Enzyme-Responsive Multifunctional Magnetic Nanoparticles for Tumor Intracellular Drug Delivery and Imaging

Design and evaluation of nanoscale materials with programmed responsivity towards epigenetic enzymes

Self-assembled materials capable of modulating their assembly properties in response to specific enzymes play a pivotal role in advancing 'intelligent' encapsulation platforms for biotechnological applications. Here, we introduce a previously unreported class of synthetic nanomaterials that programmatically interact with histone deacetylase (HDAC) as the triggering stimulus for disassembly. These nanomaterials consist of co-polypeptides comprising poly(acetyl L-lysine) and poly(ethylene glycol) blocks. Under neutral pH conditions, they self-assemble into particles. The hydrodynamic diameters of particles were typically withing the range of 108-190 nm, depending on degree of acetylation of the hydrophobic block. However, their stability is compromised upon exposure to HDACs, depending on enzyme concentration and exposure time. Our investigation, utilizing HDAC8 as the model enzyme, revealed that the primary mechanism behind disassembly involves a decrease in amphiphilicity within the block copolymer due to the deacetylation of lysine residues within the particles' hydrophobic domains. To elucidate the response mechanism, we encapsulated a fluorescent dye within these nanoparticles. Upon incubation with HDAC, the nanoparticle structure collapsed, leading to controlled release of the dye over time. Notably, this release was not triggered by denatured HDAC8, other proteolytic enzymes like trypsin, or the co-presence of HDAC8 and its inhibitor. We also demonstrated the biocompatibility and cellular effects of these materials in the context of drug delivery in different types of anticancer cell lines, such as MIA PaCa-2, PANC-1, cancer like stem cells (CSCs), and non-cancerous HPNE cells. We observed that the release of a model drug (such as a STAT3 pathway inhibitor, Napabucasin) can be loaded into these nanoparticles, with >90% of the dosage can be released over 3 h under the influence of HDAC8 enzyme in a controlled fashion. Further, we conducted a comprehensive computational study to unveil the possible interaction mechanism between enzymes and particles. By drawing parallels to the mechanism of naturally occurring histone proteins, this research represents a pioneering step toward developing functional materials capable of harnessing the activity of epigenetic enzymes such as HDACs.

Design and Evaluation of Nanoscale Materials with Programmed Responsivity towards Epigenetic Enzymes

Self-assembled materials capable of modulating their assembly properties in response to specific enzymes play a pivotal role in advancing 'intelligent' encapsulation platforms for biotechnological applications. Here, we introduce a previously unreported class of synthetic nanomaterials that programmatically interact with histone deacetylase (HDAC) as the triggering stimulus for disassembly. These nanomaterials consist of co-polypeptides comprising poly (acetyl L-lysine) and poly(ethylene glycol) blocks. Under neutral pH conditions, they self-assemble into particles. However, their stability is compromised upon exposure to HDACs, depending on enzyme concentration and exposure time. Our investigation, utilizing HDAC8 as the model enzyme, revealed that the primary mechanism behind disassembly involves a decrease in amphiphilicity within the block copolymer due to the deacetylation of lysine residues within the particles' hydrophobic domains. To elucidate the response mechanism, we encapsulated a fluorescent dye within these nanoparticles. Upon incubation with HDAC, the nanoparticle structure collapsed, leading to controlled release of the dye over time. Notably, this release was not triggered by denatured HDAC8, other proteolytic enzymes like trypsin, or the co-presence of HDAC8 and its inhibitor. We further demonstrated the biocompatibility and cellular effects of these materials and conducted a comprehensive computational study to unveil the possible interaction mechanism between enzymes and particles. By drawing parallels to the mechanism of naturally occurring histone proteins, this research represents a pioneering step toward developing functional materials capable of harnessing the activity of epigenetic enzymes such as HDACs.

Tumor Therapy Strategies Based on Microenvironment-Specific Responsive Nanomaterials

The tumor microenvironment (TME) is a complex and variable region characterized by hypoxia, low pH, high redox status, overexpression of enzymes, and high-adenosine triphosphate concentrations. In recent years, with the continuous in-depth study of nanomaterials, more and more TME-specific response nanomaterials are used for tumor treatment. However, the complexity of the TME causes different types of responses with various strategies and mechanisms of action. Aiming to systematically demonstrate the recent advances in research on TME-responsive nanomaterials, this work summarizes the characteristics of TME and outlines the strategies of different TME responses. Representative reaction types are illustrated and their merits and demerits are analyzed. Finally, forward-looking views on TME-response strategies for nanomaterials are presented. It is envisaged that such emerging strategies for the treatment of cancer are expected to exhibit dramatic trans-clinical capabilities, demonstrating the extensive potential for the diagnosis and therapy of cancer.

Smart Magnetic Drug Delivery Systems for the Treatment of Cancer

Cancer remains the most devastating disease, being one of the main factors of death and morbidity worldwide since ancient times. Although early diagnosis and treatment represent the correct approach in the fight against cancer, traditional therapies, such as chemotherapy, radiotherapy, targeted therapy, and immunotherapy, have some limitations (lack of specificity, cytotoxicity, and multidrug resistance). These limitations represent a continuous challenge for determining optimal therapies for the diagnosis and treatment of cancer. Cancer diagnosis and treatment have seen significant achievements with the advent of nanotechnology and a wide range of nanoparticles. Due to their special advantages, such as low toxicity, high stability, good permeability, biocompatibility, improved retention effect, and precise targeting, nanoparticles with sizes ranging from 1 nm to 100 nm have been successfully used in cancer diagnosis and treatment by solving the limitations of conventional cancer treatment, but also overcoming multidrug resistance. Additionally, choosing the best cancer diagnosis, treatment, and management is extremely important. The use of nanotechnology and magnetic nanoparticles (MNPs) represents an effective alternative in the simultaneous diagnosis and treatment of cancer using nano-theranostic particles that facilitate early-stage detection and selective destruction of cancer cells. The specific properties, such as the control of the dimensions and the specific surface through the judicious choice of synthesis methods, and the possibility of targeting the target organ by applying an internal magnetic field, make these nanoparticles effective alternatives for the diagnosis and treatment of cancer. This review discusses the use of MNPs in cancer diagnosis and treatment and provides future perspectives in the field.

Role of Iron Oxide (Fe2O3) Nanocomposites in Advanced Biomedical Applications: A State-of-the-Art Review

Nanomaterials have demonstrated a wide range of applications and recently, novel biomedical studies are devoted to improving the functionality and effectivity of traditional and unmodified systems, either drug carriers and common scaffolds for tissue engineering or advanced hydrogels for wound healing purposes. In this regard, metal oxide nanoparticles show great potential as versatile tools in biomedical science. In particular, iron oxide nanoparticles with different shape and sizes hold outstanding physiochemical characteristics, such as high specific area and porous structure that make them idoneous nanomaterials to be used in diverse aspects of medicine and biological systems. Moreover, due to the high thermal stability and mechanical strength of Fe₂O₃, they have been combined with several polymers and employed for various nano-treatments for specific human diseases. This review is focused on summarizing the applications of Fe₂O₃-based nanocomposites in the biomedical field, including nanocarriers for drug delivery, tissue engineering, and wound healing. Additionally, their structure, magnetic properties, biocompatibility, and toxicity will be discussed.

Theranostic applications of stimulus-responsive systems based on Fe2O3

According to the interaction of nanoparticles with biological systems, enthusiasm for nanotechnology in biomedical applications has been developed in the past decades. Fe2O3 nanoparticles, as the most stable iron oxide, have special merits that make them useful widely for detecting diseases, therapy, drug delivery, and monitoring the therapeutic process. This review presents the fabrication methods of Fe2O3-based materials and their photocatalytic and magnetic properties. Then, we highlight the application of Fe2O3-based nanoparticles in diagnosis and imaging, different therapy methods, and finally, stimulus-responsive systems, such as pH-responsive, magnetic-responsive, redox-responsive, and enzyme-responsive, with an emphasis on cancer treatment. In addition, the potential of Fe2O3 to combine diagnosis and therapy within a single particle called theranostic agent will be discussed.

Magnetic Particle Imaging: An Emerging Modality with Prospects in Diagnosis, Targeting and Therapy of Cancer

BACKGROUND

Magnetic Particle Imaging (MPI) is an emerging imaging modality for quantitative direct imaging of superparamagnetic iron oxide nanoparticles (SPION or SPIO). With different physics from MRI, MPI benefits from ideal image contrast with zero background tissue signal. This enables clear visualization of cancer with image characteristics similar to PET or SPECT, but using radiation-free magnetic nanoparticles instead, with infinite-duration reporter persistence in vivo. MPI for cancer imaging: demonstrated months of quantitative imaging of the cancer-related immune response with in situ SPION-labelling of immune cells (e.g., neutrophils, CAR T-cells). Because MPI suffers absolutely no susceptibility artifacts in the lung, immuno-MPI could soon provide completely noninvasive early-stage diagnosis and treatment monitoring of lung cancers. MPI for magnetic steering: MPI gradients are ~150 × stronger than MRI, enabling remote magnetic steering of magneto-aerosol, nanoparticles, and catheter tips, enhancing therapeutic delivery by magnetic means. MPI for precision therapy: gradients enable focusing of magnetic hyperthermia and magnetic-actuated drug release with up to 2 mm precision. The extent of drug release from the magnetic nanocarrier can be quantitatively monitored by MPI of SPION's MPS spectral changes within the nanocarrier.

CONCLUSION

MPI is a promising new magnetic modality spanning cancer imaging to guided-therapy.

Comparison and recent progress of molecular imprinting technology and dummy template molecular imprinting technology

Molecular imprinting technology for the preparation of polymers with specific molecular recognition function had become one of the current research hotspots. It has been widely applied in chromatographic separation, antibody and receptor mimetics, solid-phase extraction, bio-sensors, and other fields in the last decades. In this study, molecular imprinting technology was summarized from the points of templates and dummy templates, and four typical target analytes were selected to compare the differences between templates and dummy templates. The current status and prospects of molecular imprinting technology were also proposed.

Multifunctional and stimuli-responsive nanocarriers for targeted therapeutic delivery

INTRODUCTION

Nanocarrier-based delivery systems offer multiple benefits to overcome limitations of the traditional drug dosage forms, such as protection of the drug, enhanced bioavailability, targeted delivery to disease site, etc. Nanocarriers have exhibited tremendous successes in targeted delivery of therapeutics to the desired tissues and cells with improved bioavailability, high drug loading capacity, enhanced intracellular delivery, and better therapeutic effect. A specific design of stimuli-responsive nanocarriers allows for changing their structural and physicochemical properties in response to exogenous and endogenous stimuli. These nanocarriers show a promise in site specific controlled release of therapeutics under certain physiological conditions or external stimuli.

AREAS COVERED

This review highlights recent progresses on the multifunctional and stimuli-sensitive nanocarriers for targeted therapeutic drug delivery applications.

EXPERT OPINION

The progress from single functional to multifunctional nanocarriers has shown tremendous potential for targeted delivery of therapeutics. On our opinion, the future of targeted delivery of drugs, nucleic acids, and other substances belongs to the site-targeted multifunctional and stimuli-based nanoparticles with controlled release. Targeting of nanocarriers to the disease site enhance the efficacy of the treatment by delivering more therapeutics specifically to the affected cells and substantially limiting adverse side effects upon healthy organs, tissues, and cells.

Magnetic Heterostructures: Interface Control to Optimize Magnetic Property and Multifunctionality

Generally, magnetic heterostructures are obtained by the growth of another component on the surface of seed nanoparticles. The direct electrical and magnetic interactions between the solid-state interfaces would endow the heterostructures with properties beyond the individual components. We have devoted the past few years to magnetic-optical, magnetic-catalytic, and exchange-coupled heterostructures, where the interface effects regulate and optimize the optical, catalytic, and magnetic properties, respectively. In this Spotlight on Applications, we describe our recent progress on magnetic heterostructures. Upon the understanding on the interface control, we then discuss our recent efforts to synthesize core-shell, dimer, and nanocomposite structures, while the regulation of their magnetic, optical, and catalytic properties is addressed in turn. Finally, we give the perspectives of magnetic heterostructures.

Photosensitive properties, synergistic antibacterial abilities of intelligent response-type self-assembled nanoparticle TiO2@V2O5

Representative pathogenic bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are widespread in nature and pose a threat to human health. To control the propagation of these pathogens from the source, the key is to design broad-spectrum antibacterial materials to reduce the serious damage of pathogenic bacteria. At present, more and more nanoparticles are widely researched and applied due to their multi-pathway antibacterial properties, such as regulating physiology, biochemistry and physical chemistry. In this work, we synthesized a uniformly dispersed and stable spherical nanoparticle (TiO₂@V₂O₅) synthesized by self-assembly of tianium dioxide and vanadium pentoxide. Based on its excellent photosensitive properties, TiO₂@V₂O₅ nanoparticles have showed excellent antibacterial properties under the light irradiation due to the production of hydroxyl radicals in antibacterial and mechanism tests. In addtion, related cell and plant experiments have showed that TiO₂@V₂O₅ nanoparticles are excellent biocompatible materials, it could be widely used in environmental pollution control, limiting the serious damage caused by pathogens.

Nanotechnology as a Platform for the Development of Injectable Parenteral Formulations: A Comprehensive Review of the Know-Hows and State of the Art

Within recent decades, the development of nanotechnology has made a significant contribution to the progress of various fields of study, including the domains of medical and pharmaceutical sciences. A substantially transformed arena within the context of the latter is the development and production of various injectable parenteral formulations. Indeed, recent decades have witnessed a rapid growth of the marketed and pipeline nanotechnology-based injectable products, which is a testimony to the remarkability of the aforementioned contribution. Adjunct to the ability of nanomaterials to deliver the incorporated payloads to many different targets of interest, nanotechnology has substantially assisted to the development of many further facets of the art. Such contributions include the enhancement of the drug solubility, development of long-acting locally and systemically injectable formulations, tuning the onset of the drug’s release through the endowment of sensitivity to various internal or external stimuli, as well as adjuvancy and immune activation, which is a desirable component for injectable vaccines and immunotherapeutic formulations. The current work seeks to provide a comprehensive review of all the abovementioned contributions, along with the most recent advances made within each domain. Furthermore, recent developments within the domains of passive and active targeting will be briefly debated.

Emerging Strategies in Stimuli-Responsive Nanocarriers as the Drug Delivery System for Enhanced Cancer Therapy

The conventional Drug Delivery System (DDS) has limitations such as leakage of the drug, toxicity to normal cells and loss of drug efficiency, while the stimuli-responsive DDS is non-toxic to cells, avoiding the leakage and degradation of the drug because of its targeted drug delivery to the pathological site. Thus nanomaterial chemistry enables - the development of smart stimuli-responsive DDS over the conventional DDS. Stimuliresponsive DDS ensures spatial or temporal, on-demand drug delivery to the targeted cancer cells. The DDS is engineered by using the organic (synthetic polymers, liposomes, peptides, aptamer, micelles, dendrimers) and inorganic (zinc oxide, gold, magnetic, quantum dots, metal oxides) materials. Principally, these nanocarriers release the drug at the targeted cells in response to external and internal stimuli such as temperature, light, ultrasound and magnetic field, pH value, redox potential (glutathione), and enzyme. The multi-stimuli responsive DDS is more promising than the single stimuli-responsive DDS in cancer therapy, and it extensively increases drug release and accumulation in the targeted cancer cells, resulting in better tumor cell ablation. In this regard, a handful of multi-stimuli responsive DDS is in clinical trials for further approval. A comprehensive review is crucial for addressing the existing knowledge about multi-stimuli responsive DDS, and hence, we summarized the emerging strategies in tailored ligand functionalized stimuli-responsive nanocarriers as the DDS for cancer therapies.

Cathepsin-sensitive nanoscale drug delivery systems for cancer therapy and other diseases

Cathepsins are an important category of enzymes that have attracted great attention for the delivery of drugs to improve the therapeutic outcome of a broad range of nanoscale drug delivery systems. These proteases can be utilized for instance through actuation of polymer-drug conjugates (e.g., triggering the drug release) to bypass limitations of many drug candidates. A substantial amount of work has been witnessed in the design and the evaluation of Cathepsin-sensitive drug delivery systems, especially based on the tetra-peptide sequence (Gly-Phe-Leu-Gly, GFLG) which has been extensively used as a spacer that can be cleaved in the presence of Cathepsin B. This Review Article will give an in-depth overview of the design and the biological evaluation of Cathepsin-sensitive drug delivery systems and their application in different pathologies including cancer before discussing Cathepsin B-cleavable prodrugs under clinical trials.

The use of aggregation-induced emission probe doped silica nanoparticles for the immunoassay of human epididymis protein 4

A sensitive sandwich immunoassay for the sensing of human epididymis protein 4 (HE4) is developed based on aggregation-induced emission probe doped silica nanoparticles. Fluorescent silica nanoparticles (TSiO₂) with excellent performance were prepared using a tetraphenylethylene based probe (TPE-C4-4) to produce a controlled aggregation effect, and HE4 was detected using antibody-functionalized fluorescent silica nanoparticles. The fluorescent silica nanoparticles possess good photophysical properties. The TSiO₂ NPs were surface modified with carboxyl groups, and the antibody was covalently attached onto the surface of the nanoparticles. In addition, magnetic beads were modified with N-hydroxysulfosuccinimide sodium salt (NHS) on their surface, capable of forming stable peptide bonds with the antibody. TSiO₂ NPs modified by an antibody and the magnetic beads modified by an antibody were used for the sandwich immunoassay for HE4 protein. The assay is quite sensitive and selective. The detection limit of HE4 is estimated to be 40 pM. The assay shows promising applications for the early diagnosis of ovarian cancer and the development of ovarian cancer-related drugs.

A perspective on magnetic core-shell carriers for responsive and targeted drug delivery systems

Magnetic core-shell nanocarriers have been attracting growing interest owing to their physicochemical and structural properties. The main principles of magnetic nanoparticles (MNPs) are localized treatment and stability under the effect of external magnetic fields. Furthermore, these MNPs can be coated or functionalized to gain a responsive property to a specific trigger, such as pH, heat, or even enzymes. Current investigations have been focused on the employment of this concept in cancer therapies. The evaluation of magnetic core-shell materials includes their magnetization properties, toxicity, and efficacy in drug uptake and release. This review discusses some categories of magnetic core-shell drug carriers based on Fe2O3 and Fe3O4 as the core, and different shells such as poly(lactic-co-glycolic acid), poly(vinylpyrrolidone), chitosan, silica, calcium silicate, metal, and lipids. In addition, the review addresses their recent potential applications for cancer treatment.

Multifunctional Magnetic Mesoporous Silica Nanoagents for in vivo Enzyme-Responsive Drug Delivery and MR Imaging

In this study, we report novel multifunctional nanoagents for in vivo enzyme-responsive anticancer drug delivery and magnetic resonance imaging (MRI), based on mesoporous silica coated iron oxide nanoparticles (Fe3O4@MSNs). The anticancer drug, DOX, was encapsulated in the porous cavities with a MMP-2 enzyme responsive peptide being covalently linked to the nanoparticles surface. The in vitro experiment results indicated that the enzyme responsive nanoagents own high specificity for controlled drug release in the cell line with high MMP-2 expression. Furthermore, the targeted delivery of the nanoagents to the tumor site purpose has been successfully achieved through magnet-guided nanocarrier accumulation by utilizing the magnetic properties of the Fe3O4 nanocores, which resulted in efficient inhibition of the tumor growth. Additionally, these novel nanoagents can also be used as MRI agent for the real-time diagnosis the tumor treatment process of living animals. Taking the advantages of high specificity, controllable drug release and real-time MRI imaging, we believe these multifunctional nanoagents could also be used as a general platform for the design of stimulus-responsive multifunctional nanomaterials for the aim of accurate diagnosis and efficient treatment of other diseases.

Enzymatically promoted release of organic molecules linked to magnetic nanoparticles

Magnetite-based magnetic nanoparticles have been successfully coupled to an organic system constituted of a fluorescent molecule, a tripeptide specifier and a spacer. The system is able to selectively release the fluorescent molecule upon targeted enzymatic hydrolysis promoted by a lysine/arginine specific protease.

Protease-Sensitive Nanomaterials for Cancer Therapeutics and Imaging

Many diseases can be characterized by the abnormal activity exhibited by various biomolecules, the targeting of which can provide therapeutic and diagnostic utility. Recent trends in medicine and nanotechnology have prompted the development of protease-sensitive nanomaterials systems for therapeutic, diagnostic, and theranostic applications. These systems can act specifically in response to the target enzyme and its associated disease conditions, thus enabling personalized treatment and improved prognosis. In this Review, we discuss recent advancements in the development of protease-responsive materials for imaging and drug delivery and analyze several representative systems to illustrate their key design principles.

Theranostic Probes for Targeting Tumor Microenvironment: An Overview

Long gone is the time when tumors were thought to be insular masses of cells, residing independently at specific sites in an organ. Now, researchers gradually realize that tumors interact with the extracellular matrix (ECM), blood vessels, connective tissues, and immune cells in their environment, which is now known as the tumor microenvironment (TME). It has been found that the interactions between tumors and their surrounds promote tumor growth, invasion, and metastasis. The dynamics and diversity of TME cause the tumors to be heterogeneous and thus pose a challenge for cancer diagnosis, drug design, and therapy. As TME is significant in enhancing tumor progression, it is vital to identify the different components in the TME such as tumor vasculature, ECM, stromal cells, and the lymphatic system. This review explores how these significant factors in the TME, supply tumors with the required growth factors and signaling molecules to proliferate, invade, and metastasize. We also examine the development of TME-targeted nanotheranostics over the recent years for cancer therapy, diagnosis, and anticancer drug delivery systems. This review further discusses the limitations and future perspective of nanoparticle based theranostics when used in combination with current imaging modalities like Optical Imaging, Magnetic Resonance Imaging (MRI) and Nuclear Imaging (Positron Emission Tomography (PET) and Single Photon Emission Computer Tomography (SPECT)).

Nanostructures for NIR light-controlled therapies

In general, effective clinical treatment demands precision medicine, which requires specific perturbation to disease cells with no damage to normal tissue. Thus far, guaranteeing that selective therapeutic effects occur only at targeted disease areas remains a technical challenge. Among the various endeavors to achieve such an outcome, strategies based on light-controlled therapies have received special attention, mostly due to their unique advantages, including the low-invasive property and the capability to obtain spatial and temporal precision at the targeted sites via specific wavelength light irradiation. However, most conventional light-mediated therapies, especially those based on short-wavelength UV or visible light irradiation, have potential issues including limited penetration depth and harmful photo damage to healthy tissue. Therefore, the implemention of near-infrared (NIR) light illumination, which can travel into deeper tissues without causing obvious photo-induced cytotoxcity, has been suggested as a preferable option for precise phototherapeutic applications in vitro and in vivo. In this article, an overview is presented of existing therapeutic applications through NIR light-absorbed nanostructures, such as NIR light-controlled drug delivery, NIR light-mediated photothermal and photodynamic therapies. Potential challenges and relevant future prospects are also discussed.

Smart materials on the way to theranostic nanorobots: Molecular machines and nanomotors, advanced biosensors, and intelligent vehicles for drug delivery

BACKGROUND

Theranostics, a fusion of two key parts of modern medicine - diagnostics and therapy of the organism's disorders, promises to bring the efficacy of medical treatment to a fundamentally new level and to become the basis of personalized medicine. Extrapolating today's progress in the field of smart materials to the long-run prospect, we can imagine future intelligent agents capable of performing complex analysis of different physiological factors inside the living organism and implementing a built-in program thereby triggering a series of therapeutic actions. These agents, by analogy with their macroscopic counterparts, can be called nanorobots. It is quite obscure what these devices are going to look like but they will be more or less based on today's achievements in nanobiotechnology.

SCOPE OF REVIEW

The present Review is an attempt to systematize highly diverse nanomaterials, which may potentially serve as modules for theranostic nanorobotics, e.g., nanomotors, sensing units, and payload carriers.

MAJOR CONCLUSIONS

Biocomputing-based sensing, externally actuated or chemically "fueled" autonomous movement, swarm inter-agent communication behavior are just a few inspiring examples that nanobiotechnology can offer today for construction of truly intelligent drug delivery systems.

GENERAL SIGNIFICANCE

The progress of smart nanomaterials toward fully autonomous drug delivery nanorobots is an exciting prospect for disease treatment. Synergistic combination of the available approaches and their further development may produce intelligent drugs of unmatched functionality.

Nanoparticles in practice for molecular-imaging applications: An overview

Nanoparticles (NPs) are playing a progressively more significant role in multimodal and multifunctional molecular imaging. The agents like Superparamagnetic iron oxide (SPIO), manganese oxide (MnO), gold NPs/nanorods and quantum dots (QDs) possess specific properties like paramagnetism, superparamagnetism, surface plasmon resonance (SPR) and photoluminescence respectively. These specific properties make them able for single/multi-modal and single/multi-functional molecular imaging. NPs generally have nanomolar or micromolar sensitivity range and can be detected via imaging instrumentation. The distinctive characteristics of these NPs make them suitable for imaging, therapy and delivery of drugs. Multifunctional nanoparticles (MNPs) can be produced through either modification of shell or surface or by attaching an affinity ligand to the nanoparticles. They are utilized for targeted imaging by magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), positron emission tomography (PET), computed tomography (CT), photo acoustic imaging (PAI), two photon or fluorescent imaging and ultra sound etc. Toxicity factor of NPs is also a very important concern and toxic effect should be eliminated. First generation NPs have been designed, developed and tested in living subjects and few of them are already in clinical use. In near future, molecular imaging will get advanced with multimodality and multifunctionality to detect diseases like cancer, neurodegenerative diseases, cardiac diseases, inflammation, stroke, atherosclerosis and many others in their early stages. In the current review, we discussed single/multifunctional nanoparticles along with molecular imaging modalities.

STATEMENT OF SIGNIFICANCE

The present article intends to reveal recent avenues for nanomaterials in multimodal and multifunctional molecular imaging through a review of pertinent literatures. The topic emphasises on the distinctive characteristics of nanomaterial which makes them, suitable for biomedical imaging, therapy and delivery of drugs. This review is more informative of indicative technologies which will be helpful in a way to plan, understand and lead the nanotechnology related work.

A dual-targeting drug co-delivery system for tumor chemo- and gene combined therapy

Regulation of gene expression using p53 is a promising strategy for treatment of numerous cancers, and chemotherapeutic drug dichloroacetate (DCA) induces apoptosis and growth inhibition in tumor, without apparent toxicity in normal tissues. Combining DCA and p53 gene could be an effective way to treat tumors. The progress towards broad applications of DCA/p53 combination requires the development of safe and efficient vectors that target to specific cells. In this study, we developed a DSPE-PEG-AA (1,2-distearoryl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol-2000)] ammonium salt-anisamide) modified reconstituted high-density lipoprotein-based DCA/p53-loaded nanoparticles (DSPE-PEG-AA/rHDL/DCA-PEI/p53 complexes), which was fabricated as a drug/gene dual-targeting co-delivery system for potential cancer therapy. Here, DCA-PEI was utilized to effectively condense the p53 plasmid, to incorporate the plasmid into rHDL and to act as an antitumor drug to inhibit tumor cell growth. The DSPE-PEG-AA/rHDL/DCA-PEI/p53 complexes exhibited desirable and homogenous particle size, neutral surface charge and low cytotoxicity for normal cells in vitro. The results of confocal laser scanning microscopy (CLSM) and flow cytometry confirmed that the scavenger receptor class B type I (SR-BI) and sigma receptor mediated dual-targeting function of the complexes inducing efficient cytoplasmic drug delivery and gene transfection in human lung adenocarcinoma cell line A549. And in vivo investigation on nude mice bearing A549 tumor xenografts revealed that DSPE-PEG-AA/rHDL/DCA-PEI/p53 complexes possessed specific tumor targeting and strong antitumor activity. The work described here demonstrated that the DSPE-PEG-AA/rHDL/DCA-PEI/p53 complexes might offer a promising tool for effective cancer therapy.

Co-delivery of drugs and plasmid DNA for cancer therapy

Cancer is an extremely complex disease involving multiple signaling pathways that enable tumor cells to evade programmed cell death, thus making cancer treatment extremely challenging. The use of combination therapy involving both gene therapy and chemotherapy has resulted in enhanced anti-cancer effects and has become an increasingly important strategy in medicine. This review will cover important design parameters that are incorporated into delivery systems for the co-administration of drug and plasmid-based nucleic acids (pDNA and shRNA), with particular emphasis on polymers as delivery materials. The unique challenges faced by co-delivery systems and the strategies to overcome such barriers will be discussed. In addition, the advantages and disadvantages of combination therapy using separate carrier systems versus the use of a single carrier will be evaluated. Finally, future perspectives in the design of novel platforms for the combined delivery of drugs and genes will be presented.

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.

Supramolecular nanofibers of self-assembling peptides and DDP to inhibit cancer cell growth

The addition of cis-dichlorodiamineplatinum(ii) to a taxol-peptide amphiphile results in hydrogelations.

Tumor-targeted docetaxel-loaded hyaluronic acid-quercetin polymeric micelles with p-gp inhibitory property for hepatic cancer therapy

Herein, a novel targeted drug delivery nanosystem based on hyaluronic acid (HA) and quercetin (QU) was designed to improve the in vivo therapeutic efficacy of DTX on HC through HA-CD44 mediated targeting and QU-based p-gp efflux inhibition.

A self-assembled system for tumor-targeted co-delivery of drug and gene

A new cationic polymer eprosartan-graft-PEI (ESP) containing eprosartan (ES) and polyethylenimine 1.8K was successfully developed and employed as a safe gene vector to assemble a drug (ES) and gene co-delivery complex (ESP/pDNA). Chondroitin sulfate (CS) was then used as a coating polymer to shield the surface charge of ESP/pDNA complexes, as well as a tumor targeting entity to ensure specific delivery of CS/ESP/pDNA complexes. The CS/ESP/pDNA complexes with desirable particle size and zeta potential, exhibited amidase-responsive drug release and CS-mediated endocytosis in vitro. As compared with ESP/pDNA complexes, in vivo imaging results demonstrated decreased reticuloendothelial system uptake and remarkably increased tumor accumulation of CS/ESP/pDNA complexes. All these findings indicated the potential of CS/ESP/pDNA as a promising tumor-targeted drug and gene co-delivery system.

Human transport protein carrier for controlled photoactivation of antitumor prodrug and real-time intracellular tumor imaging

Current anticancer chemotherapy often suffers from poor tumor selectivity and serious drug resistance. Proper vectors for targeted delivery and controlled drug release play crucial roles in improving the therapeutic selectivity to tumor areas and also overcoming the resistance of cancer cells. In this work, we developed a novel human serum albumin (HSA) protein-based nanocarrier system, which combines the photoactivatable Pt(IV) antitumor prodrug for realizing the controlled release and fluorescent light-up probe for evaluations of drug action and efficacy. The constructed Pt(IV)-probe@HSA platform can be locally activated by light irradiation to release the active Pt species, which results in enhanced cell death at both drug-sensitive A2780 and cisplatin-resistant A2780cis cell lines when compared to the free prodrug molecules. Simultaneously, the cytotoxicity caused by light controlled drug release would further lead to the cellular apoptosis and trigger the activation of caspases 3, one crucial protease enzyme in apoptotic process, which could cleave the recognition peptide moiety (DEVD) with a flanking fluorescent resonance energy transfer (FRET) pair containing near-infrared (NIR) fluorophore Cy5 and quencher Qsy21 on the HSA nanocarrier surface. The turn-on fluorescence in response to caspase-3 could be assessed by fluorescence microscopy and flow cytometry analysis. Our results supported the hypothesis that such a unique design may present a successful platform for multiple roles: (i) a biocompatible protein-based nanocarrier for drug delivery, (ii) the controlled drug release with strengthened therapeutic effects, (iii) real-time monitoring of antitumor drug efficacy at the earlier stage.

Biomolecules-conjugated nanomaterials for targeted cancer therapy

Biomolecules perform vital functions in biology. These functional biomolecules with diverse modifications hold great promise for further applications in bioanalysis and cancer therapy. However, these functional biomolecules face challenges, especially in the field of drug delivery for cancer therapy. For example, functional biomolecules are typically unstable when taken up by cells, as they are easily digested by enzymes. To address this obstacle, nanomaterials have been employed as drug carriers or vehicles, which are powerful nanoplatforms for imaging and cancer treatment. Multifunctionality of these nanoplatforms offers great advantages over conventional reagents, including targeting to a diseased site to minimize systemic toxicity, and the ability to solubilize hydrophobic or labile drugs to improved pharmacokinetics. In this review, we summarize typical functional biomolecule-conjugated nanomaterials for targeting drug delivery. Under the appropriate conditions, targeted drug delivery can be achieved from a high density of biomolecules that are bound to the surface of nanomaterials, resulting in a high affinity for the targets. The high density of biomolecules then leads to a high local concentration, being able to prevent degradation by enzymes. Furthermore, biomolecule-nanomaterial conjugates have been identified to enter cells more easily than free biomolecules, and controllable drug release can then be obtained by a response to a stimulus, such as redox, pH, light, thermal, enzyme-trigged strategies. Now and in the future, with the development of artificial biomolecules as well as nanomaterials, targeted drug delivery based on elegant biomolecule-nanomaterial conjugation approaches is expected to achieve great versatility, additional functions, and further advances.

Enzyme-responsive cell-penetrating peptide conjugated mesoporous silica quantum dot nanocarriers for controlled release of nucleus-targeted drug molecules and real-time intracellular fluorescence imaging of tumor cells

Here, a set of novel and personalized nanocarriers are presented for controlled nucleus-targeted antitumor drug delivery and real-time imaging of intracellular drug molecule trafficking by integrating an enzyme activatable cell penetrating peptide (CPP) with mesoporous silica coated quantum dots nanoparticles. Upon loading of antitumor drug, doxorubicin (DOX) and further exposure to proteases in tumor cell environment, the enzymatic cleavage of peptide sequence activates oligocationic TAT residues on the QDs@mSiO2 surface and direct the DOX delivery into cellular nucleus. The systematic cell imaging and cytotoxicity studies confirm that the enzyme responsive DOX-loaded CPP-QDs@mSiO2 nanoparticles can selectively release DOX in the tumor cells with high cathepsin B enzyme expression and greatly facilitate DOX accumulation in targeted nucleus, thus exhibiting enhanced antitumor activity in these cells. As contrast, there is limited nuclear-targeted drug accumulation and lower tumor cytotoxicity observed in the cells without enzyme expression. More importantly, significant antitumor DOX accumulation and higher tumor inactivation is also found in the drug resistant tumor cells with targeted enzyme expression. Such simple and specific enzyme responsive mesoporous silica-QDs nanoconjugates provide great promise for rational design of targeted drug delivery into biological system, and may thus greatly facilitate the medical theranostics in the near future.

A chitosan-graft-PEI-candesartan conjugate for targeted co-delivery of drug and gene in anti-angiogenesis cancer therapy

A multifunctional copolymer-anticancer conjugate chitosan-graft-polyethyleneimine-candesartan (CPC) containing low molecular weight chitosan (CS) backbone and polyethyleneimine (PEI) arms with candesartan (CD) conjugated via an amide bond was fabricated as a targeted co-delivery nanovector of drug and gene for potential cancer therapy. Here, CD was utilized to specifically bind to overexpressed angiotensin II type 1 receptor (AT1R) of tumor cells, strengthen endosomal buffering capacity of CPC and suppress tumor angiogenesis. The self-assembled CPC/pDNA complexes exhibited desirable and homogenous particle size, moderate positive charges, superior stability, and efficient release of drug and gene in vitro. Flow cytometry and confocal laser scanning microscopy analyses confirmed that CD-targeted function and CD-enhanced buffering capacity induced high transfection, specific cellular uptake and efficient intracellular delivery of CPC/pDNA complexes in AT1R-overexpressed PANC-1 cells. In addition, CPC/wt-p53 complexes co-delivering CD and wild type p53 (wt-p53) gene achieved synergistic angiogenesis suppression by more effectively downregulating the expression of vascular endothelial growth factor (VEGF) mRNA and protein via different pathways in vitro, as compared to mono-delivery and mixed-delivery systems. In vivo investigation on nude mice bearing PANC-1 tumor xenografts revealed that CPC/wt-p53 complexes possessed high tumor-targeting capacity and strong anti-tumor activity. Additional analysis of microvessel density (MVD) demonstrated that CPC/wt-p53 complexes significantly inhibited tumor-associated angiogenesis. These findings suggested that CPC could be an ideal tumor-targeting nanovector for simultaneous transfer of drug and gene, and a multifunctional CPC/wt-p53 co-delivery system with tumor-specific targetability, enhanced endosomal buffering capacity and synergistic anti-angiogenesis efficacy might be a new promising strategy for effective tumor therapy.

Peptide–perylene diimide functionalized magnetic nano-platforms for fluorescence turn-on detection and clearance of bacterial lipopolysaccharides

A simple and novel dual-functional peptide magnetic nanoplatform has been successfully designed for sensitive detection and rapid clearance of bacterial endotoxins.

Non-invasive optical imaging of cathepsin B with activatable fluorogenic nanoprobes in various metastatic models

An increasing number of treatments of metastases rely on diagnostics and imaging these days. The facts that the activity of cathepsin B (CB) is markedly linked to the metastatic process and that CB is found highly expressed in the pericellular regions in this process make CB an attractive target for diagnosing metastases. We have developed a CB-sensitive nanoprobe (CB-CNP) consisting of self-quenched CB-sensitive fluorogenic peptide probes conjugated onto the surface of tumor-targeting glycol chitosan nanoparticles (CNPs). The freshly prepared CB-CNP formed a spherical nanoparticle structure (280 nm in diameter) and the fluorescence intensity of CB-CNP was strongly quenched in physiological condition. However, self-quenched CB-CNP boosted strong fluorescence signals in the presence of CB, not of cathepsin l or cathepsin d, due to the CB-specific cleavage of self-quenched peptide probes. Importantly, the intravenously injected CB-CNP demonstrated the potential to discriminate metastases in vivo in three metastatic mouse models, including 4T1-luc2 liver metastases, RFP-B16F10 lung metastases and HT1080 peritoneal metastases. Indeed, Western blot analysis confirmed that the CB expression of metastases had increased compared to normal organ in these metastatic mouse models. CB-CNPs may be useful for depicting metastases through non-invasive CB molecular imaging.

Triggered Nanoparticles as Therapeutics

Drug delivery systems (DDSs) face several challenges including site-specific delivery, stability, and the programmed release of drugs. Engineered nanoparticle (NP) surfaces with responsive moieties can enhance the efficacy of DDSs for in vitro and in vivo systems. This triggering process can be achieved through both endogenous (biologically controlled release) and exogenous (external stimuli controlled release) activation. In this review, we will highlight recent examples of the use of triggered release strategies of engineered nanomaterials for in vitro and in vivo applications.

NIR light controlled photorelease of siRNA and its targeted intracellular delivery based on upconversion nanoparticles

The most notable role of small interfering RNA (siRNA) is in RNA interference (RNAi) and post-transcriptional gene silencing, which leads to a surge of interest in RNAi for both biomedical research and therapeutic applications. However, "naked" siRNA cannot cross cellular membranes freely because of highly negative charges which limits its utility for gene therapy. In this work, a system of near-infrared (NIR) light-induced siRNA release from silica coated upconversion nanoparticles (Si-UCNPs) is presented. These Si-UCNPs were functionalized with cationic photocaged linkers through covalent bonding, which could effectively adsorb anionic siRNA through electrostatic attractions and were easily internalized by living cells. Upon NIR light irradiation, the photocaged linker on the Si-UCNPs surface could be cleaved by the upconverted UV light and thus initiated the intracellular release of the siRNA. The in vitro agarose gel electrophoresis and intracellular imaging results indicated that the Si-UCNPs-based gene carrier system allowed effective siRNA delivery and the applications of NIR light instead of direct high energy UV irradiation may greatly guarantee less cell damage.

Nanotechnology-based approaches in anticancer research

Cancer is a highly complex disease to understand, because it entails multiple cellular physiological systems. The most common cancer treatments are restricted to chemotherapy, radiation and surgery. Moreover, the early recognition and treatment of cancer remains a technological bottleneck. There is an urgent need to develop new and innovative technologies that could help to delineate tumor margins, identify residual tumor cells and micrometastases, and determine whether a tumor has been completely removed or not. Nanotechnology has witnessed significant progress in the past few decades, and its effect is widespread nowadays in every field. Nanoparticles can be modified in numerous ways to prolong circulation, enhance drug localization, increase drug efficacy, and potentially decrease chances of multidrug resistance by the use of nanotechnology. Recently, research in the field of cancer nanotechnology has made remarkable advances. The present review summarizes the application of various nanotechnology-based approaches towards the diagnostics and therapeutics of cancer.