Multifunctional pH-sensitive magnetic nanoparticles for simultaneous imaging, sensing and targeted intracellular anticancer drug delivery

Preliminary investigation on the impact of engineered PVP-capped and uncapped silver nanoparticles on Eudrilus eugeniae, a terrestrial ecosystem model

Recently, the production of silver nanoparticles and their commercial products has generated increased concern and caused a hazardous impact on the ecosystem. Therefore, the present study examines the toxic effect of chemically engineered silver nanoparticles (SNPs) and polyvinylpyrrolidone-capped silver nanoparticles (PVP-SNPs) on the earthworm Eudrilus eugeniae (E. eugeniae). The SNPs and PVP-SNPs were synthesized, and their characterization was determined by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The toxicity of SNPs and PVP-SNPs was evaluated using E. eugeniae. The present result indicates that the lethal concentration (LC₅₀) of SNPs and PVP-SNPs were achieved at 22.66 and 43.27 μg/mL, respectively. The activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was increased in SNPs compared to PVP-SNPs. Importantly, we have noticed that the E. eugeniae can amputate its body segments after exposure to SNPs and PVP-SNPs. This exciting phenomenon is named "autotomy," which describes a specific feature of E. eugeniae to escape from the toxic contaminants and predators. Accordingly, we have suggested this unique behavior may facilitate to assess the toxic effect of SNPs and PVP-SNPs in E. eugeniae.

Study the Adsorption of Letrozole Drug on the Silicon Doped Graphdiyne Monolayer: a DFT Investigation

In the current study, by employing first-principles computations, the adsorption behavior of letrozole (LET) was investigated on the pristine graphdiyne nanosheet (GDY) as well as Si-doped graphdiyne (SiGDY). According to the adsorption energy, charge transfer value, and the change in the bang gap energy, the tendency of the pristine GDY towards LET is insignificant. However, the interaction of LET with SiGDY was strong and the adsorption energy was approximately − 19.20 kcal/mol. In addition, the associated electrical conductivity with SiGDY increased by approximately 23.53 % following the adsorption of LET. The results show that SiGDY can be employed as an electronic sensor to detect LET. Furthermore, LET is detected by SiGDY in the water phase based on the magnitude of solvation energy. Finally, a considerable charge-transfer between LET and SiGDY is a precondition for the adsorption of the LET molecule with proper binding energies, which delivers the Si atoms with a significant positive charge.

Development, Characterization and Cell Viability Inhibition of PVA Spheres Loaded with Doxorubicin and 4'-Amino-1-Naphthyl-Chalcone (D14) for Osteosarcoma

Chalcones (1,3-diaryl-2-propen-1-ones) are naturally occurring polyphenols with known anticancer activity against a variety of tumor cell lines, including osteosarcoma (OS). In this paper, we present the preparation and characterization of spheres (~2 mm) from polyvinyl alcohol (PVA) containing a combination of 4′-Amino-1-Naphthyl-Chalcone (D14) and doxorubicin, to act as a new polymeric dual-drug anticancer delivery. D14 is a potent inhibitor of osteosarcoma progression and, when combined with doxorubicin, presents a synergetic effect; hence, physically crosslinked PVA spheres loaded with D14 and doxorubicin were prepared using liquid nitrogen and six freeze–thawing cycles. Physical-chemical characterization using a scanning electron microscope (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) presented that the drugs were incorporated into the spheres via weak interactions between the drugs and the polymeric chains, resulting in overall good drug stability. The cytotoxicity activity of the PVA spheres co-encapsulating both drugs was tested against the U2OS human osteosarcoma cell line by 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) assay, and compared to the spheres carrying either D14 or doxorubicin alone. The co-delivery showed a cytotoxic effect 2.6-fold greater than doxorubicin alone, revealing a significant synergistic effect with a coefficient of drug interaction (CDI) of 0.49. The obtained results suggest this developed PVA sphere as a potential dual-drug delivery system that could be used for the prominent synergistic anticancer activity of co-delivering D14 and doxorubicin, providing a new potential strategy for improved osteosarcoma treatment.

Graphene quantum dot formulation for cancer imaging and redox-based drug delivery

This work develops a new multifunctional biocompatible anticancer nanoformulation to provide targeted image-guided cancer-selective therapeutics. It consists of three active covalently bound components: (1) biocompatible nitrogen-doped graphene quantum dots (GQDs) as a multifunctional delivery and imaging platform, (2) hyaluronic acid (HA) unit targeted to the CD44 receptors on a variety of cancer cells, and (3) oxidative stress-based cancer-selective ferrocene (Fc) therapeutic. The biocompatible GQD platform synthesized from glucosamine exhibits high-yield intrinsic fluorescence. It is utilized for tracking Fc-GQD-HA formulation in vitro indicating internalization enhancement in HeLa cells targeted by the HA over non-cancer HEK-293 cells not overexpressing CD44 receptor. Fc-GQD-HA, non-toxic at 1 mg/mL to HEK-293 cells, induces cytotoxic response in HeLa enhanced over time, while therapeutic ROS generation by Fc-GQD-HA is ~3 times greater than that of Fc alone. This outlines the targeted delivery, imaging, and cancer-specific treatment capabilities of the new Fc-GQD-HA formulation enabling desired cancer-focused nanotherapeutic approach.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

Stimuli-responsive natural gums-based drug delivery systems for cancer treatment

Chemotherapy as the main cancer treatment method has non-specific effects and various side-effects. Accordingly, significant attempts have been conducted to enhance its efficacy through design and development of "smart" drug delivery systems (DDSs). In this context, natural gums, as a nice gift by the nature, can be exploited as stimuli-responsive DDSs for cancer treatment in part due to their renewability, availability, low cost, bioactivity, biocompatibility, low immunogenicity, biodegradability, and acceptable stability in both in vitro and in vivo conditions. However, some shortcomings (e.g., poor mechanical properties and high hydration rate) restrict their biomedical application ranges that can be circumvented through modification process (e.g., grafting of stimuli-responsive polymers or small molecules) to obtain tailored biomaterials. This review article aimed to compile the stimuli-responsive DDSs based on natural gums. In addition, different types of stimuli, the fundamental features of natural gums, as well as their chemical modification approaches are also shortly highlighted.

Gum polysaccharide/nanometal hybrid biocomposites in cancer diagnosis and therapy

Biopolymers are of prime importance among which gum polysaccharides hold an eminent standing owing to their high availability and non-toxic nature. Gum biopolymers offer a greener alternative to synthetic polymers and toxic chemicals in the synthesis of metal nanostructures. Metal nanostructures accessible via eco-friendly means endow astounding characteristics to gum-based biocomposites in the field of diagnosis and therapy towards cancer diseases. In this review, assorted approaches for the assembly of nanomaterials mediated by gum biopolymers are presented and their utility in cancer diagnosis and therapy, e.g., bioimaging, radiotherapy, and phototherapy, are deliberated to provide a groundwork for future stimulative research.

Study the adsorption process of 5-Fluorouracil drug on the pristine and doped graphdiyne nanosheet

The electronic properties of pristine graphdiyne nanosheet (GDY) and boron-doped graphdiyne (BGDY) were scrutinized using the first-principles calculation. Furthermore, the adsorption energy, charge transfer, and electrical conductivity variation of the 5-fluorouracil (5FU) drugs on both the GDY and BGDY sheet surfaces were reported and were employed to investigate the binding among them. The tendency of pristine GDY to 5FU drug was already identified to be negligible. Moreover, the band gap energy was changed only around 3.31% after 5FU adsorption on the GDY sheet. The adsorption energy of 5FU on the BGDY was computed in both gas and water solvent media and was about - 32.72 and - 41.96 kcal/mol, respectively. The moderate amount of solvation energy indicates the good solubility of the implemented drugs in the aqueous medium. Moreover, significant transfer of charge from the 5FU to the BGDY sheet results in a substantially positive charge for B, which is a prerequisite of the adsorption of the 5FU molecule with the suitable binding energy. In addition, after 5FU adsorption, the electrical conductivity of BGDY was increased by about 25.5%, and based on this result, the BGDY is a suitable electronic sensor for 5FU detection unlike to pristine GDY.

Mucus-penetrating PEGylated polysuccinimide-based nanocarrier for intravaginal delivery of siRNA battling sexually transmitted infections

Intravaginal delivery of siRNA for prevention of sexually transmitted infections faces obstacles such as the acidic environment and vaginal mucus barrier. To achieve effective protection and delivery of siRNA, we developed a polysuccinimide (PSI)-based nanocarrier (PSI-PEG-API-PMA, PPAP) by conjugating methoxy polyethylene glycol amine (Me-PEG-NH₂, Mw 5000), 1-(3-aminopropyl)imidazole (API), and 1-pyrenemethylamine hydrochloride (PMA) to PSI. PPAP demonstrated a spherical self-assembled nanostructure before and after encapsulation of a model siRNA. Variable electrostatic interaction between API and siRNA at acidic vs. neutral pH accomplished significantly lower burst release at pH 4.2 (4 ± 1%) than pH 7.0 (26 ± 5%) within 1 h. PEGylation enabled siRNA-PPAP to achieve higher mucus penetration efficiency (64 ± 17%) than free siRNA (27 ± 5%) for 24 h. Moreover, in vitro study showed minimal toxicity, successful internalization of siRNA-PPAP in HeLa cells and improved gene knockdown (97.5 ± 0.4%). Overall, PPAP is promising for developing preventative treatments for battling sexually transmitted infections.

Iron-Based Core-Shell Nanowires for Combinatorial Drug Delivery and Photothermal and Magnetic Therapy

Combining different therapies into a single nanomaterial platform is a promising approach for achieving more efficient, less invasive, and personalized treatments. Here, we report on the development of such a platform by utilizing nanowires with an iron core and iron oxide shell as drug carriers and exploiting their optical and magnetic properties. The iron core has a large magnetization, which provides the foundation for low-power magnetic manipulation and magnetomechanical treatment. The iron oxide shell enables functionalization with doxorubicin through a pH-sensitive linker, providing selective intracellular drug delivery. Combined, the core-shell nanostructure features an enhanced light-matter interaction in the near-infrared region, resulting in a high photothermal conversion efficiency of >80% for effective photothermal treatment. Applied to cancer cells, the collective effect of the three modalities results in an extremely efficient treatment with nearly complete cell death (∼90%). In combination with the possibility of guidance and detection, this platform provides powerful tools for the development of advanced treatments.

Magnetic iron oxide nanoparticles as drug carriers: preparation, conjugation and delivery

Magnetic nanoparticles (MNPs), particularly made of iron oxides, have been extensively studied as diagnostic imaging agents and therapeutic delivery vehicles. In this review, special emphasis is set on the 'recent advancements of drug-conjugated MNPs used for therapeutic applications'. The most prevalent preparation methods and chemical functionalization strategies required for translational biomedical nanoformulations are outlined. Particular attention is, then, devoted to the tailored conjugation of drugs to the MNP carrier according to either noncovalent or covalent attachments, with advantages and drawbacks of both pathways conferred. Notable examples are presented to demonstrate the advantages of MNPs in respective drug-delivery applications. Understanding of the preparation, conjugation and delivery processes will definitely bring, in the next decades, a novel magneto-nanovehicle for effective theranostics.

Preparation and characterization of superparamagnetic iron oxide nanoparticles for magnetically guided drug delivery

Iron oxide nanoparticles have unique magnetic properties and therefore readily respond to applied magnetic fields. Moreover, their surfaces can be used to attach active molecules via various covalent or noncovalent interactions. Thus, they can be used as drug carriers for magnetically controlled delivery to specific biological sites of interest. In the present study, we have synthesized aqueous dispersed samples of citric acid-capped iron oxide nanoparticles, and the anticancer drug doxorubicin was then linked with these superparamagnetic iron oxide nanoparticles via a simple noncovalent interaction. Our results show that the conjugated drug releases from the nanoparticles in a sustained manner. The cellular uptake of these nanoparticles was found to be substantial, although it can be further enhanced using magnetic guidance. These nanoparticles (drug free) were found to be nontoxic to cells; however, upon drug conjugation, drug-induced toxicity was observed, owing to the slow release of drug from the nanoparticles.

Detailed toxicity evaluation of β-cyclodextrin coated iron oxide nanoparticles for biomedical applications

The application of iron oxide nanoparticles [IONPs] in biomedical research is progressively increasing, leading to the rapid development of biocompatible and surface modified IONPs. However, there is still a need of information pertaining to its cellular and acute toxicity profile. This work reports the synthesis of β-cyclodextrin coated iron oxide nanoparticles (βCD-IONPs) and their characterization using spectroscopic (FT-IR), thermal (TGA) and surface analysis (TEM, SEM, BET and Zeta potential). All the characterization techniques displayed the synthesis of well dispersed, rod shaped βCD-IONPs of 45nm. Time dependent cellular uptake of these nanoparticles was also evaluated using Prussian blue staining. Further, cytocompatibility analysis was executed in mouse fibroblast cell line (NIH 3T3) using MTT and LDH assays, respectively which did not show any cytotoxic indications of βCD-IONPs. Finally, acute toxicity analysis was carried out in female Wistar rats according to OECD guidelines 420. Rats were exposed to the highest dose (2000mg/kg) of βCD-IONPs along with control and observed for 14days. After two weeks of administration, tissues and blood were collected and subjected to histopathological and biochemical analysis (SGOT, SGPT and ALP). Animals were sacrificed and gross necropsy was carried out. It has been shown that βCD-IONPs does not have any significant toxic effect at the cellular level. Thus, this study provides new perspectives for future biomedical applications.

Functionalized magnetic nanowires for chemical and magneto-mechanical induction of cancer cell death

Exploiting and combining different properties of nanomaterials is considered a potential route for next generation cancer therapies. Magnetic nanowires (NWs) have shown good biocompatibility and a high level of cellular internalization. We induced cancer cell death by combining the chemotherapeutic effect of doxorubicin (DOX)-functionalized iron NWs with the mechanical disturbance under a low frequency alternating magnetic field. (3-aminopropyl)triethoxysilane (APTES) and bovine serum albumin (BSA) were separately used for coating NWs allowing further functionalization with DOX. Internalization was assessed for both formulations by confocal reflection microscopy and inductively coupled plasma-mass spectrometry. From confocal analysis, BSA formulations demonstrated higher internalization and less agglomeration. The functionalized NWs generated a comparable cytotoxic effect in breast cancer cells in a DOX concentration-dependent manner, (~60% at the highest concentration tested) that was significantly different from the effect produced by free DOX and non-functionalized NWs formulations. A synergistic cytotoxic effect is obtained when a magnetic field (1 mT, 10 Hz) is applied to cells treated with DOX-functionalized BSA or APTES-coated NWs, (~70% at the highest concentration). In summary, a bimodal method for cancer cell destruction was developed by the conjugation of the magneto-mechanical properties of iron NWs with the effect of DOX producing better results than the individual effects.

Polymeric protective agents for nanoparticles in drug delivery and targeting

Surface modification/functionalization of nanoparticles (NPs) using polymeric protective agents is an issue of great importance and actuality for drug delivery and targeting. Improving the blood circulation half-life of surface-protected nanocarriers is closely related to the elimination of main biological barriers and limiting factors (protein absorption and opsonization), due to the phagocytic activity of reticuloendothelial system. For passive or active targeted delivery, in biomedical area, surface-functionalized NPs with tissue-recognition ligands were designed and optimized as a result of modern research techniques. Also, multi-functionalized nanostructures are characterized by enhanced bioavailability, efficacy, targeted localization, active cellular uptake, and low side effects. Surface-protected NPs are obtained from biocompatible, biodegradable and less toxic natural polymers (dextran, β-cyclodextrin, chitosan, hyaluronic acid, heparin, gelatin) or synthetic polymers, such as poly(lactic acid), poly(lactic-co-glycolic) acid, poly(ε-caprolactone) and poly(alkyl cyanoacrylates). PEGylation is one of the most important functionalization methods providing steric stabilization, long circulating and 'stealth' properties for both polymeric and inorganic-based nanosystems. In addition, for their antimicrobial, antiviral and antitumor effects, cutting-edge researches in the field of pharmaceutical nanobiotechnology highlighted the importance of noble metal (platinum, gold, silver) NPs decorated with biopolymers.

Design and Fabrication of Multifunctional Sericin Nanoparticles for Tumor Targeting and pH-Responsive Subcellular Delivery of Cancer Chemotherapy Drugs

The severe cytotoxicity of cancer chemotherapy drugs limits their clinical applications. Various protein-based nanoparticles with good biocompatibility have been developed for chemotherapy drug delivery in hope of reducing drugs' side effects. Sericin, a natural protein from silk, has no immunogenicity and possesses diverse bioactivities that have prompted sericin's application studies. However, the potential of sericin as a multifunctional nanoscale vehicle for cancer therapy have not been fully explored. Here we report the successful fabrication and characterization of folate-conjugated sericin nanoparticles with cancer-targeting capability for pH-responsive release of doxorubicin (these nanoparticles are termed "FA-SND"). DOX is covalently linked to sericin through pH-sensitive hydrazone bonds that render a pH-triggered release property. The hydrophobicity of DOX and the hydrophilicity of sericin promote the self-assembly of sericin-DOX (SND) nanoconjugates. Folate (FA) is then covalently grafted to SND nanoconjugates as a binding unit for actively targeting cancer cells that overexpress folate receptors. Our characterization study shows that FA-SND nanoparticles exhibit negative surface charges that would reduce nonspecific clearance by circulation. These nanoparticles possess good cytotoxicity and hemocompatibiliy. Acidic environment (pH 5.0) triggers effective DOX release from FA-SND, 5-fold higher than does a neutral condition (pH 7.4). Further, FA-SND nanoparticles specifically target folate-receptor-rich KB cells, and endocytosed into lysosomes, an acidic organelle. The acidic microenvironment of lysosomes promotes a rapid release of DOX to nuclei, producing cancer specific chemo-cytotoxicity. Thus, FA-mediated cancer targeting and lysosomal-acidity promoting DOX release, two sequentially-occurring cellular events triggered by the designed components of FA-SND, form the basis for FA-SND to achieve its localized and intracellular chemo-cytotoxicity. Together, this study suggests that these FA-SND nanoparticles may be a potentially effective carrier particularly useful for delivering hydrophobic chemotherapeutic agents for treating cancers with high-level expression of folate receptors.

Doxorubicin-conjugated CuS nanoparticles for efficient synergistic therapy triggered by near-infrared light

A CuS–DOX NP drug delivery system was synthesized by conjugating carboxyl-functionalized copper sulfide nanoparticles (CuS NPs) and DOX through hydrazone bonds. The platform exhibits high in vitro and in vivo anti-cancer efficacy due to the combined chemo- and photothermal therapeutic effect upon 808 nm laser irradiation.

Tailored functionalization of iron oxide nanoparticles for MRI, drug delivery, magnetic separation and immobilization of biosubstances

In this critical review, we outline various covalent and non-covalent approaches for the functionalization of iron oxide nanoparticles (IONPs). Tuning the surface chemistry and design of magnetic nanoparticles are described in relation to their applicability in advanced medical technologies and biotechnologies including magnetic resonance imaging (MRI) contrast agents, targeted drug delivery, magnetic separations and immobilizations of proteins, enzymes, antibodies, targeting agents and other biosubstances. We review synthetic strategies for the controlled preparation of IONPs modified with frequently used functional groups including amine, carboxyl and hydroxyl groups as well as the preparation of IONPs functionalized with other species, e.g., epoxy, thiol, alkane, azide, and alkyne groups. Three main coupling strategies for linking IONPs with active agents are presented: (i) chemical modification of amine groups on the surface of IONPs, (ii) chemical modification of bioactive substances (e.g. with fluorescent dyes), and (iii) the activation of carboxyl groups mainly for enzyme immobilization. Applications for drug delivery using click chemistry linking or biodegradable bonds are compared to non-covalent methods based on polymer modified condensed magnetic nanoclusters. Among many challenges, we highlight the specific surface engineering allowing both therapeutic and diagnostic applications (theranostics) of IONPs and magnetic/metallic hybrid nanostructures possessing a huge potential in biocatalysis, green chemistry, magnetic bioseparations and bioimaging.

Self-assembled nanoaggregates based on polyaspartamide graft copolymers for pH-controlled release of doxorubicin

The hydrazone group was effectively cleaved to release doxorubicin (DOX) conjugated on PASPAM in an acidic environment.

Imaging of doxorubicin release from theranostic macromolecular prodrugs via fluorescence resonance energy transfer

Herein we present a FRET-based theranostic macromolecular prodrug (TMP) composed of (a) dendritic polyglycerol (PG) as polymeric nanocarrier, (b) doxorubicin (Dox) linked via a pH-sensitive hydrazone to (c) a tri-functional linker, and (d) an indodicarbocyanine dye (IDCC) attached in close proximity to Dox. The drug fluorescence is quenched via intramolecular FRET until the pH-sensitive hydrazone bond between the TMP and Dox is cleaved at acidic pH. By measuring its fluorescence, we characterized the TMP cleavage kinetics at different pH values in vitro. The intracellular release of Dox from the carrier was monitored in real time in intact cancer cells, giving more insight into the mode of action of a polymer drug conjugate.

Multifunctionalization of magnetic nanoparticles for controlled drug release: a general approach

In this study, a general approach for the multifunctionalization of magnetic nanoparticles (MNPs) with drugs (Doxorubicin and Gemcitabine) and targeting moieties (Nucant pseudopeptide) for controlled and selective release is described. The functionalization is achieved by the formation of disulfide bonds between MNPs and drugs derivatives synthesized in this work. Our strategy consists in the introduction of a pyridyldisulfide moiety to the drugs that react efficiently with sulfhydryl groups of pre-activated MNPs. This approach also allows the quantification of the covalently immobilized drug by measuring the amount of the 2-pyridinethione released during the process. The linkers developed here allow the release of drugs without any chemical modification. This process is triggered under highly reducing environment, such as that present inside the cells. Complete release of drugs is achieved within 5-8 h under intracellular conditions whereas negligible percentage of release is observed in extracellular conditions. We propose here a modular general approach for the functionalization of nanoparticles that can be used for different types of drugs and targeting agents.

pH-sensitive drug-delivery systems for tumor targeting

Drug-delivery system responses to stimuli have been well investigated recently. As pH decrease is observed in most solid tumors, drug-delivery systems responsive to the slightly acidic extracellular pH environment of solid tumors have been developed as a general strategy for tumor targeting. Drug vehicles that are sensitive to acidic endosome/lysosome pH have been constructed for efficient drug release in tumor cells. This review explains the mechanisms of acidic pH in the tumor microenvironment and endocytic-related organelles, endosomes and lysosomes. Nanoparticle responses to acidic extracellular pH are discussed, along with approaches for improving tumor-specific therapy. Endosome/lysosome pH-triggered vehicles are reviewed, which achieve rapid drug release in tumor cells and overcome multidrug resistance.

Recent advances in nanoparticle-based Förster resonance energy transfer for biosensing, molecular imaging and drug release profiling

Förster resonance energy transfer (FRET) may be regarded as a "smart" technology in the design of fluorescence probes for biological sensing and imaging. Recently, a variety of nanoparticles that include quantum dots, gold nanoparticles, polymer, mesoporous silica nanoparticles and upconversion nanoparticles have been employed to modulate FRET. Researchers have developed a number of "visible" and "activatable" FRET probes sensitive to specific changes in the biological environment that are especially attractive from the biomedical point of view. This article reviews recent progress in bringing these nanoparticle-modulated energy transfer schemes to fruition for applications in biosensing, molecular imaging and drug delivery.

Doxorubicin conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles for therapy and sensing of drug delivery by luminescence resonance energy transfer

In this study, we report an anticancer drug delivery system based on doxorubicin (DOX)-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles. The as-synthesized nanoparticles consist of uniform spherical nanoparticles with an average diameter of 25 nm. The drug delivery system demonstrates the ability to release DOX by cleavage of the hydrazone bond in mildly acidic environments. The spectra overlap between emission of donor NaYF(4):Yb(3+)/Tm(3+) nanoparticles at 452 nm ((1)D(2)→(3)F(4)) and 477 nm ((1)G(4)→(3)H(6)) and the broad absorbance of acceptor DOX centered at around 480 nm enables energy transfer to occur between the nanoparticles and DOX. The quenching and recovery of the up-conversion luminescence of NaYF(4):Yb(3+)/Tm(3+) by DOX due to luminescence resonance energy transfer (LRET) mechanism are applied as optical probe to confirm the DOX conjunction and monitor the release of DOX. The DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells via MTT assay. Meanwhile, the endocytosis process of DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles by SKVO3 cells was demonstrated through confocal laser scanning microscopy (CLSM), flow cytometry and ICP-OES. Such drug delivery system, which combines pH-triggered drug-release and up-converting nanoparticles-based LRET property, has excellent potential applications in cancer therapy and smart imaging.

Intracellular nucleic acid interactions facilitated by quantum dots: conceptualizing theranostics

The concept of theranostics arises from the unification of both diagnostic and therapeutic applications into a single package. The implementation of nanoparticles, such as semiconductor quantum dots (QDs), to achieve theranostic applications, offers great potential for development of methods that are suitable for personalized medicine. Researchers have taken advantage of the physiochemical properties of QDs to elicit novel bioconjugation techniques that enable the attachment of multifunctional moieties on the surface of QDs. In this review, the diagnostic and therapeutic applications of QDs that feature the use of nucleic acids are highlighted with a particular emphasis on the possibility of combinatorial applications. Nucleic acid research is of particular interest for gene therapy, and is relevant to the understanding of gene regulation pathways and gene expression dynamics. Recent toxicity studies featuring multifunctional QDs are also examined. Future perspectives discussing the expected development of this field conclude the article.

The controlled display of biomolecules on nanoparticles: a challenge suited to bioorthogonal chemistry

Interest in developing diverse nanoparticle (NP)-biological composite materials continues to grow almost unabated. This is motivated primarily by the desire to simultaneously exploit the properties of both NP and biological components in new hybrid devices or materials that can be applied in areas ranging from energy harvesting and nanoscale electronics to biomedical diagnostics. The utility and effectiveness of these composites will be predicated on the ability to assemble these structures with control over NP/biomolecule ratio, biomolecular orientation, biomolecular activity, and the separation distance within the NP-bioconjugate architecture. This degree of control will be especially critical in creating theranostic NP-bioconjugates that, as a single vector, are capable of multiple functions in vivo, including targeting, image contrast, biosensing, and drug delivery. In this review, a perspective is given on current and developing chemistries that can provide improved control in the preparation of NP-bioconjugates. The nanoscale properties intrinsic to several prominent NP materials are briefly described to highlight the motivation behind their use. NP materials of interest include quantum dots, carbon nanotubes, viral capsids, liposomes, and NPs composed of gold, lanthanides, silica, polymers, or magnetic materials. This review includes a critical discussion on the design considerations for NP-bioconjugates and the unique challenges associated with chemistry at the biological-nanoscale interface-the liabilities of traditional bioconjugation chemistries being particularly prominent therein. Select bioorthogonal chemistries that can address these challenges are reviewed in detail, and include chemoselective ligations (e.g., hydrazone and Staudinger ligation), cycloaddition reactions in click chemistry (e.g., azide-alkyne cyclyoaddition, tetrazine ligation), metal-affinity coordination (e.g., polyhistidine), enzyme driven modifications (e.g., HaloTag, biotin ligase), and other site-specific chemistries. The benefits and liabilities of particular chemistries are discussed by highlighting relevant NP-bioconjugation examples from the literature. Potential chemistries that have not yet been applied to NPs are also discussed, and an outlook on future developments in this field is given.

Highly porous, water-soluble, superparamagnetic, and biocompatible magnetite nanocrystal clusters for targeted drug delivery

Magnetic particles have become very promising materials for drug delivery. However, preparation of magnetite particles with high surface area, biocompatibility, strong magnetic response, and suitable particle size still remains a major challenge. In this report, magnetite nanocrystal clusters with high surface areas were fabricated through a solvothermal process by introducing ammonium acetate as a porogen and trisodium citrate as a surface modification agent. The porosity, which was controlled by the reactant concentration, has been investigated in detail. The surface area of the nanocrystal clusters was as high as 141 m(2) g(-1). Ibuprofen, as a model drug, was entrapped into the magnetite carriers. The interfacial interaction between the carboxylic groups on the drug molecules and the carboxylate groups on the carriers enhanced the loading efficiency. Low cytotoxicity in MCF-7 cell and in vitro constant drug release behavior combined with the high drug loading efficiency and high saturation magnetization values demonstrated the potential of the as-synthesized magnetite materials in targeted drug release systems.