relatively low cost and high throughput. The incorporation of monitoring capabilities in the MCMS has also been explored to evaluate in real time biophysical and chemical parameters of the system, for example temperature, oxygen, pH, and metabolites. Electrochemical sensing is considered as one of the most sensitive and commercially adapted technologies for bio-sensing applications. Amalgamation of electrochemical biosensing with cell culture in microfluidic devices with improved sensitivity and performance are the future of 3D systems. Particularly in cancer, such models with integrated sensing capabilities can be crucial to assess the multiple parameters involved in tumour formation, proliferation, and invasion. In this review, we are focusing on existing 3D cell culture systems with integrated electrochemical sensing for potential applications in cancer models to advance diagnosis and treatment. We discuss their design, sensing principle, and application in the biomedical area to understand the potential relevance of miniaturized electrochemical hybrid systems for the next generation of diagnostic platforms for precision medicine.

Aptamer-functionalized metal-organic frameworks (MOFs) for biosensing

As a class of crystalline porous materials, metal-organic frameworks (MOFs) have attracted increasing attention. Due to the nanoscale framework structure, adjustable pore size, large specific surface area, and good chemical stability, MOFs have been applied widely in many fields such as biosensors, biomedicine, electrocatalysis, energy storage and conversions. Especially when they are combined with aptamer functionalization, MOFs can be utilized to construct high-performance biosensors for numerous applications ranging from medical diagnostics and food safety inspection, to environmental surveillance. Herein, this article reviews recent innovations of aptamer-functionalized MOFs-based biosensors and their bio-applications. We first briefly introduce different functionalization methods of MOFs with aptamers, which provide a foundation for the construction of MOFs-based aptasensors. Then, we comprehensively summarize different types of MOFs-based aptasensors and their applications, in which MOFs serve as either signal probes or signal probe carriers for optical, electrochemical, and photoelectrochemical detection, with an emphasis on the former. Given recent substantial research interests in stimuli-responsive materials and the microfluidic lab-on-a-chip technology, we also present the stimuli-responsive aptamer-functionalized MOFs for sensing, followed by a brief overview on the integration of MOFs on microfluidic devices. Current limitations and prospective trends of MOFs-based biosensors are discussed at the end.

Recent Developments in Carbon Quantum Dots: Properties, Fabrication Techniques, and Bio-Applications

Carbon dots have gained tremendous interest attributable to their unique features. Two approaches are involved in the fabrication of quantum dots (Top-down and Bottom-up). Most of the synthesis methods are usually multistep, required harsh conditions, and costly carbon sources that may have a toxic effect, therefore green synthesis is more preferable. Herein, the current review presents the green synthesis of carbon quantum dots (CQDs) and graphene quantum dots (GQDs) that having a wide range of potential applications in bio-sensing, cellular imaging, and drug delivery. However, some drawbacks and limitations are still unclear. Other biomedical and biotechnological applications are also highlighted.