Doxorubicin-loaded redox-responsive micelles based on dextran and indomethacin for resistant breast cancer

Dextran-based Drug Delivery Approaches for Lung Diseases: A Review

Respiratory disorders, such as tuberculosis, cystic fibrosis, chronic obstructive pulmonary disease, asthma, lung cancer, and pulmonary inflammation, are among the most prevalent ailments in today's world. Dextran, an exopolysaccharide formed by Leuconostoc mesenteroides (slimeproducing bacteria), and its derivatives are investigated for several therapeutic utilities. Dextranbased drug delivery system can become an innovative strategy in the treatment of several respiratory ailments as it offers numerous advantages, such as mucolytic action, airway hydration, antiinflammatory properties, and radioprotective effect as compared to other polysaccharides. Being biocompatible, flexible hydrophilic nature, biodegradable, tasteless, odourless, non-mutagenic, watersoluble and non-toxic edible polymer, dextran-based drug delivery systems have been explored for a wide range of therapeutic applications, especially in lungs and respiratory diseases. The present article comprehensively discusses various derivatives of dextran with their attributes to be considered for drug delivery and extensive therapeutic benefits, with a special emphasis on the armamentarium of dextran-based formulations for the treatment of respiratory disorders and associated pathological conditions. The information provided will act as a platform for formulation scientists as important considerations in designing therapeutic approaches for lung and respiratory diseases. With an emphasis on lung illnesses, this article will offer an in-depth understanding of dextran-based delivery systems in respiratory illnesses.

Indomethacin Induces Spermidine/Spermine-N1-Acetyltransferase-1 via the Nucleolin-CDK1 Axis and Synergizes with the Polyamine Oxidase Inhibitor Methoctramine in Lung Cancer Cells

Indomethacin is a non-selective NSAID used against pain and inflammation. Although cyclooxygenase (COX) inhibition is considered indomethacin's primary action mechanism, COX-independent ways are associated with beneficial effects in cancer. In colon cancer cells, the activation of the peroxisome proliferator-activated receptor-γ (PPAR-γ) is related to the increase in spermidine/spermine-N1-acetyltransferase-1 (SSAT-1), a key enzyme for polyamine degradation, and related to cell cycle arrest. Indomethacin increases the SSAT-1 levels in lung cancer cells; however, the mechanism relying on the SSAT-1 increase is unclear. Thus, we asked for the influence of the PPAR-γ on the SSAT-1 expression in two lung cancer cell lines: H1299 and A549. We found that the inhibition of PPAR-γ with GW9662 did not revert the increase in SSAT-1 induced by indomethacin. Because the mRNA of SSAT-1 suffers a pre-translation retention step by nucleolin, a nucleolar protein, we explored the relationship between indomethacin and the upstream translation regulators of SSAT-1. We found that indomethacin decreases the nucleolin levels and the cyclin-dependent kinase 1 (CDK1) levels, which phosphorylates nucleolin in mitosis. Overexpression of nucleolin partially reverts the effect of indomethacin over cell viability and SSAT-1 levels. On the other hand, Casein Kinase, known for phosphorylating nucleolin during interphase, is not modified by indomethacin. SSAT-1 exerts its antiproliferative effect by acetylating polyamines, a process reverted by the polyamine oxidase (PAOX). Recently, methoctramine was described as the most specific inhibitor of PAOX. Thus, we asked if methoctramine could increase the effect of indomethacin. We found that, when combined, indomethacin and methoctramine have a synergistic effect against NSCLC cells in vitro. These results suggest that indomethacin increases the SSAT-1 levels by reducing the CDK1-nucleolin regulatory axis, and the PAOX inhibition with methoctramine could improve the antiproliferative effect of indomethacin.

Advancements in dextran-based nanocarriers for treatment and imaging of breast cancer

Breast cancer is the most prevalent type of cancer worldwide,particularly among women, with substantial side effects after therapy. Despite the availability of numerous therapeutic approaches, particularly chemotherapy, the survival rates for breast cancer have declined over time. The therapies currently utilized for breast cancer treatment do not specifically target cancerous cells, resulting in significant adverse effects and potential harm to healthy cells alongside the cancer cells. As a result, nanoparticle-based drug delivery systems have emerged. Among various types of nanoparticles, natural polysaccharide-based nanoparticles have gained significant attention due to their ability to precisely control the drug release and achieve targeted drug delivery. Moreover, polysaccharides are biocompatible, biodegradable, easily modifiable, and renewable, which makes them a unique material for nanoformulation. In recent years, dextran and its derivatives have gained much interest in the field of breast cancer therapy. Dextran is a hydrophilic polysaccharide composed of a main chain formed by α-1,6 linked glucopyranoside residues and a side chain composed of residues linked in α-1,2/3/4 positions. Different dextran-antitumor medication conjugates enhancethe efficacy of anticancer agents. With this context, the present review provides brief insights into dextran and its modification. Further, it meticulously discusses the role of dextran-based nanoparticles in breast cancer therapy and imaging, followed by snippets on their toxicity. Lastly, it presents clinical trials and future perspectives of dextran-based nanoparticles in breast cancer treatment.

Traversing the diverse avenues of exopolysaccharides-based nanocarriers in the management of cancer

Exopolysaccharides are unique polymers generated by living organisms such as algae, fungi and bacteria to protect them from environmental factors. After a fermentative process, these polymers are extracted from the medium culture. Exopolysaccharides have been explored for their anti-viral, anti-bacterial, anti-tumor, and immunomodulatory effects. Specifically, they have acquired massive attention in novel drug delivery strategies owing to their indispensable properties like biocompatibility, biodegradability, and lack of irritation. Exopolysaccharides such as dextran, alginate, hyaluronic acid, pullulan, xanthan gum, gellan gum, levan, curdlan, cellulose, chitosan, mauran, and schizophyllan exhibited excellent drug carrier properties. Specific exopolysaccharides, such as levan, chitosan, and curdlan, have demonstrated significant antitumor activity. Moreover, chitosan, hyaluronic acid and pullulan can be employed as targeting ligands decorated on nanoplatforms for effective active tumor targeting. This review shields light on the classification, unique characteristics, antitumor activities and nanocarrier properties of exopolysaccharides. In addition, in vitro human cell line experiments and preclinical studies associated with exopolysaccharide-based nanocarriers have also been highlighted.

Doxorubicin-loaded micelles in tumor cell-specific chemotherapy

Nanomedicine is a field that combines biology and engineering to improve disease treatment, particularly in cancer therapy. One of the promising techniques utilized in this area is the use of micelles, which are nanoscale delivery systems that are known for their simple preparation, high biocompatibility, small particle size, and the ability to be functionalized. A commonly employed chemotherapy drug, Doxorubicin (DOX), is an effective inhibitor of topoisomerase II that prevents DNA replication in cancer cells. However, its efficacy is frequently limited by resistance resulting from various factors, including increased activity of drug efflux transporters, heightened oncogenic factors, and lack of targeted delivery. This review aims to highlight the potential of micelles as new nanocarriers for delivering DOX and to examine the challenges involved with employing chemotherapy to treat cancer. Micelles that respond to changes in pH, redox, and light are known as stimuli-responsive micelles, which can improve the targeted delivery of DOX and its cytotoxicity by facilitating its uptake in tumor cells. Additionally, micelles can be utilized to administer a combination of DOX and other drugs and genes to overcome drug resistance mechanisms and improve tumor suppression. Furthermore, micelles can be used in phototherapy, both photodynamic and photothermal, to promote cell death and increase DOX sensitivity in human cancers. Finally, the alteration of micelle surfaces with ligands can further enhance their targeted delivery for cancer suppression.

Construction of poly(amino acid)s nano-delivery system and sustained release with redox-responsive

A series of novel poly(amino acid)s materials were designed to prepare drug-loaded nanoparticles by physical encapsulation and chemical bonding. The side chain of the polymer contains a large number of amino groups, which effectively increases the loading rate of doxorubicin (DOX). The structure contains disulfide bonds that showing a strong response to the redox environment, which can achieve targeted drug release in the tumor microenvironment. Nanoparticles mainly present spherical morphology with the suitable size for participating in systemic circulation. cell experiments demonstrate the non-toxicity and good cellular uptake behavior of polymers. In vivo anti-tumor experiments shows nanoparticles could inhibit tumor growth and effectively reduce the side effects of DOX.

Docetaxel-loaded redox-sensitive nanoparticles self-assembling from poly(caprolactone) conjugates with disulfide-linked poly(ethylene glycol)

In this study, novel redox-sensitive nanoparticles (NPs) were fabricated from the poly(caprolactone) conjugates with disulfide-linked poly(ethylene glycol) (DDMAT- mPEG-S-S-PCL, DPSP). The DPSP polymer was synthesized by ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. The obtaining of the DPSP polymer was confirmed by the ¹H nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy (FTIR) spectra. The DPSP NPs were fabricated with the solvent-evaporation method. Docetaxel (DTX) was employed as a model drug and encapsulated into the DPSP NPs. The in vitro anti-tumor activity of the DTX-loaded DPSP NPs and free DTX against the breast cancer cells (4T1) were evaluated by MTT assay. The cargo-free DPSP NPs were in circular shapes with an average diameter of 107.8 ± 0.4 nm. These NPs displayed redox-responsive behavior in the presence of glutathione. Animal experiments indicated that the DPSP NPs showed excellent blood compatibility and good bio-security. Cell tests suggested that the DPSP NPs could be taken in by 4T1 cells, smoothly, which improved the anti-tumor activity of free DTX.

Advancements in redox-sensitive micelles as nanotheranostics: A new horizon in cancer management

World Health Organisation (WHO) delineated cancer as one of the foremost reasons for mortality with 10 million deaths in the year 2020. Early diagnosis and effective drug delivery are of utmost importance in cancer management. The entrapment of both bio-imaging dyes and drugs will open novel avenues in the area of tumor theranostics. Elevated levels of reactive oxygen species (ROS) and glutathione (GSH) are the characteristic features of the tumor microenvironment (TME). Researchers have taken advantage of these specific TME features in recent years to develop micelle-based theranostic nanosystems. This review focuses on the advantages of redox-sensitive micelles (RSMs) and supramolecular self-assemblies for tumor theranostics. Key chemical linkers employed for the tumor-specific release of the cargo have been discussed. In vitro characterisation techniques used for the characterization of RSMs have been deliberated. Potential bottlenecks that may present themselves in the bench-to-bedside translation of this technology and the regulatory considerations have been deliberated.

Co-encapsulation of flavonoids with anti-cancer drugs: a challenge ahead

Flavonoids have been considered as promising molecules for cancer treatment due to their pleiotropic properties such as anti-carcinogenic, anti-angiogenic or efflux proteins inhibition. However, due to their lipophilic properties and their chemical instability, vectorization seems compulsory to administer flavonoids. Flavonoids have been co-encapsulated with other anti-cancer agents in a broad range of nanocarriers aiming to i) achieve a synergistic/additive effect at the tumor site, ii) delay drug resistance apparition by combining agents with different action mechanisms or iii) administer a lower dose of the anti-cancer drug, reducing its toxicity. However, co-encapsulation could lead to a change in the nanoparticles' diameter and drug-loading, as well as a decrease in their stability during storage. The preparation process should also take into accounts the physico-chemical properties of both the flavonoid and the anti-cancer agent. Moreover, the co-encapsulation could affect the release and activity of each drug. This review aims to study the formulation, preparation and characterization strategies of these co-loaded nanomedicines, as well as their stability. The in vitro assays to predict the nanomedicines' behavior in biological fluids, as well as their in vivo efficacy, are also discussed. A special focus concerns the evaluation of their synergistic effect on tumor treatment.

Bioreducible polyethylenimine core-shell nanostructures as efficient and non-toxic gene and drug delivery vectors

Low molecular weight branched polyethylenimine (LMW bPEIs 1.8 kDa) have received considerable attention for the fabrication of nucleic acid carriers due to their biocompatible and non-toxic nature. However, due to the inadequate nucleic acid complexation ability and transportation across the cell membrane, these show poor transfection efficacy, limiting their clinical applications. Therefore, to overcome these challenges, in this study, we have grafted bPEI 1.8 kDa with a disulfide bond containing hydrophobic moiety, 3-(2-pyridyldithio) propionic acid (PDPA), via amide linkages through EDC/NHS-mediated coupling to obtain N-[3-(2-pyridyldithio)] propionoyl polyethylenimine (PDPP) conjugates. The best formulation for nucleic acid transfection was evaluated after preparing a series of PDPP conjugates by varying the amount of PDPA. In an aqueous environment, these PDPP conjugates self-assembled to form spherical shaped core-shell PDPP nanostructures with size ranging from ∼188-307 nm and zeta-potential from ∼ +3 to +19 mV. The positively charged surface of the core-shell nanocomposites helps in the binding of plasmid DNA (pDNA), its transportation inside the cell, and protection against enzymes. Evaluation of PDPP/pDNA complexes on mammalian cells revealed that all these complexes showed significantly improved transfection efficacy without hampering cytocompatibility. Amongst all, the pDNA complex of PDPP-2 exhibited the best transfection efficiency (i.e. >6-fold) in comparison to pDNA complex of the native bPEI. The nanocomposites exhibited the redox responsive behavior advantageous for therapeutic delivery to the tumor cells. The core of the nanostructures facilitate the encapsulation of a hydrophobic model drug, ornidazole. In vitro drug release analysis showed a faster release rate in response to a reductant mimicking the cellular environment. Altogether, these nanostructures have great potential to co-deliver both drug and gene simultaneously in response to tumor cell reductive microenvironment in vitro and could be used as the next-generation delivery system.

Solid-Phase Synthesized Copolymers for the Assembly of pH-Sensitive Micelles Suitable for Drug Delivery Applications

Diblock copolymers of polyhistidine are known for their self-assembly into micelles and their pH-dependent disassembly due to the amphiphilic character of the copolymer and the unsaturated imidazole groups that undergo a hydrophobic-to-hydrophilic transition in an acidic pH. This property has been largely utilized for the design of drug delivery systems that target a tumor environment possessing a slightly lower extracellular pH (6.8–7.2). The main purpose of this study was to investigate the possibility of designed poly(ethylene glycol)-polyhistidine sequences synthesized using solid-phase peptide synthesis (SPPS), to self-assemble into micelles, to assess the ability of the corresponding micelles to be loaded with doxorubicin (DOX), and to investigate the drug release profile at pH values similar to a malignant extracellular environment. The designed and assembled free and DOX-loaded micelles were characterized from a physico-chemical point of view, their cytotoxicity was evaluated on a human breast cancer cell line (MDA-MB-231), while the cellular areas where micelles disassembled and released DOX were assessed using immunofluorescence. We concluded that the utilization of SPPS for the synthesis of the polyhistidine diblock copolymers yielded sequences that behaved similarly to the copolymeric sequences synthesized using ring-opening polymerization, while the advantages of SPPS may offer facile tuning of the histidine site or the attachment of a large variety of functional molecules.

Two-Pronged Anti-Tumor Therapy by a New Polymer-Paclitaxel Conjugate Micelle with an Anti-Multidrug Resistance Effect

Introduction

Cancerous tumors are still a major disease that threatens human life, with tumor multidrug resistance (MDR) being one of the main reasons for the failure of chemotherapy. Thus, reversing tumor MDR has become a research focus of medical scientists.

Methods

Here, a reduction-sensitive polymer prodrug micelle, mPEG-DCA-SS-PTX (PDSP), was manufactured with a new polymer inhibitor of drug resistance as a carrier to overcome MDR and improve the anti-tumor effect of PTX.

Results

The PDSP micelles display good stability, double-responsive drug release, and excellent biocompatibility. The PDSP micelles reduced the cytotoxicity of PTX to normal HL-7702 cells and enhanced that to SMMC-7721 and MCF-7 cells in vitro. Improved sensitivity of A549/ADR to PDSP was also observed in vitro. Furthermore, in vivo experiments show reduced systemic toxicity and enhanced therapeutic efficacy of PTX to H22 subcutaneous tumor-bearing mice.

Conclusion

This work proves that the reduction-sensitive polymer prodrug micelles carried by the new polymer inhibitor can be used as an alternative delivery system to target tumors and reverse MDR for paclitaxel and other tumor-resistant drugs.

Co-delivery of doxorubicin and SIS3 by folate-targeted polymeric micelles for overcoming tumor multidrug resistance

Multidrug resistance (MDR) is considered as a critical limiting factor for the successful chemotherapy, which is mainly characterized by the overexpression of ATP-binding cassette (ABC) transporter ABCB1 or ABCG2. In this study, folate-targeted polymeric micellar carrier was successfully constructed to co-delivery of doxorubicin (DOX) and SIS3 (FA/DOX/SIS3 micelles), a specific Smad3 inhibitor which sensitizes ABCB1- and ABCG2-overexpressing cancer cells to chemotherapeutic agents. The ratio of DOX to SIS3 in polymeric micelles was determined based on the anti-tumor activity against resistant breast cells. In addition, FA/DOX/SIS3 micelles exhibited a much longer circulation time in blood and were preferentially accumulated in resistant tumor tissue. Pharmacodynamic studies showed that FA/DOX/SIS3 micelles possessed superior anti-tumor activity than other DOX-based treatments. Overall, FA/DOX/SIS3 micelles are a promising formulation for the synergistic treatment of drug-resistant tumor.

A review of nanoparticle drug delivery systems responsive to endogenous breast cancer microenvironment

Breast cancer, as a malignant disease that seriously threatens women's health, urgently needs to be researched to develop effective and safe therapeutic drugs. Nanoparticle drug delivery systems (NDDS), provide a powerful means for drug targeting to the breast cancer, enhancing the bioavailability and reducing the adverse effects of anticancer drug. However, the breast cancer microenvironment together with heterogeneity of cancer, impedes the tumor targeting effect of NDDS. Breast cancer microenvironment, exerts endogenous stimuli, such as hypoxia, acidosis, and aberrant protease expression, shape a natural shelter for tumor growth, invasion and migration. On the basis of the ubiquitous of endogenous stimuli in the breast cancer microenvironment, researchers exploited them to design the stimuli-responsive NDDS, which response to endogenous stimulus, targeted release drug in breast cancer microenvironment. In this review, we highlighted the effect of the breast cancer microenvironment, summarized innovative NDDS responsive to the internal stimuli in the tumor microenvironment, including the material, the targeting groups, the loading drugs, targeting position and the function of stimuli-responsive nanoparticle drug delivery system. The limitations and potential applications of the stimuli-responsive nanoparticle drug delivery systems for breast cancer treatment were discussed to further the application.

Drug Resistance in Metastatic Breast Cancer: Tumor Targeted Nanomedicine to the Rescue

Breast cancer, specifically metastatic breast, is a leading cause of morbidity and mortality in women. This is mainly due to relapse and reoccurrence of tumor. The primary reason for cancer relapse is the development of multidrug resistance (MDR) hampering the treatment and prognosis. MDR can occur due to a multitude of molecular events, including increased expression of efflux transporters such as P-gp, BCRP, or MRP1; epithelial to mesenchymal transition; and resistance development in breast cancer stem cells. Excessive dose dumping in chemotherapy can cause intrinsic anti-cancer MDR to appear prior to chemotherapy and after the treatment. Hence, novel targeted nanomedicines encapsulating chemotherapeutics and gene therapy products may assist to overcome cancer drug resistance. Targeted nanomedicines offer innovative strategies to overcome the limitations of conventional chemotherapy while permitting enhanced selectivity to cancer cells. Targeted nanotheranostics permit targeted drug release, precise breast cancer diagnosis, and importantly, the ability to overcome MDR. The article discusses various nanomedicines designed to selectively target breast cancer, triple negative breast cancer, and breast cancer stem cells. In addition, the review discusses recent approaches, including combination nanoparticles (NPs), theranostic NPs, and stimuli sensitive or “smart” NPs. Recent innovations in microRNA NPs and personalized medicine NPs are also discussed. Future perspective research for complex targeted and multi-stage responsive nanomedicines for metastatic breast cancer is discussed.

A novel GSH-triggered polymeric nanomicelles for reversing MDR and enhancing antitumor efficiency of hydroxycamptothecin

Tumor multidrug resistance (MDR) is one of the main reasons for the failure of clinical chemotherapy. Here, a bio-responsive anti-drug-resistant polymer micelle that can respond to the reductive GSH in the tumor microenvironment (TME) for delivery of HCPT was designed. A new type of polymer with anti-drug resistance and anti-tumor effect was synthesized and used to encapsulated HCPT to form reduction-sensitive micelles (PDSAH) by a thin-film dispersion method. It is demonstrated that the micelle formulation improves the anti-tumor activity and biosafety of HCPT, and also plays a significant role in reversing the drug resistance, which contributes to inhibiting the tumor growth and prolonging the survival time of H22 tumor-bearing mice. The results indicate that this nanoplatform can serve as a flexible and powerful system for delivery of other drugs that are tolerated by tumors or bacteria.

Lipid Formulations and Bioconjugation Strategies for Indomethacin Therapeutic Advances

Indomethacin (IND) is a drug which after successful clinical trials became available for general prescription in 1965 and from that time is one of the most widely used anti-inflammatory drug with the highest potencies in the in vitro and in vivo models. However, despite its high therapeutic efficacy in relieving the symptoms of certain arthritis and in treating gout or collagen diseases, administration of IND causes a number of adverse effects, such as gastrointestinal ulceration, frequent central nervous system disorders and renal toxicity. These obstacles significantly limit the practical applications of IND and make that 10-20% of patients discontinue its use. Therefore, during the last three decades many attempts have been made to design novel formulations of IND aimed to increase its therapeutic benefits minimizing its adverse effects. In this review we summarize pharmacological information about IND and analyze its new lipid formulations and lipid bioconjugates as well as discuss their efficacy and potential application.

Cross Talk between COVID-19 and Breast Cancer

Cancer patients are more susceptible to COVID-19; however, the prevalence of COVID-19 in different types of cancer is still inconsistent and inconclusive. Here, we delineate the intricate relationship between breast cancer and COVID-19. Breast cancer and COVID-19 share the involvement of common comorbidities, hormonal signalling pathways, gender differences, rennin- angiotensin system (RAS), angiotensin-converting enzyme-2 (ACE-2), transmembrane protease serine 2 (TMPRSS2) and dipeptidyl peptidase-IV (DPP-IV). We also shed light on the possible effects of therapeutic modalities of COVID-19 on breast cancer outcomes. Briefly, we conclude that breast cancer patients are more susceptible to COVID-19 in comparison with their normal counterparts. Women are more resistant to the occurrence and severity of COVID-19. Increased expressions of ACE2 and TMPRSS2 are correlated with occurrence and severity of COVID-19, but higher expression of ACE2 and lower expression of TMPRSS2 are prognostic markers for overall disease free survival in breast cancer. The ACE2 inhibitors and ibuprofen therapies for COVID-19 treatment may aggravate the clinical condition of breast cancer patients through chemo-resistance and metastasis. Most of the available therapeutic modalities for COVID-19 were also found to exert positive effects on breast cancer outcomes. Besides drugs in clinical trend, TMPRSS2 inhibitors, estrogen supplementation, androgen deprivation and DPP-IV inhibitors may also be used to treat breast cancer patients infected with SARS-CoV-2. However, drug-drug interactions suggest that some of the drugs used for the treatment of COVID-19 may modulate the drug metabolism of anticancer therapies which may lead to adverse drug reaction events.

The Therapeutic Efficacy of Dendrimer and Micelle Formulations for Breast Cancer Treatment

Breast cancer is among the most common types of cancer in women and it is the cause of a high rate of mortality globally. The use of anticancer drugs is the standard treatment approach used for this type of cancer. However, most of these drugs are limited by multi-drug resistance, drug toxicity, poor drug bioavailability, low water solubility, poor pharmacokinetics, etc. To overcome multi-drug resistance, combinations of two or more anticancer drugs are used. However, the combination of two or more anticancer drugs produce toxic side effects. Micelles and dendrimers are promising drug delivery systems that can overcome the limitations associated with the currently used anticancer drugs. They have the capability to overcome drug resistance, reduce drug toxicity, improve the drug solubility and bioavailability. Different classes of anticancer drugs have been loaded into micelles and dendrimers, resulting in targeted drug delivery, sustained drug release mechanism, increased cellular uptake, reduced toxic side effects of the loaded drugs with enhanced anticancer activity in vitro and in vivo. This review article reports the biological outcomes of dendrimers and micelles loaded with different known anticancer agents on breast cancer in vitro and in vivo.

Reduction-sensitive poly(ethylene glycol)-polypeptide conjugate micelles for highly efficient intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

The non-specific biodistribution of traditional chemotherapeutic drugs against tumors is the key factor that causes systemic toxicity and hinders their clinical application. In this study, a reduction-sensitive polymer conjugate micelle was manufactured to achieve tumor-specific targeting, reduce toxic side-effects and improve anti-tumor activity of a natural anti-cancer drug, hydroxycamptothecin (HCPT). Therefore, HCPT was conjugated with methoxy-poly(ethylene glycol)-poly(β-benzyl-L-aspartate) (mPEG-PBLA) by a disulfide bond or succinate bond for the first time to obtain the mPEG-PBLA-SS-HCPT (PPSH) and mPEG-PBLA-CC-HCPT (PPCH) that would form micelles after high-speed agitation and dialysis. The PPSH micelles showed an average particle size of 126.3 nm, a low polydispersity index of 0.209, and a negative surface charge of -21.1 mV zeta potential. Transmission electron microscopy showed the PPSH micelles to have spherical morphology. PPSH had a low critical micelle concentration of 1.29 μg ml^-1 with high dilution stability, storage stability and reproducibility. Moreover, the particle size of the PPSH micelles had no significant change after incubation with rat plasma for 72 h, probably resulting in high long circulation in the blood. The PPSH micelles showed significant reduction sensitivity to glutathione. Their sizes increased by 403.2 nm after 24 h post-incubation, and 87.6% drug release was achieved 48 h post-incubation with 40 mM glutathione solutions. The PPSH micelles showed stronger inhibition of HepG2 cells in vitro and growth of H-22 tumor in vivo than the PPCH and HCPT solutions after intravenous injection. The accumulation of PPSH micelles in the tumor tissue contributed to the high anti-tumor effect with little side-effect on the normal tissues. The reduction-sensitive PPSH micelles were a promising carrier of HCPT and other poorly soluble anti-cancer drugs.

Preparation and application of dextran and its derivatives as carriers

As a natural and renewable biological macromolecule, dextran not only has excellent biodegradability, but also has good biocompatibility. Dextran and its derivatives are functional polymers for the construction of targeted drug delivery systems. Herein, the application of dextran as prodrug and nanoparticle/nanogel/microsphere/micelle carrier for targeting drug delivery system was summarized. It is clarified that dextran is an important biomaterial with application value.

Redox-Responsive Disulfide Bond-Bridged mPEG-PBLA Prodrug Micelles for Enhanced Paclitaxel Biosafety and Antitumor Efficacy

The toxicity and side effects of traditional chemotherapeutic drugs are the main causes of chemotherapy failure. To improve the specificity and selectivity of chemotherapeutic drugs for tumor cells, a novel redox-sensitive polymer prodrug, polyethylene glycol-poly (β-benzyl-L-aspartate) (PEG-PBLA)-SS-paclitaxel (PPSP), was designed and synthesized in this study. The PPSP micelle was manufactured via high-speed dispersion stirring and dialysis. The particle size and zeta potential of this prodrug micelle were 63.77 ± 0.91 nm and −25.8 ± 3.24 mV, respectively. The micelles were uniformly distributed and presented a spherical morphology under a transmission electron microscope. In the tumor physiological environment, the particle size of the PPSP micelles and the release rate of paclitaxel (PTX) were significantly increased compared with those of mPEG-PBLA-CC-PTX (PPCP) micelles, reflecting the excellent redox-sensitive activity of the PPSP micelles. The inhibitory effect of PPSP on HepG2, MCF-7 and HL-7702 cell proliferation was investigated with MTT assays, and the results demonstrated that PPSP is superior to PTX with respect to the inhibition of two tumor cell types at different experimental concentration. Simultaneously PPSP has lower toxicity against HL-7702 cells then PTX and PPCP. Moreover, the blank micelle from mPEG-PBLA showed no obvious toxicity to the two tumor cells at different experimental concentrations. In summary, the redox-sensitive PPSP micelle significantly improved the biosafety and the anti-tumor activity of PTX.

Self-Assembled Indomethacin Dimer Nanoparticles Loaded with Doxorubicin for Combination Therapy in Resistant Breast Cancer

An ortho-ester-linked indomethacin (IND) dimer-based nanodrug delivery system was prepared to improve the therapeutic effect of doxorubicin (DOX) by reversing the multidrug resistance. The synthesized dimer (IND-OE) could form stable nanoparticles (IND-OE/DOX) loaded with DOX via the single-emulsion method. Compare to insensitive nanoparticles (IND-C12/DOX), IND-OE/DOX showed a rapid degradation behavior and accelerated drug release at mildly acidic environments. In vitro cell experiments verified that IND-OE nanoparticles could increase DOX concentration due to the efficient intracellular drug release by the degradation of the ortho ester as well as reduced DOX efflux by IND-mediated P-gp downregulation. In vivo studies further demonstrated that IND-OE/DOX displayed the maximized synergetic antitumor efficacy than free DOX or IND-C12/DOX, and the tumor inhibition rates versus saline were 46.78% (free DOX), 60.23% (IND-C12/DOX), and 80.62% (IND-OE/DOX). Overall, this strategy of combination with chemosensitizers and ortho ester linkage has great potential to serve as an amplifying chemotherapy platform against various drug-resistant tumors.

A polymeric micelle with an endosomal pH-sensitivity for intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

Amphiphilic poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) and poly(ethylene glycol)-poly(benzyl-l-aspartate) (PPA) block copolymers were synthesized as pH-responsive and pH-nonresponsive copolymers, respectively. Polymer micelles were fabricated by the film dispersion method, and hydroxycamptothecin (HCPT) was physically encapsulated into the micelles. The average diameter of the HCPT-loaded PIPA micelles (PIPAH micelles) was approximately 230 nm, which was slightly smaller than that of the HCPT-loaded PPA micelles (PPAH micelles, approximately 260 nm). The drug-loading content and encapsulation efficiency of the PIPAH micelles (3.33% and 68.89%, respectively) were slightly higher than those of the PPAH micelles (2.90% and 59.68%, respectively). The PIPAH micelles exhibited better colloid stability, storage stability, and plasma stability than the PPAH micelles. Drug release from the PIPAH micelles with imino groups was pH dependent, and more than 75% or 65% of the loaded HCPT was released within 24 h in weakly acidic media (pH 5.0 or 6.0, respectively). An in vitro cell assay demonstrated that the pH-sensitive micelles exhibited potent suppression of cancer cell proliferation and little cytotoxicity on normal cells. Additionally, these micelles could be efficiently internalized by the tumor cells through macropinocytosis- and caveolin-mediated endocytotic pathways. HCPT-loaded micelles had longer circulation time than the HCPT solution in a pharmacokinetic study. In vivo antitumor experiments indicate that the PIPAH micelles had better antitumor efficacy than the pH-insensitive PPAH micelles and the HCPT solution. Therefore, the pH-responsive PIPAH micelles have great potential for high-efficiency delivery of HCPT. STATEMENT OF SIGNIFICANCE: In this study, a new type of pH-responsive amphiphilic copolymer, poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) block copolymer, was synthesized. This copolymer had then self-assembled to form nanomicelles for tumor intracellular delivery of hydroxycamptothecin (HCPT) for the first time. In in vitro test, the PIPAH micelles exhibited adequate stability and pH-dependent drug release. To one's excitement, the PIPAH micelles exhibited better antitumor efficacy and biosafety than the pH-insensitive micelles (PPAH) and the HCPT solution in in vitro and in vivo antitumor experiments. Therefore, the pH-responsive micelles in this study have significant potential to be used for high-performance delivery of HCPT and potentially for the targeted delivery of other cancer therapeutic agents. The polymer designed in this study can be used as a carrier of poorly soluble drugs or other active ingredients.

Reversibly disulfide cross-linked micelles improve the pharmacokinetics and facilitate the targeted, on-demand delivery of doxorubicin in the treatment of B-cell lymphoma

Doxorubicin (DOX) is commonly used to treat human malignancies, and its efficacy can be maximized by limiting the cardiac toxicity when combined with nanoparticles. Here, we reported a unique type of reversibly disulfide cross-linked micellar formulation of DOX (DOX-DCMs) for the targeted therapy of B-cell lymphoma. DOX-DCMs exhibited high drug loading capacity, optimal particle sizes (15-20 nm), outstanding stability in human plasma, and stimuli-responsive drug release profile under reductive conditions. DOX-DCMs significantly improved the pharmacokinetics of DOX, and its elimination half-life (t1/2) and area under curve (AUC) were 5.5 and 12.4 times of that of free DOX, respectively. Biodistribution studies showed that DOX-DCMs were able to preferentially accumulate in the tumor site and significantly reduce the cardiac uptake of DOX. In a xenograft model of human B-cell lymphoma, compared with the equivalent dose of free DOX and non-crosslinked counterpart, DOX-DCMs not only significantly inhibited the tumor growth and prolonged the survival rate, but also remarkably reduced DOX-associated cardiotoxicity. Furthermore, the exogenous administration of N-acetylcysteine (NAC) at 24 h further improved the therapeutic efficacy of DOX-DCMs, which provides a "proof-of-concept" for precise drug delivery on-demand, and may have great translational potential as future cancer nano-therapeutics.

Polyamidoamine dendrimers-based nanomedicine for combination therapy with siRNA and chemotherapeutics to overcome multidrug resistance

Multidrug resistance (MDR) significantly decreases the therapeutic efficiency of anti-cancer drugs. Its reversal could serve as a potential method to restore the chemotherapeutic efficiency. Downregulation of MDR-related proteins with a small interfering RNA (siRNA) is a promising way to reverse the MDR effect. Additionally, delivery of small molecule therapeutics simultaneously with siRNA can enhance the efficiency of chemotherapy by dual action in MDR cell lines. Here, we conjugated the dendrimer, generation 4 polyamidoamine (G4 PAMAM), with a polyethylene glycol (PEG)-phospholipid copolymer. The amphiphilic conjugates obtained spontaneously self-assembled into a micellar nano-preparation, which can be co-loaded with siRNA onto PAMAM moieties and sparingly water-soluble chemotherapeutics into the lipid hydrophobic core. This system was co-loaded with doxorubicin (DOX) and therapeutic siRNA (siMDR-1) and tested for cytotoxicity against MDR cancer cells: human ovarian carcinoma (A2780 ADR) and breast cancer (MCF7 ADR). The combination nanopreparation effectively downregulated P-gp in MDR cancer cells and reversed the resistance towards DOX.

Advances in redox-responsive drug delivery systems of tumor microenvironment

With the improvement of nanotechnology and nanomaterials, redox-responsive delivery systems have been studied extensively in some critical areas, especially in the field of biomedicine. The system constructed by redox-responsive delivery can be much stable when in circulation. In addition, redox-responsive vectors can respond to the high intracellular level of glutathione and release the loaded cargoes rapidly, only if they reach the site of tumor tissue or targeted cells. Moreover, redox-responsive delivery systems are often applied to significantly improve drug concentrations in targeted cells, increase the therapeutic efficiency and reduce side effects or toxicity of primary drugs. In this review, we focused on the structures and types of current redox-responsive delivery systems and provided a comprehensive overview of relevant researches, in which the disulfide bond containing delivery systems are of the utmost discussion.

Quercetin and doxorubicin co-delivery using mesoporous silica nanoparticles enhance the efficacy of gastric carcinoma chemotherapy

BACKGROUND

Effective gastric carcinoma (GC) chemotherapy is subject to many in vitro and in vivo barriers, such as tumor microenvironment and multidrug resistance.

MATERIALS AND METHODS

Herein, we developed a hyaluronic acid (HA)-modified silica nanoparticle (HA-SiLN/QD) co-delivering quercetin and doxorubicin (DOX) to enhance the efficacy of GC therapy (HA-SiLN/QD). The HA modification was done to recognize overexpressed CD44 receptors on GC cells and mediate selective tumor targeting. In parallel, quercetin delivery decreased the expression of Wnt16 and P-glycoprotein, thus remodeling the tumor microenvironment and reversed multidrug resistance to facilitate DOX activity.

RESULTS

Experimental results demonstrated that HA-SiLN/QD was nanoscaled particles with preferable stability and sustained release property. In vitro cell experiments on SGC7901/ADR cells showed selective uptake and increased DOX retention as compared to the DOX mono-delivery system (HA-SiLN/D).

CONCLUSION

In vivo anticancer assays on the SGC7901/ADR tumor-bearing mice model also revealed significantly enhanced efficacy of HA-SiLN/QD than mono-delivery systems (HA-SiLN/Q and HA-SiLN/D).

Redox-responsive nano-carriers as tumor-targeted drug delivery systems

With ever increasing scientific knowledge and awareness, research is underway around the globe to design new types of stimuli (external/internal) responsive nano-carriers for biotechnological applications at large and biomedical/pharmaceutical in particular. Based on literature evidence, stimuli-responsive carriers have been classified into four major categories, i.e. (1) physical, (2) chemical, (3) biological, and (4) dual (combination of any of the first three classes). Among various types, redox-responsive nano-carriers are of supreme interests and discussed here in this review. The difference in redox potential in tumor and normal tissue is considered as a potential target for tumor targeting leading to the development of redox-responsive drug delivery systems (DDS). In this regard, a high concentration of glutathione in tumor/intracellular environment has extensively been exploited. Disulfide bonds were found as a promising tool for designing redox-responsive which tend to cleave in a reductive environment forming sulfhydryl groups. Many nano-carriers have been explored widely to control tumor growth. These systems were used against the tumor xenograft animal model and showed improved tumor targeting with tumor growth inhibition. Herein, an effort has been made to summarize various aspects from design to development of numerous types of redox-responsive DDS including liposomes, micelles, nanoparticles, nanogel and prodrug based nanomedicines. An emphasis is also given on various types of nano-carriers with special reference to the tumor-targeted drug delivery applications. Also, dual responsive nano-carriers (in addition to redox-responsive) have also been briefly discussed. Towards the end of the chapter, the information is also given on their future perspectives.

Tumor microenvironment-responsive nanoparticles for cancer theragnostic applications

BACKGROUND

Cancer is one of the deadliest threats to human health. Abnormal physiochemical conditions and dysregulated biosynthetic intermediates in the tumor microenvironment (TME) play a significant role in modulating cancer cells to evade or defend conventional anti-cancer therapy such as surgery, chemotherapy and radiotherapy. One of the most important challenges in the development of anti-tumor therapy is the successful delivery of therapeutic and imaging agents specifically to solid tumors.

MAIN BODY

The recent progresses in development of TME responsive nanoparticles offers promising strategies for combating cancer by making use of the common attributes of tumor such as acidic and hypoxic microenvironments. In this review, we discussed the prominent strategies utilized in the development of tumor microenvironment-responsive nanoparticles and mode of release of therapeutic cargo.

CONCLUSION

Tumor microenvironment-responsive nanoparticles offers a universal approach for anti-cancer therapy.

Indomethacin-based stimuli-responsive micelles combined with paclitaxel to overcome multidrug resistance

Development of multidrug resistance against antitumor agents is a major limiting factor for the successful chemotherapy. Currently, both amphiphilic polymeric micelles and chemosensitizers have been proposed to overcome MDR during chemotherapy. Herein, the redox-responsive polymeric micelles composed of dextran and indomethacin (as chemosensitizer) using a disulfide bond as the linker are prepared (DEX-SS-IND) for delivery of antitumor agent paclitaxel (PTX). The high level of glutathione in tumor cells selectively breaks the disulfide bond, leading to the rapid breakdown and deformation of redox-responsive polymeric micelles. The data show that DEX-SS-IND can spontaneously form the stable micelles with high loading content (9.48 ± 0.41%), a favorable size of 45 nm with a narrow polydispersity (0.157), good stability, and glutathione-triggered drug release behavior due to the rapid breakdown of disulfide bond between DEX and IND. In vitro antitumor assay shows DEX-SS-IND/PTX micelles effectively inhibit the proliferation of PTX-resistant breast cancer (MCF-7/PTX) cells. More impressively, DEX-SS-IND/PTX micelles possess the improved plasma pharmacokinetics, enhanced antitumor efficacy on tumor growth in the xenograft models of MCF-7/PTX cells, and better in vivo safety. Overall, DEX-SS-IND/PTX micelles display a great potential for cancer treatment, especially for multidrug resistance tumors.