Targeted bioimaging and sensing of folate receptor-positive cancer cells using folic acid-conjugated sulfur-doped graphene quantum dots

Electrochemical biosensor based on PAMAM functionalized MXene nanoplatform for detection of folate receptor

The level of folate receptor (FR) has become one of the independent factors for measuring human tumor diseases. The precise quantification of FR is helpful for the early diagnosis and subsequent treatment of tumors. The modification of electrodes is a key issue in ensuring and enhancing the electrochemical biosensing ability. In this study, we in-situ synthesized a nanocomposite material with excellent conductivity and stability by grafting first-generation poly(amidoamine) dendrimers onto the MXene (Ti3C2TX) as the immobilized matrix (PAMAM@MXene). An electrochemical sensor was developed for FR monitor by loading the PAMAM@MXene on screen-printed carbon electrodes (SPCEs). Scanning electron microscopy (SEM) supported the effective synthesis of PAMAM@MXene. Under optimal conditions, the prepared sensor achieved the quantification of FR with a wide range of concentrations from 10 ng/mL to 1000 ng/mL with a detection limit (LOD) of 5.6 ng/mL. It also exhibited satisfactory selectivity, reproducibility, and stability, which provided the possibility for expanding new pathways in the detection of clinical FR.

Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer

Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.

Selective cytotoxic effects of nitrogen-doped graphene coated mixed iron oxide nanoparticles on HepG2 as a new potential therapeutic approach

New selective therapeutics are needed for the treatment of hepatocellular carcinoma (HCC), the 7th most common cancer. In this study, we compared the cytotoxic effect induced by the release of pH-dependent iron nanoparticles from nitrogen-doped graphene-coated mixed iron oxide nanoparticles (FexOy/N-GN) with the cytotoxic effect of nitrogen-doped graphene (N-GN) and commercial graphene nanoflakes (GN) in Hepatoma G2 (HepG2) cells and healthy cells. The cytotoxic effect of nanocomposites (2.5-100 ug/ml) on HepG2 and healthy fibroblast (BJ) cells (12-48 h) was measured by Cell Viability assay, and the half maximal inhibitory concentration (IC50) was calculated. After the shortest (12 h) and longest incubation (48 h) incubation periods in HepG2 cells, IC50 values of FexOy/N-GN were calculated as 21.95 to 2.11 µg.mL-1, IC50 values of N-GN were calculated as 39.64 to 26.47 µg.mL-1 and IC50 values of GN were calculated as 49.94 to 29.94, respectively. After 48 h, FexOy/N-GN showed a selectivity index (SI) of 10.80 for HepG2/BJ cells, exceeding the SI of N-GN (1.27) by about 8.5-fold. The high cytotoxicity of FexOy/N-GN was caused by the fact that liver cancer cells have many transferrin receptors and time-dependent pH changes in their microenvironment increase iron release. This indicates the potential of FexOy/N-GN as a new selective therapeutic.

Package delivered: folate receptor-mediated transporters in cancer therapy and diagnosis

Neoplasias pose a significant threat to aging society, underscoring the urgent need to overcome the limitations of traditional chemotherapy through pioneering strategies. Targeted drug delivery is an evolving frontier in cancer therapy, aiming to enhance treatment efficacy while mitigating undesirable side effects. One promising avenue utilizes cell membrane receptors like the folate receptor to guide drug transporters precisely to malignant cells. Based on the cellular folate receptor as a cancer cell hallmark, targeted nanocarriers and small molecule-drug conjugates have been developed that comprise different (bio) chemistries and/or mechanical properties with individual advantages and challenges. Such modern folic acid-conjugated stimuli-responsive drug transporters provide systemic drug delivery and controlled release, enabling reduced dosages, circumvention of drug resistance, and diminished adverse effects. Since the drug transporters' structure-based de novo design is increasingly relevant for precision cancer remediation and diagnosis, this review seeks to collect and debate the recent approaches to deliver therapeutics or diagnostics based on folic acid conjugated Trojan Horses and to facilitate the understanding of the relevant chemistry and biochemical pathways. Focusing exemplarily on brain and breast cancer, recent advances spanning 2017 to 2023 in conjugated nanocarriers and small molecule drug conjugates were considered, evaluating the chemical and biological aspects in order to improve accessibility to the field and to bridge chemical and biomedical points of view ultimately guiding future research in FR-targeted cancer therapy and diagnosis.

In vivo imaging of prostate tumor-targeted folic acid conjugated quantum dots

Cancer is a major threat to human health; thus, early detection is imperative for successful management. Rapid diagnosis can be achieved by imaging primary (subcutaneous) tumors using fluorophores conjugated with tumor markers. Here, the application of biocompatible, quantum efficient, monodisperse, and photostable polymer-coated quantum dots (PQDs) is demonstrated for targeted prostate tumor imaging in living SCID mice. Briefly, PQDs (blue) are conjugated to folic acid (FA-PQDs) using DCC-NHS chemistry. Initially, in vitro targeted imaging via FA-PQDs is evaluated in LNCaP cells. The confocal microscopic evaluation demonstrates the uptake of FA-PQDs. To understand the dispersion of PQDs in vivo, the biodistribution of PQDs is assessed at different time intervals (1- 180 min) using whole-body fluorescence imaging and computed tomography (CT) scan. PQDs are seen to accumulate in organs like the liver, kidneys, spleen, lungs, and urinary bladder within 60 min, however, PQDs are not observed at 180 min indicating renal clearance. Further, to target the prostate tumor (~ 200 mm3) in mice, FA-PQDs are injected intravenously, and whole-body fluorescence imaging along with a CT scan is recorded. FA-PQDs are seen at the tumor site as compared to PQDs. The results confirm that the FA-PQDs function as excellent nanoprobes for targeted tumor imaging in vivo.

Interaction between carbon dots from folic acid and their cellular receptor: a qualitative physicochemical approach

According to the World Health Organization, the number of cancers (all cancers, both sexes, all ages and worldwide) in 2020 reached a total of 19 292 789 new cases leading to 9 958 133 deaths during the same period. Many cancers could be cured if detected early. Preventing cancer and detecting it early are two essential strategies for controlling this pathology. For this purpose, several strategies have been described for imaging cancer cells. One of them is based on the use of carbon nanoparticles called carbon dots, tools of physical chemistry. The literature describes that cancer cells can be imaged using carbon dots obtained from folic acid and that the in cellulo observed photoluminescence probably results from the interaction of these nanoparticles with the folic acid-receptor, a cell surface protein overexpressed in many malignant cells. However, this interaction has never been directly demonstrated yet. We investigated it, for the first time, using (i) freshly synthesized and fully characterized carbon dots, (ii) folate binding protein, a folic acid-receptor model protein and (iii) fluorescence spectroscopy and isothermal titration calorimetry, two powerful methods for detecting molecular interactions. Our results even highlight a selective interaction between these carbon made nano-objects and their biological target.

Probe sonication-assisted rapid synthesis of highly fluorescent sulfur quantum dots

A new type of heavy-metal free single-element nanomaterial, called sulfur quantum dots (SQDs), has gained significant attention due to its advantages over traditional semiconductor QDs for several biomedical and optoelectronic applications. A straightforward and rapid synthesis approach for preparing highly fluorescent SQDs is needed to utilize this nanomaterial for technological applications. Until now, only a few synthesis approaches have been reported; however, these approaches are associated with long reaction times and low quantum yields (QY). Herein, we propose a novel optimized strategy to synthesize SQDs using a mix of probe sonication and heating, which reduces the reaction time usually needed from 125 h to a mere 15 min. The investigation employs cavitation and vibration effects of high energy acoustic waves to break down the bulk sulfur into nano-sized particles in the presence of highly alkaline medium and oleic acid. In contrast to previous reports, the obtained SQDs exhibited excellent aqueous solubility, desirable photostability, and a relatively high photoluminescence QY up to 10.4% without the need of any post-treatment. Additionally, the as-synthesized SQDs show excitation-dependent emission and excellent stability in different pH (2-12) and temperature (20 °C-80 °C) environments. Hence, this strategy opens a new pathway for rapid synthesis of SQDs and may facilitate the use of these materials for biomedical and optoelectronic applications.

Distinguishing the Cellular Transport of Folic Acid Conjugated Nano-Drugs among Different Cell Lines by Using Force Tracing Technique

Folic acid (FA) is a ligand that has been renowned for its strong binding to FA receptor (FR), and the robustness of the specific interaction has led to the generation of multitudinous tumor-targeted nano-drug delivery systems. However, selecting the appropriate FA targeted nano-drugs according to types of cancerous cells to achieve a high effect is critical. Understanding of how the drug is transported through the cell membrane and is delivered intracellularly is very important in screening ideal targeted nano-drugs for cancerous changes in different organs. Herein, by using a force tracing technique based on atomic force microscopy (AFM), the dynamic process of FA-polyamidoamine-Doxorubicin (FA-PAMAM-DOX) entry into different tumor cells (HeLa and A549) and normal cells (Vero) was monitored in real time. The cell membrane transport efficacy of FA-PAMAM-DOX in tumor cells with an FR high overexpression level (HeLa) and FR low overexpression level (A549) is analyzed, which is significantly higher than that in normal cells (Vero), especially for HeLa cells. Subsequently, the intracellular delivery efficiency of FA-PAMAM-DOX in different cell lines was measured by using fluorescence imaging and AFM-based nanoindentation techniques. This report will help to discover the cellular transport mechanism of nano-drugs and screen out optimal therapeutic nano-drugs for different types of tumors.

A biocompatible polyurethane fluorescent emulsion with aggregation-induced emission for targeted tumor imaging

The applications of fluorescence imaging in tumor detection and assistance in tumor resection have become progressively more widespread. Biocompatible fluorescent nanoparticles with high sensitivity and selectivity are a challenge for biological fluorescence imaging. Ligand-mediated targeting of nanoparticles to tumors is an appealing tactic for improving imaging efficiency. Herein, tetraphenyl ethylene (TPE) and phenylboronic acid (PBA) were introduced into polyurethane to synthesize a PU-TPE-PBA (PTP) fluorescent emulsion with aggregation-induced emission (AIE) for targeted tumor imaging. The PTP emulsion with a size of less than 50 nm shows excellent stability and high fluorescence sensitivity (extremely low TPE concentrations of 0.31 μg mL^-1). Since PBA can selectively recognize and bind to sialic acid (SA) which is widely overexpressed in tumor cells, such PTP nanoparticles can be enriched in tumors and retained for longer periods due to enhanced permeability and retention (EPR) as well as active targeting effects. In addition, the PTP emulsion exhibits good biocompatibility and biosafety. Therefore, the novel PTP emulsion is promising for tumor cell imaging.

Fluorescence anisotropy cytosensing of folate receptor positive tumor cells using 3D polyurethane-GO-foams modified with folic acid: molecular dynamics and in vitro studies

Integrated polyurethane (PU)-based foams modified with PEGylated graphene oxide and folic acid (PU@GO-PEG-FA) were developed with the goal of capturing and detecting tumor cells with precision. The detection of the modified PU@GO-PEG surface through FA against folate receptor-overexpressed tumor cells is the basis for tumor cell capture. Molecular dynamics (MD) simulations were applied to study the strength of FA interactions with the folate receptor. Based on the obtained results, the folate receptor has intense interactions with FA, which leads to the reduction in the FA interactions with PEG, and so decreases the fluorescence intensity of the biosensor. The synergistic interactions offer the FA-modified foams a high efficiency for capturing the tumor cell. Using a turn-off fluorescence technique based on the complicated interaction of FA-folate receptor generated by target recognition, the enhanced capture tumor cells could be directly read out at excitation-emission wavelengths of 380-450 nm. The working range is between 1×10 ² to 2×10 ⁴ cells mL ^-1 with a detection limit of 25 cells mL ^-1 and good reproducibility with relative standard deviation of 2.35%. Overall, findings demonstrate that the fluorescence-based biosensor has a significant advantage for early tumor cell diagnosis.

The effect of charge on Zn tetra morpholine porphyrin conjugated to folic acid-nitrogen doped graphene quantum dots for photodynamic therapy studies

Zinc tetra morpholine porphyrin (complex 2), and its quaternized derivative (complex 3) were synthesized and conjugated to folic acid nitrogen doped graphene quantum dots (FA-NGQDs) through π-π stacking to study their photodynamic therapy (PDT) efficacy. Photophysiochemical properties of complexes 2, 3, and their conjugates (2-FA-NGQDs, 3-FA-NGQDs) were studied. It was found that complex 3 had higher ϕ_Δ of 0.56 compared to complex 2 with ϕ_Δ of 0.24, and respective composites: 3-FA-NGQDs had higher ϕ_Δ compared to 2-FA-NGQDs. The PDT studies were conducted for nanoparticles (FA-NGQDs), complexes (2, 3), and respective composites (2-FA-NGQDs, and 3-FA-NGQDs) using MCF-7 breast cancer cell. Dark toxicity of all compounds was above 90% which is negligible. At a highest concentration of 40 µg/mL, 3-FA-NGQDs gave the lowest cell viability of 28% compared to all other conjugates and porphyrins alone.

Printed Low-Cost PEDOT:PSS/PVA Polymer Composite for Radiation Sterilization Monitoring

During the γ-radiation sterilization process, the levels of radiation exposure to a medical device must be carefully monitored to achieve the required sterilization without causing deleterious effects on its intended physical and chemical properties. To address this issue, here we have demonstrated the development of an all-printed disposable low-cost sensor that exploits the change in electrical impedance of a semi-interpenetrating polymer network (SIPN) composed of poly(vinyl alcohol) (PVA) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as a functional polymer composite for radiation sterilization monitoring applications. Specifically, the PEDOT:PSS acts as the electrically conductive medium, while the PVA provides the ductility and stability of the printed sensors. During irradiation exposure, chain scission and cross-linking events occur concurrently in the PEDOT:PSS and PVA polymer chains, respectively. The concurrent scissoring of the PEDOT polymer and cross-linking of the PVA polymer network leads to the formation of a stable SIPN with reduced electrical conductivity, which was verified through FTIR, Raman, and TGA analysis. Systematic studies of different ratios of PEDOT:PSS and PVA mixtures were tested to identify the optimal ratio that provided the highest radiation sensitivity and stability performance. The results showed that PEDOT:PSS/PVA composites with 10 wt % PVA produced sensors with relative impedance changes of 30% after 25 kGy and up to 370% after 53 kGy (which are two of the most commonly used radiation exposure levels for sterilization applications). This composition showed high electrical impedance stability with less than ±5% change over 18 days after irradiation exposure. These findings demonstrate the feasibility of utilizing a printing technology for scalable manufacturing of low-cost, flexible radiation sensors for more effective monitoring of radiation sterilization processes.

Designing of a pH-activatable carbon dots as a luminescent nanoprobe for recognizing folate receptor-positive cancer cells

During recent years, cancer has been recognized as a well-known disorder all over the world. One of the important factors to tackle this problem better than past decades is early diagnosis that takes into practice by state-of-the-art visual equipment for detection cancer cells. Herein, in this research, we synthesized carbon dots with pH-dependent behavior from a green source by hydrothermal method with high quantum yield and blue fluorescence. Folic acid-conjugated carbon dots by an efficient and optimal conjugation method were set upped which determined cancer cells visually. These synthesized and conjugated nanoparticles entered into the cancer cells more comprehensive than normal cells by receptor-mediated endocytosis and could distinguish cancer cells from normal ones by fluorescence imaging. Ultimately, synthesized nanoparticles in this research can be considered as an efficient fluorescent nanoprobe for cancer pre-diagnosis.

Antiviral performance of graphene-based materials with emphasis on COVID-19: A review

Coronavirus disease-2019 has been one of the most challenging global epidemics of modern times with a large number of casualties combined with economic hardships across the world. Considering that there is still no definitive cure for the recent viral crisis, this article provides a review of nanomaterials with antiviral activity, with an emphasis on graphene and its derivatives, including graphene oxide, reduced graphene oxide and graphene quantum dots. The possible interactions between surfaces of such nanostructured materials with coronaviruses are discussed. The antiviral mechanisms of graphene materials can be related to events such as the inactivation of virus and/or the host cell receptor, electrostatic trapping and physico-chemical destruction of viral species. These effects can be enhanced by functionalization and/or decoration of carbons with species that enhances graphene-virus interactions. The low-cost and large-scale preparation of graphene materials with enhanced antiviral performances is an interesting research direction to be explored.

Carbon Based Nanodots in Early Diagnosis of Cancer

Detection of cancer at an early stage is one of the principal factors associated with successful treatment outcome. However, current diagnostic methods are not capable of making sensitive and robust cancer diagnosis. Nanotechnology based products exhibit unique physical, optical and electrical properties that can be useful in diagnosis. These nanotech-enabled diagnostic representatives have proved to be generally more capable and consistent; as they selectively accumulated in the tumor site due to their miniscule size. This article rotates around the conventional imaging techniques, the use of carbon based nanodots viz Carbon Quantum Dots (CQDs), Graphene Quantum Dots (GQDs), Nanodiamonds, Fullerene, and Carbon Nanotubes that have been synthesized in recent years, along with the discovery of a wide range of biomarkers to identify cancer at early stage. Early detection of cancer using nanoconstructs is anticipated to be a distinct reality in the coming years.

Targeted Bioimaging of Cancer Cells Using Free Folic Acid-Sensitive Molybdenum Disulfide Quantum Dots through Fluorescence "Turn-Off"

In the present study, a proficient way for targeted bioimaging of folate receptor (FR)-positive cancer cells using free folic acid (FA)- and MoS₂ QD-based nanoprobes is discussed along with its advantages over the preparation of orthodox direct FA-nanoprobe bioconjugates for the imaging. The water-soluble MoS₂ QDs of size 4-5 nm with cysteine functionalization are synthesized by a simplistic bottom-up hydrothermal method. The as-prepared MoS₂ QDs exhibit the blue emission with the highest emission intensity at 444 nm upon excitation of 370 nm. The MoS₂ QDs are too sensitive toward FA to produce an effective and stable nanofiber structure through supramolecular interaction, which demonstrates ∼97% quenching of fluorescence. Moreover, the high selectivity and sensitivity of MoS₂ QDs toward FA make the MoS₂ QD-based nanoprobe an appropriate candidate for FA-targeted "turn-off" imaging probes for in vivo study of FA-pretreated FR-overexpressed cancer cells. It is obvious from the confocal microscopy images that the FA-pretreated B16F10 cancer cells show higher population of dimmed fluorescence compared to untreated cancer cells and HEK-293 normal cells. The flow cytometry study quantitatively reveals the significant difference of the geometric mean of fluorescence between FA-pretreated and untreated B16F10 cancer cells. Hence, these MoS₂ QD-based nanoprobes can be applied as potential nanoprobes for the prediagnosis of cancer through targeted bioimaging.

Outstanding Graphene Quantum Dots from Carbon Source for Biomedical and Corrosion Inhibition Applications: A Review

Graphene quantum dots (GQD) is an efficient nanomaterial composed of one or more layers of graphene with unique properties that combine both graphene and carbon dots (CDs). It can be synthesized using carbon-rich materials as precursors, such as graphite, macromolecules polysaccharides, and fullerene. This contribution emphasizes the utilization of GQD-based materials in the fields of sensing, bioimaging, energy storage, and corrosion inhibitors. Inspired by these numerous applications, various synthetic approaches have been developed to design and fabricate GQD, particularly bottom-up and top-down processes. In this context, the prime goal of this review is to emphasize possible eco-friendly and sustainable methodologies that have been successfully employed in the fabrication of GQDs. Furthermore, the fundamental and experimental aspects associated with GQDs such as possible mechanisms, the impact of size, surface alteration, and doping with other elements, together with their technological and industrial applications have been envisaged. Till now, understanding simple photo luminance (PL) operations in GQDs is very critical as well as there are various methods derived from the optical properties of manufactured GQDs can differ. Lack of determining exact size and morphology is highly required without loss of their optical features. Finally, GQDs are promising candidates in the after-mentioned application fields.