DNA and aptamer stabilized gold nanoparticles for targeted delivery of anticancer therapeutics

Improving synthesis and binding affinities of nucleic acid aptamers and their therapeutics and diagnostic applications

Nucleic acid aptamers have captivated the attention of analytical and medicinal scientists globally due to their several advantages as recognition molecules over conventional antibodies because of their small size, simple and inexpensive synthesis, broad target range, and high stability in varied environmental conditions. These recognition molecules can be chemically modified to make them resistant to nuclease action in blood serum, reduce rapid renel clearance, improve the target affinity and selectivity, and make them amenable to chemically conjugate with a support system that facilitates their selective applications. This review focuses on the development of efficient aptamer candidates and their application in clinical diagnosis and therapeutic applications. Significant advances have been made in aptamer-based diagnosis of infectious and non-infectious diseases. Collaterally, the progress made in therapeutic applications of aptamers is encouraging, as evident from their use in diagnosing cancer, neurodegenerative diseases, microbial infection, and in imaging. This review also updates the progress on clinical trials of many aptamer-based products of commercial interests. The key development and critical issues on the subject have been summarized in the concluding remarks.

Aptamers combined with immune checkpoints for cancer detection and targeted therapy: A review

In recent years, remarkable strides have been made in the field of immunotherapy, which has emerged as a standard treatment for many cancers. As a kind of immunotherapy drug, monoclonal antibodies employed in immune checkpoint therapy have proven beneficial for patients with diverse cancer types. However, owing to the extensive heterogeneity of clinical responses and the complexity and variability of the immune system and tumor microenvironment (TME), accurately predicting its efficacy remains a challenge. Recent advances in aptamers provide a promising approach for monitoring alterations within the immune system and TME, thereby facilitating targeted immunotherapy, particularly focused on immune checkpoint blockade, with enhanced antitumor efficiency. Aptamers have been widely used in tumor cell detection, biosensors, drug discovery, and biomarker screening due to their high specificity and high affinity with their targets. This review aims to comprehensively examine the research status and progress of aptamers in cancer diagnosis and immunotherapy, with a specific emphasis on those related to immune checkpoints. Additionally, we will discuss the future research directions and potential therapeutic targets for aptamer-based immune checkpoint therapy, aiming to provide a theoretical basis for targeting immunotherapy molecules and blocking tumor immune escape.

Surface Functionalization of Gold Nanoparticles for Targeting the Tumor Microenvironment to Improve Antitumor Efficiency

Gold nanoparticles (AuNPs) have undergone significant research for their use in the treatment of cancer. Numerous researchers have established their potent antitumor properties, which have greatly impacted the treatment of cancer. AuNPs have been used in four primary anticancer treatment modalities, namely radiation, photothermal therapy, photodynamic therapy, and chemotherapy. However, the ability of AuNPs to destroy cancer is lacking and can even harm healthy cells without the right direction to transport them to the tumor microenvironment. Consequently, a suitable targeting technique is needed. Based on the distinct features of the human tumor microenvironment, this review discusses four different targeting strategies that target the four key features of the tumor microenvironment, including abnormal vasculature, overexpression of specific receptors, an acidic microenvironment, and a hypoxic microenvironment, to direct surface-functionalized AuNPs to the tumor microenvironment and increase antitumor efficacies. In addition, some current completed or ongoing clinical trials of AuNPs will also be discussed below to further reinforce the concept of using AuNPs in anticancer therapy.

Nanomedicine in therapeutic warfront against estrogen receptor-positive breast cancer

Breast cancer (BC) is the most frequently diagnosed malignancy in women worldwide. Almost 70-80% of cases of BC are curable at the early non-metastatic stage. BC is a heterogeneous disease with different molecular subtypes. Around 70% of breast tumors exhibit estrogen-receptor (ER) expression and endocrine therapy is used for the treatment of these patients. However, there are high chances of recurrence in the endocrine therapy regimen. Though chemotherapy and radiation therapy have substantially improved survival rates and treatment outcomes in BC patients, there is an increased possibility of the development of resistance and dose-limiting toxicities. Conventional treatment approaches often suffer from low bioavailability, adverse effects due to the non-specific action of chemotherapeutics, and low antitumor efficacy. Nanomedicine has emerged as a conspicuous strategy for delivering anticancer therapeutics in BC management. It has revolutionized the area of cancer therapy by increasing the bioavailability of the therapeutics and improving their anticancer efficacy with reduced toxicities on healthy tissues. In this article, we have highlighted various mechanisms and pathways involved in the progression of ER-positive BC. Further, different nanocarriers delivering drugs, genes, and natural therapeutic agents for surmounting BC are the spotlights of this article.

Nanomedicine, a valuable tool for skeletal muscle disorders: Challenges, promises, and limitations

Muscular dystrophies are a group of rare genetic disorders characterized by progressive muscle weakness, which, in the most severe forms, leads to the patient's death due to cardiorespiratory problems. There is still no cure available for these diseases and significant effort is being placed into developing new strategies to either correct the genetic defect or to compensate muscle loss by stimulating skeletal muscle regeneration. However, the vast anatomical extension of the target tissue poses great challenges to these goals, highlighting the need for complementary strategies. Nanomedicine is an actively evolving field that merges nanotechnologies with biomedical and pharmaceutical sciences. It holds great potential in regenerative medicine, both in supporting tissue engineering and regeneration, and in optimizing drug and oligonucleotide delivery and gene therapy strategies. In this review, we will summarize the state‐of‐the‐art in the field of nanomedicine applied to skeletal muscle regeneration. We will discuss the recent work toward the development of nanopatterned scaffolds for tissue engineering, the efforts in the synthesis of organic and inorganic nanoparticles for gene therapy and drug delivery applications, as well as their use as immune modulators. Although nanomedicine holds great promise for muscle and other degenerative diseases, many challenges still need to be systematically addressed to assure a smooth transition from the bench to the bedside.

This article is categorized under:

Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement

Conjugation of Nucleic Acids and Drugs to Gold Nanoparticles

Gold nanoparticles (AuNPs) can be used as carriers for biomolecules or drugs in cell culture and animal models. Particularly, AuNPs ease their internalization into the cell and prevent their degradation. In addition, engineered AuNPs can be employed as sensors of a variety of biomarkers, where the electronic and optical properties of the AuNPs are exploited for a convenient, easy, and fast read out. However, in all these applications, a key step requires the conjugation of the different molecules to the nanoparticles. The most common approach exploits the great affinity of sulfur for gold. Herein, we summarize the methods used by our group for the conjugation of different molecules with AuNPs. The procedure is easy and takes around 2 days, where the reagents are slowly added, following an incubation at room temperature to ensure the complete conjugation. Finally, the unbound material is removed by centrifugation.

Stimuli-responsive nanomaterials for cancer treatment: boundaries, opportunities and applications

Small molecule drugs, including most chemotherapies, are rapidly degraded and/or eliminated from the body, which is why high doses of these drugs are necessary, potentially producing toxic effects. Several types of nanoparticles loaded with anti-cancer drugs have been designed to overcome the disadvantages of conventional therapies. Modified nanoparticles can circulate for a long time, thus improving the solubility and biodistribution of drugs. Furthermore, they also allow the controlled release of the payload once its target tissue has been reached. These mechanisms can reduce the exposure of healthy tissues to chemotherapeutics, since the drugs are only released in the presence of specific tumour stimuli. Overall, these properties can improve the effectiveness of treatments while reducing undesirable side effects. In this article, we review the recent advances in stimuli-responsive albumin, gold and magnetic nanostructures for controlled anti-cancer drug delivery. These nanostructures were designed to release drugs in response to different internal and external stimuli of the cellular environment, including pH, redox, light and magnetic fields. We also describe various examples of applications of these nanomaterials. Overall, we shed light on the properties, potential clinical translation and limitations of stimuli-responsive nanoparticles for cancer treatment.

Magnetic nanoparticles in theranostics of malignant melanoma

Malignant melanoma is an aggressive tumor with a tendency to metastasize early and with an increasing incidence worldwide. Although in early stage, melanoma is well treatable by excision, the chances of cure and thus the survival rate decrease dramatically after metastatic spread. Conventional treatment options for advanced disease include surgical resection of metastases, chemotherapy, radiation, targeted therapy and immunotherapy. Today, targeted kinase inhibitors and immune checkpoint blockers have for the most part replaced less effective chemotherapies. Magnetic nanoparticles as novel agents for theranostic purposes have great potential in the treatment of metastatic melanoma. In the present review, we provide a brief overview of treatment options for malignant melanoma with different magnetic nanocarriers for theranostics. We also discuss current efforts of designing magnetic particles for combined, multimodal therapies (e.g., chemotherapy, immunotherapy) for malignant melanoma.

Recent advances in active targeting of nanomaterials for anticancer drug delivery

One of the challenges in cancer chemotherapy is the low target to non-target ratio of therapeutic agents which incur severe adverse effect on the healthy tissues. In this regard, nanomaterials have tremendous potential for impacting cancer therapy by altering the toxicity profile of the drug. Some of the striking advantages provided by the nanocarriers mediated targeted drug delivery are relatively high build-up of drug concentration at the tumor site, improved drug content in the formulation and enhanced colloidal stability. Further, nanocarriers with tumor-specific moieties can be targeted to the cancer cell through cell surface receptors, tumor antigens and tumor vasculatures with high affinity and accuracy. Moreover, it overcomes the bottleneck of aimless drug biodistribution, undesired toxicity and heavy dosage of administration. This review discusses the recent developments in active targeting of nanomaterials for anticancer drug delivery through cancer cell surface targeting, organelle specific targeting and tumor microenvironment targeting strategies. Special emphasis has been given towards cancer cell surface and organelle specific targeting as delivery of anticancer drugs through these routes have made paradigm change in cancer management. Further, the current challenges and future prospects of nanocarriers mediated active drug targeting are also demonstrated.

The effects of surface functionality and size of gold nanoparticles on neuronal toxicity, apoptosis, ROS production and cellular/suborgan biodistribution

Gold nanoparticles are emerging as promising nanomaterials to create nanoscale therapeutic delivery systems. The aim of the study was to synthesis of highly monodisperse and stable gold nanoparticles functionalized with polyethyleneimine (PEI) and polyethylene glycol (PEG), multiparametric investigation of their neuronal toxicological effects and evaluation of the cellular/suborgan biodistribution. Gold nanoparticles (AuNP₂₀ and AuNP₅₀) were synthesized and their surfaces were electrostatically modified by PEI and PEG. Dorsal root ganglion (DRG) sensory neurones were isolated from BALB/c mice. Cell viability, apoptosis and ROS production were evaluated in vitro. Cellular and suborgan biodisribution of the AuNPs were investigated using inductively coupled plasma mass spectrometry (ICP-MS) technique. PEI and PEG surface coating increased both biocompatibility and biodistribution of the AuNPs. ICP-MS measurements showed the presence of gold in liver, spleen, kidney, heart, blood and brain within a 30 days period. The size and surface chemistry of the AuNPs are important parameters for potential nanoteranostic applications in the future studies.

G-Quadruplex-Based Drug Delivery Systems for Cancer Therapy

G-quadruplexes (G4s) are a class of nucleic acids (DNA and RNA) with single-stranded G-rich sequences. Owing to the selectivity of some G4s, they are emerging as targeting agents to overtake side effects of several potential anticancer drugs, and delivery systems of small molecules to malignant cells, through their high affinity or complementarity to specific targets. Moreover, different systems are being used to improve their potential, such as gold nano-particles or liposomes. Thus, the present review provides relevant data about the different studies with G4s as drug delivery systems and the challenges that must be overcome in the future research.

CD147 Monoclonal Antibody Targeted Reduction-Responsive Camptothecin Polyphosphoester Nanomedicine for Drug Delivery in Hepatocellular Carcinoma Cells

In the treatment of tumor-targeted small-molecule anti-cancer drugs, antibody-mediated therapies, especially for antibody-drug conjugates (ADCs), have revealed great latent force. However, the therapeutic drugs provided by ADCs possess limitation. Considering that the combination of antibodies and nano-drugs can broaden their applicability in the field of tumor treatment, herein, we developed an antibody conjugated polymeric prodrug nanoparticles SAE-PEG-b-PBYP-ss-CPT for targeted camptothecin (CPT) delivery to liver tumor cells. The diblock copolymer was composed of PEG and biodegradable polyphosphoester (PBYP) containing alkynyl groups in the side chain. A derivative of CPT (CPT-ss-N₃) was bonded to the PBYP via "click" reaction. The diethyl squarate (SAE) in the terminal of PEG chain was used as a functional group to bond with CD147 monoclonal antibody (CD147 mAb). The particle size and size distribution of the both nanoparticles, with antibody binding (namely CD147-CPT NPs) and without antibody (abbreviated as CPT-loaded NPs), were measured by dynamic light scattering (DLS). The morphologies of both two kinds of nanoparticles were observed by transmission electron microscope (TEM). The results of X-ray photoelectron spectroscopy (XPS) showed that CD147 mAb had been coupled to the surface of CPT-loaded NPs. Endocytosis test indicated that CD147-CPT NPs had higher uptake rate and accumulation in HepG2 cells than those of CPT-loaded NPs without antibodies, due to CD147 mAb can specifically bind to CD147 protein overexpressed in HepG2 cells. We establish a method to bond monoclonal antibodies to anti-cancer polymeric prodrugs, and endow biodegradable polymeric prodrugs with precise targeting functions to liver cancer cells.

Albumin-based nanostructures for uveal melanoma treatment

Uveal melanoma (UM) is an intraocular tumor which is almost lethal at the metastatic stage due to the lack of effective treatments. In this regard, we have developed an albumin-based nanostructure (ABN) containing AZD8055 (ABN-AZD), which is a potent mTOR kinase inhibitor, for its efficient delivery to the tumors. The drug has been conjugated to ABN using tailored linkers that have a disulfide moiety, allowing its release selectively and effectively in the presence of an elevated concentration of glutathione, such as inside the tumoral cells. Our therapeutic approach induced significant cellular toxicity in uveal melanoma cells, but not in non-tumoral keratinocytes, highlighting the excellent selectivity of the system. In addition, these nanostructures showed excellent activity in vivo, decreasing the tumor surface compared to the free AZD8055 in mice models. Remarkably, the results obtained were achieved employing a dose 23 times lower than those used in previous reports.

Designing Mesoporous Silica Nanoparticles to Overcome Biological Barriers by Incorporating Targeting and Endosomal Escape

The several biological barriers that nanoparticles might encounter when administered to a patient constitute the major bottleneck of nanoparticle-mediated tumor drug delivery, preventing their successful translation into the clinic and reducing their therapeutic profile. In this work, mesoporous silica nanoparticles have been employed as a platform to engineer a versatile nanomedicine able to address such barriers, achieving (a) excessive premature drug release control, (b) accumulation in tumor tissues, (c) selective internalization in tumoral cells, and (d) endosomal escape. The nanoparticles have been decorated with a self-immolative redox-responsive linker to prevent excessive premature release, to which a versatile and polyvalent peptide that is able to recognize tumoral cells and induce the delivery of the nanoparticles to the cytoplasm via endosomal escape has been grafted. The excellent biological performance of the carrier has been demonstrated using 2D and 3D in vitro cell cultures and a tumor-bearing chicken embryo model, demonstrating in all cases high biocompatibility and cytotoxic effect, efficient endosomal escape and tumor penetration, and accumulation in tumors grown on the chorioallantoic membrane of chicken embryos.

Chemotherapeutic drug-DNA hybrid nanostructures for anti-tumor therapy

Compared to traditional drug delivery systems, DNA nanostructure-based drug delivery systems have several advantages including programmable sequences, precise size and shape, high drug payloads, excellent biocompatibility and biodegradability. To date, a wide range of chemotherapeutic drug-DNA hybrid nanostructures have been developed for anti-tumor therapy. In this review, the constructions of various DNA nanostructures for anticancer drug delivery are firstly summarized. Next, the anticancer drug loading methods for DNA nanostructures are presented. Then, the recent applications of chemotherapeutic drug-DNA hybrid nanostructures for drug delivery are highlighted. In the end, the challenges and opportunities of the chemotherapeutic drug-DNA hybrid nanostructure-based delivery system are discussed. The designs of drug-DNA hybrid systems, including the constructions of nanostructures and the strategies for drug loading, largely influence the efficiency of drug delivery. Recent studies have focused on the development of novel drug-DNA hybrid systems to acquire more precise and efficient therapy for various diseases. A systematic review of the design strategies of chemotherapeutic drug-DNA hybrid nanostructures will benefit the innovation and development of the chemotherapeutic drug-based chemotherapy in clinics.

Aptamers used for biosensors and targeted therapy

Aptamers are single-stranded nucleic acid sequences that can bind to target molecules with high selectivity and affinity. Most aptamers are screened in vitro by a combinatorial biology technique called systematic evolution of ligands by exponential enrichment (SELEX). Since aptamers were discovered in the 1990s, they have attracted considerable attention and have been widely used in many fields owing to their unique advantages. In this review, we present an overview of the advancements made in aptamers used for biosensors and targeted therapy. For the former, we will discuss multiple aptamer-based biosensors with different principles detected by various signaling methods. For the latter, we will focus on aptamer-based targeted therapy using aptamers as both biotechnological tools for targeted drug delivery and as targeted therapeutic agents. Finally, challenges and new perspectives associated with these two regions were further discussed. We hope that this review will help researchers interested in aptamer-related biosensing and targeted therapy research.

Aptamer-Functionalized Nanoparticles in Targeted Delivery and Cancer Therapy

Using nanoparticles to carry and delivery anticancer drugs holds much promise in cancer therapy, but nanoparticles per se are lacking specificity. Active targeting, that is, using specific ligands to functionalize nanoparticles, is attracting much attention in recent years. Aptamers, with their several favorable features like high specificity and affinity, small size, very low immunogenicity, relatively low cost for production, and easiness to store, are one of the best candidates for the specific ligands of nanoparticle functionalization. This review discusses the benefits and challenges of using aptamers to functionalize nanoparticles for active targeting and especially presents nearly all of the published works that address the topic of using aptamers to functionalize nanoparticles for targeted drug delivery and cancer therapy.

Active targeting of gold nanoparticles as cancer therapeutics

Gold nanoparticles (AuNPs) are of increasing interest for their unique properties and their biocompatability, minimal toxicity, multivalency and size tunability make them exciting drug carriers. The functionalisaton of AuNPs with targeting moieties allows for their selective delivery to cancers, with antibodies, proteins, peptides, aptamers, carbohydrates and small molecules all exploited. Here, we review the recent advances in targeted-AuNPs for the treatment of cancer, with a particular focus on these classes of targeting ligands. We highlight the benefits and potential drawbacks of each ligand class and propose directions in which the field could grow.

Aptamer-conjugated PLGA nanoparticles for delivery and imaging of cancer therapeutic drugs

Most problems associated with chemotherapeutic agents involve non-specific cytotoxicity, low intratumoral accumulation and drug resistance. Targeted drug delivery systems (TDDS) based on nanoparticles (NPs) are a new strategy for better therapeutic efficiency, along with reduction of side effects commonly seen with cancer drugs. Poly (lactic-co-glycolic acid) (PLGA), as one of the furthest developed synthetic polymer, has gained significant attention because of excellent properties-including biodegradability and biocompatibility, controlled release of drug, protection of drug or gene from decomposition and ability to modify surface with targeting agents for both cancer diagnosis and therapy. Aptamers are single-stranded RNA or DNA that can fold through intramolecular interactions into specific three-dimensional structures to selectively and exclusively bind with interested biomarkers. In this review, we explain the latest developments regarding the application of aptamer-decorated PLGA NPs in delivery of therapeutic agents or cancer-related genes into cancer cells. Additionally, we discuss the most recent efforts in the field of aptamer-grafted PLGA-based NPs as theranostics and stimuli-responsive agents.

Laser-triggered collaborative chemophotothermal effect of gold nanoparticles for targeted colon cancer therapy

Nanotechnology has shown advantages for cancer treatment. Multimodal nanoparticles (NPs) combining chemotherapy and photothermal therapy are promising and elicit synergetic benefit. However, there were still less multifunctional nanomaterials with good targeting and anti-tumor property applied as the colon cancer therapeutic strategy. In this study, we designed the gold NPs modified with AS1411 and DNA riched of GC intercalation (hairpin DNA) with doxorubicin (DOX) for targeted chemotherapy and NIR laser-triggered chemo-photothermal effect (PTT). We took advantage of PTT effect to realize DOX release from hairpin DNA. We also demonstrated AS1411 based NPs exhibited remarkable targeted binding towards SW480 colon cancer cells in vitro and enhanced uptake inside the cells. Strikingly, AS1411 based NPs exhibited the most efficient cytotoxicity and markedly enhanced inhibition effect on cells proliferation to SW480 cells under laser exposure when compared to the NPs merely with PTT or chemotherapy. Our study appears to provide an alternative nanoplatform with good targeted and chemo-photothermal therapy against colon cancer.

Aptamer-Based Targeted Drug Delivery Systems: Current Potential and Challenges

Aptamers are single-stranded DNA or RNA with 20-100 nucleotides in length that can specifically bind to target molecules via formed three-dimensional structures. These innovative targeting molecules have attracted an increasing interest in the biomedical field. Compared to traditional protein antibodies, aptamers have several advantages, such as small size, high binding affinity, specificity, good biocompatibility, high stability and low immunogenicity, which all contribute to their wide application in the biomedical field. Aptamers can bind to the receptors on the cell membrane and mediate themselves or conjugated nanoparticles to enter into cells. Therefore, aptamers can be served as ideal targeting ligands for drug delivery. Since their excellent properties, different aptamer-mediated drug delivery systems had been developed for cancer therapy. This review provides a brief overview of recent advances in drug delivery systems based on aptamers. The advantages, challenges and future prospectives are also discussed.

Cortajarena A, Simões BM, Latorre A, Somoza Á, Clarke RB, Miranda R, Villanueva A. Tailored Functionalized Magnetic Nanoparticles to Target Breast Cancer Cells Including Cancer Stem-Like Cells

Nanotechnology-based approaches hold substantial potential to avoid chemoresistance and minimize side effects. In this work, we have used biocompatible iron oxide magnetic nanoparticles (MNPs) called MF66 and functionalized with the antineoplastic drug doxorubicin (DOX) against MDA-MB-231 cells. Electrostatically functionalized MNPs showed effective uptake and DOX linked to MNPs was more efficiently retained inside the cells than free DOX, leading to cell inactivation by mitotic catastrophe, senescence and apoptosis. Both effects, uptake and cytotoxicity, were demonstrated by different assays and videomicroscopy techniques. Likewise, covalently functionalized MNPs using three different linkers—disulfide (DOX-S-S-Pyr, called MF66-S-S-DOX), imine (DOX-I-Mal, called MF66-I-DOX) or both (DOX-I-S-S-Pyr, called MF66-S-S-I-DOX)—were also analysed. The highest cell death was detected using a linker sensitive to both pH and reducing environment (DOX-I-S-S-Pyr). The greatest success of this study was to detect also their activity against breast cancer stem-like cells (CSC) from MDA-MB-231 and primary breast cancer cells derived from a patient with a similar genetic profile (triple-negative breast cancer). In summary, these nanoformulations are promising tools as therapeutic agent vehicles, due to their ability to produce efficient internalization, drug delivery, and cancer cell inactivation, even in cancer stem-like cells (CSCs) from patients.

Delivery of thymoquinone to cancer cells with as1411-conjugated nanodroplets

Systemic delivery of conventional chemotherapies can cause negative systemic toxicity, including reduced immunity and damage to organs such as the heart and kidneys-limiting the maximum dose that can be administered. Targeted therapies appear to address this problem by having a specific target while mitigating off-target effects. Biocompatible perfluorocarbon-based nanodroplet emulsions encapsulated by a phospholipid shell are in development for delivery of molecular compounds and hold promise as vehicles for targeted delivery of chemotherapeutics to tumors. When ultrasound is applied, perfluorocarbon will undergo a phase change-ultimately inducing transient perforation of the cell membrane when in close proximity, which is more commonly known as "sonoporation." Sonoporation allows enhanced intracellular delivery of molecular compounds and will reseal to encapsulate the molecular compound intracellularly. In this study, we investigated delivery of thymoquinone (TQ), a natural hydrophobic phytochemical compound with bioactivity in cancer cells. In addition, we conjugated a G-quadruplex aptamer, 'AS1411', to TQ-loaded nanodroplets and explored their effects on multiple human cancer cell lines. AS1411 binds nucleolin, which is over-expressed on the surface of cancer cells, and in addition to its tumor-targeting properties AS1411 has also been shown to induce anti-cancer effects. Thymoquinone was loaded onto AS1411-conjugated nanodroplet emulsion to assess activity against cancer cells. Confocal microscopy indicated uptake of AS1411-conjugated nanodroplets by cancer cells. Furthermore, AS1411-conjugated nanoemulsions loaded with TQ significantly enhanced cytotoxicity in cancer cells compared to free compound. These results demonstrate that AS1411 can be conjugated onto nanodroplet emulsions for targeted delivery to human cancer cells. This novel formulation offers significant potential for targeted delivery of hydrophobic chemotherapeutics to tumors for cancer treatment.

Disulfide-Based Self-Immolative Linkers and Functional Bioconjugates for Biological Applications

It is of vital importance to reversibly mask and selectively activate bioactive agents for advanced therapeutic and diagnostic purposes, aiming to efficiently suppress background interferences and attenuate systemic toxicity. This strategy has been involved in diverse applications spanning from chemical/biological sensors and diagnostics to drug delivery nanocarriers. Among these, redox-responsive disulfide linkages have been extensively utilized by taking advantage of extracellular and intracellular glutathione (GSH) gradients. However, direct conjugation of cleavable triggers to bioactive agents through disulfide bonds suffers from bulky steric hindrance and limited choice of trigger-drug combinations. Fortunately, the emergence of disulfide self-immolative linkers (DSILs) provides a general and robust strategy to not only mask various bioactive agents through the formation of dynamic disulfide linkages but also make it possible to be selectively activated upon disulfide cleavage in the reductive cytoplasmic milieu. In this review, recent developments in DSILs are focused with special attention on emerging chemical design strategies and functional applications in the biomedical field.

Nucleolin-based targeting strategies for cancer therapy: from targeted drug delivery to cytotoxic ligands

Cancer is currently the second leading cause of death worldwide and current therapeutic approaches remain ineffective in several cases. Therefore, there is a need to develop more efficacious therapeutic agents, especially for subtypes of cancer lacking targeted therapies. Limited drug penetration into tumors impairs the efficacy of therapies targeting cancer cells. One of the strategies to overcome this problem is targeting the more accessible tumor vasculature via molecules such as nucleolin, which is expressed at the surface of cancer and angiogenic endothelial cells, thus enabling a dual cellular targeting strategy. In this review, we present and discuss nucleolin-based targeting strategies that have been developed for cancer therapy, with a special focus on recent antibody-based approaches.

Multifunctional Albumin-Stabilized Gold Nanoclusters for the Reduction of Cancer Stem Cells

Controlled delivery of multiple chemotherapeutics can improve the effectiveness of treatments and reduce side effects and relapses. Here in, we used albumin-stabilized gold nanoclusters modified with doxorubicin and SN38 (AuNCs-DS) as combined therapy for cancer. The chemotherapeutics are conjugated to the nanostructures using linkers that release them when exposed to different internal stimuli (Glutathione and pH). This system has shown potent antitumor activity against breast and pancreatic cancer cells. Our studies indicate that the antineoplastic activity observed may be related to the reinforced DNA damage generated by the combination of the drugs. Moreover, this system presented antineoplastic activity against mammospheres, a culturing model for cancer stem cells, leading to an efficient reduction of the number of oncospheres and their size. In summary, the nanostructures reported here are promising carriers for combination therapy against cancer and particularly to cancer stem cells.

The appliances and prospects of aurum nanomaterials in biodiagnostics, imaging, drug delivery and combination therapy

Aurum nanomaterials (ANM), combining the features of nanotechnology and metal elements, have demonstrated enormous potential and aroused great attention on biomedical applications over the past few decades. Particularly, their advantages, such as controllable particle size, flexible surface modification, higher drug loading, good stability and biocompatibility, especially unique optical properties, promote the development of ANM in biomedical field. In this review, we will discuss the advanced preparation process of ANM and summarize their recent applications as well as their prospects in diagnosis and therapy. Besides, multi-functional ANM-based theranostic nanosystems will be introduced in details, including radiotherapy (RT), photothermal therapy (PTT), photodynamic therapy (PDT), immunotherapy (IT), and so on.

Reprogramming Cells for Synergistic Combination Therapy with Nanotherapeutics against Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignant tumor in adults and around half of the patients develop metastasis and die shortly after because of the lack of effective therapies for metastatic UM. Consequently, new therapeutic approaches to this disease are welcome. In this regard, microRNAs have been shown to have a key role in neoplasia progression and have the potential to be used as therapeutic tools. In addition, in different cancers including UM, a particular microRNA signature appears that is different from healthy cells. Thus, restoring the regular levels of microRNAs could restore the normal behavior of cells. In this study, four microRNAs downregulated in UM have been chosen to reprogram cancer cells, to promote cell death or increase their sensitivity to the chemotherapeutic SN38. Furthermore, to improve the internalization, stability and/or solubility of the therapeutic molecules employed in this approach, gold nanoparticles (AuNPs) were used as carriers. Remarkably, this study found a synergistic effect when the four oligonucleotides were employed and when the chemotherapeutic drug was added.

Immune lipoprotein nanostructures inspired relay drug delivery for amplifying antitumor efficiency

Chemo-immunotherapy represents an appealing approach to improving cancer treatment. Simultaneously administrating chemotherapeutics with immunoadjuvants can elicit potent tumor death and immune responses. Herein, high density lipoprotein (HDL) inspired immune lipoprotein was proposed for relay drug delivery and amplifying antitumor therapy. Lipophilic AS1411 aptamer-immunoadjuvant CpG fused sequences (Apt-CpG-DSPE) were conjugated to facilitate decoration onto HDLs; and doxorubicin (Dox) was successively intercalated into the consecutive base pairs of Apt-CpG to complete immune HDL nanodrug imHDL/Apt-CpG-Dox. For relay drug delivery, imHDL/Apt-CpG-Dox underwent site-specific structure collapse in tumor intercellular substances inspired from HDL biofunctions (sequential module I); subsequently, dissociated Apt-CpG-Dox was endocytosed into tumor cells mediated by the recognition of AS1411 and nucleolin (sequential module II), translocating Dox to nucleus and enabling tumor ablation and antigens release. The liberated CpG motif further evoked antigen recognition, induced vast secretion of pro-inflammatory cytokines and potentiated host antitumor immunity. Our studies demonstrated that HDL biomimetic platform based relay drug delivery strategy outperformed the monotherapy counterparts in malignant tumor models, eventually generating an augmented antitumor efficacy.

Aptamer chemistry

Aptamers are single-stranded DNA or RNA molecules capable of tightly binding to specific targets. These functional nucleic acids are obtained by an in vitro Darwinian evolution method coined SELEX (Systematic Evolution of Ligands by EXponential enrichment). Compared to their proteinaceous counterparts, aptamers offer a number of advantages including a low immunogenicity, a relative ease of large-scale synthesis at affordable costs with little or no batch-to-batch variation, physical stability, and facile chemical modification. These alluring properties have propelled aptamers into the forefront of numerous practical applications such as the development of therapeutic and diagnostic agents as well as the construction of biosensing platforms. However, commercial success of aptamers still proceeds at a weak pace. The main factors responsible for this delay are the susceptibility of aptamers to degradation by nucleases, their rapid renal filtration, suboptimal thermal stability, and the lack of functional group diversity. Here, we describe the different chemical methods available to mitigate these shortcomings. Particularly, we describe the chemical post-SELEX processing of aptamers to include functional groups as well as the inclusion of modified nucleoside triphosphates into the SELEX protocol. These methods will be illustrated with successful examples of chemically modified aptamers used as drug delivery systems, in therapeutic applications, and as biosensing devices.

A novel combinatorial treatment option for metastatic uveal melanoma

Uveal melanoma (UM) is the most frequent intraocular tumor in adult patients. When metastases occur, systemic therapy with alkylating agents (fotemustine or dacarbazine (DTIC)) has shown only modest efficacy. The common chemotherapeutic drug doxorubicin (DOX) is not used to treat metastatic UM (mUM). To expand the chemotherapeutic arsenal for mUM, we tested the effect of DOX on UM cell mortality. We have previously shown that CREB knockdown enhances sensitivity to DOX. UM cells infected with recombinant MuLV-based replicative competent retroviruses (RCR) expressing shRNA targeting CREB were co-treated with either DTIC or DOX. We found that CREB knockdown increases the sensitivity of these cells to both DOX and DTIC in normoxia and more so in hypoxia as measured by cell survival and Caspase 3 activation. The ability to combine CREB knockdown by infection with the RCR recombinant virus which preferentially infects replicating tumor cells and chemotherapy to achieve the same amount of cell death in lower concentrations may result in fewer side effects of the drugs. This combination is a possible new treatment for mUM.

Effect of adsorption kinetics on dissociation of DNA-nucleobases on gold nanoparticles under pulsed laser illumination

Photothermal therapy is a novel approach to destroy cancer cells by an increase of temperature due to laser illumination of gold nanoparticles (GNPs) that are incorporated into the cells. Here, we study the decomposition of DNA nucleobases via irradiation of gold nanoparticles with ns-laser pulses. The kinetics of the adsorption and decomposition process is described by a theoretical model based on the Langmuir assumptions and correlated with experimentally determined reaction rates revealing a strong influence of the nucleobase specific adsorption. Beside the four nucleobases, their brominated analogs, which are potential radiosensitizers in cancer therapy, are also investigated and show a significant modification of the decomposition rates. The fastest decomposition rates are observed for adenine, 8-bromoadenine, 8-bromoguanine and 5-bromocytosine. These results are in good agreement with the relative adsorption rates that are determined from the aggregation kinetics of the GNPs taking the effect of an inhomogeneous surface into account. For adenine and its brominated analog, the decomposition products are further analyzed by surface enhanced Raman scattering (SERS) indicating a strong fragmentation of the molecules into their smallest subunits.

Nucleic Acid Aptamers: Emerging Applications in Medical Imaging, Nanotechnology, Neurosciences, and Drug Delivery

Recent progresses in organic chemistry and molecular biology have allowed the emergence of numerous new applications of nucleic acids that markedly deviate from their natural functions. Particularly, DNA and RNA molecules-coined aptamers-can be brought to bind to specific targets with high affinity and selectivity. While aptamers are mainly applied as biosensors, diagnostic agents, tools in proteomics and biotechnology, and as targeted therapeutics, these chemical antibodies slowly begin to be used in other fields. Herein, we review recent progress on the use of aptamers in the construction of smart DNA origami objects and MRI and PET imaging agents. We also describe advances in the use of aptamers in the field of neurosciences (with a particular emphasis on the treatment of neurodegenerative diseases) and as drug delivery systems. Lastly, the use of chemical modifications, modified nucleoside triphosphate particularly, to enhance the binding and stability of aptamers is highlighted.

Polymer decorated gold nanoparticles in nanomedicine conjugates

Noble metal, especially gold nanoparticles and their conjugates with biopolymers have immense potential for disease diagnosis and therapy on account of their surface plasmon resonance (SPR) enhanced light scattering and absorption. Conjugation of noble metal nanoparticles to ligands specifically targeted to biomarkers on diseased cells allows molecular-specific imaging and detection of disease. The development of smart gold nanoparticles (AuNPs) that can deliver therapeutics at a sustained rate directly to cancer cells may provide better efficacy and lower toxicity for treating cancer tumors. We highlight some of the promising classes of targeting systems that are under development for the delivery of gold nanoparticles. Nanoparticles designed for biomedical applications are often coated with polymers containing reactive functional groups to conjugate targeting ligands, cell receptors or drugs. Using targeted nanoparticles to deliver chemotherapeutic agents in cancer therapy offers many advantages to improve drug/gene delivery and to overcome many problems associated with conventional radiotherapy and chemotherapy. The targeted nanoparticles were found to be effective in killing cancer cells which were studied using various anticancer assays. Cell morphological analysis shows the changes occurred in cancer cells during the treatment with AuNPs. The results determine the influence of particle size and concentration of AuNPs on their absorption, accumulation, and cytotoxicity in model normal and cancer cells. As the mean particle diameter of the AuNPs decreased, their rate of absorption by the intestinal epithelium cells increased. These results provide important insights into the relationship between the dimensions of AuNPs and their gastrointestinal uptake and potential cytotoxicity. Furthermore gold nanoparticles efficiently convert the absorbed light into localized heat, which can be exploited for the selective laser photothermal therapy of cancer. We also review the emerging technologies for the fabrication of targeted gold colloids as imagining agents.

Improving gold nanorod delivery to the central nervous system by conjugation to the shuttle Angiopep-2

AIM

To improve the in vivo delivery of gold nanorods (GNRs) to the central nervous system of rats, these gold nanoparticles were conjugated to Angiopep-2, a shuttle peptide that can cross the blood-brain barrier.

MATERIALS & METHODS

GNRs were synthesized and modified using polyethylene glycol and Angiopep-2 (GNR-PEG-Angiopep-2). The physicochemical properties, in vitro cytotoxicity and ex vivo biodistribution of the conjugate were examined.

RESULTS

GNR-PEG-Angiopep-2 was stable over the following days, and the different concentrations that were tested did not affect the viability of microvascular endothelial cells. The conjugation of Angiopep-2 to GNRs enhanced the endocytosis of these particles (in vitro) and the accumulation in brains (in vivo), when compared with GNRs modified only with PEG.

CONCLUSION

This study provides evidence that Angiopep-2 improves the delivery of GNRs to the brain parenchyma. This property is highly relevant for future applications of GNRs as platforms for photothermal and theranostic purposes.

Biomedical Applications of DNA-Conjugated Gold Nanoparticles

Gold nanoparticles (AuNPs) are useful for diagnostic and biomedical applications, mainly because of their ease in preparation and conjugation, biocompatibility, and size-dependent optical properties. However, bare AuNPs do not possess specificity for targets. AuNPs conjugated with DNA aptamers offer specificity for various analytes, such as proteins and small molecules/ions. Although DNA aptamers themselves have therapeutic and target-recognizing properties, they are susceptible to degradation in vivo. When DNA aptamers are conjugated to AuNPs, their stability and cell uptake efficiency both increase, making aptamer-AuNPs suitable for biomedical applications. Additionally, drugs can be efficiently conjugated with DNA aptamer-AuNPs to further enhance their therapeutic efficiency. This review focuses on the applications of DNA aptamer-based AuNPs in several biomedical areas, including anticoagulation, anticancer, antibacterial, and antiviral applications.

Ultrasmall inorganic nanoparticles: State-of-the-art and perspectives for biomedical applications

Ultrasmall nanoparticulate materials with core sizes in the 1-3nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications. This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.

Trends in aptamer selection methods and applications

Aptamers are target specific ssDNA, RNA or peptide sequences generated by an in vitro selection and amplification method called SELEX (Systematic Evolution of Ligands by EXponential Enrichment), which involves repetitive cycles of binding, recovery and amplification steps. Aptamers have the ability to bind with a variety of targets such as drugs, proteins, heavy metals, and pathogens with high specificity and selectivity. Aptamers are similar to monoclonal antibodies regarding their binding affinities, but they offer a number of advantages over the existing antibody-based detection methods, which make the aptamers promising diagnostic and therapeutic tools for future biomedical and analytical applications. The aim of this review article is to provide an overview of the recent advancements in aptamer screening methods along with a concise description of the major application areas of aptamers including biomarker discovery, diagnostics, imaging and nanotechnology.

Nanotechnology-based strategies for combating toxicity and resistance in melanoma therapy

Drug toxicity and resistance remain formidable challenges in cancer treatment and represent an area of increasing attention in the case of melanoma. Nanotechnology represents a paradigm-shifting field with the potential to mitigate drug resistance while improving drug delivery and minimizing toxicity. Recent clinical and pre-clinical studies have demonstrated how a diverse array of nanoparticles may be harnessed to circumvent known mechanisms of drug resistance in melanoma to improve therapeutic efficacy. In this review, we discuss known mechanisms of resistance to various melanoma therapies and possible nanotechnology-based strategies that could be used to overcome these barriers and improve the pharmacologic arsenal available to combat advanced stage melanoma.

Assembly of designed protein scaffolds into monolayers for nanoparticle patterning

The controlled assembly of building blocks to achieve new nanostructured materials with defined properties at different length scales through rational design is the basis and future of bottom-up nanofabrication. This work describes the assembly of the idealized protein building block, the consensus tetratricopeptide repeat (CTPR), into monolayers by oriented immobilization of the blocks. The selectivity of thiol-gold interaction for an oriented immobilization has been verified by comparing a non-thiolated protein building block. The physical properties of the CTPR protein thin biomolecular films including topography, thickness, and viscoelasticity, are characterized. Finally, the ability of these scaffolds to act as templates for inorganic nanostructures has been demonstrated by the formation of well-packed gold nanoparticles (GNPs) monolayer patterned by the CTPR monolayer.