Quantum dots as versatile probes in medical sciences: Synthesis, modification and properties

Nanoformulations in Pharmaceutical and Biomedical Applications: Green Perspectives

This study provides a brief discussion of the major nanopharmaceuticals formulations as well as the impact of nanotechnology on the future of pharmaceuticals. Effective and eco-friendly strategies of biofabrication are also highlighted. Modern approaches to designing pharmaceutical nanoformulations (e.g., 3D printing, Phyto-Nanotechnology, Biomimetics/Bioinspiration, etc.) are outlined. This paper discusses the need to use natural resources for the "green" design of new nanoformulations with therapeutic efficiency. Nanopharmaceuticals research is still in its early stages, and the preparation of nanomaterials must be carefully considered. Therefore, safety and long-term effects of pharmaceutical nanoformulations must not be overlooked. The testing of nanopharmaceuticals represents an essential point in their further applications. Vegetal scaffolds obtained by decellularizing plant leaves represent a valuable, bioinspired model for nanopharmaceutical testing that avoids using animals. Nanoformulations are critical in various fields, especially in pharmacy, medicine, agriculture, and material science, due to their unique properties and advantages over conventional formulations that allows improved solubility, bioavailability, targeted drug delivery, controlled release, and reduced toxicity. Nanopharmaceuticals have transitioned from experimental stages to being a vital component of clinical practice, significantly improving outcomes in medical fields for cancer treatment, infectious diseases, neurological disorders, personalized medicine, and advanced diagnostics. Here are the key points highlighting their importance. The significant challenges, opportunities, and future directions are mentioned in the final section.

Development of ZnCdSe/ZnS quantum dot-based fluorescence immunochromatographic assay for the rapid visual and quantitative detection 25⁃hydroxyvitamins D in human serum

Vitamin D deficiency is associated with various diseases such as obesity, digestive problems, osteoporosis, depression, and infections, and has therefore emerged as a topic of great interest in public healthcare. The quantitative assessment of 25-hydroxyvitamin D (25-OH VD) in human serum may accurately reflect the nutritional status of vitamin D in the human body, which is significant for the prevention and treatment of vitamin D-deficient patients. In this study, we developed an assay for quantitative detection of 25-OH VD based on the 25-OH VD monoclonal antibody (mAb), and identified the optimal process parameters. The following process settings were found to be suitable for the test strips: pH of 7.6, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) ratio of 1:2000, and the anti-25-OH VD mAb ratio was 1:8. The equilibration time of the immune dynamic assay was 15 min. Under optimal conditions, the quantum dot nanoparticle-based fluorescent immunochromatographic assay (QDs-FICA) exhibited dynamic linear detection of 25-OH VD in PBS, from 5 ng/mL to 100 ng/mL, and the strip quantitative curve could be represented by the following regression equation: y = -0.02088 logx)+1.444 (R2 = 0.9050). The IC50 of the QDs-FICA was 39.6 ± 1.33 ng/mL. The specificity of the QDs-FICA was evaluated by running several structurally related analogues, including 25-OH VD2, 25-OH VD3, 1,25-OH2VD3, 1,25-OH2VD2, VD2, and VD3. The coefficients of variation were all below 10%. The shelf life of the test strips in this study was about 160 days at room temperature. Briefly, this study is the first to perform QDs-FICA for the rapid visual and quantitative detection of 25-OH VD, with great potential significance for clinical diagnosis of vitamin D-associated diseases.

Blue-emitting SiO2-coated Si-doped ZnSeS quantum dots conjugated aptamer-molecular beacon as an electrochemical and metal-enhanced fluorescence biosensor for SARS-CoV-2 spike protein

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which was first reported in early January 2020, continues to devastate the worlds public health system. Herein, we report on the development of a novel metal-enhanced fluorescence (MEF) and electrochemical biosensor for SARS-CoV-2 spike (S) protein. To develop the MEF biosensor, SiO2-coated Si-doped ZnSeS quantum dots (QDs) were newly synthesized and conjugated to an aptamer-molecular beacon (Apta-MB) probe. Thereafter, cationic AuNPs, used as a localised surface plasmon resonance (LSPR) signal amplifier, were self-assembled on the QDs-Apta-MB conjugate to form a QDs-Apta-MB-AuNP probe. To develop the electrochemical biosensor, the QDs-Apta-MB assay was carried out on a carbon nanofiber-modified screen-printed carbon electrode. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode surface whilst spectrophotometric, spectroscopic, fluorescence polarization and electron microscopic techniques were used to characterize the materials. Under optimal experimental conditions, the QDs binding to the Apta-MB, quenched the QDs' fluorescence and with SARS-CoV-2 S protein binding to the Apta-MB, LSPR signal from cationic AuNPs of different sizes and shapes were used to tune the fluorescence signal to obtain enhanced sensitivity. On the other hand, using [Fe(CN)6]/K3-/4- buffered with NaAc-KAc-TrizmaAc-KSCN-Borax as the electrolyte solution, anodic peaks of the QDs from the CV and DPV plots were unravelled. Electrochemical detection of SARS-CoV-2 S protein was accomplished by a systematic increase in the QDs anodic peak current generated from the DPV plots. The limits of detection obtained for the SARS-CoV-2 S protein were 8.9 fg/mL for the QDs-Apta-MB-AuNP MEF probe and ∼0.5 pg/mL for the QDs-Apta-MB electrochemical probe. Detection of SARS-CoV-2 S protein in saliva was demonstrated using the QDs-Apta-MB-AuNP MEF probe.

Review on Metal-Based Theranostic Nanoparticles for Cancer Therapy and Imaging

Theranostic agents are promising due to their ability to diagnose, treat and monitor different types of cancer using a variety of imaging modalities. The advantage specifically of nanoparticles is that they can accumulate easily at the tumor site due to the large gaps in blood vessels near tumors. Such high concentration of theranostic agents at the target site can lead to enhancement in both imaging and therapy. This article provides an overview of nanoparticles that have been used for cancer theranostics, and the different imaging, treatment options and signaling pathways that are important when using nanoparticles for cancer theranostics. In particular, nanoparticles made of metal elements are emphasized due to their wide applications in cancer theranostics. One important aspect discussed is the ability to combine different types of metals in one nanoplatform for use as multimodal imaging and therapeutic agents for cancer.

Energy-efficient Preparation of Amino and Sulfhydryl Functionalized Biomass Carbon Dots via a Reverse Microemulsion for Specific Recognition of Fe3+ and L-cysteine

Amino- and sulfhydryl- functionalized biomass carbon dots (BCDs) were prepared by one-pot reverse microemulsion for specific recognition of ferric ions (Fe³⁺) and L-cysteine (L-Cys). Green grapefruit peel was used as the carbon source while aminosilane and mercaptosilane were used as N- and S-supplier. Following the adsorption of Fe³⁺ on the surfaces of BCDs-NH₂ and BCDs-SH, the fluorescence responses was quenched step by step, while adding L-Cys to the BCDs-NH₂/Fe³⁺ system restored the fluorescence. The BCDs-NH₂ and BCDs-SH system exhibited extremely low limits of detection for Fe³⁺ of 3.2 and 3.0 nM, respectively, within a wide linear ranges of 0.006-200 μM and 0.004-200 μM, respectively. The BCDs-NH₂/Fe³⁺ systems were used as an optosensor for L-Cys in the concentration ranges of 0.08-30 and 30-1000 μM with a detection limit of 65 nM. Developed BCDs-NH₂ and BCDs-SH were able to respond to Fe³⁺ in water samples with satisfactory recoveries of 100.1%-103.1% and 94.6%-108.5%, respectively, and the BCDs-NH₂/Fe³⁺ system was also able to respond to BCDs-NH₂/Fe³⁺ in actual lake water samples with recoveries from 87.3% to 98.8%. Meanwhile, The BCDs-NH₂ exhibited good photoluminescence and stability, and the with a fluorescence quantum yield was as high as 25%. This work demonstrates the feasibility of using such materials to remove hazardous ions from water and employing the resulting complexes for optosensing in a sustainable manner.

Measuring the refractive index and sub-nanometre surface functionalisation of nanoparticles in suspension

Direct measurements to determine the degree of surface coverage of nanoparticles by functional moieties are rare, with current strategies requiring a high level of expertise and expensive equipment. Here, a practical method to determine the ratio of the volume of the functionalisation layer to the particle volume based on measuring the refractive index of nanoparticles in suspension is proposed. As a proof of concept, this technique is applied to poly(methyl methacrylate) (PMMA) nanoparticles and semicrystalline carbon dots functionalised with different surface moieties, yielding refractive indices that are commensurate to those from previous literature and Mie theory. In doing so, it is demonstrated that this technique is able to optically detect differences in surface functionalisation or composition of nanometre-sized particles. This non-destructive and rapid method is well-suited for in situ industrial particle characterisation and biological applications.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Bioactive Graphene Quantum Dots Based Polymer Composite for Biomedical Applications

Today, nanomedicine seeks to develop new polymer composites to overcome current problems in diagnosing and treating common diseases, especially cancer. To achieve this goal, research on polymer composites has expanded so that, in recent years, interdisciplinary collaborations between scientists have been expanding day by day. The synthesis and applications of bioactive GQD-based polymer composites have been investigated in medicine and biomedicine. Bioactive GQD-based polymer composites have a special role as drug delivery carriers. Bioactive GQDs are one of the newcomers to the list of carbon-based nanomaterials. In addition, the antibacterial and anti-diabetic potentials of bioactive GQDs are already known. Due to their highly specific surface properties, π-π aggregation, and hydrophobic interactions, bioactive GQD-based polymer composites have a high drug loading capacity, and, in case of proper correction, can be used as an excellent option for the release of anticancer drugs, gene carriers, biosensors, bioimaging, antibacterial applications, cell culture, and tissue engineering. In this paper, we summarize recent advances in using bioactive GQD-based polymer composites in drug delivery, gene delivery, thermal therapy, thermodynamic therapy, bioimaging, tissue engineering, bioactive GQD synthesis, and GQD green resuscitation, in addition to examining GQD-based polymer composites.

Biomass-Based Carbon Dots: Current Development and Future Perspectives

Carbon dots have been considered as a solution to the challenges that semiconductor quantum dots have encountered because they are more biocompatible and can be synthesized from abundant and nontoxic materials such as biomass. This review will highlight the advantages of these biomass-based carbon dots in terms of synthesis, properties, and applications in the biomedical field. Furthermore, future applications especially in the biomedical field of biomass-based carbon dots as well as the challenges of semiconductor quantum dots such as biocompatibility, photobleaching, environmental challenges, toxicity, and poor solubility will be discussed in detail. Biomass-derived quantum dots, a subsection of carbon dots that are the most desirable for future research, will be focused upon including from synthesis to applications. Finally, the future development of biomass derived quantum dots in the biomedical field will be discussed and evaluated to unlock the potential for their applications.

Quick extracellular biosynthesis of low-cadmium Zn x Cd1-x S quantum dots with full-visible-region tuneable high fluorescence and its application potential assessment in cell imaging

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields. In the arena of chemical routes, however, biosynthesis has long been criticized for its low productivity, time-consuming process, and poor control over size, shape and crystallinity, keeping the much-needed technology away from practical application. In this work, a rapid and extracellular biosynthesis of multi-colour ternary Zn x Cd1-x S QDs by a mixed sulfate-reducing bacteria (SRB)-derived supernatant was carried out for the first time to solve the problems plaguing this field of biosynthesis. The results showed that about 3.5 g L-1 of Zn x Cd1-x S QDs with size of 3.50-4.64 nm were achieved within 30 minutes. The PL emission wavelength of Zn x Cd1-x S QDs increased from 450 to 590 nm to yield multicolor QDs by altering the molar ratio of Cd2+ to Zn2+. The SRB-biogenic Zn x Cd1-x S QDs have high stability in gastric acid and at high temperature, as well as excellent biocompatibility and biosafety, successfully entering growing HeLa cells and labelling them without detectable harm to cells. The SRB-secreted peculiar extracellular proteins (EPs) play a decisive function in the time-saving, high-yield biosynthesis of PL-tuned multicolor QDs, which cover an abnormally high concentration of acidic amino acids to provide tremendous negatively charged sites for the absorption of Cd2+/Zn2+ for rapid nucleation and biosynthesis. The strongly electrostatic connection between the QDs and the EPs and the increasing amount of EPs attached to the QDs in response to the increase of Cd2+ concentration account for their high stability and excellent biocompatibility.

Electrochemical DNA detection of hepatitis E virus genotype 3 using PbS quantum dot labelling

The aim of this study was to develop a highly specific electrochemical DNA sensor using functionalized lead sulphide (PbS) quantum dots for hepatitis E virus genotype 3 (HEV3) DNA target detection. Functionalized-PbS quantum dots (QDs) were used as an electrochemical label for the detection of HEV3-DNA target by the technique of square wave anodic stripping voltammetry (SWASV). The functionalized-PbS quantum dots were characterized by UV-vis, FTIR, XRD, TEM and zeta potential techniques. As-prepared, functionalized-PbS quantum dots have an average size of 4.15 ± 1.35 nm. The detection platform exhibited LOD and LOQ values of 1.23 fM and 2.11 fM, respectively. HEV3-DNA target spiked serum is also reported.Graphical abstract.

Carbon-Based Quantum Dots for Electrochemical Detection of Monoamine Neurotransmitters-Review

Imbalance in the levels of monoamine neurotransmitters have manifested in severe health issues. Electrochemical sensors have been designed for their determination, with good sensitivity recorded. Carbon-based quantum dots have proven to be an important component of electrochemical sensors due to their high conductivity, low cytotoxicity and opto-electronic properties. The quest for more sensitive electrodes with cheaper materials led to the development of electrochemical sensors based on carbon-based quantum dots for the detection of neurotransmitters. The importance of monoamine neurotransmitters (NTs) and the good electrocatalytic activity of carbon and graphene quantum dots (CQDs and GQDs) make the review of the efforts made in the design of such sensors for monoamine NTs of huge necessity. The differences and the similarities between these two quantum dots are highlighted prior to a discussion of their application in electrochemical sensors over the last ten years. Compared to other monoamine NTs, dopamine (DA) was the most studied with GQDs and CQD-based electrochemical sensors.

Colloidal synthesis of tunably luminescent AgInS-based/ZnS core/shell quantum dots as biocompatible nano-probe for high-contrast fluorescence bioimaging

Tremendous demands for simultaneous imaging of biological entities, along with the drawback of photobleaching in fluorescent dyes, have encouraged scientists to apply novel and non-toxic colloidal quantum dots (QDs) in biomedical researches. Herein, a novel aqueous-phase approach for the preparation of multicomponent In-based QDs is reported. Absorption and photoluminescence emission spectra of the as-prepared QDs were tuned by alteration of QDs' composition as Zn-Ag-In-S/ZnS, Ag-In-S/ZnS and Cu-Ag-In-S/ZnS core/shell QDs. In order to reach reproducibly intense and tunable light-emissive colloidal QDs with green, amber, and red color, various optimization steps were carefully performed. The structural characterizations such as EDX, ICP-AES, XRD, TEM and FT-IR measurements were also carried out to demonstrate the success of the present method to prepare extremely quantum-confined QDs capped with functional groups. Then, to ensure their promising biomedical applications, the generated intracellular reactive oxygen species (ROS) by QDs were quantitatively and qualitatively measured in dark conditions and under 405 nm laser irradiation. Our results verified an enhancement in the generation of reactive oxygen species (ROS) and cytotoxic effects in the presence of laser irradiation while their muted toxic effects in dark conditions confirmed biocompatible properties of un-excited In-based QDs. Moreover, bioimaging analysis revealed strong merits of the suggested synthetic route to achieve ideal fluorescent QDs as bright/multi-color optical nano-probes in imaging and transporting pumps in the cell membrane. This further emphasized the potential ability of the present AgInS-based/ZnS QDs in obtaining required results as theranostic agents for simultaneous treatment and imaging of cancer. The harmonized advantages in simplicity and effectiveness of synthesis procedure, excellent structural/optical properties enriched with confirmed biomedical merits in high contrast imaging and potential treatment highlight the present work.

Synthesis of green-emitting carbon quantum dots with double carbon sources and their application as a fluorescent probe for selective detection of Cu2+ ions

Green-emitting carbon quantum dots (G-CQDs) were prepared using tartaric acid and bran by one-pot solvothermal treatment and had photoluminescence quantum yields (PL QY) as high as 46%. The morphology of the G-CQDs is characterized by TEM, which shows the average diameter of G-CQDs is approximately ∼4.85 nm. The FT-IR spectra display the presence of -OH, C-N, N-H and -COOH on the surface of the G-CQDs. The emission wavelength of the G-CQDs was ∼539 nm in the case of ∼450 nm excitation wavelength, which corresponds to the green fluorescence. Furthermore, the G-CQDs were used as a fluorescent probe for detection Cu2+ ions, and demonstrated a linear distribution between ln(F/F 0) and the Cu2+ ions concentration. Specifically, the Cu2+ ion concentration should fall in the G-CQD concentration range of 0-0.5 mM and the detection limit is 0.0507 μM. Thus, due to the excellent chemical stability and good luminescence performance, these G-CQDs could be excellent probes widely used in detection fields.

Optically Active Nanomaterials for Bioimaging and Targeted Therapy

Non-invasive tracking for monitoring the selective delivery and transplantation of biotargeted agents in vivo has been employed as one of the most effective tools in the field of nanomedicine. Different nanoprobes have been developed and applied to bioimaging tissues and the treatment of diseases ranging from inflammatory and cardiovascular diseases to cancer. Herein, we will review the recent advances in the development of optics-responsive nanomaterials, including organic and inorganic nanoparticles, for multimodal bioimaging and targeted therapy. The main focus is placed on nanoprobe fabrication, mechanistic illustrations, and diagnostic, or therapeutical applications. These nanomedicine strategies have promoted a better understanding of the biological events underlying diverse disease etiologies, thereby facilitating diagnosis, illness evaluation, therapeutic effect, and drug discovery.

Synthesis of new multivalent metal ion functionalized mesoporous silica and studies of their enhanced antimicrobial and cytotoxicity activities

In the present study, we have reported the synthesis of a transition metal (Me = Ti, V, and Pd) incorporated into MCM-41 mesoporous molecular sieves (Si/Me = 20) synthesized by the sol-gel method. Their physicochemical properties were studied in detail by standard techniques like low angle powder X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDXS), transmission electron microscopy (TEM), N₂ adsorption/desorption studies, and thermogravimetric-differential thermal (TG-DTA) analysis and spectral studies like Fourier transform infrared spectroscopic analysis (FT-IR), diffuse reflectance ultraviolet-visible spectroscopic analysis (UV-Visible-DRS), and X-ray photoelectron spectroscopy (XPS). The XRD patterns prove that the material's phase identity is the same irrespective of metal incorporation. SEM displayed the uniform shape and size of the nanoparticles. The presence of elements such as Ti, V, Pd, Si and O in respective materials is revealed using the EDXS analysis. Around 30% weight loss arose upon calcination from room temperature to 800 °C. BET surface area analysis presented that the parent materials have a high surface area (1024 m² g^-1) which was reduced upon metal incorporation. FT-IR analysis exhibited the framework vibrations of the synthesised materials. UV-Visible-DRS analysis indicated the presence of tetrahedrally coordinated transition metal ions. The multivalent-metal-ion-functionalized mesoporous materials showed significant enhancement in potent antimicrobial and anticancer activity. The antimicrobial activity is because of its low lipophilicity, which no longer allows the materials to enter via the lipid membrane. Thus, the new materials neither obstruct the metal-binding sites nor inhibit the growth of microbe enzymes. Further, the results show that the transition metal ion-containing mesoporous materials possessing good anticancer activity arising from their excessive surface area to volume ratio provided appropriate association with a tumour cell due to the direct penetration of mesoporous materials into the cell wall, causing membrane damage and cell death.

Enhancement of Photodynamic Cancer Therapy by Physical and Chemical Factors

The viable use of photodynamic therapy (PDT) in cancer therapy has never been fully realized because of its undesirable effects on healthy tissues. Herein we summarize some physicochemical factors that can make PDT a more viable and effective option to provide future oncological patients with better-quality treatment options. These physicochemical factors include light sources, photosensitizer (PS) carriers, microwaves, electric fields, magnetic fields, and ultrasound. This Review is meant to provide current information pertaining to PDT use, including a discussion of in vitro and in vivo studies. Emphasis is placed on the physicochemical factors and their potential benefits in overcoming the difficulty in transitioning PDT into the medical field. Many advanced techniques, such as employing X-rays as a light source, using nanoparticle-loaded stem cells and bacteriophage bio-nanowires as a photosensitizer carrier, as well as integration with immunotherapy, are among the future directions.

RGD peptide-decorated micelles assembled from polymer-paclitaxel conjugates towards gastric cancer therapy

Development of polymer-drug conjugate capable of controlled drug release is urgently needed for gastric cancer therapy. Herein, arginine-glycine-aspartic acid (RGD)-decorated polyethylene glycol (PEG)-paclitaxel (PTX) conjugates containing disulfide linkage were synthesized. The amphiphilic PEG-PTX conjugates were found to assemble into micelles (RGD@Micelles), which would be decomposed under the reduction of glutathione (GSH) and finally release PTX in weakly acidic conditions characteristic of intracellular environment. The RGD@Micelles were spherical nanoparticles with an average hydrodynamic size of ˜50 nm, which were stable in physiological environment. The release of PTX from the micelles in response to GSH was investigated. In vitro cell assay suggested that the RGD@Micelles could target the gastric cancer cells and inhibit cell proliferation by inducing apoptosis. In vivo experiments indicated that the RGD@Micelles could be delivered to the tumor site and inhibit the tumor growth efficiently by releasing PTX inside the tumor cells. This type of micelles exhibited high therapeutic efficacy and low side effects, providing new insights into targeted drug delivery for gastric cancer therapy.

Synthesis and self-assembly of thiol-modified tellurophenes

An asymmetric thiol-modified tellurophene was designed and synthesized, and the ability of the compound to form a monolayer on a gold electrode was confirmed. The surface-active tellurophene was synthesized using Cadiot–Chodkiewicz coupling followed by ring closing and thiol modification. The tellurophene compound forms a monolayer on gold surfaces from a concentrated solution within 24 h. The ability of the compound to conjugate to gold is confirmed by X-ray photoelectron spectroscopy (XPS). A surface blocking experiment was used to evaluate the extent of formation of a monolayer on a gold electrode.

Practical Three-Minute Synthesis of Acid-Coated Fluorescent Carbon Dots with Tuneable Core Structure

We report a one-pot, three-minute synthesis of carboxylic acid-decorated fluorescent carbon dots (COOH-FCDs) with tuneable core morphology dependent on the surface passivating agent. Mechanism investigations highlighted the presence of key pyrazine and polyhydroxyl aromatic motifs, which are formed from the degradation of glucosamine in the presence of a bifunctional linker bearing acid and amine groups. The novel COOH-FCDs are selective Fe3+ and hemin sensors. Furthermore, the FCDs are shown to be non-toxic, fluorescent bioimaging agents for cancer cells.

Quantum dot-decorated semiconductor micro- and nanoparticles: A review of their synthesis, characterization and application in photocatalysis

Quantum dot (QD)-decorated semiconductor micro- and nanoparticles are a new class of functional nanomaterials that have attracted considerable interest for their unique structural, optical and electronic properties that result from the large surface-to-volume ratio and the quantum confinement effect. In addition, because of QDs' excellent light-harvesting capacity, unique photoinduced electron transfer, and up-conversion behaviour, semiconductor nanoparticles decorated with quantum dots have been used widely in photocatalytic applications for the degradation of organic pollutants in both the gas and aqueous phases. This review is a comprehensive overview of the recent progress in synthesis methods for quantum dots and quantum dot-decorated semiconductor composites with an emphasis on their composition, morphology and optical behaviour. Furthermore, various approaches used for the preparation of QD-based composites are discussed in detail with respect to visible and UV light-induced photoactivity. Finally, an outlook on future development is proposed with the goal of overcoming challenges and stimulating further research into this promising field.

Mechanochemistry of Chitosan-Coated Zinc Sulfide (ZnS) Nanocrystals for Bio-imaging Applications

The ZnS nanocrystals were prepared in chitosan solution (0.1 wt.%) using a wet ultra-fine milling. The obtained suspension was stable and reached high value of zeta potential (+57 mV). The changes in FTIR spectrum confirmed the successful surface coating of ZnS nanoparticles by chitosan. The prepared ZnS nanocrystals possessed interesting optical properties verified in vitro. Four cancer cells were selected (CaCo-2, HCT116, HeLa, and MCF-7), and after their treatment with the nanosuspension, the distribution of ZnS in the cells was studied using a fluorescence microscope. The particles were clearly seen; they passed through the cell membrane and accumulated in cytosol. The biological activity of the cells was not influenced by nanoparticles, they did not cause cell death, and only the granularity of cells was increased as a consequence of cellular uptake. These results confirm the potential of ZnS nanocrystals using in bio-imaging applications.

Strategies for optimizing the delivery to tumors of macrocyclic photosensitizers used in photodynamic therapy (PDT)

This review briefly summaries the principles and mechanisms of action of photodynamic therapy (PDT) as concerns its application in the oncological field, highlighting its drawbacks and some of the strategies that have been or are being explored to overcome them. The major aim is to increase the efficiency and selectivity of the photosensitizer (PS) uptake in the cancer cells for optimizing the PDT effects on tumors while sparing normal cells. Some attempts to achieve this are based on the conjugation of the PS to biomolecules (small ligands, peptides) functioning as carriers with the ability to efficiently penetrate cells and/or specifically recognize and bind proteins/receptors overexpressed on the surface of cancer cells. Alternatively, the PS can be entrapped in nanocarriers derived from various types of materials that can target the tumor by exploiting the enhanced permeability and retention (EPR) effects. The use of nanocarriers is particularly attractive because it allows the simultaneous delivery of more than one drug with the possibility of combining PDT with other therapeutic modalities.

Dual-Quantum-Dots-Labeled Lateral Flow Strip Rapidly Quantifies Procalcitonin and C-reactive Protein

In the article, a dual-quantum-dots-labeled (dual-QDs-labeled) lateral flow strip (LFS) method was developed for the simultaneous and rapid quantitative detection of procalcitonin (PCT) and C-reactive protein (CRP) in the blood. Two QD-antibody conjugates with different fluorescence emission spectra were produced and sprayed on the LFS to capture PCT and CRP in the blood. Furthermore, a double antibody sandwich method for PCT and, meanwhile, a competitive inhibition method for CRP were employed in the LFS. For PCT and CRP in serum assayed by the dual-QDs-labeled LFS, their detection sensitivities reached 0.1 and 1 ng/mL, respectively, and their linear quantitative detection ranges were from 0.3 to 200 ng/mL and from 50 to 250 μg/mL, respectively. There was little evidence that the PCT and CRP assays would be interfered with each other. The correlations for testing CRP and PCT in clinical samples were 99.75 and 97.02 %, respectively, between the dual-QDs-labeled LFS we developed and commercial methods. The rapid quantification of PCT and CRP on dual-QDs-labeled LFS is of great clinical value to distinguish inflammation, bacterial infection, or viral infection and to provide guidance for the use of antibiotics or other medicines.

Comparative study on toxicity of extracellularly biosynthesized and laboratory synthesized CdTe quantum dots

Nanobiosynthesis belongs to the most recent methods for synthesis of nanoparticles. This type of synthesis provides many advantages including the uniformity in particle shape and size. The biosynthesis has also a significant advantage regarding chemical properties of the obtained particles. In this study, we characterized the basic properties and composition of quantum dots (QDs), obtained by the extracellular biosynthesis by Escherichia coli. Furthermore, the toxicity of the biosynthesized QDs was compared to QDs prepared by microwave synthesis. The obtained results revealed the presence of cyan CdTe QDs after removal of substantial amounts of organic compounds, which stabilized the nanoparticle surface. QDs toxicity was evaluated using three cell lines Human Foreskin Fibroblast (HFF), Human Prostate Cancer cells (PC-3) and Breast Cancer cells (MCF-7) and the MTT assay. The test revealed differences in the toxicity between variants of QDs, varying about 10% in the HFF and 30% in the MCF-7 cell lines. The toxicity of the biosynthesized QDs to the PC-3 cell lines was about 35% lower in comparison with the QDs prepared by microwave synthesis.

Chitosan-based core-shell nanomaterials for pH-triggered release of anticancer drug and near-infrared bioimaging

As a naturally-abundant biopolymer, chitosan (CS) exhibit pH-sensitive structural transformation within a narrow pH range. Integrating hydrophobic groups to CS molecules gives modified CS polymers with more adjustable pH responsiveness. In this paper, near-infrared (NIR) photoluminescent Ag₂S QDs capped by long-chain carboxylic acid were synthesized and then conjugated with CS via esterification reaction. The anticancer drug doxorubicin (DOX) has an affinity for the hydrophobic oleoyl groups and was entrapped by them to produce Ag₂S(DOX)@CS nanospheres. A variety of experiments were performed to characterize the nanospheres. In vitro and in vivo experiments showed that the nanospheres can release DOX at lowered pH in tumor cells and have high antitumor efficacy. In addition, the strong NIR signal derived from the encapsulated Ag₂S QDs makes real-time monitoring of the nanosphere distribution in a body possible. This study provides a new CS-based nanocomposite drug carrier for efficient cancer therapy.

Mechanochemical approach for the capping of mixed core CdS/ZnS nanocrystals: Elimination of cadmium toxicity

The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. l-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using l-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS- and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium(II) was higher in comparison to the l-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications.

Solid lipid nanoparticles as attractive drug vehicles: Composition, properties and therapeutic strategies

This work briefly reviews up-to-date developments in solid lipid nanoparticles (SLNs) as effective nanocolloidal system for drug delivery. It summarizes SLNs in terms of their preparation, surface modification and properties. The application of SLNs as a carrier system enables to improve the therapeutic efficacy of drugs from various therapeutic groups. Present uses of SLNs include cancer therapy, dermatology, bacterial infections, brain targeting and eye disorders among others. The usage of SLNs provides enhanced pharmacokinetic properties and modulated release of drugs. SLN ubiquitous application results from their specific features such as possibility of surface modification, increased permeation through biological barriers, resistance to chemical degradation, possibility of co-delivery of various therapeutic agents or stimuli-responsiveness. This paper will be useful to the scientists working in the domain of SLN-based drug delivery systems.

Preparation of fluorescent Au–SiO2 core–shell nanoparticles and nanorods with tunable silica shell thickness and surface modification for immunotargeting

Scalable methods for preparing and modifying Au–SiO₂ core–shell nanoparticles provide a platform for engineering size-dependent multifunctional properties for in vivo biomedical applications.

Amphiphilic drug–drug assembly via dual-responsive linkages for small-molecule anticancer drug delivery

Amphiphilic drug–drug assembly nanoparticles based on dual-responsive H-bonding-instructed disulfide bonds can release irinotecan and doxorubicin simultaneously in cancer cells for anticancer purposes.

Semiconductor and carbon-based fluorescent nanodots: the need for consistency

The need for establishing the bases and definitions of photoluminescent nanodots is discussed and their state-of-the-art in analytical and biomedical research fields is highlighted.

Assessing potential harmful effects of CdSe quantum dots by using Drosophila melanogaster as in vivo model

Since CdSe QDs are increasingly used in medical and pharmaceutical sciences careful and systematic studies to determine their biosafety are needed. Since in vivo studies produce relevant information complementing in vitro data, we promote the use of Drosophila melanogaster as a suitable in vivo model to detect toxic and genotoxic effects associated with CdSe QD exposure. Taking into account the potential release of cadmium ions, QD effects were compared with those obtained with CdCl2. Results showed that CdSe QDs penetrate the intestinal barrier of the larvae reaching the hemolymph, interacting with hemocytes, and inducing dose/time dependent significant genotoxic effects, as determined by the comet assay. Elevated ROS production, QD biodegradation, and significant disturbance in the conserved Hsps, antioxidant and p53 genes were also observed. Overall, QD effects were milder than those induced by CdCl2 suggesting the role of Cd released ions in the observed harmful effects of Cd based QDs. To reduce the observed side-effects of Cd based QDs biocompatible coats would be required to avoid cadmium's undesirable effects.

Quantum Dots Encapsulated with Canine Parvovirus-Like Particles Improving the Cellular Targeted Labeling

Quantum dots (QDs) have a promising prospect in live-cell imaging and sensing because of unique fluorescence features. QDs aroused significant interest in the bio-imaging field through integrating the fluorescence properties of QDs and the delivery function of biomaterial. The natural tropism of Canine Parvovirus (CPV) to the transferrin receptor can target specific cells to increase the targeting ability of QDs in cell imaging. CPV virus-like particles (VLPs) from the expression of the CPV-VP2 capsid protein in a prokaryotic expression system were examined to encapsulate the QDs and deliver to cells with an expressed transferrin receptor. CPV-VLPs were used to encapsulate QDs that were modified using 3-mercaptopropionic acid. Gel electrophoresis, fluorescence spectrum, particle size, and transmission electron microscopy verified the conformation of a complex, in which QDs were encapsulated in CPV-VLPs (CPV-VLPs-QDs). When incubated with different cell lines, CPV-VLPs-QDs significantly reduced the cytotoxicity of QDs and selectively labeled the cells with high-level transferrin receptors. Cell-targeted labeling was achieved by utilizing the specific binding between the CPV capsid protein VP2 of VLPs and cellular receptors. CPV-VLPs-QDs, which can mimic the native CPV infection, can recognize and attach to the transferrin receptors on cellular membrane. Therefore, CPV-VLPs can be used as carriers to facilitate the targeted delivery of encapsulated nanomaterials into cells via receptor-mediated pathways. This study confirmed that CPV-VLPs can significantly promote the biocompatibility of nanomaterials and could expand the application of CPV-VLPs in biological medicine.

CdS/ZnS nanocomposites: from mechanochemical synthesis to cytotoxicity issues

CdS/ZnS nanocomposites have been prepared by a two-step solid-state mechanochemical synthesis. CdS has been prepared from cadmium acetate and sodium sulfide precursors in the first step. The obtained cubic CdS (hawleyite, JCPDS 00-010-0454) was then mixed in the second step with the cubic ZnS (sphalerite, JCPDS 00-005-0566) synthesized mechanochemically from the analogous precursors. The crystallite sizes of the new type CdS/ZnS nanocomposite, calculated based on the XRD data, were 3-4 nm for both phases. The synthesized nanoparticles have been further characterized by high-resolution transmission electron microscopy (HRTEM) and micro-photoluminescence (μPL) spectroscopy. The PL emission peaks in the PL spectra are attributed to the recombination of holes/electrons in the nanocomposites occurring in depth associated with Cd, Zn vacancies and S interstitials. Their photocatalytic activity was also measured. In the photocatalytic activity tests to decolorize Methyl Orange dye aqueous solution, the process is faster and its effectivity is higher when using CdS/ZnS nanocomposite, compared to single phase CdS. Very low cytotoxic activity (high viability) of the cancer cell lines (selected as models of living cells) has been evidenced for CdS/ZnS in comparison with CdS alone. This fact is in a close relationship with Cd(II) ions dissolution tested in a physiological solution. The concentration of cadmium dissolved from CdS/ZnS nanocomposites with variable Cd:Zn ratio was 2.5-5.0 μg.mL(-1), whereas the concentration for pure CdS was much higher - 53 μg.ml(-1). The presence of ZnS in the nanocrystalline composite strongly reduced the release of cadmium into the physiological solution, which simulated the environment in the human body. The obtained CdS/ZnS quantum dots can serve as labeling media and co-agents in future anti-cancer drugs, because of their potential in theranostic applications.