A novel β-Cyclodextrin-QDs optical biosensor for the determination of amantadine and its application in cell imaging

Bioresponsive and multifunctional cyclodextrin-based non-viral nanocomplexes in cancer therapy: Building foundations for gene and drug delivery, immunotherapy and bioimaging

The interest towards application of nanomaterials in field of cancer therapy is that the drawbacks of conventional therapies including chemoresistance, radio-resistance and lack of specific targeting of tumor cells can be solved by nanotechnology. Cyclodextrins (CDs) are amphiphilic cyclic oligosaccharides that can be present in three forms of α-, β- and γ-CDs, and they can be synthesized from natural sources. The application of CDs in cancer shows an increasing trend due to benefits of these nanocomplexes in improving solubility and bioavailability of current bioactives and therapeutics for cancer. CDs are widely utilized in delivery of drugs and genes in cancer therapy, and by targeted delivery of these therapeutics into target site, they improve anti-proliferative and anti-cancer potential. The blood circulation time and tumor site accumulation of therapeutics can be improved using CD-based nanostructures. More importantly, the stimuli-responsive types of CDs including pH-, redox- and light-sensitive types can accelerate release of bioactive compound at tumor site. Interestingly, the CDs are able to mediate photothermal and photodynamic impact in impairing tumorigenesis in cancer, enhancing cell death and improving response to chemotherapy. In improving the targeting ability of CDs, their surface functionalization with ligands has been conducted. Moreover, CDs can be modified with green products such as chitosan and fucoidan, and they can be embedded in green-based nanostructures to suppress tumorigenesis. The internalization of CDs into tumor cells can occur through endocytosis and this can be clethrin-, caveolae- or receptor-mediated endocytosis. Furthermore, CDs are promising candidates in bioimaging, cancer cell and organelle imaging as well as isolating tumor cells. The main benefits of using CDs in cancer therapy including sustained and low release of drugs and genes, targeted delivery, bioresponsive release of cargo, ease of surface functionalization and complexation with other nanostructures. The application of CDs in overcoming drug resistance requires more investigation.

Construction of CdTe@γ-CD@RBD nanoprobe for Fe3+-sensing based on FRET mechanism in human serum

A Fe³⁺ optical sensor (CdTe@γ-CD@RBD) has been developed by using gamma-cyclodextrin (γ-CD) as a bridge to link CdTe quantum dots (QDs) and a Rhodamine B derivative (RBD). The RBD molecule can enter the cavity of the γ-CD anchored onto the surfaces of the QDs. In the presence of Fe³⁺, the fluorescence resonance energy transfer (FRET) process from QDs to RBD will be initiated, rendering the nanoprobe to display a response to Fe³⁺. The degree of fluorescence quenching presented a satisfactory linearity between 10 and 60 μΜ with the incremental concentrations of Fe³⁺, and the calculated limit of detection was 2.51 μΜ. Through sample pretreatment procedures, the probe has been used in the determination of Fe³⁺ in human serum. The average recoveries in the spiking levels are ranged from 98.60 % to 107.20 % with a relative standard deviation of around 1.43 %-2.96 %. This finding leads to a method for fluorescent detection of Fe³⁺ with high sensitivity and exceptional selectivity. We believe that this study can give a new insight into the rational design and application of FRET-based nanoprobes.

Quantum Dots for Cancer-Related miRNA Monitoring

Quantum dots (QDs) possess exceptional optoelectronic properties that enable their use in the most diverse applications, namely, in the medical field. The prevalence of cancer has increased and has been considered the major cause of death worldwide. Thus, there has been a great demand for new methodologies for diagnosing and monitoring cancer in cells to provide an earlier prognosis of the disease and contribute to the effectiveness of treatment. Several molecules in the human body can be considered relevant as cancer markers. Studies published over recent years have revealed that micro ribonucleic acids (miRNAs) play a crucial role in this pathology, since they are responsible for some physiological processes of the cell cycle and, most important, they are overexpressed in cancer cells. Thus, the analytical sensing of miRNA has gained importance to provide monitoring during cancer treatment, allowing the evaluation of the disease's evolution. Recent methodologies based on nanochemistry use fluorescent quantum dots for sensing of the miRNA. Combining the unique characteristics of QDs, namely, their fluorescence capacity, and the fact that miRNA presents an aberrant expression in cancer cells, the researchers created diverse strategies for miRNA monitoring. This review aims to present an overview of the recent use of QDs as biosensors in miRNA detection, also highlighting some tutorial descriptions of the synthesis methods of QDs, possible surface modification, and functionalization approaches.

Cyclodextrins and inorganic nanoparticles: Another tale of synergy

In this review, we summarize the recent research focused on the combination of inorganic nanoparticles and α-, β- and γ- cyclodextrins. Our intention is to highlight the most relevant publications on the synthesis of nanoparticle-cyclodextrin (NP-CD) nanohybrids, with CDs acting as reducing agents or through the post-synthetic modification of inorganic nanoparticles with CDs. We also discuss the new or enhanced properties that arise from the host-guest capabilities of the CDs and inorganic nanoparticles. Finally, we illustrate the potential applications of these materials in numerous research fields.

Co-delivery of 5-fluorouracil and miRNA-34a mimics by host-guest self-assembly nanocarriers for efficacious targeted therapy in colorectal cancer patient-derived tumor xenografts

Rationale: A co-delivery system that can transport chemotherapeutic drugs and nucleotide drugs to distinct targets in tumors is an attractive strategy for cancer therapy. In this study, well-defined targeted quantum dot (QD)-based multifunctional nanocarriers were developed through self-assembly driven by host-guest interactions. 5-fluorouracil (5-FU) and microRNA-34a mimics (miR-34a(m)) were co-administered to achieve synergistic effects for colorectal cancer (CRC) therapy for the first time. Furthermore, the CRC patient-derived tumor xenograft (PDX) model, which closely mimics human CRC tumor pathological properties, was used for evaluating the therapeutic effect in this research.

Methods: Multiple β-cyclodextrin (CD)-attached QD nanoparticles were used as host molecules. An adamantane (ADA)-modified TCP1 peptide-targeting ligand (TCP1) was used as the guest molecule. 5-FU and miR-34a(m) were loaded into TCP1-CD-QD nanocarriers, which were used to treat CRC in vitro and in vivo. In addition, the CRC PDX model was used to evaluate the treatment efficacy of this co-delivery system.

Results: 5-FU and miR-34a(m) can be efficiently encapsulated into TCP1-CD-QD nanocarriers and delivered into CRC cells, which led to the inhibition of the proliferation and migration of CRC cells in vitro and suppression of tumor growth in a CRC cell-derived tumor xenograft model. The obtained data further suggested that co-delivery of 5-FU and miR-34a(m) could achieve synergistic effects for CRC therapy. Notably, targeted therapy via the co-delivery of 5-FU and miR-34a(m) by TCP1-CD-QD nanocarriers significantly inhibited the growth of PDX tumors.

Conclusions: These studies strongly indicate that such a nanocarrier-based co-delivery system is a promising combined therapeutic strategy that utilizes chemotherapeutic drugs and nucleotide drugs for enhancing colorectal cancer targeting and synergistic therapy.

Quantum dots as nanosensors for detection of toxics: a literature review

Great advances have been made in sensor-based methods for chemical analysis owing to their high sensitivity, selectivity, less testing time, and minimal usage of chemical reagents. Quantum Dots (QDs) having excellent optical properties have been thoroughly explored for variety of scientific applications wherein light plays an important role. In recent years, there have been an increasing number of publications on the applications of QDs as photoluminescent nanosensors for the detection of chemicals and biomolecules. However, there has been hardly any publication describing the use of QDs in the detection of various toxic chemicals at one place. Hence, a literature survey has been made on the applications of QDs as chemosensors for the detection of gaseous, anionic, phenolic, metallic, drug-overdose, and pesticide poison so as to open a new perspective towards the role of sensors in analytical toxicology. In this review, the QD-based analysis of biospecimens for poison detection in clinical and forensic toxicology laboratories is highlighted.

Determination of melamine in milk based on β-cyclodextrin modified carbon nanoparticles via host-guest recognition

Illegal addition of melamine (MEL) to milk has caused serious food safety accident. It is urgent to develop a highly sensitive method for detecting MEL in milk. β-Cyclodextrin with inner hydrophobic and outer hydrophilic cavities have been widely used in smart sensors design. In this study, an "ON-OFF-ON" sensor for MEL detection was constructed based on β-cyclodextrin modified carbon nanoparticles (β-CD-CNPs). The sensor is switched "OFF" when Fe³⁺ interacts with β-CD-CNPs and switched "ON" when MEL replaces Fe³⁺. Fluorescence recovery of β-CD-CNPs exhibits good linear correlations with MEL concentration ranging from 10.00 ng/mL ~ 180.00 ng/mL and 180.00 ~ 1000.00 ng/mL, the detection limit is 6.82 ng/mL. The sensor was applied to analysis melamine in milk samples with recovery between 94.80% ~ 102.05%, and RSD bellow 12.61%. The results show that this method can meet the requirements of real sample analysis.

Targeted delivery of nanomaterials with chemical cargoes in plants enabled by a biorecognition motif

Current approaches for nanomaterial delivery in plants are unable to target specific subcellular compartments with high precision, limiting our ability to engineer plant function. We demonstrate a nanoscale platform that targets and delivers nanomaterials with biochemicals to plant photosynthetic organelles (chloroplasts) using a guiding peptide recognition motif. Quantum dot (QD) fluorescence emission in a low background window allows confocal microscopy imaging and quantitative detection by elemental analysis in plant cells and organelles. QD functionalization with β-cyclodextrin molecular baskets enables loading and delivery of diverse chemicals, and nanoparticle coating with a rationally designed and conserved guiding peptide targets their delivery to chloroplasts. Peptide biorecognition provides high delivery efficiency and specificity of QD with chemical cargoes to chloroplasts in plant cells in vivo (74.6 ± 10.8%) and more specific tunable changes of chloroplast redox function than chemicals alone. Targeted delivery of nanomaterials with chemical cargoes guided by biorecognition motifs has a broad range of nanotechnology applications in plant biology and bioengineering, nanoparticle-plant interactions, and nano-enabled agriculture.

Quantum dots are conventionally applicable for wide-profiling of wall polymer distribution and destruction in diverse cells of rice

Plant cell walls represent enormous biomass resources for biofuels, and it thus becomes important to establish a sensitive and wide-applicable approach to visualize wall polymer distribution and destruction during plant growth and biomass process. Despite quantum dots (QDs) have been applied to label biological specimens, little is reported about its application in plant cell walls. Here, semiconductor QDs (CdSe/ZnS) were employed to label the secondary antibody directed to the epitopes of pectin or xylan, and sorted out the optimal conditions for visualizing two polysaccharides distribution in cell walls of rice stem. Meanwhile, the established QDs approach could simultaneously highlight wall polysaccharides and lignin co-localization in different cell types. Notably, this work demonstrated that the QDs labeling was sensitive to profile distinctive wall polymer destruction between alkali and acid pretreatments with stem tissues of rice. Hence, this study has provided a powerful tool to characterize wall polymer functions in plant growth and development in vivo, as well as their distinct roles during biomass process in vitro.

Light emission enhancement by supramolecular complexation of chemiluminescence probes designed for bioimaging

Chemiluminescence offers advantages over fluorescence for bioimaging, since an external light source is unnecessary with chemiluminescent agents. This report demonstrates the first encapsulation of chemiluminescence phenoxy-adamantyl-1,2-dioxetane probes with trimethyl β-cyclodextrin. Clear proof for the formation of a 1 : 1 host-guest complex between the adamantyl-1,2-dioxetane probe and trimethyl β-cyclodextrin was provided by mass spectroscopy and NMR experiments. The calculated association constant of this host-guest system, 253 M-1, indicates the formation of a stable inclusion complex. The inclusion complex significantly amplified the light emission intensity relative to the noncomplexed probe under physiological conditions. Complexation of adamantyl-dioxetane with fluorogenic dye-tethered cyclodextrin resulted in light emission through energy transfer to a wavelength that corresponds to the fluorescent emission of the conjugated dye. Remarkably, the light emission intensity of this inclusion complex was approximately 1500-fold higher than that of the non-complexed adamantyl-dioxetane guest. We present the first demonstration of microscopic cell images obtained using a chemiluminescence supramolecular dioxetane probe and demonstrate the utility of these supramolecular complexes by imaging of enzymatic activity and bio-analytes in vitro and in vivo. We anticipate that the described chemiluminescence supramolecular dioxetane probes will find use in various biological applications.

Chemistry and engineering of cyclodextrins for molecular imaging

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides bearing a basket-shaped topology with an "inner-outer" amphiphilic character. The abundance of hydroxyl groups enables CDs to be functionalized with multiple targeting ligands and imaging elements. The imaging time, and the payload of different imaging elements, can be tuned by taking advantage of the commercial availability of CDs with different sizes of the cavity. This review aims to offer an outlook of the chemistry and engineering of CDs for the development of molecular probes. Complexation thermodynamics of CDs, and the corresponding implications for probe design, are also presented with examples demonstrating the structural and physiochemical roles played by CDs in the full ambit of molecular imaging. We hope that this review not only offers a synopsis of the current development of CD-based molecular probes, but can also facilitate translation of the incremental advancements from the laboratory to real biomedical applications by illuminating opportunities and challenges for future research.

An electrodeposited molecularly imprinted quartz crystal microbalance sensor sensitized with AuNPs and rGO material for highly selective and sensitive detection of amantadine

In the present work, a new amantadine (AM) imprinted quartz crystal microbalance (QCM) sensor sensitized by Au nanoparticles (AuNPs) and reduced graphene oxide (rGO) material was fabricated by electrodeposition in the presence of o-aminothiophenol (o-AT) by cyclic voltammetry scanning. AuNPs and graphene, with the advantages of great chemical stability, electrical conductivity, and large surface area, show exceptionally high sensitivity. The results of different modifications of the QCM sensor fabrication process were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. Under the optimal experimental conditions, the frequency shift of the MIP-QCM sensor showed a linear relationship with the concentration of the AM template in the range of 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mmol L⁻¹ with a limit of detection (LOD) of 5.40 × 10⁻⁶ mmol L⁻¹. The imprinting factor for AM reached 7.1, the selectivity coefficient for the analogues rimantadine (RT), adamantine (AMT) and 1-chloroadamantane (CMT) were 7.3, 5.6, and 6.1, respectively. Here, a highly sensitive, selective and stable QCM sensor prepared via the imprinting approach is reported for the first time for detection of AM from animal-derived food samples.

In the present work, a new amantadine imprinted quartz crystal microbalance sensor sensitized by Au nanoparticles and reduced graphene oxide material was fabricated by electrodeposition of o-aminothiophenol by cyclic voltammetry scanning.

Covalent Surface Functionalization of Semiconducting Polymer Dots with β-Cyclodextrin for Fluorescent Ratiometric Assay of Cholesterol through Host-Guest Inclusion and FRET

Special functionalization of semiconducting polymer dots (Pdots) is highly desired to expand their applications in chemo/biosening. Herein, carboxyl-functionalized poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)] dots covalently tagged with aminated β-cyclodextrin (NH₂-CD) have been designed to construct a ratiometric sensor for cholesterol (Cho). Using CD-Pdots as energy donors with rhodamine B (RB) as energy acceptors, a fluorescence resonance energy transfer (FRET) pair has been built because the host-guest interaction between RB and CD attached to Pdots brings donors and acceptors into close proximity. In the presence of Cho, the acceptors will depart from the donors because of the competitive inclusion interaction between Cho and RB with CD, resulting in the hindering of the FRET process between CD-Pdots and RB. On the basis of the turn-on fluorescence of CD-Pdots and turn-off fluorescence of RB, a sensitive ratiometric method for the determination of Cho in the concentration range from 25 to 350 nM with a detection limit of 4.9 nM was achieved. The proposed method was validated to determine free Cho in human serum samples with satisfactory results.

Highly sensitive detection of acid phosphatase by using a graphene quantum dots-based förster resonance energy transfer

A novel and effective fluorescence strategy was developed for sensitive and selective detection of acid phosphatase (ACP). A förster resonance energy transfer (FRET) biosensor was established by attaching nile red (NR) to graphene quantum dots (GQDs) via lecithin/β-Cyclodextrin (lecithin/β-CD) complex as the linker. The introduction of lecithin/β-CD would brought GQDs-NR pair close enough through both electrostatic interaction and hydrophobic interaction, thereby making the FRET occur and thus resulting in the fluorescence quenching of GQDs (donor) and meanwhile the fluorescence enhancement of NR (acceptor). The presence of ACP in the sensing system would catalyze the hydrolysis of lecithin into two parts, resulting in the GQDs-NR pair separation. Meanwhile, considerable fluorescence recovery of GQDs and decreasing of NR was observed due to the inhibition of FRET progress. In this method, the limit of detection (LOD) is 28µUmL^-1 which was considerably low for ACP detection. Using the GQDs-based fluorescence biosensor, we successfully performed in vitro imaging of human prostate cancer cells.

Multifunctional Quantum Dot Nanoparticles for Effective Differentiation and Long-Term Tracking of Human Mesenchymal Stem Cells In Vitro and In Vivo

Human mesenchymal stem cells (hMSCs) hold great potential for regenerative medicine. Efficient induction of hMSC differentiation and better understanding of hMSCs behaviors in vitro and in vivo are essential to the clinical translation of stem cell therapy. Here a quantum dots (QDs)-based multifunctional nanoparticle (RGD-β-CD-QDs) is developed for effective enhancing differentiation and long-term tracking of hMSCs in vitro and in vivo. The RGD-β-CD-QDs are modified with β-cyclodextrin (β-CD) and Cys-Lys-Lys-Arg-Gly-Asp (CKKRGD) peptide on the surface. The β-CD can harbor hydrophobic osteogenic small molecule dexamethasone (Dex) and the RGD peptide not only facilitates the complexation of siRNA and delivers siRNA into hMSCs but also leads to cellular uptake of nanoparticles by RGD receptor. Co-delivery of Dex and siRNA by RGD-β-CD-QDs nanocarrier significantly expedites and enhances the osteogenesis differentiation of hMSCs in vitro and in vivo by combined effect of small molecule and RNAi. Furthermore, the RGD-β-CD-QDs can be labeled with hMSCs for a long-term tracking (3 weeks) in vivo to observe the behaviors of implanted hMSCs in animal level. These findings demonstrate that the RGD-β-CD-QDs nanocarrier provides a powerful tool to simultaneously enhance differentiation and long-term tracking of hMSCs in vitro and in vivo for regenerative medicine.

Sensitive fluorimetric assays for α-glucosidase activity and inhibitor screening based on β-cyclodextrin-coated quantum dots

A fluorescence method was established for a α-glucosidase activity assay and inhibitor screening based on β-cyclodextrin-coated quantum dots. p-Nitrophenol, the hydrolysis product of the α-glucosidase reaction, could quench the fluorescence of β-cyclodextrin-coated quantum dots via an electron transfer process, leading to fluorescence turn-off, whereas the fluorescence of the system turned on in the presence of α-glucosidase inhibitors. Taking advantage of the excellent properties of quantum dots, this method provided a very simple, rapid and sensitive screening method for α-glucosidase inhibitors. Two α-glucosidase inhibitors, 2,4,6-tribromophenol and acarbose, were used to evaluate the feasibility of this screening model, and IC50 values of 24 μM and 0.55 mM were obtained respectively, which were lower than those previously reported. The method may have potential application in screening α-glucosidase inhibitors.

A novel water-soluble quantum dot–neutral red fluorescence resonance energy transfer probe for the selective detection of megestrol acetate

Megestrol acetate can specifically quench the fluorescence intensity of the β-CD-QD–NR FRET probe at low concentration levels.

In situ detection of salicylic acid binding sites in plant tissues

The determination of hormone-binding sites in plants is essential in understanding the mechanisms behind hormone function. Salicylic acid (SA) is an important plant hormone that regulates responses to biotic and abiotic stresses. In order to label SA-binding sites in plant tissues, a quantum dots (QDs) probe functionalized with a SA moiety was successfully synthesized by coupling CdSe QDs capped with 3-mercaptopropionic acid (MPA) to 4-amino-2-hydroxybenzoic acid (PAS), using 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide (EDC) as the coupling agent. The probe was then characterized by dynamic light scattering and transmission electron microscopy, as well as UV/vis and fluorescence spectrophotometry. The results confirmed the successful conjugation of PAS to CdSe QDs and revealed that the conjugates maintained the properties of the original QDs, with small core diameters and adequate dispersal in solution. The PAS-CdSe QDs were used to detect SA-binding sites in mung bean and Arabidopsis thaliana seedlings in vitro and in vivo. The PAS-CdSe QDs were effectively transported into plant tissues and specifically bound to SA receptors in vivo. In addition, the effects of the PAS-CdSe QDs on cytosolic Ca(2+) levels in the tips of A. thaliana seedlings were investigated. Both SA and PAS-CdSe QDs had similar effects on the trend in cytosolic-free Ca(2+) concentrations, suggesting that the PAS-CdSe QDs maintained the bioactivity of SA. To summarize, PAS-CdSe QDs have high potential as a fluorescent probe for the in vitro/in vivo labeling and imaging of SA receptors in plants.

Simple preparation of green fluorescent protein conjugated with β-cyclodextrin in a site specific manner

We have site-directedly linked a green fluorescent protein (GFP) variant and a β-cyclodextrin (β-CD) with a simple method to develop a basic complex for sophisticated supramolecules. We have confirmed β-CD grafting on GFP with several methods including matrix-assisted laser desorption/ionization linear time-of-flight mass spectrometry (MALDI-TOF MS) without protease digestion and characterized the complex as well. In consideration of the resulting properties, the product we plainly and efficiently obtained could have applications related to sensing devices and drug delivery systems.