Release of photoactivatable drugs from plasmonic nanoparticles for targeted cancer therapy

DNA nanostructure-based drug delivery nanosystems in cancer therapy

DNA as a novel biomaterial can be used to fabricate different kinds of DNA nanostructures based on its principle of GC/AT complementary base pairing. Studies have shown that DNA nanostructure is a nice drug carrier to overcome big obstacles existing in cancer therapy such as systemic toxicity and unsatisfied drug efficacy. Thus, different types of DNA nanostructure-based drug delivery nanosystems have been designed in cancer therapy. To improve treating efficacy, they are also developed into more functional drug delivery nanosystems. In recent years, some important progresses have been made. The objective of this review is to make a retrospect and summary about these different kinds of DNA nanostructure-based drug delivery nanosystems and their latest progresses: (1) active targeting; (2) mutidrug co-delivery; (3) construction of stimuli-responsive/intelligent nanosystems.

Utilizing light-triggered plasmon-driven catalysis reactions as a template for molecular delivery and release

Due to the facile manipulation and non-invasive nature of light-triggered release, it is one of the most potent ways to selectively and remotely deliver a molecular target. Among the various carrier platforms, plasmonic nanoparticles possess advantages such as enhanced cellular uptake and easy loading of "cargo" molecules. Two general strategies are currently utilized to achieve light-induced molecule release from plasmonic nanoparticles. The first uses femtosecond laser pulses to directly break the bond between the nanoparticle and the loaded target. The other requires significant photo-thermal effects to weaken the interaction between the cargo molecules and nanoparticle-attached host molecules. Different from above mechanisms, herein, we introduce a new light-controlled molecular-release method by taking advantage of a plasmon-driven catalytic reaction at the particle surface. In this strategy, we link the target to a plasmon responsive molecule, 4-aminobenzenethiol (4-ABT), through the robust and simple EDC coupling reaction and subsequently load the complex onto the particles via the strong Au-thiol interaction. Upon continuous-wave (CW) laser illumination, the excited surface plasmon catalyzes the formation of 4,4'-dimercaptoazobenzenethiol (DMAB) and simultaneously releases the loaded molecules with high efficiency. This method does not require the use of high-power pulsed lasers, nor does it rely on photo-thermal effects. We believe that plasmon-driven release strategies open a new direction for the designing of next-generation light-triggered release processes.

Plasmonic Nano-Oven by Concatenation of Multishell Photothermal Enhancement

Metallodielectric multishell nanoparticles are capable of hosting collective plasmon oscillations distributed among different metallic layers, which result in large near-field enhancement at specific regions of the structure, where light absorption is maximized. We exploit this capability of multishell nanoparticles, combined with thermal boundary resistances and spatial tailoring of the optical near fields, to design plasmonic nano-ovens capable of achieving high temperatures at the core region using moderate illumination intensities. We find a large optical intensity enhancement of ∼10⁴ over a relatively broad core region with a simple design consisting of three metal layers. This provides an unusual thermal environment, which together with the high pressures of ∼10⁵ atm produced by concatenated curved layers holds great potential for exploring physical and chemical processes under extreme optical/thermal/pressure conditions in confined nanoscale spaces, while the outer surface of the nano-oven is close to ambient conditions.

In Vivo Cancer Cells Elimination Guided by Aptamer-Functionalized Gold-Coated Magnetic Nanoparticles and Controlled with Low Frequency Alternating Magnetic Field

Biomedical applications of magnetic nanoparticles under the influence of a magnetic field have been proved useful beyond expectations in cancer therapy. Magnetic nanoparticles are effective heat mediators, drug nanocarriers, and contrast agents; various strategies have been suggested to selectively target tumor cancer cells. Our study presents magnetodynamic nanotherapy using DNA aptamer-functionalized 50 nm gold-coated magnetic nanoparticles exposed to a low frequency alternating magnetic field for selective elimination of tumor cells in vivo. The cell specific DNA aptamer AS-14 binds to the fibronectin protein in Ehrlich carcinoma hence helps deliver the gold-coated magnetic nanoparticles to the mouse tumor. Applying an alternating magnetic field of 50 Hz at the tumor site causes the nanoparticles to oscillate and pull the fibronectin proteins and integrins to the surface of the cell membrane. This results in apoptosis followed by necrosis of tumor cells without heating the tumor, adjacent healthy cells and tissues. The aptamer-guided nanoparticles and the low frequency alternating magnetic field demonstrates a unique non-invasive nanoscalpel technology for precise cancer surgery at the single cell level.

Application of aptamers in treatment and diagnosis of leukemia

Leukemia is a cancer of blood cells and bone marrow, leading to death in many patients mainly in children. Over the last several years, aptamers generated by SELEX (Systematic evolution of ligands by exponential enrichment) method, have quickly become a new class of targeting ligands for drug delivery applications and recently have been widely exploited in different biomedical applications, due to several potent properties such as high binding affinity and selectivity, low or no immunogenicity and toxicity, low cost and thermal stability. In this review, we presented in details about aptamers involved in targeting, and treatment of leukemia. Moreover, some analytical approaches such as electrochemical and optical aptasensors were introduced for detection and diagnosis of leukemia. Finally, we discussed about the directions and challenges of aptamer application in this field.

Targeted Magnetic Nanotheranostics of Cancer

Current advances in targeted magnetic nanotheranostics are summarized in this review. Unique structural, optical, electronic and thermal properties of magnetic materials in nanometer scale are attractive in the field of biomedicine. Magnetic nanoparticles functionalized with therapeutic molecules, ligands for targeted delivery, fluorescent and other chemical agents can be used for cancer diagnostic and therapeutic purposes. High selectivity, small size, and low immunogenicity of synthetic nucleic acid aptamers make them attractive delivery agents for therapeutic purposes. Properties, production and functionalization of magnetic nanoparticles and aptamers as ligands for targeted delivery are discussed herein. In recent years, magnetic nanoparticles have been widely used in diagnostic methods, such as scintigraphy, single photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), and Raman spectroscopy. Therapeutic purposes of magnetic nanoconstructions are also promising. They are used for effective drug delivery, magnetic mediated hypertermia, and megnetodynamic triggering of apoptosis. Thus, magnetic nanotheranostics opens a new venue for complex differential diagnostics, and therapy of metastatic cancer.

Gold and Hairpin DNA Functionalization of Upconversion Nanocrystals for Imaging and In Vivo Drug Delivery

Although multifunctional upconversion imaging probes have recently attracted considerable interest in biomedical research, there are currently few methods for stabilizing these luminescent nanoprobes with oligonucleotides in biological systems. Herein, a method to robustly disperse upconversion nanoprobes in physiological buffers based on rational design and synthesis of nanoconjugates comprising hairpin-DNA-modified gold nanoparticles is presented. This approach imparts the upconversion nanoprobes with excellent biocompatibility and circumvents the problem of particle agglomeration. By combining single-band anti-Stokes near-infrared emission and the photothermal effect mediated by the coupling of gold to upconversion nanoparticles, a simple, versatile nanoparticulate system for simultaneous deep-tissue imaging and drug molecule release in vivo is demonstrated.

Photo-controlled aptamers delivery by dual surface gold-magnetic nanoparticles for targeted cancer therapy

Dual surfaced dumbbell-like gold magnetic nanoparticles (Au-Fe₃O₄) were synthesized for targeted aptamers delivery. Their unique biological properties were characterized as a smart photo-controlled drug carrier. DNA aptamers targeting vascular endothelial growth factor (VEGF) were assembled onto the surface of Au-Fe₃O₄ by electrostatic absorption. The binding capacity of the nanoparticles with VEGF aptamers was confirmed by gel electrophoresis. The targeted recognization of ovarian cancer cells by the aptamers-functionalized Au-Fe₃O₄ nanoparticles (Apt-Au-Fe₃O₄ NPs) was observed by confocal microscopy. Apt-Au-Fe₃O₄ was found to bind with SKOV-3 ovarian cancer cells specifically, leading to marked intracellular release of aptamers upon plasmon-resonant light (605nm) radiation, and to enhance the in vitro inhibition against tumor cell proliferation. The results show high potential of Apt-Au-Fe₃O₄as a targeted cancer hyperthermia carrier by remote control with high spatial/temporal resolution.

Aptamer delivery of siRNA, radiopharmaceutics and chemotherapy agents in cancer

Aptamers are oligonucleotide reagents with high affinity and specificity, which among other therapeutic and diagnostic applications have the capability of acting as delivery agents. Thus, aptamers are capable of carrying small molecules, nanoparticles, radiopharmaceuticals or fluorescent agents as well as nucleic acid therapeutics specifically to their target cells. In most cases, the molecules may possess interesting therapeutic properties, but their lack of specificity for a particular cell type, or ability to internalise in such a cell, hinders their clinical development, or cause unwanted side effects. Thus, chemotherapy or radiotherapy agents, famous for their side effects, can be coupled to aptamers for specific delivery. Equally, siRNA have great therapeutic potential and specificity, but one of their shortcomings remain the delivery and internalisation into cells. Various methodologies have been proposed to date, including aptamers, to resolve this problem. Therapeutic or imaging reagents benefit from the adaptability and ease of chemical manipulation of aptamers, their high affinity for the specific marker of a cell type, and their internalisation ability via cell mediated endocytosis. In this review paper, we explore the potential of the aptamers as delivery agents and offer an update on current status and latest advancements.

Optimization of Nanoparticle-Based SERS Substrates through Large-Scale Realistic Simulations

Surface-enhanced Raman scattering (SERS) has become a widely used spectroscopic technique for chemical identification, providing unbeaten sensitivity down to the single-molecule level. The amplification of the optical near field produced by collective electron excitations -plasmons- in nanostructured metal surfaces gives rise to a dramatic increase by many orders of magnitude in the Raman scattering intensities from neighboring molecules. This effect strongly depends on the detailed geometry and composition of the plasmon-supporting metallic structures. However, the search for optimized SERS substrates has largely relied on empirical data, due in part to the complexity of the structures, whose simulation becomes prohibitively demanding. In this work, we use state-of-the-art electromagnetic computation techniques to produce predictive simulations for a wide range of nanoparticle-based SERS substrates, including realistic configurations consisting of random arrangements of hundreds of nanoparticles with various morphologies. This allows us to derive rules of thumb for the influence of particle anisotropy and substrate coverage on the obtained SERS enhancement and optimum spectral ranges of operation. Our results provide a solid background to understand and design optimized SERS substrates.

Understanding Resonant Light-Triggered DNA Release from Plasmonic Nanoparticles

Nanoparticle-based platforms for gene therapy and drug delivery are gaining popularity for cancer treatment. To improve therapeutic selectivity, one important strategy is to remotely trigger the release of a therapeutic cargo from a specially designed gene- or drug-laden near-infrared (NIR) absorbing gold nanoparticle complex with NIR light. While there have been multiple demonstrations of NIR nanoparticle-based release platforms, our understanding of how light-triggered release works in such complexes is still limited. Here, we investigate the specific mechanisms of DNA release from plasmonic nanoparticle complexes using continuous wave (CW) and femtosecond pulsed lasers. We find that the characteristics of nanoparticle-based DNA release vary profoundly from the same nanoparticle complex, depending on the type of laser excitation. CW laser illumination drives the photothermal release of dehybridized single-stranded DNA, while pulsed-laser excitation results in double-stranded DNA release by cleavage of the Au-S bond, with negligible local heating. This dramatic difference in DNA release from the same DNA-nanoparticle complex has very important implications in the development of NIR-triggered gene or drug delivery nanocomplexes.

Remotely Triggered Nano-Theranostics For Cancer Applications

Nanotechnology has enabled the development of smart theranostic platforms that can concurrently diagnose disease, start primary treatment, monitor response, and, if required, initiate secondary treatments. Recent in vivo experiments demonstrate the promise of using theranostics in the clinic. In this paper, we review the use of remotely triggered theranostic nanoparticles for cancer applications, focusing heavily on advances in the past five years. Remote triggering mechanisms covered include photodynamic, photothermal, phototriggered chemotherapeutic release, ultrasound, electro-thermal, magneto-thermal, X-ray, and radiofrequency therapies. Each section includes a brief overview of the triggering mechanism and summarizes the variety of nanoparticles employed in each method. Emphasis in each category is placed on nano-theranostics with in vivo success. Some of the nanotheranostic platforms highlighted include photoactivatable multi-inhibitor nanoliposomes, plasmonic nanobubbles, reduced graphene oxide-iron oxide nanoparticles, photoswitching nanoparticles, multispectral optoacoustic tomography using indocyanine green, low temperature sensitive liposomes, and receptor-targeted iron oxide nanoparticles loaded with gemcitabine. The studies reviewed here provide strong evidence that the field of nanotheranostics is rapidly evolving. Such nanoplatforms may soon enable unique advances in the clinical management of cancer. However, reproducibility in the synthesis procedures of such "smart" platforms that lend themselves to easy scale-up in their manufacturing, as well as the development of new and improved models of cancer that are more predictive of human responses, need to happen soon for this field to make a rapid clinical impact.

Aptamer-Mediated Targeted Delivery of Therapeutics: An Update

The selective delivery of drugs in a cell- or tissue-specific manner represents the main challenge for medical research; in order to reduce the occurrence of unwanted off-target effects. In this regard, nucleic acid aptamers have emerged as an attractive class of carrier molecules due to their ability to bind with high affinity to specific ligands; their high chemical flexibility; as well as tissue penetration capability. To date, different aptamer-drug systems and aptamer-nanoparticles systems, in which nanoparticles function together with aptamers for the targeted delivery, have been successfully developed for a wide range of therapeutics, including toxins; peptides; chemotherapeutics and oligonucleotides. Therefore, aptamer-mediated drug delivery represents a powerful tool for the safe and effective treatment of different human pathologies, including cancer; neurological diseases; immunological diseases and so on. In this review, we will summarize recent progress in the field of aptamer-mediated drug delivery and we will discuss the advantages, the achieved objectives and the challenges to be still addressed in the near future, in order to improve the effectiveness of therapies.

Plasmonically Engineered Nanoprobes for Biomedical Applications

The localized surface plasmon resonance of metal nanoparticles is the collective oscillation of electrons on particle surface, induced by incident light, and is a particle composition-, morphology-, and coupling-dependent property. Plasmonic engineering deals with highly precise formation of the targeted nanostructures with targeted plasmonic properties (e.g., electromagnetic field distribution and enhancement) via controlled synthetic, assembling, and atomic/molecular tuning strategies. These plasmonically engineered nanoprobes (PENs) have a variety of unique and beneficial physical, chemical, and biological properties, including optical signal enhancement, catalytic, and local temperature-tuning photothermal properties. In particular, for biomedical applications, there are many useful properties from PENs including LSPR-based sensing, surface-enhanced Raman scattering, metal-enhanced fluorescence, dark-field light-scattering, metal-mediated fluorescence resonance energy transfer, photothermal effect, photodynamic effect, photoacoustic effect, and plasmon-induced circular dichroism. These properties can be utilized for the development of new biotechnologies and biosensing, bioimaging, therapeutic, and theranostic applications in medicine. This Perspective introduces the concept of plasmonic engineering in designing and synthesizing PENs for biomedical applications, gives recent examples of biomedically functional PENs, and discusses the issues and future prospects of PENs for practical applications in bioscience, biotechnology, and medicine.

Aptamers as a promising approach for the control of parasitic diseases

Aptamers are short single-stranded RNA or DNA oligonucleotides that are capable of binding various biological targets with high affinity and specificity. Their identification initially relies on a molecular process named SELEX (Systematic Evolution of Ligands by EXponential enrichment) that has been later modified in order to improve aptamer sensitivity, minimize duration and cost of the assay, as well as increase target types. Several biochemical modifications can help to enhance aptamer stability without affecting significantly target interaction. As a result, aptamers have generated a large interest as promising tools to compete with monoclonal antibodies for detection and inhibition of specific markers of human diseases. One aptamer-based drug is currently authorized and several others are being clinically evaluated. Despite advances in the knowledge of parasite biology and host–parasite interactions from “omics” data, protozoan parasites still affect millions of people around the world and there is an urgent need for drug target discovery and novel therapeutic concepts. In this context, aptamers represent promising tools for pathogen identification and control. Recent studies have reported the identification of “aptasensors” for parasite diagnosis, and “intramers” targeting intracellular proteins. Here we discuss various strategies that have been employed for intracellular expression of aptamers and expansion of their possible application, and propose that they may be suitable for the clinical use of aptamers in parasitic infections.

Recent Advances of Light-Mediated Theranostics

Currently, precision theranostics have been extensively demanded for the effective treatment of various human diseases. Currently, efficient therapy at the targeted disease areas still remains challenging since most available drug molecules lack of selectivity to the pathological sites. Among different approaches, light-mediated therapeutic strategy has recently emerged as a promising and powerful tool to precisely control the activation of therapeutic reagents and imaging probes in vitro and in vivo, mostly attributed to its unique properties including minimally invasive capability and highly spatiotemporal resolution. Although it has achieved initial success, the conventional strategies for light-mediated theranostics are mostly based on the light with short wavelength (e.g., UV or visible light), which may usually suffer from several undesired drawbacks, such as limited tissue penetration depth, unavoidable light absorption/scattering and potential phototoxicity to healthy tissues, etc. Therefore, a near-infrared (NIR) light-mediated approach on the basis of long-wavelength light (700-1000 nm) irradiation, which displays deep-tissue penetration, minimized photo-damage and low autofluoresence in living systems, has been proposed as an inspiring alternative for precisely phototherapeutic applications in the last decades. Despite numerous NIR light-responsive molecules have been currently proposed for clinical applications, several inherent drawbacks, such as troublesome synthetic procedures, low water solubility and limited accumulation abilities in targeted areas, heavily restrict their applications in deep-tissue therapeutic and imaging studies. Thanks to the amazing properties of several nanomaterials with large extinction coefficient in the NIR region, the construction of NIR light responsive nanoplatforms with multifunctions have become promising approaches for deep-seated diseases diagnosis and therapy. In this review, we summarized various light-triggered theranostic strategies and introduced their great advances in biomedical applications in recent years. Moreover, some other promising light-assisted techniques, such as photoacoustic and Cerenkov radiation, were also systemically discussed. Finally, the potential challenges and future perspectives for light-mediated deep-tissue diagnosis and therapeutics were proposed.

Aptamer-Functionalized Nanoparticles as "Smart Bombs": The Unrealized Potential for Personalized Medicine and Targeted Cancer Treatment

Conventional delivery of chemotherapeutic agents leads to multiple systemic side effects and toxicity, limiting the doses that can be used. The development of targeted therapies to selectively deliver anti-cancer agents to tumor cells without damaging neighboring unaffected cells would lead to higher effective local doses and improved response rates. Aptamers are single-stranded oligonucleotides that bind to target molecules with both high affinity and high specificity. The high specificity exhibited by aptamers promotes localization and uptake by specific cell populations, such as tumor cells, and their conjugation to anti-cancer drugs has been explored for targeted therapy. Advancements in the development of polymeric nanoparticles allow anti-cancer drugs to be encapsulated in protective nonreactive shells for controlled drug delivery with reduced toxicity. The conjugation of aptamers to nanoparticle-based therapeutics may further enhance direct targeting and personalized medicine. Here we present how the combinatorial use of aptamer and nanoparticle technologies has the potential to develop "smart bombs" for targeted cancer treatment, highlighting recent pre-clinical studies demonstrating efficacy for the direct targeting to particular tumor cell populations. However, despite these pre-clinical promising results, there has been little progress in moving this technology to the bedside.

pH-Responsive Core-Shell Structured Nanoparticles for Triple-Stage Targeted Delivery of Doxorubicin to Tumors

The application of cytotoxic chemotherapeutics in cancer therapy has been largely restricted by their lack of selectivity. Despite the existence of numerous targeted delivery systems, it is practically challenging to develop one single system to simultaneously cover tumor-targeted delivery of chemotherapeutics at the tissue, cellular, and subcellular levels. To solve this problem, pH-responsive core-shell structured nanoparticles (CSNPs) were self-assembled in this study to provide triple-stage targeted delivery of doxorubicin (DOX) from the injection site to the nuclei of cancer cells. Amino-functionalized mesoporous silica nanoparticles (MSN) were doubly modified with TAT peptide and acid-cleavable polyethylene glycol (PEG) as the DOX-loaded cationic core. The anionic shell was constituted by galactose-modified poly(allylamine hydrochloride)-citraconic anhydride, a hepato-carcinoma-targeting polymer with charge-reversible property. In vitro results showed that PEG effectively reduced protein adsorption and phagocytic capture of CSNPs in the circulating blood (pH 7.4), thus facilitating passive accumulation in tumors (tissue level). Following PEG detachment via acidic hydrolysis in tumor microenvironment (pH 6.5), the exposed galactose ligands endowed CSNPs with active internalization into hepato-carcinoma cells (cellular level). Afterward, the acidity in endosomes and lysosomes (pH 5.0) triggered the conversion of anionic shell into positive charges, leading to core-shell disassembly and subsequent TAT-mediated delivery of DOX to the nuclei (subcellular level). Importantly, the efficiencies of each targeting moiety were nicely preserved when combining together in CSNPs. As a result, improved tumorous distribution and potent therapeutic efficacy of CSNPs were noted in tumor-bearing mice at a relatively low dose. CSNPs therefore provide an efficient and nontoxic platform for the targeted delivery of antitumor drugs.

Cellular Delivery of RNA Nanoparticles

RNA nanostructures can be programmed to exhibit defined sizes, shapes and stoichiometries from naturally occurring or de novo designed RNA motifs. These constructs can be used as scaffolds to attach functional moieties, such as ligand binding motifs or gene expression regulators, for nanobiology applications. This review is focused on four areas of importance to RNA nanotechnology: the types of RNAs of particular interest for nanobiology, the assembly of RNA nanoconstructs, the challenges of cellular delivery of RNAs in vivo, and the delivery carriers that aid in the matter. The available strategies for the design of nucleic acid nanostructures, as well as for formulation of their carriers, make RNA nanotechnology an important tool in both basic research and applied biomedical science.

Aptamer-nanoparticle complexes as powerful diagnostic and therapeutic tools

Correct diagnosis and successful therapy are extremely important to enjoy a healthy life when suffering from a disease. To achieve these aims, various cutting-edge technologies have been designed and fabricated to diagnose and treat specific diseases. Among these technologies, aptamer-nanomaterial hybrids have received considerable attention from scientists and doctors because they have numerous advantages over other methods, such as good biocompatibility, low immunogenicity and controllable selectivity. In particular, aptamers, oligonucleic acids or peptides that bind to a specific target molecule, are regarded as outstanding biomolecules. In this review, several screening techniques for aptamers, also called systematic evolution of ligands by exponential enrichment (SELEX) methods, are introduced, and diagnostic and therapeutic aptamer applications are also presented. Furthermore, we describe diverse aptamer-nanomaterial conjugate designs and their applications for diagnosis and therapy.

Photoactivated drug delivery and bioimaging

Among the various types of diseases, cancer remains one of the most leading causes of mortality that people are always suffering from and fighting with. So far, the effective cancer treatment demands accurate medical diagnosis, precise surgery, expensive medicine administration, which leads to a significant burden on patients, their families, and the whole national healthcare system around the world. In order to increase the therapeutic efficiency and minimize side effects in cancer treatment, various kinds of stimuli-responsive drug delivery systems and bioimaging platforms have been extensively developed within the past decades. Among them, the strategy of photoactivated approach has attracted considerable research interest because light enables the precise control, in a highly spatial and temporal manner, the release of drug molecules as well as the activation of bioimaging agents. In general, several appropriate photoresponsive systems, which are normally sensitive to ultraviolet (UV) or visible light irradiation to undergo the multiple reaction pathways such as photocleavage and photoisomerization strategy etc. have been mainly involved in the light activated cancer therapies. Considering the potential issues of poor tissue penetration and high photoctotoxicity of short wavelength light, the recently emerged therapies based on long-wavelength irradiation, e.g., near-infrared (NIR) light (700-1000 nm), have displayed distinct advantages in biomedical applications. The light irradiation at NIR window indicates minimized photodamage, deep penetration, and low autofluorescence in living cells and tissues, which are of clinical importance in the desired diagnosis and therapy. In this review article, we introduce the recent advances in light-activated drug release and biological imaging mainly for anticancer treatment. Various types of strategies such as photocage, photo-induced isomerization, optical upconversion, and photothermal release by which different wavelength ranges of light can play the important roles in the controlled therapeutic or imaging agents delivery, and activation will be systemically discussed. In addition, the challenges and future perspectives for photo-based cancer theranostics will be also summarized. WIREs Nanomed Nanobiotechnol 2017, 9:e1408. doi: 10.1002/wnan.1408 For further resources related to this article, please visit the WIREs website.

The Combination of Laser Therapy and Metal Nanoparticles in Cancer Treatment Originated From Epithelial Tissues: A Literature Review

Several methods have been employed for cancer treatment including surgery, chemotherapy and radiation therapy. Today, recent advances in medical science and development of new technologies, have led to the introduction of new methods such as hormone therapy, Photodynamic therapy (PDT), treatments using nanoparticles and eventually combinations of lasers and nanoparticles. The unique features of LASERs such as photo-thermal properties and the particular characteristics of nanoparticles, given their extremely small size, may provide an interesting combined therapeutic effect. The purpose of this study was to review the simultaneous application of lasers and metal nanoparticles for the treatment of cancers with epithelial origin. A comprehensive search in electronic sources including PubMed, Google Scholar and Science Direct was carried out between 2000 and 2013. Among the initial 400 articles, 250 articles applied nanoparticles and lasers in combination, in which more than 50 articles covered the treatment of cancer with epithelial origin. In the future, the combination of laser and nanoparticles may be used as a new or an alternative method for cancer therapy or diagnosis. Obviously, to exclude the effect of laser's wavelength and nanoparticle's properties more animal studies and clinical trials are required as a lack of perfect studies.

Functional nanomaterials for near-infrared-triggered cancer therapy

The near-infrared (NIR) region (700-1100 nm) is the so-called transparency "therapeutic window" for biological applications owing to its deeper tissue penetration and minimal damage to healthy tissues. In recent years, various NIR-based therapeutic and interventional strategies, such as NIR-triggered drug delivery, photothermal therapy (PTT) and photodynamic therapy (PDT), are under research in intensive preclinical and clinical investigations for cancer treatment. The NIR control in these cancer therapy systems is considered crucial to boost local effective tumor suppression while minimizing side effects, resulting in improved therapeutic efficacy. Some researchers even predict the NIR-triggered cancer therapy to be a new and exciting possibility for clinical nanomedicine applications. In this review, the rapid development of NIR light-responsive cancer therapy based on various smartly designed nanocomposites for deep tumor treatments is introduced. In detail, the use of NIR-sensitive materials for chemotherapy, PTT as well as PDT is highlighted, and the associated challenges and potential solutions are discussed. The applications of NIR-sensitive cancer therapy modalities summarized here can highlight their potential use as promising nanoagents for deep tumor therapy.

Smart micro/nanoparticles in stimulus-responsive drug/gene delivery systems

New achievements in the realm of nanoscience and innovative techniques of nanomedicine have moved micro/nanoparticles (MNPs) to the point of becoming actually useful for practical applications in the near future. Various differences between the extracellular and intracellular environments of cancerous and normal cells and the particular characteristics of tumors such as physicochemical properties, neovasculature, elasticity, surface electrical charge, and pH have motivated the design and fabrication of inventive "smart" MNPs for stimulus-responsive controlled drug release. These novel MNPs can be tailored to be responsive to pH variations, redox potential, enzymatic activation, thermal gradients, magnetic fields, light, and ultrasound (US), or can even be responsive to dual or multi-combinations of different stimuli. This unparalleled capability has increased their importance as site-specific controlled drug delivery systems (DDSs) and has encouraged their rapid development in recent years. An in-depth understanding of the underlying mechanisms of these DDS approaches is expected to further contribute to this groundbreaking field of nanomedicine. Smart nanocarriers in the form of MNPs that can be triggered by internal or external stimulus are summarized and discussed in the present review, including pH-sensitive peptides and polymers, redox-responsive micelles and nanogels, thermo- or magnetic-responsive nanoparticles (NPs), mechanical- or electrical-responsive MNPs, light or ultrasound-sensitive particles, and multi-responsive MNPs including dual stimuli-sensitive nanosheets of graphene. This review highlights the recent advances of smart MNPs categorized according to their activation stimulus (physical, chemical, or biological) and looks forward to future pharmaceutical applications.

Multifunctional Hybrid Fe2O3-Au Nanoparticles for Efficient Plasmonic Heating

One of the most widely used methods for manufacturing colloidal gold nanospherical particles involves the reduction of chloroauric acid (HAuCl4) to neutral gold Au(0) by reducing agents, such as sodium citrate or sodium borohydride. The extension of this method to decorate iron oxide or similar nanoparticles with gold nanoparticles to create multifunctional hybrid Fe2O3-Au nanoparticles is straightforward. This approach yields fairly good control over Au nanoparticle dimensions and loading onto Fe2O3. Additionally, the Au metal size, shape, and loading can easily be tuned by changing experimental parameters (e.g., reactant concentrations, reducing agents, surfactants, etc.). An advantage of this procedure is that the reaction can be done in air or water, and, in principle, is amenable to scaling up. The use of such optically tunable Fe2O3-Au nanoparticles for hyperthermia studies is an attractive option as it capitalizes on plasmonic heating of gold nanoparticles tuned to absorb light strongly in the VIS-NIR region. In addition to its plasmonic effects, nanoscale Au provides a unique surface for interesting chemistries and catalysis. The Fe2O3 material provides additional functionality due to its magnetic property. For example, an external magnetic field could be used to collect and recycle the hybrid Fe2O3-Au nanoparticles after a catalytic experiment, or alternatively, the magnetic Fe2O3 can be used for hyperthermia studies through magnetic heat induction. The photothermal experiment described in this report measures bulk temperature change and nanoparticle solution mass loss as functions of time using infrared thermocouples and a balance, respectively. The ease of sample preparation and the use of readily available equipment are distinct advantages of this technique. A caveat is that these photothermal measurements assess the bulk solution temperature and not the surface of the nanoparticle where the heat is transduced and the temperature is likely to be higher.

Engineered gold nanoparticles for photothermal cancer therapy and bacteria killing

Gold nanoparticle mediated photothermal therapy in future medicine.

Nucleic acid aptamers in cancer research, diagnosis and therapy

Aptamers are single-stranded DNA or RNA oligomers, identified from a random sequence pool, with the ability to form unique and versatile tertiary structures that bind to cognate molecules with superior specificity. Their small size, excellent chemical stability and low immunogenicity enable them to rival antibodies in cancer imaging and therapy applications. Their facile chemical synthesis, versatility in structural design and engineering, and the ability for site-specific modifications with functional moieties make aptamers excellent recognition motifs for cancer biomarker discovery and detection. Moreover, aptamers can be selected or engineered to regulate cancer protein functions, as well as to guide anti-cancer drug design or screening. This review summarizes their applications in cancer, including cancer biomarker discovery and detection, cancer imaging, cancer therapy, and anti-cancer drug discovery. Although relevant applications are relatively new, the significant progress achieved has demonstrated that aptamers can be promising players in cancer research.

Multifunctional theranostic nanoplatform for cancer combined therapy based on gold nanorods

Nanomaterials that integrate diagnostic and therapeutic functions within a single nanoplatform promise great advances in revolutionizing cancer therapy. A smart multifunctional theranostic drug-delivery system (DDS) based on gold nanorods (abbreviated as GNR/TSDOX) is designed for cancer-targeted imaging and imaging-guided therapy. In this intelligent theranostic DDS, the active targeting ligand biotin is introduced to track cancer sites in vivo. With the aid of photothermal/photoacoustic imaging, GNR/TSDOX can ablate cancer specifically and effectively. When stimulated with a single near-infrared (NIR) light source, this NIR light energy is effectively absorbed and converted into heat by GNR/TSDOX for localized photothermal therapy and the increase in temperature also further triggers the cascaded release of the anticancer drug for combined thermo-chemotherapy. More importantly, the in vivo cure effect can be well guided by regulating the irradiation time and intensity of the NIR light.

Progress and Challenges in Developing Aptamer-Functionalized Targeted Drug Delivery Systems

Aptamers, which can be screened via systematic evolution of ligands by exponential enrichment (SELEX), are superior ligands for molecular recognition due to their high selectivity and affinity. The interest in the use of aptamers as ligands for targeted drug delivery has been increasing due to their unique advantages. Based on their different compositions and preparation methods, aptamer-functionalized targeted drug delivery systems can be divided into two main categories: aptamer-small molecule conjugated systems and aptamer-nanomaterial conjugated systems. In this review, we not only summarize recent progress in aptamer selection and the application of aptamers in these targeted drug delivery systems but also discuss the advantages, challenges and new perspectives associated with these delivery systems.

Biomimetic Acoustically-Responsive Vesicles for Theranostic Applications

In recent years, biomimetic cell membrane-derived particles have emerged as a new class of drug delivery system with advantages of biocompatibility, ease of isolation and long circulation profile. Here we report the development and potential theranostic applications of a new biomimetic acoustically-responsive droplet system derived from mammalian red blood cell membrane (RBCM). We hypothesized that drug-loaded RBCM droplets (RBCMDs) would undergo a transition from liquid (droplets) to gas (bubbles) upon high intensity focused ultrasound (HIFU) insonation, resulting in on-demand drug release. The generated microbubbles could also serve as a contrast agent to enhance ultrasound imaging. As-synthesized RBCMDs exhibited uniform size, good dispersity and preservation of RBCM-associated proteins that prevented uptake by macrophages. Camptothecin (CPT), an anti-cancer drug, was successfully loaded in the RBCMDs with a loading efficiency of 2-3% and an encapsulation efficiency of 62-97%. A short (3 min) exposure to HIFU irradiation triggered release of CPT from the RBCMDs and the physical explosion of droplets damaged nearby cancer cells resulting in significant cell death. In addition, the acoustically vaporized RBCMDs significantly increased the ultrasound echo signal to 30 dB. Lastly, we demonstrated that RBCMDs could be acoustically vaporized in vivo in target tissues, and enhancing ultrasound imaging. Taken together, we have developed a new class of naturally derived RBCMDs which show great potential for future application in remotely triggered drug delivery and ultrasound imaging enhancement.

Efficient Delivery of DOX to Nuclei of Hepatic Carcinoma Cells in the Subcutaneous Tumor Model Using pH-Sensitive Pullulan-DOX Conjugates

A series of pullulan-doxorubicin conjugates (Pu-DOXs) were investigated for effectively delivering DOX to nuclei of hepatic carcinoma cells in subcutaneous tumor model. These Pu-DOXs were prepared by conjugating DOX onto pullulan molecule via pH-responsive hydrazone bond using spacers with different alkane chain length. The highest drug loading content of Pu-DOXs went up to nearly 50%, and the diameter of Pu-DOX nanoparticles ranged from 50 to 170 nm, as measured by DLS and TEM. These Pu-DOX nanoparticles could rapidly release DOX in the acidic environment at pH = 5.0 while being kept relatively stable in neural conditions. The in vitro cell coculture experiments revealed that these Pu-DOX nanoparticles were selectively internalized by hepatic carcinoma cells through receptor-mediated endocytosis via asialoglycoprotein receptor on the hepatic carcinoma cell surface. DOX was rapidly released from Pu-DOX nanoparticles in acidic endosome/lysosome, diffused into cell nuclei due to its strong affinity to nucleic acid, inhibited the cell proliferation, and accelerated the cell apoptosis. In the nude mice subcutaneous hepatic carcinoma model, Pu-DOX nanoparticles efficiently accumulated in the tumor site through the enhanced permeation and retention effect. Then DOX was specifically internalized by hepatic carcinoma cells and rapidly diffused into the nuclei of cells. Compared with the control group in in vivo experiments, these Pu-DOX nanoparticles effectively inhibited solid tumor growth, prolonging the lifetime of the experimental animal. These pH sensitive nanoparticles might provide an important clinical implication for targeted hepatic carcinoma therapy with high efficiency and low systematic toxicity.

Synthesis, Characterization, and Application in HeLa Cells of an NIR Light Responsive Doxorubicin Delivery System Based on NaYF4:Yb,Tm@SiO2-PEG Nanoparticles

Herein, we present a phototriggered drug delivery system based on light responsive nanoparticles, which is able to release doxorubicin upon NIR light illumination. The proposed system is based on upconversion fluorescence nanoparticles of β-NaYF4:Yb,Tm@SiO2-PEG with a mean diameter of 52±2.5 nm that absorb the NIR light and emit UV light. The UV radiation causes the degradation of photodegradable ortho-nitrobenzyl alcohol derivates, which are attached on one side to the surface of the nanoparticles and on the other to doxorubicin. This degradation triggers the doxorubicin release. This drug delivery system has been tested "in vitro" with HeLa cells. The results of this study demonstrated that this system caused negligible cytotoxicity when they were not illuminated with NIR light. In contrast, under NIR light illumination, the HeLa cell viability was conspicuously reduced. These results demonstrated the suitability of the proposed system to control the release of doxorubicin via an external NIR light stimulus.

Aptamer-Drug Conjugates

Western medicine often aims to specifically treat diseased tissues or organs. However, the majority of current therapeutics failed to do so owing to their limited selectivity and the consequent "off-target" side effects. Targeted therapy aims to enhance the selectivity of therapeutic effects and reduce adverse side effects. One approach toward this goal is to utilize disease-specific ligands to guide the delivery of less-specific therapeutics, such that the therapeutic effects can be guided specifically to diseased tissues or organs. Among these ligands, aptamers, also known as chemical antibodies, have emerged over the past decades as a novel class of targeting ligands that are capable of specific binding to disease biomarkers. Compared with other types of targeting ligands, aptamers have an array of unique advantageous features, which make them promising for developing aptamer-drug conjugates (ApDCs) for targeted therapy. In this Review, we will discuss ApDCs for targeted drug delivery in chemotherapy, gene therapy, immunotherapy, photodynamic therapy, and photothermal therapy, primarily of cancer.

Gold nanoparticles for photothermally controlled drug release

In this article, we describe how nanoparticles work in photothermally triggered drug delivery, starting with a description of the plasmon resonance and the photothermal effect, and how this is used to release a drug. Then, we describe the four major functionalization strategies and each of their different applications. Finally, we discuss the biodistribution and toxicity of these systems and the necessary requirements for the use of gold nanoparticles for spatially and temporally controlling drug release through the photothermal effect.

Inorganic nanomaterials for bioimaging, targeted drug delivery and therapeutics

Inorganic nanomaterials including gold nanoparticles, mesoporous silica nanoparticles, graphene, magnetic nanoparticles, quantum dots and layered double hydroxides have become one of the most active research fields in biochemistry, biotechnology and biomedicine. Benefiting from the facile synthesis/modification, intrinsically physicochemical properties and good biocompatibility, inorganic nanomaterials have shown great potential in bioimaging, targeted drug delivery and cancer therapies. This Feature Article summarizes recent progress on various inorganic nanocarriers, including the background, synthesis, modification, cytotoxicity, physicochemical properties as well as their applications in biomedicine.

Photothermal therapeutic response of cancer cells to aptamer-gold nanoparticle-hybridized graphene oxide under NIR illumination

The objective of this study was to synthesize a nanocomposite, aptamer-gold nanoparticle-hybridized graphene oxide (Apt-AuNP-GO), to facilitate targeted treatment of tumor cells by near-infrared (NIR) light-activatable photothermal therapy. We also investigated whether Apt-AuNP-GO with NIR illumination modulates heat shock proteins (HSPs) expression leading to therapeutic response in human breast cancer cells. These findings can provide strategies for improving the photothermal therapy efficacy of cancer. The self-assembled Apt-AuNP-GO nanocomposite could selectively target MUC1-positive human breast cancer cells (MCF-7) due to the specific interaction between the MUC1-binding-aptamer and the MUC1 (type I transmembrane mucin glycoprotein) on cell membrane. In addition, Apt-AuNP-GO has a high light-to-heat conversion capability for photoabsorption of NIR light, and it is able to exert therapeutic effects on MCF-7 cells at an ultralow concentration without inducing adverse effects in healthy cells. The Apt-AuNP-GO nanocomposites combine the advantages of GOs, AuNPs, and Apts, possess specific targeting capability, excellent biocompatibility, and tumor cell destruction ability, suggesting great potential for application in the photothermal therapy of breast cancer. Under NIR illumination, Apt-AuNP-GO induced transient increase in HSP70 expression, which decreased thereafter. This phenomenon may cause irreversible damage to Apt-AuNP-GO-treated MCF-7 cell under NIR illumination. We also demonstrated that the combination therapy of heat and HSP70 inhibitor could synergistically generate marked tumoricidal effects against breast cancer. These results suggest that the degree and duration of HSP70 protein expression are correlated with therapeutic effects against breast cancer for Apt-AuNP-GO-assisted photothermal therapy. We believe that such a nanocomposite can be readily extended to the construction of HSP70 inhibitors-loaded Apt-AuNP-GO, which could deliver both heat and HSP70 inhibitors to tumorigenic regions for the chemo-photothermal therapy.

Aptamers: active targeting ligands for cancer diagnosis and therapy

Aptamers, including DNA, RNA and peptide aptamers, are a group of promising recognition units that can specifically bind to target molecules and cells. Due to their excellent specificity and high affinity to targets, aptamers have attracted great attention in various fields in which selective recognition units are required. They have been used in biosensing, drug delivery, disease diagnosis and therapy (especially for cancer treatment). In this review, we summarized recent applications of DNA and RNA aptamers in cancer theranostics. The specific binding ability of aptamers to cancer-related markers and cancer cells ensured their high performance for early diagnosis of cancer. Meanwhile, the efficient targeting ability of aptamers to cancer cells and tissues provided a promising way to deliver imaging agents and drugs for cancer imaging and therapy. Furthermore, with the development of nanoscience and nanotechnology, the conjugation of aptamers with functional nanomaterials paved an exciting way for the fabrication of theranostic agents for different types of cancers, which might be a powerful tool for cancer treatment.

From macro to micro to nano: the development of a novel lysine based hydrogel platform and enzyme triggered self-assembly of macro hydrogel into nanogel

Development of a novel lysine based hydrogel platform and the enzyme triggered self-assembly of macro hydrogel into nanogel.

Targeting cancer cells using aptamers: cell-SELEX approach and recent advancements

Aptamers are short single stranded nucleic acid based therapeutic and diagnostic molecules which can be isolated from a random pool of oligonucleotides by Systematic Evolution of Ligands by EXponential Enrichment (SELEX).

CPMV-induced synthesis of hollow mesoporous SiO2 nanocapsules with excellent performance in drug delivery

Synthesis of CPMV- hollow silica nanocapsules and their use in nanomedicine.

Photothermal healing of a glass fiber reinforced composite interface by gold nanoparticles

Scheme of interfacial healing process.