Targeted intracellular codelivery of chemotherapeutics and nucleic acid with a well-defined dendrimer-based nanoglobular carrier

Organocatalytic synthetic route to esters and their application in hydrosilylation process

A facile esterification of α,β-unsaturated aldehydes with alcohols has been developed for the synthesis of esters by using bulky N-heterocyclic (NHC) carbene as a metal-free and eco-friendly organocatalyst. This new protocol has been proved to be effective with a wide substrate scope, giving selective esters in yields greater than 84% under mild conditions. Moreover, proposed synthetic strategy enables modification of various types of silsesquioxanes (SQ) which cannot or are technically difficult to be carried out with known protocols. For the first time, a one-pot sequential esterification/hydrosilylation has been successfully carried out.

Polyhedral Oligomeric Silsesquioxane-Based Nanoparticles for Efficient Chemotherapy of Glioblastoma

Glioblastoma (GBM) is the most common lethal brain tumor with dismal treatment outcomes and poor response to chemotherapy. As the regulatory center of cytogenetics and metabolism, most tumor chemotherapeutic molecules exert therapeutic effects in the nucleus. Nanodrugs showing the nuclear aggregation effect are expected to eliminate and fundamentally suppress tumor cells. In this study, a nanodrug delivery system based on polyhedral oligomeric silsesquioxane (POSS) is introduced to deliver drugs into the nuclei of GBM cells, effectively enhancing the therapeutic efficacy of chemotherapy. The nanoparticles are modified with folic acid and iRGD peptides molecules to improve their tumor cell targeting and uptake via receptor-mediated endocytosis. Nuclear aggregation allows for the direct delivery of chemotherapeutic drug temozolomide (TMZ) to the tumor cell nuclei, resulting in more significant DNA damage and inhibition of tumor cell proliferation. Herein, TMZ-loaded POSS nanoparticles can significantly improve the survival of GBM-bearing mice. Therefore, the modified POSS nanoparticles may serve as a promising drug-loaded delivery platform to improve chemotherapy outcomes in GBM patients.

Role and Application of Biocatalysts in Cancer Drug Discovery

A biocatalyst is an enzyme that speeds up or slows down the rate at which a chemical reaction occurs and speeds up certain processes by 108 times. It is used as an anticancer agent because it targets drug activation inside the tumor microenvironment while limiting damage to healthy cells. Biocatalysts have been used for the synthesis of different heterocyclic compounds and is also used in the nano drug delivery systems. The use of nano-biocatalysts for tumor-targeted delivery not only aids in tumor invasion, angiogenesis, and mutagenesis, but also provides information on the expression and activity of many markers related to the microenvironment. Iosmapinol, moclobemide, cinepazide, lysine dioxygenase, epothilone, 1-homophenylalanine, and many more are only some of the anticancer medicines that have been synthesised using biocatalysts. In this review, we have highlighted the application of biocatalysts in cancer therapies as well as the use of biocatalysts in the synthesis of drugs and drug-delivery systems in the tumor microenvironment.

Delivering the Promise of Gene Therapy with Nanomedicines in Treating Central Nervous System Diseases

Central Nervous System (CNS) diseases, such as Alzheimer's diseases (AD), Parkinson's Diseases (PD), brain tumors, Huntington's disease (HD), and stroke, still remain difficult to treat by the conventional molecular drugs. In recent years, various gene therapies have come into the spotlight as versatile therapeutics providing the potential to prevent and treat these diseases. Despite the significant progress that has undoubtedly been achieved in terms of the design and modification of genetic modulators with desired potency and minimized unwanted immune responses, the efficient and safe in vivo delivery of gene therapies still poses major translational challenges. Various non-viral nanomedicines have been recently explored to circumvent this limitation. In this review, an overview of gene therapies for CNS diseases is provided and describes recent advances in the development of nanomedicines, including their unique characteristics, chemical modifications, bioconjugations, and the specific applications that those nanomedicines are harnessed to deliver gene therapies.

Nanoparticles-Based Strategies to Improve the Delivery of Therapeutic Small Interfering RNA in Precision Oncology

Small interfering RNA (siRNA) can selectively suppress the expression of disease-causing genes, holding great promise in the treatment of human diseases, including malignant cancers. In recent years, with the development of chemical modification and delivery technology, several siRNA-based therapeutic drugs have been approved for the treatment of non-cancerous liver diseases. Nevertheless, the clinical development of siRNA-based cancer therapeutics remains a major translational challenge. The main obstacles of siRNA therapeutics in oncology include both extracellular and intracellular barriers, such as instability under physiological conditions, insufficient tumor targeting and permeability (particularly for extrahepatic tumors), off-target effects, poor cellular uptake, and inefficient endosomal escape. The development of clinically suitable and effective siRNA delivery systems is expected to overcome these challenges. Herein, we mainly discuss recent strategies to improve the delivery and efficacy of therapeutic siRNA in cancer, including the application of non-viral nanoparticle-based carriers, the selection of target genes for therapeutic silencing, and the combination with other therapeutic modalities. In addition, we also provide an outlook on the ongoing challenges and possible future developments of siRNA-based cancer therapeutics during clinical translation.

Emerging concepts in designing next-generation multifunctional nanomedicine for cancer treatment

Nanotherapy has emerged as an improved anticancer therapeutic strategy to circumvent the harmful side effects of chemotherapy. It has been proven to be beneficial to offer multiple advantages, including their capacity to carry different therapeutic agents, longer circulation time and increased therapeutic index with reduced toxicity. Over time, nanotherapy evolved in terms of their designing strategies like geometry, size, composition or chemistry to circumvent the biological barriers. Multifunctional nanoscale materials are widely used as molecular transporter for delivering therapeutics and imaging agents. Nanomedicine involving multi-component chemotherapeutic drug-based combination therapy has been found to be an improved promising approach to increase the efficacy of cancer treatment. Next-generation nanomedicine has also utilized and combined immunotherapy to increase its therapeutic efficacy. It helps in targeting tumor immune response sparing the healthy systemic immune function. In this review, we have summarized the progress of nanotechnology in terms of nanoparticle designing and targeting cancer. We have also discussed its further applications in combination therapy and cancer immunotherapy. Integrating patient-specific proteomics and biomarker based information and harnessing clinically safe nanotechnology, the development of precision nanomedicine could revolutionize the effective cancer therapy.

Craft of Co-encapsulation in Nanomedicine: A Struggle To Achieve Synergy through Reciprocity

Achieving synergism, often by combination therapy via codelivery of chemotherapeutic agents, remains the mainstay of treating multidrug-resistance cases in cancer and microbial strains. With a typical core-shell architecture and surface functionalization to ensure facilitated targeting of tissues, nanocarriers are emerging as a promising platform toward gaining such synergism. Co-encapsulation of disparate theranostic agents in nanocarriers-from chemotherapeutic molecules to imaging or photothermal modalities-can not only address the issue of protecting the labile drug payload from a hostile biochemical environment but may also ensure optimized drug release as a mainstay of synergistic effect. However, the fate of co-encapsulated molecules, influenced by temporospatial proximity, remains unpredictable and marred with events with deleterious impact on therapeutic efficacy, including molecular rearrangement, aggregation, and denaturation. Thus, more than just an art of confining multiple therapeutics into a 3D nanoscale space, a co-encapsulated nanocarrier, while aiming for synergism, should strive toward achieving a harmonious cohabitation of the encapsulated molecules that, despite proximity and opportunities for interaction, remain innocuous toward each other and ensure molecular integrity. This account will inspect the current progress in co-encapsulation in nanocarriers and distill out the key points toward accomplishing such synergism through reciprocity.

Tetrahedral DNA nanostructures for effective treatment of cancer: advances and prospects

Recently, DNA nanostructures with vast application potential in the field of biomedicine, especially in drug delivery. Among these, tetrahedral DNA nanostructures (TDN) have attracted interest worldwide due to their high stability, excellent biocompatibility, and simplicity of modification. TDN could be synthesized easily and reproducibly to serve as carriers for, chemotherapeutic drugs, nucleic acid drugs and imaging probes. Therefore, their applications include, but are not restricted to, drug delivery, molecular diagnostics, and biological imaging. In this review, we summarize the methods of functional modification and application of TDN in cancer treatment. Also, we discuss the pressing questions that should be targeted to increase the applicability of TDN in the future.

Co-delivery of Dexamethasone and a MicroRNA-155 Inhibitor Using Dendrimer-Entrapped Gold Nanoparticles for Acute Lung Injury Therapy

Development of nanomedicines for effective therapy of acute lung injury (ALI), a common critical respiratory failure syndrome, remains to be challenging. We report here a unique design of a functional nanoplatform based on generation 5 (G5) poly(amidoamine) dendrimer-entrapped gold nanoparticles (Au DENPs) to co-deliver dexamethasone (Dex) and a microRNA-155 inhibitor (miR-155i) for combination chemotherapy and gene therapy of ALI. In this study, we synthesized Au DENPs with 10 Dex moieties attached per G5 dendrimer and an Au core diameter of 2.1 nm and used them to compress miR-155i. The generated polyplexes own a positive zeta potential (16-26 mV) and a small hydrodynamic diameter (175-230 nm) and display desired cytocompatibility and efficient miR-155i delivery to lipopolysaccharide (LPS)-activated alveolar macrophages, thus upregulating the suppressor of cytokine signaling 1 and IL-10 expression and downregulating the pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6). Likewise, as a synthetic glucocorticoid with a potent anti-inflammatory property, the attached Dex on the surface of Au DENPs could inhibit pro-inflammatory cytokine secretion by down-regulating cyclooxygenase-2 expression in the LPS-activated alveolar macrophages. The integration of Dex and miR-155i within one nanoformulation enables superior downregulation of pro-inflammatory cytokines for successful repair of damaged lung tissues in an ALI model, as demonstrated by histological examinations and pro-inflammatory cytokine downregulation in ALI lesion at the gene and protein levels. Such a combined chemotherapy and gene therapy strategy enabled by dendrimer nanotechnology may hold great promise to treat other types of inflammatory diseases.

Use of Polyhedral Oligomeric Silsesquioxane (POSS) in Drug Delivery, Photodynamic Therapy and Bioimaging

Polyhedral oligomeric silsesquioxanes (POSS) have attracted considerable attention in the design of novel organic-inorganic hybrid materials with high performance capabilities. Features such as their well-defined nanoscale structure, chemical tunability, and biocompatibility make POSS an ideal building block to fabricate hybrid materials for biomedical applications. This review highlights recent advances in the application of POSS-based hybrid materials, with particular emphasis on drug delivery, photodynamic therapy and bioimaging. The design and synthesis of POSS-based materials is described, along with the current methods for controlling their chemical functionalization for biomedical applications. We summarize the advantages of using POSS for several drug delivery applications. We also describe the current progress on using POSS-based materials to improve photodynamic therapies. The use of POSS for delivery of contrast agents or as a passivating agent for nanoprobes is also summarized. We envision that POSS-based hybrid materials have great potential for a variety of biomedical applications including drug delivery, photodynamic therapy and bioimaging.

Integrated POSS-dendrimer nanohybrid materials: current status and future perspective

Polyhedral oligomeric silsesquioxane (POSS)-dendrimer hybrid materials have attracted great interest in the past ten years. The integration of inorganic POSS and organic dendrimer blocks in a single-phase material offers numerous possibilities to access desirable mechanical, optical, and biomedical properties for various applications. In this review article, we describe several kinds of POSS-dendrimer hybrid materials (POSS as the core, surface functionality, repeating unit of dendrimers and the POSS-dendron conjugates) with an emphasis on their synthetic strategies, tunable macroscopic properties, and potential applications. Moreover, the current trends, challenges and future directions of POSS-dendrimer hybrid materials are elaborated.

PAMAM Dendrimer Nanomolecules Utilized as Drug Delivery Systems for Potential Treatment of Glioblastoma: A Systematic Review

Glioblastoma (GB) is a grade IV astrocytoma that maintains a poor prognosis with respect to current treatment options. Despite major advancements in the fields of surgery and chemoradiotherapy over the last few decades, the life expectancy for someone with glioblastoma remains virtually unchanged and warrants a new approach for treatment. Poly(amidoamine) (PAMAM) dendrimers are a type of nanomolecule that ranges in size (between 1 and 100 nm) and shape and can offer a new viable solution for the treatment of intracranial tumors, including glioblastoma. Their ability to deliver a variety of therapeutic cargo and penetrate the blood-brain barrier (BBB), while preserving low cytotoxicity, make them a favorable candidate for further investigation into the treatment of glioblastoma. Here, we present a systematic review of the current advancements in PAMAM dendrimer technology, including the wide spectrum of dendrimer generations formulated, surface modifications, core modifications, and conjugations developed thus far to enhance tumor specificity and tumor penetration for treatment of glioblastoma. Furthermore, we highlight the extensive variety of therapeutics capable of delivery by PAMAM dendrimers for the treatment of glioblastoma, including cytokines, peptides, drugs, siRNAs, miRNAs, and organic polyphenols. While there have been prolific results stemming from aggressive research into the field of dendrimer technology, there remains a nearly inexhaustible amount of questions that remain unanswered. Nevertheless, this technology is rapidly developing and is nearing the cusp of use for aggressive tumor treatment. To that end, we further highlight future prospects in focus as researchers continue developing more optimal vehicles for the delivery of therapeutic cargo.

Three-dimensional DNA nanostructures for dual-color microRNA imaging in living cells via hybridization chain reaction

A well-defined 3D DNA nanostructure was developed by combination of DNA tetrahedron and Y-shaped DNA, which allowed multiplexed, signal amplified fluorescent imaging of miRNAs in living cells via hybridization chain reaction.

Co-delivery of doxorubicin and TRAIL plasmid by modified PAMAM dendrimer in colon cancer cells, in vitro and in vivo evaluation

One strategy for cancer treatment is combination therapy using nanoparticles (NPs), which has resulted in enhanced anti-cancer effects and reduced cytotoxicity of therapeutic agents. Polyamidoamine dendrimer (PAMAM) has attracted considerable attention because of its potential applications ranging from drug delivery to molecular encapsulation and gene therapy. In this study, PAMAM G5 modified with cholesteryl chloroformate and alkyl-PEG was applied for co-delivery of doxorubicin (DOX) and plasmid encoding TRAIL into colon cancer cells, in vitro and in vivo. The results showed DOX was efficiently encapsulated in modified carrier (M-PAMAM) with loading level about 90%, and the resulting DOX-loaded M-PAMAM complexed with TRAIL plasmid showed much stronger antitumor effect than M-PAMAM containing DOX or TRAIL plasmid. On the other hand, the obtained results demonstrated that the treatment of mice bearing C26 colon carcinoma with this developed co-delivery system significantly decreased tumor growth rate. Thus, this modified PAMAM G5 can be considered as a potential carrier for co-delivery of drug and gene in cancer therapy.

Glycyrrhizin Acid and Glycyrrhetinic Acid Modified Polyethyleneimine for Targeted DNA Delivery to Hepatocellular Carcinoma

In the last 2-3 decades, gene therapy represented a promising option for hepatocellular carcinoma (HCC) treatment. However, the design of safe and efficient gene delivery systems is still one of the major challenges that require solutions. In this study, we demonstrate a versatile method for covalent conjugation of glycyrrhizin acid (GL) or glycyrrhetinic acid (GA) to increase the transfection efficiency of Polyethyleneimine (PEI, Mw 1.8K) and improve their targeting abilities of hepatoma carcinoma cells. GA and GL targeting ligands were grafted to PEI via N-acylation, and we systematically investigated their biophysical properties, cytotoxicity, liver targeting and transfection efficiency, and endocytosis pathway trafficking. PEI-GA0.75, PEI-GL10.62 and PEI-GL20.65 conjugates caused significant increases in gene transfection efficiency and superior selectivity for HepG2 cells, with all three conjugates showing specific recognition of HepG2 cells by the free GA competition assay. The endocytosis inhibition and intracellular trafficking results indicated that PEI-GA0.75 and GL10.62 conjugates behaved similarly to SV40 virus, by proceeding via the caveolae- and clathrin-independent mediated endocytosis pathway and bypassing entry into lysosomes, with an energy independent manner, achieving their high transfection efficiencies. In the HepG2 intraperitoneal tumor model, PEI-GA0.75 and PEI-GL10.62 carrying the luciferase reporter gene gained high gene expression, suggesting potential use for in vivo application.

Small interfering RNAs (siRNAs) in cancer therapy: a nano-based approach

Cancer is one of the most complex diseases that has resulted in multiple genetic disorders and cellular abnormalities. Globally, cancer is the most common health concern disease that is affecting human beings. Great efforts have been made over the past decades in biology with the aim of searching novel and more efficient tools in therapy. Thus, small interfering RNAs (siRNAs) have been considered one of the most noteworthy developments which are able to regulate gene expression following a process known as RNA interference (RNAi). RNAi is a post-transcriptional mechanism that involves the inhibition of gene expression through promoting cleavage on a specific area of a target messenger RNA (mRNA). This technology has shown promising therapeutic results for a good number of diseases, especially in cancer. However, siRNA therapeutics have to face important drawbacks in therapy including stability and successful siRNA delivery in vivo. In this regard, the development of effective siRNA delivery systems has helped addressing these issues by opening novel therapeutic windows which have allowed to build up important advances in Nanomedicine. In this review, we discuss the progress of siRNA therapy as well as its medical application via nanoparticle-mediated delivery for cancer treatment.

RNAi therapeutic and its innovative biotechnological evolution

Recently, United States Food and Drug Administration (FDA) and European Commission (EC) approved Alnylam Pharmaceuticals' RNA interference (RNAi) therapeutic, ONPATTRO™ (Patisiran), for the treatment of the polyneuropathy of hereditary transthyretin-mediated (hATTR) amyloidosis in adults. This is the first RNAi therapeutic all over the world, as well as the first FDA-approved treatment for this indication. As a milestone event in RNAi pharmaceutical industry, it means, for the first time, people have broken through all development processes for RNAi drugs from research to clinic. With this achievement, RNAi approval may soar in the coming years. In this paper, we introduce the basic information of ONPATTRO and the properties of RNAi and nucleic acid therapeutics, update the clinical and preclinical development activities, review its complicated development history, summarize the key technologies of RNAi at early stage, and discuss the latest advances in delivery and modification technologies. It provides a comprehensive view and biotechnological insights of RNAi therapy for the broader audiences.

Delivering Combination Chemotherapies and Targeting Oncogenic Pathways via Polymeric Drug Delivery Systems

The side-effects associated with chemotherapy necessitates better delivery of chemotherapeutics to the tumor. Nanoparticles can load higher amounts of drug and improve delivery to tumors, increasing the efficacy of treatment. Polymeric nanoparticles, in particular, have been used extensively for chemotherapeutic delivery. This review describes the efforts made to deliver combination chemotherapies and inhibit oncogenic pathways using polymeric drug delivery systems. Combinations of chemotherapeutics with other drugs or small interfering RNA (siRNA) combinations have been summarized. Special attention is given to the delivery of drug combinations that involve either paclitaxel or doxorubicin, two popular chemotherapeutics in clinic. Attempts to inhibit specific pathways for oncotherapy have also been described. These include inhibition of oncogenic pathways (including those involving HER2, EGFR, MAPK, PI3K/Akt, STAT3, and HIF-1α), augmentation of apoptosis by inhibiting anti-apoptosis proteins (Bcl-2, Bcl-xL, and survivin), and targeting dysregulated pathways such as Wnt/β-catenin and Hedgehog.

Threatening cancer with nanoparticle aided combination oncotherapy

Employing combination therapy has become obligatory in cancer cases exhibiting high tumor load, chemoresistant tumor population, and advanced disease stages. Realization of this fact has now led many of the combination oncotherapies to become an integral part of anticancer regimens. Combination oncotherapy may encompass a combination of anticancer agents belonging to a similar therapeutic category or that of different therapeutic categories (e.g. chemotherapy + gene therapy). Differences in the physicochemical properties, pharmacokinetics and biodistribution pattern of different payloads are the major constraints that are faced by combination chemotherapy. Concordant efforts in the field of nanotechnology and oncology have emerged with several approaches to solve the major issues encountered by combination therapy. Unique colloidal behaviors of various types of nanoparticles and differential targeting strategies have accorded an unprecedented ability to optimize combination oncotherapeutic delivery. Nanocarrier based delivery of the various types of payloads such as chemotherapeutic agents and other anticancer therapeutics such as small interfering ribonucleic acid (siRNA), chemosensitizers, radiosensitizers, and antiangiogenic agents have been addressed in the present review. Various nano-delivery systems like liposomes, polymeric nanoparticles, polymerosomes, dendrimers, micelles, lipid based nanoparticles, prodrug based nanocarriers, polymer-drug conjugates, polymer-lipid hybrid nanoparticles, carbon nanotubes, nanosponges, supramolecular nanocarriers and inorganic nanoparticles (gold nanoparticles, silver nanoparticles, magnetic nanoparticles and mesoporous silica based nanoparticles) that have been extensively explored for the formulation of multidrug delivery is an imperative part of discussion in the review. The present review features the outweighing benefits of combination therapy over mono-oncotherapy and discusses several existent nanoformulation strategies that facilitate a successful combination oncotherapy. Several obstacles that may impede in transforming nanotechnology-based combination oncotherapy from bench to bedside, and challenges associated therein have also been discussed in the present review.

A multifunctional persistent luminescent nanoprobe for imaging guided dual-stimulus responsive and triple-synergistic therapy of drug resistant tumor cells

A novel multifunctional persistent luminescent nanoprobe was fabricated for imaging guided dual-stimulus responsive and triple-synergistic therapy for multiple drug resistant tumor cells.

Co-delivery of resveratrol and docetaxel via polymeric micelles to improve the treatment of drug-resistant tumors

Co-delivery of anti-cancer drugs is promising to improve the efficacy of cancer treatment. This study was aiming to investigate the potential of concurrent delivery of resveratrol (RES) and docetaxel (DTX) via polymeric nanocarriers to treat breast cancer. To this end, methoxyl poly(ethylene glycol)-poly(d,l-lactide) copolymer (mPEG-PDLA) was prepared and characterized using FTIR and 1H NMR, and their molecular weights were determined by GPC. Isobologram analysis and combination index calculation were performed to find the optimal ratio between RES and DTX to against human breast adenocarcinoma cell line (MCF-7 cells). Subsequently, RES and DTX were loaded in the mPEG-PDLA micelles simultaneously, and the morphology, particle size distribution, in vitro release, pharmacokinetic profiles, as well as cytotoxicity to the MCF-7 cells were characterized. IC50 of RES and DTX in MCF-7 cells were determined to be 23.0 µg/ml and 10.4 µg/ml, respectively, while a lower IC50 of 4.8 µg/ml of the combination of RES and DTX was obtained. The combination of RES and DTX at a ratio of 1:1 (w/w) generated stronger synergistic effect than other ratios in the MCF-7 cells. RES and DTX loaded mPEG-PDLA micelles exhibited prolonged release profiles, and enhanced cytotoxicity in vitro against MCF-7 cells. The AUC(0→ t ) of DTX and RES in mPEG-PDLA micelles after i.v. administration to rats were 3.0-fold and 1.6-fold higher than that of i.v. injections of the individual drugs. These findings indicated that the co-delivery of RES and DTX using mPEG-PDLA micelles could have better treatment of tumors.

Evaluation of Amino-Functional Polyester Dendrimers Based on Bis-MPA as Nonviral Vectors for siRNA Delivery

Herein, we present the first evaluation of cationic dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) as nonviral vectors for transfection of short interfering RNA (siRNA) in cell cultures. The study encompassed dendrimers of generation one to four (G1⁻G4), modified to bear 6⁻48 amino end-groups, where the G2⁻G4 proved to be capable of siRNA complexation and protection against RNase-mediated degradation. The dendrimers were nontoxic to astrocytes, glioma (C6), and glioblastoma (U87), while G3 and G4 exhibited concentration dependent toxicity towards primary neurons. The G2 showed no toxicity to primary neurons at any of the tested concentrations. Fluorescence microscopy experiments suggested that the dendrimers are highly efficient at endo-lysosomal escape since fluorescently labeled dendrimers were localized specifically in mitochondria, and diffuse cytosolic distribution of fluorescent siRNA complexed by dendrimers was observed. This is a desired feature for intracellular drug delivery, since the endocytic pathway otherwise transfers the drugs into lysosomes where they can be degraded without reaching their intended target. siRNA-transfection was successful in C6 and U87 cell lines using the G3 and G4 dendrimers followed by a decrease of approximately 20% of target protein p42-MAPK expression.

Drug Delivery in Cancer Therapy, Quo Vadis?

The treatment of malignancies has undergone dramatic changes in the past few decades. Advances in drug delivery techniques and nanotechnology have allowed for new formulations of old drugs, so as to improve the pharmacokinetics, to enhance accumulation in solid tumors, and to reduce the significant toxic effects of these important therapeutic agents. Here, we review the published clinical data in cancer therapy of several major drug delivery systems, including targeted radionuclide therapy, antibody-drug conjugates, liposomes, polymer-drug conjugates, polymer implants, micelles, and nanoparticles. The clinical outcomes of these delivery systems from various phases of clinical trials are summarized. The success and limitations of the drug delivery strategies are discussed based on the clinical observations. In addition, the challenges in applying drug delivery for efficacious cancer therapy, including physical barriers, tumor heterogeneity, drug resistance, and metastasis, are discussed along with future perspectives of drug delivery in cancer therapy. In doing so, we intend to underscore that efficient delivery of cancer therapeutics to solid malignancies remains a major challenge in cancer therapy, and requires a multidisciplinary approach that integrates knowledge from the diverse fields of chemistry, biology, engineering, and medicine. The overall objective of this review is to improve our understanding of the clinical fate of commonly investigated drug delivery strategies, and to identify the limitations that must be addressed in future drug delivery strategies, toward the pursuit of curative therapies for cancer.

UTMD-Promoted Co-Delivery of Gemcitabine and miR-21 Inhibitor by Dendrimer-Entrapped Gold Nanoparticles for Pancreatic Cancer Therapy

Conventional chemotherapy of pancreatic cancer (PaCa) suffers the problems of low drug permeability and inherent or acquired drug resistance. Development of new strategies for enhanced therapy still remains a great challenge. Herein, we report a new ultrasound-targeted microbubble destruction (UTMD)-promoted delivery system based on dendrimer-entrapped gold nanoparticles (Au DENPs) for co-delivery of gemcitabine (Gem) and miR-21 inhibitor (miR-21i).

Methods: In this study, Gem-Au DENPs/miR-21i was designed and synthesized. The designed polyplexes were characterized via transmission electron microscopy (TEM), Gel retardation assay and dynamic light scattering (DLS). Then, the optimum exposure parameters were examined by an ultrasound exposure platform. The cellular uptake, cytotoxicity and anticancer effects in vitro were analyzed by confocal laser microscopy, spectra microplate reader, flow cytometry and a chemiluminescence imaging system. Lastly, the anticancer effects in vivo were evaluated by contrast-enhanced ultrasound (CEUS), hematoxylin and eosin (H&E) staining, TUNEL staining and comparison of tumor volume.

Results: The results showed that the Gem-Au DENPs/miR-21i can be uptake by cancer cells and the cellular uptake was further facilitated by UTMD with an ultrasound power of 0.4 W/cm² to enhance the cell permeability. Further, the co-delivery of Gem and miR-21i with or without UTMD treatment displayed 82-fold and 13-fold lower IC50 values than the free Gem, respectively. The UTMD-promoted co-delivery of Gem and miR-21i was further validated by in vivo treatment and showed a significant tumor volume reduction and an increase in blood perfusion of xenografted pancreatic tumors.

Conclusion: The co-delivery of Gem and miR-21i using Au DENPs can be significantly promoted by UTMD technology, hence providing a promising strategy for effective pancreatic cancer treatments.

Co-delivery of doxorubicin and shRNA of Beclin1 by folate receptor targeted pullulan-based multifunctional nanomicelles for combinational cancer therapy

Doxorubicin (DOX) is a widely-used effective antitumor agent. However, its clinical application is limited due to its side effects including anti-apoptotic defense of cancer cells caused by DOX-induced autophagy and deleterious effects in normal tissues. Therefore, in this study, a new folate (FA)-decorated amphiphilic bifunctional pullulan-based copolymer (named as FPDP) was developed as an efficient nano-carrier for the co-delivery of DOX and short hairpin RNA of Beclin1, a pivotal autophage-related gene, to enhance the anticancer effect of DOX by the blockade of the Beclin1 protein mediated autophagy process. In FPDP molecules, pullulan was modified with lipophilic desoxycholic acid for the formation of micelles, the introduced low molecular weight (1 kDa) branched polyethylenimine (PEI) was for shBeclin1 delivery, and folate (FA) was employed as the tumor-targeting group. FPDP micelles demonstrated an average diameter of 161.9 nm, good biocompatibility, applicable storage stability, excellent loading capacities for both DOX and shBeclin1 and a sustained drug release profile. In vitro cell culture experiments demonstrated that the uptake amount of FPDP/DOX micelles in folate receptor positive (FR⁺) HeLa cells was more than that in folate receptor negative (FR⁻) HepG2 cells, leading to significantly higher cytotoxicity against FR⁺ HeLa cells. The simultaneous co-delivery of shBeclin1 and DOX to HeLa cells with FPDP micelles led to efficient reduction in the expression level of Beclin1 as well as synergistic cell apoptotic induction. Furthermore, in vivo studies revealed superior antitumor efficacy of tumor-targeted FPDP/DOX/shBeclin1 in comparison with non-FR-targeted PDP micelles and free DOX. These results highlighted that co-delivery of DOX and shRNA of Beclin1 with FPDP micelles has the potential to overcome the limitations of DOX in clinical cancer therapy.

New folate receptor targeted nano-micelles enhanced the anticancer effect of doxorubicin by shBeclin1 with the blockade of the autophagy process.

Enhanced Intestinal Permeability of Bufalin by a Novel Bufalin-Peptide-Dendrimer Inclusion through Caco-2 Cell Monolayer

Bufalin (BFL) has excellent physiological activities such as defending tumors, improving cardiac function, and so on. However, due to its poor water-solubility and bioavailability, the clinical application of BFL remains limited. In order to improve bioavailability of BFL, in our previous research, a novel peptide-dendrimer (PD) was synthesized and applied to encapsulate BFL. In the present study, we investigate the absorption property and mechanism of BFL in free form and BFL-peptide-dendrimer inclusion (BPDI) delivery system by using the Caco-2 cell monolayer model in vitro. The apparent permeability coefficient (P_app) values of BFL in free or BPDI form were over 1.0 × 10⁻⁶ cm/s. Meanwhile, their almost equal bi-directional transport and linear transport percentage with time and concentration course indicated that BFL in both forms was absorbed mainly through passive diffusion. The most important result is that the P_app values of BFL increased about three-fold more BPDI than those of its free form, which indicated the intestinal permeability of BFL could be improved while BFL was encapsulated in BPDI form. Therefore, PD encapsulation may be a potential delivery system to increase the bioavailability of BFL.

Recent advances in co-delivery systems based on polymeric nanoparticle for cancer treatment

Cancer is a broad term for a class of prevalent diseases as one in three people develop cancer during their lifetime. Although, there are few success stories of cancer therapy, most of the existing medications do not lead to complete recovery. Because of the complexity of cancer, usually a single therapeutic approach is insufficient for the suppression of cancer growth and metastasis. Simultaneous loading and co-delivery of different agents with different physiochemical characteristics to the same tumors have been suggested for minimizing the dose of anticancer drugs and achieving the synergistic therapeutic impacts in cancers treatment. Intense work to develop nanotechnology-based systems as a suitable option for cancer treatment is currently underway. The purpose of this review is to provide an overview of the co-delivery systems based on polymeric nanoparticles including polymeric micelles, dendrimers, poly-d,l-lactide-co-glycolide, polyethylenimine, poly(l-lysine) and chitosan for efficacious cancer therapy.

Function Oriented Molecular Design: Dendrimers as Novel Antimicrobials

In recent years innovative nanostructures are attracting increasing interest and, among them, dendrimers have shown several fields of application. Dendrimers can be designed and modified in plentiful ways giving rise to hundreds of different molecules with specific characteristics and functionalities. Biomedicine is probably the field where these molecules find extraordinary applicability, and this is probably due to their multi-valency and to the fact that several other chemicals can be coupled to them to obtain desired compounds. In this review we will describe the different production strategies and the tools and technologies for the study of their characteristics. Finally, we provide a panoramic overview of their applications to meet biomedical needs, especially their use as novel antimicrobials.

Peptide ligand-modified nanomedicines for targeting cells at the tumor microenvironment

Since their initial discovery more than 30years ago, tumor-homing peptides have become an increasingly useful tool for targeted delivery of therapeutic and diagnostic agents into tumors. Today, it is well accepted that cells at the tumor microenvironment (TME) contribute in many ways to cancer development and progression. Tumor-homing peptide-decorated nanomedicines can interact specifically with surface receptors expressed on cells in the TME, improve cellular uptake of nanomedicines by target cells, and impair tumor growth and progression. Moreover, peptide ligand-modified nanomedicines can potentially accumulate in the target tissue at higher concentrations than would small conjugates, thus increasing overall target tissue exposure to the therapeutic agent, enhance therapeutic efficacy and reduce side effects. This review describes the most studied peptide ligands aimed at targeting cells in the TME, discusses major obstacles and principles in the design of ligands for drug targeting and provides an overview of homing peptides in ligand-targeted nanomedicines that are currently in development for cancer therapy and diagnosis.

Angiogenesis regulation by nanocarriers bearing RNA interference

Since the approval of bevacizumab as anti-angiogenic therapy in 2004 by the FDA, an array of angiogenesis inhibitors have been developed and approved. However, results were disappointing with regard to their therapeutic efficacy. RNA interference approaches offer the possibility of rational design with high specificity, lacking in many current drug treatments for various diseases including cancer. However, in vivo delivery issues still represent a significant obstacle for widespread clinical applications. In the current review, we summarize the advances in the last decade in the field of angiogenesis-targeted RNA interference approaches, with special emphasis on oncology applications. We present pro-angiogenic and anti-angiogenic factors as potential targets, experimental evidence and clinical trials data on angiogenesis regulation by RNA interference. Consequent challenges and opportunities are discussed.

Photosensitizer (PS)/polyhedral oligomeric silsesquioxane (POSS)-crosslinked nanohybrids for enhanced imaging-guided photodynamic cancer therapy

Photodynamic therapy (PDT) has drawn extensive attention as a promising cancer treatment modality. However, most PDT nanoagents suffer from insufficient drug loading capacity, a severe self-quenching effect, premature release of drugs and/or potential toxicity. Herein, we rationally designed an inorganic-organic nanohybrid with high drug loading capacity and superior chemical stability for enhanced PDT. Polyhedral oligomeric silsesquioxane (POSS), an amine-containing cage-shaped building block, was crosslinked with chlorin e6 (Ce6), a carboxyl-containing photosensitizer, via the amine-carboxyl reaction. Polyethylene glycol (PEG) polymers were further modified on the surface of the nanoparticle to improve the aqueous dispersibility and prolong the circulation time of the final nanoconstruct (POSS-Ce6-PEG). The as-prepared POSS-Ce6-PEG has a considerably high loading rate of Ce6 (19.8 wt%) with desirable fluorescence emission and singlet oxygen generation. Besides, in vitro experiments revealed that the nanoagent exhibited enhanced cellular uptake and a preferred intracellular accumulation within mitochondria and the endoplasmic reticulum, resulting in high anticancer efficiency under light irradiation. Furthermore, in vivo imaging-guided PDT was also successfully achieved, showing the effective tumor targeting and ablation ability of POSS-Ce6-PEG. More importantly, the nanoagent possesses negligible dark cytotoxicity and systemic side effects. Therefore, POSS-Ce6-PEG as an eligible PDT theranostic agent holds great potential in clinical applications.

Dendrimers as Nanocarriers for Nucleic Acid and Drug Delivery in Cancer Therapy

Dendrimers are highly branched polymers with easily modifiable surfaces. This makes them promising structures for functionalization and also for conjugation with drugs and DNA/RNA. Their architecture, which can be controlled by different synthesis processes, allows the control of characteristics such as shape, size, charge, and solubility. Dendrimers have the ability to increase the solubility and bioavailability of hydrophobic drugs. The drugs can be entrapped in the intramolecular cavity of the dendrimers or conjugated to their functional groups at their surface. Nucleic acids usually form complexes with the positively charged surface of most cationic dendrimers and this approach has been extensively employed. The presence of functional groups in the dendrimer's exterior also permits the addition of other moieties that can actively target certain diseases and improve delivery, for instance, with folate and antibodies, now widely used as tumor targeting strategies. Dendrimers have been investigated extensively in the medical field, and cancer treatment is one of the greatest areas where they have been most used. This review will consider the main types of dendrimer currently being explored and how they can be utilized as drug and gene carriers and functionalized to improve the delivery of cancer therapy.

Unusual Enhancement of Doxorubicin Activity on Co-Delivery with Polyhedral Oligomeric Silsesquioxane (POSS)

Polyhedral oligomeric silsesquioxane (POSS), bearing eight 3-chloroammoniumpropyl substituents, was studied as a potential nanocarrier in co-delivery systems with doxorubicin (DOX). The toxicity of doxorubicin and POSS:DOX complexes at four different molar ratios (1:1; 1:2, 1:4, 1:8) towards microvascular endothelial cells (HMEC-1), breast cancer cells (MCF-7), and human cervical cancer endothelial cells (HeLa) was determined. The rate of penetration of the components into the cells, their cellular localization and the hydrodynamic diameter of the complexes was also determined. A cytotoxicity profile of POSS:DOX complexes indicated that the POSS:DOX system at the molar ratio of 1:8 was more effective than free DOX. Confocal images showed that DOX co-delivery with POSS allowed for more effective penetration of doxorubicin through the cell membrane. Taking all the results into account, it can be claimed that the polyhedral oligomeric silsesquioxane (T₈-POSS) is a promising, complex nanocarrier for doxorubicin delivery.

pH-triggered degradable polymeric micelles for targeted anti-tumor drug delivery

2-(Octadecyloxy)-1,3-dioxan-5-amine (OD) with an acid degradable ortho ester group was synthesized, and conjugated to hyaluronic acid (HA) backbone to prepare pH-responsive and tumor-targeted hyaluronic acid-2-(octadecyloxy)-1,3-dioxan-5-amine (HOD) conjugates. ¹H NMR was used to confirm the structures of the OD and HOD. The studies of pH-responsive behavior showed that HOD micelles were stable under physiological conditions while they were degraded in the tumor acidic microenvironment. Doxorubicin (DOX)-loaded HOD micelles (DOX/HOD) with a narrow size distribution were prepared and characterized. The increased release of DOX from DOX/HOD micelles was presented at low pH condition. From in vitro cytotoxicity assays against MCF-7 cells, the blank micelles exhibited low cytotoxicity, but DOX/HOD micelles had the higher cytotoxicity than pH insensitive control and free DOX. Cellular uptake experiments and confocal images demonstrated that pH-sensitive DOX/HOD micelles could be internalized efficiently by CD44 receptor mediated endocytosis, and then DOX was rapidly released due to pH-induced degradable of OD to cell nucleus compared to the non-sensitive micelles. Furthermore, endocytosis inhibition studies presented that DOX/HOD micelles were internalized into cells mainly via caveolae-mediated routes. In vivo study of micelles in tumor-bearing mice indicates that HOD micelles were more effectively accumulated into the tumor tissue than HOA micelles. These results verify that the pH-sensitive HOD micellar system is a promising nanocarrier for enhanced internalization of antitumor drugs to cancer cells.

Nanomedicine and cancer immunotherapy: focus on indoleamine 2,3-dioxygenase inhibitors

Nanomedicine application in cancer immunotherapy is currently one of the most challenging areas in cancer therapeutic intervention. Innovative solutions have been provided by nanotechnology to deliver cytotoxic agents to the cancer cells partially affecting the healthy cells of the body during the process. Nanoparticle-based drug delivery is an emerging approach to stimulate the immune responses against cancer. The inhibition of indoleamine 2,3-dioxygenase (IDO) is a pivotal area of research in cancer immunotherapy. IDO is a heme-containing immunosuppressive enzyme, which is responsible for the degradation of tryptophan while increasing the concentration of kynurenine metabolites. Various preclinical studies showed that IDO inhibition in certain diseases may result in significant therapeutic effects. Here, we provide a review of the natural and synthetic inhibitors of IDO. These inhibitors are classified according to their source, inhibitory concentrations, the chemical structure, and the mechanism of action. Tumor-targeted chemotherapy is an advanced technique and has more advantages as compared to the conventional chemotherapy. Search for more efficient and less toxic nanoparticles in conjunction with compounds to inhibit IDO is still an area of interest for several research groups worldwide, especially revealing to be an extensive and a promising area in cancer therapeutic innovations.

First step towards a model system of the drug delivery network based on amide-POSS nanocarriers

We present the synthetic and release aspects of a novel drug delivery system (DDS) based on amido-functionalized POSS. DDS after drug release hydrolyses at pH = 7.40 to non-toxic products such as carboxylic acid salts and aminopropyl-POSS.

Co-delivery of antineoplastic and protein drugs by chitosan nanocapsules for a collaborative tumor treatment

Although combination delivery (co-delivery) shows much superiority in the defect compensation of single-agent therapy, the construction and application of co-delivery systems are still challenging, especially for protein-based joint systems. In this work, a series of chitosan (CS)-amino acid derivatives (Arg-CS, Lys-CS, and Phe-CS) with different degrees of substitution (DS) were synthesized to prepare CS nanocapsules (CNCs) using a simple emulsification method in the presence of linoleic acid (LA). The hydrophobic drug can be loaded in LA droplets, and a positively charged protein stabilized the optimized Arg-CS nanocapsules (Arg-CNCs) on their negative surfaces. The in vitro antitumor efficacy of Arg-CNCs co-delivering paclitaxel and recombinant human caspase-3 was evaluated in HeLa cells. The co-delivery system displayed much lower IC₅₀ values and a higher percentage of apoptotic cells compared with the control groups. This system provides a promising and universal strategy for co-delivery, leading to collaborative tumor treatment.

Efficient delivery of therapeutic siRNA into glioblastoma cells using multifunctional dendrimer-entrapped gold nanoparticles

AIM

To synthesize the arginine-glycine-aspartic (RGD) functionalized dendrimer-entrapped gold nanoparticles (Au DENPs) for siRNA delivery to induce gene silencing of cancer cells in vitro and in vivo.

MATERIALS & METHODS

Au DENPs modified with RGD peptide via a polyethylene glycol spacer were used as a vector of two distinct small interfering RNAs (siRNAs) (VEGFvascular endothelial growth factor siRNA and B-cell lymphoma/leukemia-2 siRNA), and the physicochemical properties, cytocompatibility and transfection efficiency of Au DENP/siRNA polyplexes were characterized.

RESULTS

The Au DENP/siRNA polyplexes with good cytocompatibility and highly efficient transfection capacity can be used for the transfection of siRNAs.

CONCLUSION

The developed functional RGD-modified Au DENPs may be used for efficient gene therapy of different types of cancer.

Nano-structures mediated co-delivery of therapeutic agents for glioblastoma treatment: A review

Glioblastoma is a malignant brain tumor and leads to death in most patients. Chemotherapy is a common method for brain cancer in clinics. However, the recent advancements in the chemotherapy of brain tumors have not been efficient enough. With the advancement of nanotechnology, the used drugs can enhance chemotherapy efficiency and increase the access to brain cancers. Combination of therapeutic agents has been recently attracted great attention for glioblastoma chemotherapy. One of the early benefits of combination therapies is the high potential to provide synergistic effects and decrease adverse side effects associated with high doses of single anticancer drugs. Therefore, brain tumor treatments with combination drugs can be considered as a crucial approach for avoiding tumor growth. This review investigates current progress in nano-mediated co-delivery of therapeutic agents with focus on glioblastoma chemotherapy prognosis.

RNAi therapeutics for brain cancer: current advancements in RNAi delivery strategies

Malignant primary brain tumors are aggressive cancerous cells that invade the surrounding tissues of the central nervous system. The current treatment options for malignant brain tumors are limited due to the inability to cross the blood-brain barrier. The advancements in current research has identified and characterized certain molecular markers that are essential for tumor survival, progression, metastasis and angiogenesis. These molecular markers have served as therapeutic targets for the RNAi based therapies, which enable site-specific silencing of the gene responsible for tumor proliferation. However, to bring about therapeutic success, an efficient delivery carrier that can cross the blood-brain barrier and reach the targeted site is essential. The current review focuses on the potential of targeted, non-viral and viral particles containing RNAi therapeutic molecules as delivery strategies specifically for brain tumors.

Star-Shaped Amphiphilic Hyperbranched Polyglycerol Conjugated with Dendritic Poly(l-lysine) for the Codelivery of Docetaxel and MMP-9 siRNA in Cancer Therapy

The drug/gene codelivery is a promising strategy for cancer treatment. Herein, to realize the codelivery of docetaxel and MMP-9 siRNA plasmid efficiently into tumor cells, a star-shaped amphiphilic copolymer consisting of hyperbranched polyglycerol derivative (HPG-C18) and dendritic poly(l-lysine) (PLLD) was synthesized by the click reaction between azido-modified HPG-C18 and propargyl focal point PLLD. The obtained HPG-C18-PLLD could form the nanocomplexes with docetaxel and MMP-9, and the complexes showed good gene delivery ability in vitro by inducing an obvious decrease in MMP-9 protein expression in MCF-7 cells. The apoptosis assay showed that the complex could induce a more significant apoptosis to breast cancer cells than that of docetaxel or MMP-9 used alone. In vivo assay indicated that the codelivery strategy displayed a better effect on tumor inhibition. Moreover, HPG-C18-PLLD displayed lower toxicity as well as better blood compatibility compared to polyethylenimine PEI-25k, which may be the result of that HPG-C18-PLLD showed the comparative MMP-9 delivery ability in vivo compared with PEI-25k even if it showed the slight lower transfection efficiency in vitro. Therefore, HPG-C18-PLLD is a safe and effective carrier for the codelivery of drug/gene, which should be encouraged in tumor therapy.