Aptamer-based liposomes improve specific drug loading and release

Aptamer-controlled stimuli-responsive drug release

Aptamers have been widely researched and applied in nanomedicine due to their programmable, activatable, and switchable properties. However, there are few reviews on aptamer-controlled stimuli-responsive drug delivery. This article highlights the mechanisms and advantages of aptamers in the construction of stimuli-responsive drug delivery systems. We summarize the assembly/reconfiguration mechanisms of aptamers in controlled release systems. The assembly and drug release strategies of drug delivery systems are illustrated. Specifically, we focus on the binding mechanisms to the target and the factors that induce/inhibit the binding to the stimuli, such as strand, pH, light, and temperature. The applications of aptamer-based stimuli-responsive drug release are elaborated. The challenges are discussed, and the future directions are proposed.

Construction Strategy of Functionalized Liposomes and Multidimensional Application

Liposomes are widely used in the biological field due to their good biocompatibility and surface modification properties. With the development of biochemistry and material science, many liposome structures and their surface functional components have been modified and optimized one by one, pushing the liposome platform from traditional to functionalized and intelligent, which will better satisfy and expand the needs of scientific research. However, a main limiting factor effecting the efficiency of liposomes is the complicated environmental conditions in the living body. Currently, in order to overcome the above problem, functionalized liposomes have become a very promising strategy. In this paper, binding strategies of liposomes with four main functional elements, namely nucleic acids, antibodies, peptides, and stimuli-responsive motif have been summarized for the first time. In addition, based on the construction characteristics of functionalized liposomes, such as drug-carrying, targeting, long-circulating, and stimulus-responsive properties, a comprehensive overview of their features and respective research progress are presented. Finally, the paper critically presents the limitations of these functionalized liposomes in the current applications and also prospectively suggests the future development directions, aiming to accelerate realization of their industrialization.

AS1411aptamer conjugated liposomes for targeted delivery of arsenic trioxide in mouse xenograft model of melanoma cancer

Development of AS1411aptamer-conjugated liposomes for targeted delivery of arsenic trioxide is the primary goal of this study. AS1411aptamer was used as ligand to target nucleolin, which is highly expressed on the surface of melanoma cancer cells. The targeted liposomes were constructed by the thin film method, and arsenic trioxide was loaded as cobalt (II) hydrogen arsenite (CHA) to increase the loading efficiency and stability of the liposomes. The liposomal structure was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and field emission scanning electron microscopy (FESEM). In addition, particle sizes and zeta potential of the CHA-loaded liposomes (CHAL) and aptamer-functionalized CHA-loaded liposomes (AP-CHAL) were determined. In vitro cytotoxicity of CHAL and AP-CHAL were evaluated using MTT assay in murine melanoma (B16) and mouse embryonic fibroblast (MEF) cell lines. The encapsulation efficiency of CHAL and AP-CHAL was reported as 60.2 ± 6.5% and 58.7 ± 4.2%, respectively. In vivo antitumor activity of CHAL and AP-CHAL in the B16 tumor-xenograft mouse model was dramatically observed. All mice of both groups survived until the end of treatment and showed body weight gain. The tumor protrusion completely disappeared in 50% of the mice in these groups. Furthermore, histopathology studies demonstrated that CHAL and AP-CHAL did not induce significant toxicity in healthy mice tissues. However, unlike the CHAL group, which showed an initial increase in tumor volume, a specific antitumor effect was observed in the AP-CHAL group from the beginning of treatment. The results showed that AP-CHAL can be used as an effective drug delivery system with high potential in the treatment of solid tumors.

Aptamer-Protein Interactions: From Regulation to Biomolecular Detection

Serving as the basis of cell life, interactions between nucleic acids and proteins play essential roles in fundamental cellular processes. Aptamers are unique single-stranded oligonucleotides generated by in vitro evolution methods, possessing the ability to interact with proteins specifically. Altering the structure of aptamers will largely modulate their interactions with proteins and further affect related cellular behaviors. Recently, with the in-depth research of aptamer-protein interactions, the analytical assays based on their interactions have been widely developed and become a powerful tool for biomolecular detection. There are some insightful reviews on aptamers applied in protein detection, while few systematic discussions are from the perspective of regulating aptamer-protein interactions. Herein, we comprehensively introduce the methods for regulating aptamer-protein interactions and elaborate on the detection techniques for analyzing aptamer-protein interactions. Additionally, this review provides a broad summary of analytical assays based on the regulation of aptamer-protein interactions for detecting biomolecules. Finally, we present our perspectives regarding the opportunities and challenges of analytical assays for biological analysis, aiming to provide guidance for disease mechanism research and drug discovery.

Harnessing aptamers against COVID-19: a therapeutic strategy

The novel coronavirus crisis caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) was a global pandemic. Although various therapeutic approaches were developed over the past 2 years, novel strategies with more efficient applicability are required to target new variants. Aptamers are single-stranded (ss)RNA or DNA oligonucleotides capable of folding into unique 3D structures with robust binding affinity to a wide variety of targets following structural recognition. Aptamer-based theranostics have proven excellent capability for diagnosing and treating various viral infections. Herein, we review the current status and future perspective of the potential of aptamers as COVID-19 therapies.

Transforming a Toxic Non-Ionizable Drug into an Efficacious Liposome via Ionizable Prodrug and Remote Loading Strategies against Malignant Breast Tumors

Liposomes (lipos), one of the most successful nanotherapeutics in the clinic, have made a rapid advance over the past few years. However, still, several challenges exist for lipos for clinical practice, such as low drug loading and premature drug leakage during in vivo circulation. Paclitaxel (PTX), a commonly used first-line drug for cancer chemotherapy, was chosen as the model drug. Due to its non-ionizable and water-insoluble characteristics, the drug-loading efficiency of the marketable PTX lipos, Lipusu, is only 6.76%. Herein, we designed an ionizable PTX prodrug (PTXP) by modifying phenylboronic acid on the C2' hydroxyl group of PTX for the remote loading of liposomal formulations through the pH gradient method. Compared with Lipusu, PTXP lipos displayed a 34% higher loading efficiency and an encapsulation efficiency of approximately 95%. A series of in vitro/vivo experiments indicated that PTXP lipos possess colloidal stability, prolonged blood circulation, high tumor site accumulation, potent anti-tumor effects, and safety. A combination of ionizable prodrugs and remote loading has proved to be an effective and simple strategy to achieve high liposomal encapsulation efficiency of poorly soluble non-ionizable drugs for clinical application.

Programmable self-regulated molecular buffers for precise sustained drug delivery

Unlike artificial nanosystems, biological systems are ideally engineered to respond to their environment. As such, natural molecular buffers ensure precise and quantitative delivery of specific molecules through self-regulated mechanisms based on Le Chatelier's principle. Here, we apply this principle to design self-regulated nucleic acid molecular buffers for the chemotherapeutic drug doxorubicin and the antimalarial agent quinine. We show that these aptamer-based buffers can be programmed to maintain any specific desired concentration of free drug both in vitro and in vivo and enable the optimization of the chemical stability, partition coefficient, pharmacokinetics and biodistribution of the drug. These programmable buffers can be built from any polymer and should improve patient therapeutic outcome by enhancing drug activity and minimizing adverse effects and dosage frequency.

Cardiolipin for Enhanced Cellular Uptake and Cytotoxicity of Thermosensitive Liposome-Encapsulated Daunorubicin toward Breast Cancer Cell Lines

Daunorubicin (DNR) and cardiolipin (CL) were co-delivered using thermosensitive liposomes (TSLs). 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1-myristoyl-2-stearoyl-sn-glycero-3-phosphocholine (MSPC), cholesterol, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] or DSPE-mPEG (2000) and CL were used in the formulation of liposomes at a molar ratio of 57:40:30:3:20, respectively. CL forms raft-like microdomains that may relocate and change lipid organization of the outer and inner mitochondrial membranes. Such transbilayer lipid movement eventually leads to membrane permeabilization. TSLs were prepared by thin-film hydration (drug:lipid ratio 1:5) where DNR was encapsulated within the aqueous core of the liposomes and CL acted as a component of the lipid bilayer. The liposomes exhibited high drug encapsulation efficiency (>90%), small size (~115 nm), narrow size distribution (polydispersity index ~0.12), and a rapid release profile under the influence of mild hyperthermia. The liposomes also exhibited ~4-fold higher cytotoxicity against MDA-MB-231 cells compared to DNR or liposomes similar to DaunoXome® (p < 0.001). This study provides a basis for developing a co-delivery system of DNR and CL encapsulated in liposomes for treatment of breast cancer.

pH-Sensitive Liposomes for Enhanced Cellular Uptake and Cytotoxicity of Daunorubicin in Melanoma (B16-BL6) Cell Lines

Daunorubicin (DNR) was delivered using a pH-sensitive liposomal system in B16-BL6 melanoma cell lines for enhanced cytotoxic effects. DNR was encapsulated within liposomes and CL as a component of the lipid bilayer. PEGylated pH-sensitive liposomes, containing CL, were prepared in the molar ratio of 40:30:5:17:8 for DOPE/cholesterol/DSPE-mPEG (2000)/CL/SA using the lipid film hydration method and loaded with DNR (drug: lipid ratio of 1:5). The CL liposomes exhibited high drug encapsulation efficiency (>90%), a small size (~94 nm), narrow size distribution (polydispersity index ~0.16), and a rapid release profile at acidic pH (within 1 h). Furthermore, the CL liposomes exhibited 12.5- and 2.5-fold higher cytotoxicity compared to DNR or liposomes similar to DaunoXome®. This study provides a basis for developing DNR pH-sensitive liposomes for melanoma treatment.

Aptamer-Enabled Nanomaterials for Therapeutics, Drug Targeting and Imaging

A wide variety of nanomaterials have emerged in recent years with advantageous properties for a plethora of therapeutic and diagnostic applications. Such applications include drug delivery, imaging, anti-cancer therapy and radiotherapy. There is a critical need for further components which can facilitate therapeutic targeting, augment their physicochemical properties, or broaden their theranostic applications. Aptamers are single-stranded nucleic acids which have been selected or evolved to bind specifically to molecules, surfaces, or cells. Aptamers can also act as direct biologic therapeutics, or in imaging and diagnostics. There is a rich field of discovery at the interdisciplinary interface between nanomaterials and aptamer science that has significant potential across biomedicine. Herein, we review recent progress in aptamer-enabled materials and discuss pending challenges for their future biomedical application.

Aptamer-mediated doxorubicin delivery reduces HCC burden in 3D organoids model

Epithelial cell adhesion molecule (EpCAM) is a surface marker which is frequently overexpressed in hepatocellular carcinoma (HCC) but minimally expressed on mature hepatocytes. We developed a specific aptamer against EpCAM (EpCAM-apt) and tested its potential as a drug delivery agent for HCC. The targeting ability of EpCAM-apt was confirmed in vitro and in vivo after which the complex was conjugated with doxorubicin (Dox) to form EpCAM-apt-Dox. The targeting efficacy of the drug-loaded complex against liver cancer stem-like cells (LCSCs) and therapeutic effects in HCC were evaluated. EpCAM-expressing (EpCAM⁺) HCC cells showed characteristics of stem like cells including greater proliferative capacity and tumour sphere formation. EpCAM-apt-Dox selectively delivered Dox to EpCAM⁺ HCC cells with high drug retention and accumulation versus control. EpCAM-apt-Dox reduced the self-renewal capacity and stem-like cell frequency in vitro. Elimination of cancer stem-like cells (CSCs) with EpCAM-apt-Dox significantly inhibited the growth of HCC cells and patient-derived HCC organoids but exerted minimal cytotoxicity to normal liver organoids. Moreover, EpCAM-apt-Dox suppressed the growth of xenograft tumours derived from HCC organoids in vivo and prolonged mouse survival without inducing adverse effects to major organs. Thus, aptamer-based drug delivery to the stem-like cell population is a promising strategy for HCC treatment.

Identification and Engineering of Aptamers for Theranostic Application in Human Health and Disorders

An aptamer is a short sequence of synthetic oligonucleotides which bind to their cognate target, specifically while maintaining similar or higher sensitivity compared to an antibody. The in-vitro selection of an aptamer, applying a conjoining approach of chemistry and molecular biology, is referred as Systematic Evolution of Ligands by Exponential enrichment (SELEX). These initial products of SELEX are further modified chemically in an attempt to make them stable in biofluid, avoiding nuclease digestion and renal clearance. While the modification is incorporated, enough care should be taken to maintain its sensitivity and specificity. These modifications and several improvisations have widened the window frame of aptamer applications that are currently not only restricted to in-vitro systems, but have also been used in molecular imaging for disease pathology and treatment. In the food industry, it has been used as sensor for detection of different diseases and fungal infections. In this review, we have discussed a brief history of its journey, along with applications where its role as a therapeutic plus diagnostic (theranostic) tool has been demonstrated. We have also highlighted the potential aptamer-mediated strategies for molecular targeting of COVID-19. Finally, the review focused on its future prospective in immunotherapy, as well as in identification of novel biomarkers in stem cells and also in single cell proteomics (scProteomics) to study intra or inter-tumor heterogeneity at the protein level. Small size, chemical synthesis, low batch variation, cost effectiveness, long shelf life and low immunogenicity provide advantages to the aptamer over the antibody. These physical and chemical properties of aptamers render them as a strong biomedical tool for theranostic purposes over the existing ones. The significance of aptamers in human health was the key finding of this review.

Nanocrystals for Improving Oral Bioavailability of Drugs: Intestinal Transport Mechanisms and Influencing Factors

With the limitation of solubility and dissolution rate of insoluble drugs, following oral administration, they would rifely prove poor and volatile bioavailability, which may fail to realize its therapeutic value. The drug nanocrystals are perceived as effective tactic for oral administration of insoluble drugs attributes to possess many prominent properties such as elevating dissolution rate and saturation solubility, high drug loading capacity, and improving oral bioavailability. Based on these advantages, the application of nanocrystals in oral drug delivery has acquired significant achievement, and so far more than 20 products of drug nanocrystals have been confirmed in the market. However, the oral absorption of drug nanocrystals is still facing huge challenges due to the limitation of many factors. Intrinsic properties of the drugs and complex physiological environment of the intestinal tract are the two most important factors affecting the oral bioavailability of drugs. In addition, the research on the multi-aspect mechanisms of nanocrystals promoting gastrointestinal absorption and bioavailability has been gradually deepened. In this review, we summarized recent advances of the nanocrystals delivered orally, and provided an overview to the research progress for crossing the intestinal tract transport mechanisms of the nanocrystals by some new research techniques. Meanwhile, the factors relevant to the transport of drug nanocrystals were also elaborated in detail. Graphical Abstract.

Recent Progress in Aptamer Discoveries and Modifications for Therapeutic Applications

Aptamers are oligonucleotide sequences with a length of about 25-80 bases which have abilities to bind to specific target molecules that rival those of monoclonal antibodies. They are attracting great attention in diverse clinical translations on account of their various advantages, including prolonged storage life, little batch-to-batch differences, very low immunogenicity, and feasibility of chemical modifications for enhancing stability, prolonging the half-life in serum, and targeted delivery. In this Review, we demonstrate the emerging aptamer discovery technologies in developing advanced techniques for producing aptamers with high performance consistently and efficiently as well as requiring less cost and resources but offering a great chance of success. Further, the diverse modifications of aptamers for therapeutic applications including therapeutic agents, aptamer-drug conjugates, and targeted delivery materials are comprehensively summarized.

Programmable Repurposing of Existing Drugs as Pharmaceutical Elements for the Construction of Aptamer-Drug Conjugates

Converting marketed drug molecules into phosphoramidites may present a potential strategy to facilitate the development of aptamer-drug conjugates (ApDCs) by a DNA synthesizer in a programmable way; however, quite limited methods were reported. Herein, we demonstrated a general approach by repurposing camptothecin (CPT) species. Commonly used inactive ingredients in pharmaceuticals are investigated and selected as a bonding moiety, from which 2-mercaptoethoxy ethanol and thioglycerol were efficiently incorporated with CPT to give the precursors. Cell viability and molecular docking results of the precursors supported that incorporation of the bonding moiety would not interrupt the inhibitory activity. Therefore, corresponding phosphoramidites were prepared as pharmaceutical elements, and a series of ApDCs were constructed automatically by solid-phase synthesis. Biological studies revealed that CPT elements could be specifically delivered to HCT116 cells by an aptamer and released inside cells. This kind of programmable repurposing may take advantage of established safety data and efficacy of existing drugs resulting in a faster development of ApDCs.

Impact of Liposomal Drug Formulations on the RBCs Shape, Transmembrane Potential, and Mechanical Properties

Liposomal technologies are used in order to improve the effectiveness of current therapies or to reduce their negative side effects. However, the liposome–erythrocyte interaction during the intravenous administration of liposomal drug formulations may result in changes within the red blood cells (RBCs). In this study, it was shown that phosphatidylcholine-composed liposomal formulations of Photolon, used as a drug model, significantly influences the transmembrane potential, stiffness, as well as the shape of RBCs. These changes caused decreasing the number of stomatocytes and irregular shapes proportion within the cells exposed to liposomes. Thus, the reduction of anisocytosis was observed. Therefore, some nanodrugs in phosphatidylcholine liposomal formulation may have a beneficial effect on the survival time of erythrocytes.

The Brief Analysis of Peptide-combined Nanoparticle: Nanomedicine's Unique Value

Therapeutic peptides (TPs) are biological macromolecules which can act as neurotransmitters, hormones, ion channel ligands and growth factors. Undoubtedly, TPs are crucial in modern medicine. But low bio-stability and some special adverse reactions reduce their places to the application. With the development of nanotechnology, nanoparticles (NPs) in pharmaceutical science gained much attention. They can encapsulate the TPs into their membrane or shell. Therefore, they can protect the TPs against degradation and then increase the bioavailability, which was thought to be the biggest advantage of them. Additionally, targeting was also studied to improve the effect of TPs. However, there were some drawbacks of nano TPs like low loading efficiency and difficulty to manufacture. Nowadays, lots of studies focused on improving effect of TPs by preparing nanoparticles. In this review, we presented a brief analysis of peptide-combined nanoparticles. Their advantages and disadvantages were listed in terms of mechanism. And several examples of applications were summarized.

Recent Progress in Bioconjugation Strategies for Liposome-Mediated Drug Delivery

In nanoparticle (NP)-mediated drug delivery, liposomes are the most widely used drug carrier, and the only NP system currently approved by the FDA for clinical use, owing to their advantageous physicochemical properties and excellent biocompatibility. Recent advances in liposome technology have been focused on bioconjugation strategies to improve drug loading, targeting, and overall efficacy. In this review, we highlight recent literature reports (covering the last five years) focused on bioconjugation strategies for the enhancement of liposome-mediated drug delivery. These advances encompass the improvement of drug loading/incorporation and the specific targeting of liposomes to the site of interest/drug action. We conclude with a section highlighting the role of bioconjugation strategies in liposome systems currently being evaluated for clinical use and a forward-looking discussion of the field of liposomal drug delivery.

Aptamers in Drug Design: An Emerging Weapon to Fight a Losing Battle

Implementation of novel and biocompatible polymers in drug design is an emerging and rapidly growing area of research. Even though we have a large number of polymer materials for various applications, the biocompatibility of these materials remains as a herculean task for researchers. Aptamers provide a vital and efficient solution to this problem. They are usually small (ranging from 20 to 60 nucleotides, single-stranded DNA or RNA oligonucleotides which are capable of binding to molecules possessing high affinity and other properties like specificity. This review focuses on different aspects of Aptamers in drug discovery, starting from its preparation methods and covering the recent scenario reported in the literature regarding their use in drug discovery. We address the limitations of Aptamers and provide valuable insights into their future potential in the areas regarding drug discovery research. Finally, we explained the major role of Aptamers like medical imaging techniques, application as synthetic antibodies, and the most recent application, which is in combination with nanomedicines.

Engineering Smart Targeting Nanovesicles and Their Combination with Hydrogels for Controlled Drug Delivery

Smart engineered and naturally derived nanovesicles, capable of targeting specific tissues and cells and delivering bioactive molecules and drugs into them, are becoming important drug delivery systems. Liposomes stand out among different types of self-assembled nanovesicles, because of their amphiphilicity and non-toxic nature. By modifying their surfaces, liposomes can become stimulus-responsive, releasing their cargo on demand. Recently, the recognized role of exosomes in cell-cell communication and their ability to diffuse through tissues to find target cells have led to an increase in their usage as smart delivery systems. Moreover, engineering "smarter" delivery systems can be done by creating hybrid exosome-liposome nanocarriers via membrane fusion. These systems can be loaded in naturally derived hydrogels to achieve sustained and controlled drug delivery. Here, the focus is on evaluating the smart behavior of liposomes and exosomes, the fabrication of hybrid exosome-liposome nanovesicles, and the controlled delivery and routes of administration of a hydrogel matrix for drug delivery systems.

Directly targeting glutathione peroxidase 4 may be more effective than disrupting glutathione on ferroptosis-based cancer therapy

BACKGROUND

Cancer is one of the major threats to human health and current cancer therapies have been unsuccessful in eradicating it. Ferroptosis is characterized by iron-dependence and lipid hydroperoxides accumulation, and its primary mechanism involves the suppression of system X_c^--GSH (glutathione)-GPX4 (glutathione peroxidase 4) axis. Co-incidentally, cancer cells are also metabolically characterized by iron addiction and ROS tolerance, which makes them vulnerable to ferroptosis. This may provide a new tactic for cancer therapy.

SCOPE OF REVIEW

The general features and mechanisms of ferroptosis, and the basis that makes cancer cells vulnerable to ferroptosis are described. Further, we emphatically discussed that disrupting GSH may not be ideal for triggering ferroptosis of cancer cells in vivo, but directly inhibiting GPX4 and its compensatory members could be more effective. Finally, the various approaches to directly inhibit GPX4 without disturbing GSH were described.

MAJOR CONCLUSIONS

Targeting system X_c^- or GSH may not effectively trigger cancer cells' ferroptosis in vivo the existence of other compensatory pathways. However, directly targeting GPX4 and its compensatory members without disrupting GSH may be more effective to induce ferroptosis in cancer cells in vivo, as GPX4 is essential in preventing ferroptosis.

GENERAL SIGNIFICANCE

Cancer is a severe threat to human health. Ferroptosis-based cancer therapy strategies are promising, but how to effectively induce ferroptosis in cancer cells in vivo is still a question without clear answers. Thus, the viewpoints raised in this review may provide some references and different perspectives for researchers working on ferroptosis-based cancer therapy.

A glance over doxorubicin based-nanotherapeutics: From proof-of-concept studies to solutions in the market

Cancer is one of the leading causes of death worldwide and, as such, efforts are being done to find new chemotherapeutic drugs or, alternatively, novel approaches for the delivery of old ones. In this scope, when used as vehicles for drugs, nanomaterials may potentially maximize the efficacy of the treatment and reduce its side effects, for example by a change in drug's pharmacokinetics, cell targeting and/or specific stimuli-responsiveness. This is the case of doxorubicin (DOX) that presents a broad spectrum of activity and is one of the most widely used chemotherapeutic drugs as first-line treatment. Indeed, DOX is a very interesting example of a drug for which several nanosized delivery systems have been developed over the years. While it is true that some of these systems are already in the market, it is also true that research on this subject remains very active and that there is a continuing search for new solutions. In this sense, this review takes the example of doxorubicin, not so much with the focus on the drug itself, but rather as a case study around which very diverse and imaginative nanotechnology approaches have emerged.

Design and synthesis of aptamer AS1411-conjugated EG@TiO2@Fe2O3nanoparticles as a drug delivery platform for tumor-targeted therapy

AS1411@GMBS@EG@TiO₂@Fe₂O₃nanoparticle is an effective and safe pH-responsive sustained release system for targeted drug delivery into nucleolin-positive cells.

Liposomes modified with bio-substances for cancer treatment

In recent years, liposomes have been used in the field of biomedicine and have achieved many significant results.

Targeted ErbB3 cancer therapy: A synergistic approach to effectively combat cancer

Surface modification of nanoparticles with aptamer is gaining popularity lately due to its selective targeting and low immunogenicity. In this study, sorafenib tosylate (SFB) was loaded in biodegradable PLGA nanoparticles prepared by solvent evaporation method. The surfaces of drug deprived and drug-loaded particles (PN and PNS, respectively) were coupled with aptamer to target ErbB3 using EDC/NHS chemical modification. Nanoparticles were characterized with regard to their size, shape and chemical composition by dynamic light scattering, atomic force microscopy, FTIR and elemental analysis respectively. To evaluate the particles in vitro cell culture studies were performed. Cell viability assay, pathway analysis and apoptosis assay showed cellular toxicity in the presence of aptamer in PNS-Apt (p < 0.001). Metastatic progression assay showed decreased cell migration in the presence of aptamer and SFB. Confocal laser scanning microscopy was used to visualize the receptor-mediated time-dependent intracellular uptake and distribution of the nanoparticles throughout the cytoplasm. The findings of the current study demonstrated the potential efficacy of the surface modified SFB-loaded particles against ErbB3.

Updates on the use of liposomes for active tumor targeting in cancer therapy

In the development of cancer chemotherapy, besides the discovery of new anticancer drugs, a variety of nanocarrier systems for the delivery of previously developed and new chemotherapeutic drugs have currently been explored. Liposome is one of the most studied nanocarrier systems because of its biodegradability, simple preparation method, high efficacy and low toxicity. To make the best use of this vehicle, a number of multifunctionalized liposomal formulations have been investigated. The objective of this review is to summarize the current development of novel active targeting liposomal formulations, and to give insight into the challenges and future direction of the field. The recent studies in active targeting liposomes suggest the great potential of precise targeted anticancer drug delivery in cancer therapeutics.

Non-immunogenic, low-toxicity and effective glioma targeting MTI-31 liposomes

Liposomes with peptide motifs have been successfully used in glioma-targeted delivery of various general chemotherapy agents. However, their use for the encapsulation of low-toxicity molecularly targeted anticancer agents has been limited. In the present study, we aimed to assess the efficacy and safety of a novel low-toxicity mTORC1/mTORC2 inhibitor (MTI-31) as a treatment for glioma when encapsulated in appropriate liposomes. Since some of the peptide-modified liposomes have been determined to be immunogenic and may have life-threatening consequences in mice, an immunogenicity-based investigation with candidate liposomal carriers was conducted. Following this study, ^DVAP (^DP^DA^DV^DR^DT^DN^DS) modified liposomes (^DVAP-liposomes) were identified as an immunologically safe carrier and therefore utilized for MTI-31 encapsulation. ^DVAP is a tumor homing peptide exhibiting high binding affinity to glucose regulated protein 78 (GRP78) overexpressed in glioma, glioma stem cells, vasculogenic mimicry and neovasculature. Modification of liposomes with ^DVAP imparts a glioma-directing property. In vitro, the developed ^DVAP-liposomes/MTI-31 were efficiently internalized by U87 cells and consequently showed a potent antiproliferation effect. In vivo, the safety and anti-glioma efficiency of ^DVAP-liposomes/MTI-31 were validated in intracranial glioma bearing BALB/c nude mice. While showing both systemic and immunological safety, ^DVAP-liposome/MTI-31 treatment resulted in a significant improvement in the median survival time (24.5 days for saline, 26 days for free MTI-31, 25 days for liposomes/MTI-31 and 36 days for ^DVAP-liposome/MTI-31). The results highlight MTI-31 as an effective anti-glioma agent when encapsulated in non-immunogenic glioma-targeted liposomes, which may contribute to the development of better anti-glioma treatment.

Binding affinity data of DNA aptamers for therapeutic anthracyclines from microscale thermophoresis and surface plasmon resonance spectroscopy

Anthracyclines like daunorubicin (DRN) and doxorubicin (DOX) play an undisputed key role in cancer treatment, but their chronic administration can cause severe side effects. For precise anthracycline analytical systems, aptamers are preferable recognition elements. Here, we describe the detailed characterisation of a single-stranded DNA aptamer DRN-10 and its truncated versions for DOX and DRN detection. Binding affinities were determined from surface plasmon resonance (SPR) and microscale thermophoresis (MST) and combined with conformational data from circular dichroism (CD). Both aptamers displayed similar nanomolar binding affinities to DRN and DOX, even though their rate constants differed as shown by SPR recordings. SPR kinetic data unravelled a two-state reaction model including a 1 : 1 binding and a subsequent conformational change of the binding complex. This model was supported by CD spectra. In addition, the dissociation constants determined with MST were always lower than that from SPR, and especially for the truncated aptamer they differed by two orders of magnitude. This most probably reflects the methodological difference, namely labelling for MST vs. immobilisation for SPR. From CD recordings, we suggested a specific G-quadruplex as structural basis for anthracycline binding. We concluded that the aptamer DRN-10 is a promising recognition element for anthracycline detection systems and further selected aptamers can be also characterised with the combined methodological approach presented here.

SS30, a novel thioaptamer targeting CD123, inhibits the growth of acute myeloid leukemia cells

AIMS

CD123 represents an important acute myeloid leukemia (AML) therapeutic target. CD123 aptamers may potentially serve as tumor-homing ligands with excellent affinity and specificity for AML targeted therapy, but their complexity, laborious preparation and nuclease digestion limited pharmacological application. The aim of this study was to develop the first CD123 thioaptamer to overcome these obstacles.

MAIN METHODS

Flow cytometry was utilized to assess the binding specificity, affinity and anti-nuclease ability of thioaptamer. CCK8, Annexin-V/DAPI, and colony forming assays were used to evaluate the anti-cancer ability of thioaptamer in vitro. The tumor volume, weights, survival rate, H&E staining of organs, and serum level of organ damage biomarkers of animal model were applied to investigate the anti-cancer ability of thioaptamer in vivo. Furthermore, we explored the binding mechanism between thioaptamer and CD123.

KEY FINDINGS

CD123 thioaptamer SS30 was able to bind to CD123 structure with high specificity in complex nuclease environment, the dissociation constant of 39.1 nM for CD123 peptide and 287.6 nM for CD123⁺ AML cells, while exhibiting minimal cross-reactivity to albumin. Furthermore, SS30 inhibited the proliferation and survival of AML cell lines and human AML blasts selectively in vitro (P < 0.01). In addition, SS30 prolonged the survival and inhibited tumor growth in a mouse xenograft tumor model in vivo. Of note, SS30 blocked the interaction between IL-3 and CD123, and decreased expression of p-STAT5 and p-AKT.

SIGNIFICANCE

The proliferation inhibition and nuclease resistance ability of SS30 made it as a more promising functional molecule for AML targeted therapy.

Pea-like nanocabins enable autonomous cruise and step-by-step drug pushing for deep tumor inhibition

Pea-like nanocabins (HA@APT§DOX) were designed for deep tumor inhibition. The AS1411 aptamer (APT) constituted "core shelf" which guaranteed DOX "beans" could be embedded, while the outer HA acted as "pea shell" coating. During the circulation (primary orbit), HA@APT§DOX could autonomously cruise until leak through tumor vasculature. Upon tumor superficial site, the "pea shell" could be degraded by highly expressed hyaluronic acid enzymes (HAase) and peel-off, resulting in orbit changing of released APT§DOX to reach the deep tumor tissue. Furthermore, APT§DOX could be specifically uptaken into A549 tumor cells (secondary orbit). Finally, DOX was released under the acidic environment of lysosome, and delivered into nuclear (targeting orbit) to achieve drug pushing for deep tumor inhibition. More importantly, the in vivo imaging and anti-tumor effects evaluations showed that these nanocabins could effectively enhance drugs accumulation in tumor sites and inhibit tumor growth, with reduced systemic toxicity in 4T1 tumor-bearing mice.

Aptamer-integrated α-Gal liposomes as bispecific agents to trigger immune response for killing tumor cells

A novel bispecific α-Gal liposome was constructed by self-assembling AS1411 aptamers into the α-Gal containing liposomes. The α-Gal liposomes were prepared using cell membranes of red blood cells from rabbit, which are composed of cholesterol, phospholipids, and α-Gal glycolipids. AS1411 is a DNA aptamer with high specificity and affinity for nucleolin and could integrate into liposomes by the modification of cholesterol. The bispecific α-Gal liposomes surface-functionalized by α-Gal and AS1411 aptamer could recognize anti-Gal antibodies and nucleolin overexpressed by tumor cells simultaneously, followed by activating the immune system to attack the tumor cells, resulting in the lysis of the tumor cells by antibody dependent cell-mediated cytotoxicity. Under simulated tumor environment, the lysis rate of MCF-7 cells treated by the AS1411 modified α-Gal liposomes drastically increased compared to the liposomes without AS1411 aptamer. This study suggests that the AS1411 modified α-Gal liposomes can recognize nucleolin-overexpressing tumor cells selectively, subsequently improve the effect of the immunotherapy with high specificity. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1176-1183, 2019.

Smart aptamer-modified calcium carbonate nanoparticles for controlled release and targeted delivery of epirubicin and melittin into cancer cells in vitro and in vivo

To explore the effect of combination therapy of epirubicin (Epi) and melittin (Mel) to cancer cells, calcium carbonate nanoparticles (CCN), as carriers, were developed which were modified with MUC1-Dimer aptamers as targeting agents. Both Epi and Mel were delivered at the same time to cancer cells overexpressing the target of MUC1 aptamer, mucin 1 glycoproteins (MCF7 and C26 cells). CCN were prepared with a water-in-oil emulsion method. Epi and Mel were separately encapsulated in CCN and the nanoparticles were modified with MUC1-Dimer aptamers. In vitro studies, including MTT assay, flow cytometry analysis and fluorescence imaging were applied to investigate the targeting and cell proliferation inhibition capabilities of MUC1-Dimer aptamer-CCN-Mel complex and MUC1-Dimer aptamer-CCN-Epi complex in the target (MCF-7 and C26 cells) and nontarget (HepG2) cells. Also, the function of the developed complexes was analyzed using in vivo tumor growth inhibition. The release of Epi from MUC1-Dimer aptamer-CCN-Epi complex was pH-sensitive. Cellular uptake studies showed more internalization of the MUC1-Dimer aptamer-CCN-Epi complex into MCF-7 and C26 cells (target) compared to HepG2 cells (nontarget). Interestingly, the MUC1-Dimer aptamer-CCN-Mel complex and MUC1-Dimer aptamer-CCN-Epi complex indicated very low toxicity as compared to target cells. Moreover, co-delivery of Epi and Mel using the mixture of MUC1-Dimer aptamer-CCN-Mel complex and MUC1-Dimer aptamer-CCN-Epi complex exhibited strong synergistic cytotoxicity in MCF-7 and C26 cells. Furthermore, the presented complexes had a better function to control tumor growth in vivo compared to free Epi.

Liposome: composition, characterisation, preparation, and recent innovation in clinical applications

In the last decades, pharmaceutical interested researches aimed to develop novel and innovative drug delivery techniques in the medical and pharmaceutical fields. Recently, phospholipid vesicles (Liposomes) are the most known versatile assemblies in the drug delivery systems. The discovery of liposomes arises from self-forming enclosed phospholipid bilayer upon coming in contact with the aqueous solution. Liposomes are uni or multilamellar vesicles consisting of phospholipids produced naturally or synthetically, which are readily non-toxic, biodegradable, and are readily produced on a large scale. Various phospholipids, for instance, soybean, egg yolk, synthetic, and hydrogenated phosphatidylcholine consider the most popular types used in different kinds of formulations. This review summarises liposomes composition, characterisation, methods of preparation, and their applications in different medical fields including cancer therapy, vaccine, ocular delivery, wound healing, and some dermatological applications.

Synergistic combination chemotherapy using carrier-free celastrol and doxorubicin nanocrystals for overcoming drug resistance

A key challenge of chemotherapy in clinical treatments is multidrug resistance (MDR), which mainly arises from drug efflux-induced tumor cell survival. Thus, it is necessary to provide biocompatible chemotherapeutics to improve drug accumulation in MDR cells. Herein, two clinical small molecular drugs, celastrol (CST) and doxorubicin (DOX), were self-assembled into carrier-free and biocompatible nanoparticles (CST/DOX NPs) via a simple and green precipitation method for synergistic combination chemotherapy to overcome DOX resistance. These spherical CST/DOX NPs can improve the water-solubility of CST, reduce the dosage of DOX, and therefore significantly enhance cellular drug accumulation by activating heat shock factor 1 (HSF-1) and inhibiting NF-κB to depress P-gp expression, which results in apoptosis and autophagy of DOX resistant cells through the ROS/JNK signaling pathway. Finally, synergistic combination chemotherapy was attained in both MCF-7/MDR cells and 3D multicellular tumor spheroids. Thus, CST/DOX NPs provide an alternative for overcoming drug resistance in future clinical applications.

Programmable and Multifunctional DNA-Based Materials for Biomedical Applications

DNA encodes the genetic information; recently, it has also become a key player in material science. Given the specific Watson-Crick base-pairing interactions between only four types of nucleotides, well-designed DNA self-assembly can be programmable and predictable. Stem-loops, sticky ends, Holliday junctions, DNA tiles, and lattices are typical motifs for forming DNA-based structures. The oligonucleotides experience thermal annealing in a near-neutral buffer containing a divalent cation (usually Mg²⁺ ) to produce a variety of DNA nanostructures. These structures not only show beautiful landscape, but can also be endowed with multifaceted functionalities. This Review begins with the fundamental characterization and evolutionary trajectory of DNA-based artificial structures, but concentrates on their biomedical applications. The coverage spans from controlled drug delivery to high therapeutic profile and accurate diagnosis. A variety of DNA-based materials, including aptamers, hydrogels, origamis, and tetrahedrons, are widely utilized in different biomedical fields. In addition, to achieve better performance and functionality, material hybridization is widely witnessed, and DNA nanostructure modification is also discussed. Although there are impressive advances and high expectations, the development of DNA-based structures/technologies is still hindered by several commonly recognized challenges, such as nuclease instability, lack of pharmacokinetics data, and relatively high synthesis cost.

Bile Acid-Based Drug Delivery Systems for Enhanced Doxorubicin Encapsulation: Comparing Hydrophobic and Ionic Interactions in Drug Loading and Release

Doxorubicin (Dox) is a drug of choice in the design of drug delivery systems directed toward breast cancers, but is often limited by loading and control over its release from polymer micelles. Bile acid-based block copolymers present certain advantages over traditional polymer-based systems for drug delivery purposes, since they can enable a higher drug loading via the formation of a reservoir through their aggregation process. In this study, hydrophobic and electrostatic interactions are compared for their influence on Dox loading inside cholic acid based block copolymers. Poly(allyl glycidyl ether) (PAGE) and poly(ethylene glycol) (PEG) were grafted from the cholic acid (CA) core yielding a star-shaped block copolymer with 4 arms (CA-(PAGE- b-PEG)₄) and then loaded with Dox via a nanoprecipitation technique. A high Dox loading of 14 wt % was achieved via electrostatic as opposed to hydrophobic interactions with or without oleic acid as a cosurfactant. The electrostatic interactions confer a pH responsiveness to the system. 50% of the loaded Dox was released at pH 5 in comparison to 12% at pH 7.4. The nanoparticles with Dox loaded via hydrophobic interactions did not show such a pH responsiveness. The systems with Dox loaded via electrostatic interactions showed the lowest IC₅₀ and highest cellular internalization, indicating the pre-eminence of this interaction in Dox loading. The blank formulations are biocompatible and did not show cytotoxicity up to 0.17 mg/mL. The new functionalized star block copolymers based on cholic acid show great potential as drug delivery carriers.

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.

The use of functional epirubicin liposomes to induce programmed death in refractory breast cancer

Currently, chemotherapy is less efficient in controlling the continued development of breast cancer because it cannot eliminate extrinsic and intrinsic refractory cancers. In this study, mitochondria were modified by functional epirubicin liposomes to eliminate refractory cancers through initiation of an apoptosis cascade. The efficacy and mechanism of epirubicin liposomes were investigated on human breast cancer cells in vitro and in vivo using flow cytometry, confocal microscopy, high-content screening system, in vivo imaging system, and tumor inhibition in mice. Mechanistic studies revealed that the liposomes could target the mitochondria, activate the apoptotic enzymes caspase 8, 9, and 3, upregulate the proapoptotic protein Bax while downregulating the antiapoptotic protein Mcl-1, and induce the generation of reactive oxygen species (ROS) through an apoptosis cascade. In xenografted mice bearing breast cancer, the epirubicin liposomes demonstrated prolonged blood circulation, significantly increased accumulation in tumor tissue, and robust anticancer efficacy. This study demonstrated that functional epirubicin liposomes could significantly induce programmed death of refractory breast cancer by activating caspases and ROS-related apoptotic signaling pathways, in addition to the direct killing effect of the anticancer drug itself. Thus, we present a simple nanomedicine strategy to treat refractory breast cancer.