Water soluble polymers in tumor targeted delivery

Reversal mechanism of multidrug-resistant cancer cells by lectin as chemo-adjuvant and targeted therapy- a systematic review

BACKGROUND

Cancer is characterized as the leading cause of death, and the susceptibility of cancer cells to develop resistance due to long-term exposure to complementary chemotherapeutic treatment is referred to as multidrug resistance cancer cells (MDRC), which is a significant obstacle in the treatment of malignancies. Since complementary medicine lost its effectiveness, the development of potential alternative and novel therapeutic approaches has been elevated to a top priority in recent years. In this context, a bioactive protein lectin from plant and animal sources exhibits an invaluable source of anticancer agents with vast therapeutic potential.

PURPOSE

This manuscript's primary purpose is to enlighten the evidence-based (from 1986 to 2022) possible molecular mechanism of alternative treatment approaches using lectins over the complementary medicines used for cancer treatment.

METHODS

The PRISMA rules have been followed properly and qualitative and quantitative data are synthesized systematically. Articles were identified based on Clinical and preclinical reports published on lectin that investigated the in-depth cellular mechanisms, of reverse drug integrative oncology, as a nano-carried targeted delivery. Articles were systematically screened from 1986 to 2022 and selected based on electronic database searches, Medline (PubMed), Google Scholar, Web of Science, Encyclopaedias, Scopus, and ClinicalTrials.gov database.

RESULTS

The search turned up 4,212 publications from 38 different nations, of which 170 reference articles were used in our analysis, in 16 combination therapy and their mode of action, and 27 clinical trial studies including dosage and mechanism of action were included. Reports from the 30 lectins belonging to 28 different families have been included. The reversal mechanism of lectin and alternative therapy against MDRC is critically screened and according to a few clinical and preclinical reports, lectin can suppress the overexpressing genes like P-53, EGFR, and P-gp, MRP, and ABC transporter proteins associated with intracellular transportation of drugs. Since, the drug efflux mechanism leads to MDRC, in this phenomenon, lectin plays a key role in reversing the efflux mechanism. Few preclinical reports have mentioned that lectin shows synergism in combination with complementary medicine and as a nano drug carrier helps to deliver to the targeted site.

CONCLUSION

We have discussed the alternative therapy using lectin and an in-depth insight into the reversal drug resistance mechanisms to combat MDRC cancer, enhance the efficacy, reduce toxicity and adverse events, and ensure targeted delivery, and their application in the field of cancer diagnosis and prognosis has been discussed. However, further investigation is necessary in drug development and clinical trials which could be helpful to elaborate the reversal mechanism and unlock newer treatment modalities in MDRC cancer.

Synthesis of Polypeptides and Poly(α-hydroxy esters) from Aldehydes Using Strecker Synthesis

This report presents a versatile approach for the synthesis of new polypeptide and polyester-based biomaterials. The well-established Strecker reaction was utilized, with hexanal serving as the model aldehyde, to synthesize α-amino and α-hydroxy acids as monomer units for the polymer system. Following the formation of the corresponding amino and hydroxy acid monomers, they were subsequently converted to N-carboxy and O-carboxy-anhydrides. The resultant cyclic anhydride molecules were then polymerized via ring-opening polymerization to yield the corresponding polypeptides and polyesters. This report establishes a straightforward methodology for the synthesis of new polypeptide and poly(a-hydroxy acid)-based biomaterials, thereby expanding the existing library of polymers for various biomedical applications.

Tumor-Targeting Polymer–Drug Conjugate for Liver Cancer Treatment In Vitro

Bufalin (buf) has poor solubility in aqueous solution, poor tumor targeting, and many non-specific toxic and side effects. The advantages of high-molecular-weight polymer conjugates are that they can improve the water solubility of buf, prolong plasma half-life, and reduce non-specific toxicity. A novel water-soluble polymer–drug conjugate with buf and fluorescein pendants was prepared by the combination of reversible addition-fragmentation transfer (RAFT) polymerization and click chemistry. Its anticancer performance and cellular uptake behavior against liver cancer were investigated in vitro. The polymer–buf conjugates exhibit controlled release and tumor-targeting capabilities, showing promise for clinical applications.

Doxorubicin-Loaded Mixed Micelles Using Degradable Graft and Diblock Copolymers to Enhance Anticancer Sensitivity

Simple Summary

In this study, a long-circulating and pH responsive mixed micellar system was assembled with a degradable graft copolymer, poly(N-(2-hydroxypropyl) methacrylamide dilactate)-co-(N-(2-hydroxypropyl) methacrylamide-co-histidine)-graft-poly(d,l-lactide), and a diblock copolymer, methoxy poly(ethylene glycol)-b-poly(d,l-lactide) to load with the anticancer agent doxorubicin. The in vitro results indicate that the micellar system display high biosafety and intracellular drug-releasing behavior in cancer cells. Furthermore, the in vivo results show that the high stability of the mixed micelles leads to a high tumor accumulation and hence an excellent inhibition of tumor growth. This mixed micellar system, comprising degradable diblock and graft copolymers enables one to increase cancer cells’ sensitivity toward doxorubicin (Dox) and is feasible for further clinical use in cancer therapy.

Abstract

In this study, a graft copolymer, poly(N-(2-hydroxypropyl) methacrylamide dilactate)-co-(N-(2-hydroxypropyl) methacrylamide-co-histidine)-graft-poly(d,l-lactide), and a diblock copolymer, methoxy poly(ethylene glycol)-b-poly(d,l-lactide), were assembled into a mixed micellar system to encapsulate the anticancer drug doxorubicin (Dox). This mixed micellar system possesses the hydrophobic lactide segment of both copolymers, which reinforces its stability in physiological milieus; the histidine molecules appended on the graft copolymer provide the desired pH-responsive behavior to release Dox during internalization in cancer cells. The results demonstrate that the two copolymers were successfully prepared, and their ratios in the mixed micelles were optimized on the basis of the results of the stability tests. Under acidic conditions, the mixed micelles swell and are able to release their payloads. Therefore, the in vitro results indicate that the Dox in the mixed micelles is released effectively in response to the environmental pH of the mimetic internalization process, increasing cancer cells’ sensitivity toward Dox. The mixed micelles display low cytotoxicity due to the degradability of the polymers. The in vivo images show that the high stability of the mixed micelles ensures a high tumor accumulation. This selective tumor accumulation results in an excellent inhibition of in vivo tumor growth and a high rate of apoptosis in cancerous tissues, with low toxicity. This highly stable, mixed micellar system with a pH-dependent drug release, which enables the precise delivery of drugs to the tumor lesions, is feasible to employ clinically in cancer therapy.

Optimizing the Polymer Chemistry and Synthesis Method of PolySTAT, an Injectable Hemostat

There is a lack of prehospital hemostatic agents, especially for noncompressible hemorrhage. We previously reported PolySTAT, a unimeric, injectable hemostatic agent, that physically cross-links fibrin to strengthen clots. In this work, we sought to improve the water-solubility and synthesis yield of PolySTAT to increase the likelihood of clinical translation, reduce cost, and facilitate future mass production. First, we focused on side-chain engineering of the carrier polymer backbone to improve water-solubility. We found that substitution of the 2-hydroxyethyl methacrylate (HEMA) monomer with glycerol monomethacrylate (GmMA) significantly improved the water-solubility of PolySTAT without compromising efficacy. Both materials increased clot firmness and decreased lysis as measured by rotational thromboelastometry (ROTEM). Additionally, we confirmed the in vivo activity of GmMA-based PolySTAT by improving rat survival in a femoral artery bleed model. Second, to reduce waste, we evaluated PolySTAT synthesis via direct polymerization of peptide monomers. Methacrylamide and methacrylate peptide-monomers were synthesized and polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. This approach markedly improved the yield of PolySTAT synthesis while maintaining its biological activity in ROTEM. This work demonstrates the flexibility of PolySTAT to a variety of comonomers and synthetic routes and establishes direct RAFT polymerization of peptide monomers as a potential route of mass production.

(Amino)cyclophosphazenes as Multisite Ligands for the Synthesis of Antitumoral and Antibacterial Silver(I) Complexes

The reactivity of the multisite (amino)cyclotriphosphazene ligands, [N₃P₃(NHCy)₆] and [N₃P₃(NHCy)₃(NMe₂)₃], has been explored in order to obtain silver(I) metallophosphazene complexes. Two series of cationic silver(I) metallophosphazenes were obtained and characterized: [N₃P₃(NHCy)₆{AgL}_n](TfO)_n [n = 2, L = PPh₃ (2), PPh₂Me (4); n = 3, L = PPh₃ (3), PPh₂Me (5), TPA (TPA = 1,3,5-triaza-7-phosphaadamantane, 6)] and nongem-trans-[N₃P₃(NHCy)₃(NMe₂)₃{AgL}_n](TfO)_n [n = 2, L = PPh₃ (7), PPh₂Me (9); n = 3, L = PPh₃ (8), PPh₂Me (10)]. 5, 7, and 9 have also been characterized by single-crystal X-ray diffraction, thereby allowing key bonding information to be obtained. Compounds 2-6, 9, and 10 were screened for in vitro cytotoxic activity against two tumor human cell lines, MCF7 (breast adenocarcinoma) and HepG2 (hepatocellular carcinoma), and for antimicrobial activity against five bacterial species including Gram-positive, Gram-negative, and Mycobacteria strains. Both the IC₅₀ and MIC values revealed excellent biological activity for these metal complexes, compared with their precursors and cisplatin and also AgNO₃ and silver sulfadiazine, respectively. Both IC₅₀ and MIC values are among the lowest values found for any silver derivatives against the cell lines and bacterial strains used in this work. The structure-activity relationships were clear. The most cytotoxic and antimicrobial derivatives were those with the triphenylphosphane and [N₃P₃(NHCy)₆] ligands. A significant improvement in the activity was also observed upon a rise in the number of silver atoms linked to the phosphazene ring.

Toll-Like Receptors and Relevant Emerging Therapeutics with Reference to Delivery Methods

The built-in innate immunity in the human body combats various diseases and their causative agents. One of the components of this system is Toll-like receptors (TLRs), which recognize structurally conserved molecules derived from microbes and/or endogenous molecules. Nonetheless, under certain conditions, these TLRs become hypofunctional or hyperfunctional, thus leading to a disease-like condition because their normal activity is compromised. In this regard, various small-molecule drugs and recombinant therapeutic proteins have been developed to treat the relevant diseases, such as rheumatoid arthritis, psoriatic arthritis, Crohn’s disease, systemic lupus erythematosus, and allergy. Some drugs for these diseases have been clinically approved; however, their efficacy can be enhanced by conventional or targeted drug delivery systems. Certain delivery vehicles such as liposomes, hydrogels, nanoparticles, dendrimers, or cyclodextrins can be employed to enhance the targeted drug delivery. This review summarizes the TLR signaling pathway, associated diseases and their treatments, and the ways to efficiently deliver the drugs to a target site.

Stimuli-responsive polymer-doxorubicin conjugate: Antitumor mechanism and potential as nano-prodrug

Polymer-drug conjugates has significantly improved the anti-tumor efficacy of chemotherapeutic drugs and alleviated their side effects. N-(1,3-dihydroxypropan-2-yl) methacrylamide (DHPMA) copolymer was synthesized via RAFT polymerization and polymer-doxorubicin (DOX) (diblock pDHPMA-DOX) were formed by conjugation, resulting in a self-aggregation-induced nanoprodrug with a favorable size of 21 nm and great stability. The nanoprodrug with a molecular weight (MW) of 95 kDa released drugs in response to tumor microenvironmental pH variations and they were enzymatically hydrolyzed into low MW segments (45 kDa). The nanoprodrug was transported through the endolysosomal pathway, released the drug into the cytoplasm and some was localized in the mitochondria, resulting in disruption of the cellular actin cytoskeleton. Cellular apoptosis was also associated with reduction in the mitochondrial potential caused by the nanoprodrug. Notably, the nanoprodrug had a significantly prolonged blood circulation time with an elimination half time of 9.8 h, displayed high accumulation within tumors, and improved the in vivo therapeutic efficacy against 4T1 xenograft tumors compared to free DOX. The tumor xenograft immunohistochemistry study clearly indicated tumor inhibition was through the inhibition of cell proliferation and antiangiogenic effects. Our studies demonstrated that the diblock pDHPMA-DOX nanoprodrug with a controlled molecular structure is promising to alleviate adverse effects of free DOX and have a great potential as an efficient anticancer agent. STATEMENT OF SIGNIFICANCE: In this work, we prepared a biodegradable diblock DHPMA polymer-doxorubicin conjugate via one-pot of RAFT polymerization and conjugate chemistry. The conjugate-based nanoprodrug was internalized by endocytosis to intracellularly release DOX and further induce disruption of mitochondrial functions, actin cytoskeleton alterations and cellular apoptosis. The nanoprodrug with a high molecular weight (MW) (95 kDa) showed a long blood circulation time and achieved high accumulation into tumors. The nanoprodrug was degraded into low MW (∼45 kDa) products below the renal threshold, which ensured its biosafety. Additionally, the multi-stimuli-responsive nanoprodrug demonstrated an enhanced antitumor efficacy against 4T1 breast tumors and alleviated side effects, showing a great potential as an efficient and safe anticancer agent.

Synthesis of water-soluble star polymers based on cyclodextrins

Novel star polymers based on the water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer and cyclodextrin were synthesized and the physico-chemical behavior of these precursors was studied. Semitelechelic HPMA copolymers were grafted onto the cyclodextrin core, thus forming star-like structure. Both prepared systems were designed as possible polymer carriers for the controlled release of cytostatic drugs, which after the drug release and degradation will be eliminated from the organism. Two synthesis approaches were used to obtain similar polymer carriers with different degradation rates. All the polymers were prepared by reversible addition-fragmentation chain-transfer polymerization, which guarantees low dispersity of the prepared systems.

Simultaneous delivery of olaparib and carboplatin in PEGylated liposomes imparts this drug combination hypersensitivity and selectivity for breast tumor cells

Combination regiments involving platinum anticancer drugs and agents with unrelated mechanisms of action are a subject of widespread interest. Here, we show that synergistic toxic action in cancer cells of combinations of antitumor platinum drug carboplatin and effective PARP inhibitor olaparib is considerably improved if these combined drugs are encapsulated into liposomes. Notably, the formation of such nano-formulations, called OLICARB, leads to a marked enhancement of activity in human cancer cell lines (including those resistant to conventional platinum antitumor drugs) and selectivity towards tumor cells. We used immunofluorescence analysis of γH2AX expression and examined DNA damage in cancerous cells treated with the investigated compounds. We find that the synergistic toxic effects in cancer cells of both drugs used in combination, nonencapsulated or embedded in the OLICARB nanoparticles, positively correlates with DNA damage. These results also suggest that the enhancement of the toxic effects of carboplatin by olaparib in cancer cells is a consequence of an accumulation of cytotoxic lesions in DNA due to the inhibition of repair of platinated DNA augmented by the synergistic action of olaparib as an effective PARP inhibitor. Our findings also reveal that the combination of olaparib with carboplatin encapsulated in the OLICARB nanoparticles is particularly effective to inhibit the growth of 3D mammospheres. Collectively, the data provide convincing evidence that the encapsulation of carboplatin and olaparib into liposomal constructs to form the OLICARB nanoparticles may represent the viable approach for the treatment of tumors with the aim to eliminate the possible effects of acquired resistance.

Enhanced Antitumor Effects of Epidermal Growth Factor Receptor Targetable Cetuximab-Conjugated Polymeric Micelles for Photodynamic Therapy

Nanocarrier-based delivery systems are promising strategies for enhanced therapeutic efficacy and safety of toxic drugs. Photodynamic therapy (PDT)—a light-triggered chemical reaction that generates localized tissue damage for disease treatments—usually has side effects, and thus patients receiving photosensitizers should be kept away from direct light to avoid skin phototoxicity. In this study, a clinically therapeutic antibody cetuximab (C225) was conjugated to the surface of methoxy poly(ethylene glycol)-b-poly(lactide) (mPEG-b-PLA) micelles via thiol-maleimide coupling to allow tumor-targetable chlorin e6 (Ce6) delivery. Our results demonstrate that more C225-conjugated Ce6-loaded polymeric micelles (C225-Ce6/PM) were selectively taken up than Ce6/PM or IgG conjugated Ce6/PM by epidermal growth factor receptor (EGFR)-overexpressing A431 cells observed by confocal laser scanning microscopy (CLSM), thereby decreasing the IC₅₀ value of Ce6-mediated PDT from 0.42 to 0.173 μM. No significant differences were observed in cellular uptake study or IC₅₀ value between C225-Ce6/PM and Ce6/PM groups in lower EGFR expression HT-29 cells. For antitumor study, the tumor volumes in the C225-Ce6/PM-PDT group (percentage of tumor growth inhibition, TGI% = 84.8) were significantly smaller than those in the Ce6-PDT (TGI% = 38.4) and Ce6/PM-PDT groups (TGI% = 53.3) (p < 0.05) at day 21 through reduced cell proliferation in A431 xenografted mice. These results indicated that active EGFR targeting of photosensitizer-loaded micelles provides a possible way to resolve the dose-limiting toxicity of conventional photosensitizers and represents a potential delivery system for PDT in a clinical setting.

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.

Poly(2-ethyl-2-oxazoline) conjugates with doxorubicin for cancer therapy: In vitro and in vivo evaluation and direct comparison to poly[N-(2-hydroxypropyl)methacrylamide] analogues

We designed and synthesized a new delivery system for the anticancer drug doxorubicin based on a biocompatible hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) carrier with linear architecture and narrow molar mass distribution. The drug is connected to the polymer backbone via an acid-sensitive hydrazone linker, which allows its triggered release in the tumor. The in vitro studies demonstrate successful cellular uptake of conjugates followed by release of the cytostatic cargo. In vivo experiments in EL4 lymphoma bearing mice revealed prolonged blood circulation, increased tumor accumulation and enhanced antitumor efficacy of the PEtOx conjugate having higher molecular weight (40 kDa) compared to the lower molecular weight (20 kDa) polymer. Finally, the in vitro and in vivo anti-cancer properties of the prepared PEtOx conjugates were critically compared with those of the analogous system based on the well-established PHPMA carrier. Despite the relatively slower intracellular uptake of PEtOx conjugates, resulting also in their lower cytotoxicity, there are no substantial differences in in vivo biodistribution and anti-cancer efficacy of both classes of polymer-Dox conjugates. Considering the synthetic advantages of poly(2-alkyl-2-oxazoline)s, the presented study demonstrates their potential as a versatile alternative to well-known PEO- or PHPMA-based materials for construction of drug delivery systems.

Anticancer nanoparticulate polymer-drug conjugate

We review recent progress in polymer-drug conjugate for cancer nanomedicine. Polymer-drug conjugates, including the nanoparticle prepared from these conjugates, are designed to release drug in tumor tissues or cells in order to improve drugs' therapeutic efficacy. We summarize general design principles for the polymer-drug conjugate, including the synthetic strategies, the design of the chemical linkers between the drug and polymer in the conjugate, and the in vivo drug delivery barriers for polymer-drug conjugates. Several new strategies, such as the synthesis of polymer-drug conjugates and supramolecular-drug conjugates, the use of stimulus-responsive delivery, and triggering the change of the nanoparticle physiochemical properties to over delivery barriers, are also highlighted.

Succinoylated Poly[N-(2- Hydroxyethyl)-L-Glutamine] Derivatives for Drug Delivery

A series of succinoylated poly[N-(2-)- L-glutamine] (PHEG) derivatives was synthesized by reacting PHEG with succinic anhydride in the presence of N,N-dimethylaminopyridine as a catalyst. The size of the derivatives were measured by dynamic light scattering in buffers (pH 5.5 and 7.4, respectively) the lysosomal and physiological pH. The degradability of the succinoylated polymers toward cathepsin B was followed by gel permeation chromatography. It was demonstrated that an increase of modification results in decreased biodegradability. Conjugation of mitomycin C (MMC) with a succinoylated PHEG derivative through a collagenase-sensitive Pro-Leu-Gly-Pro- Leu spacer resulted in a water-soluble MMC conjugate. This conjugate was shown to be hydrolytically stable in buffers of lysosomal and physiological pH and able to release MMC in the presence of the bacterial collagenase clostridium histolyticum.

Self-Assembled Smart Nanocarriers for Targeted Drug Delivery

Nanostructured drug-carrier systems promise numerous benefits for drug delivery. They can be engineered to precisely control drug-release rates or to target specific sites within the body with a specific amount of therapeutic agent. However, to achieve the best therapeutic effects, the systems should be designed for carrying the optimum amount of a drug to the desired target where it should be released at the optimum rate for a specified time. Despite numerous attempts, fulfilling all of these requirements in a synergistic way remains a huge challenge. The trend in drug delivery is consequently directed toward integrated multifunctional carrier systems, providing selective recognition in combination with sustained or triggered release. Capsules as vesicular systems enable drugs to be confined for controlled release. Furthermore, carriers modified with recognition groups can enhance the capability of encapsulated drug efficacy. Here, recent advances are reviewed regarding designing and preparing assembled capsules with targeting ligands or size controllable for selective recognition in drug delivery.

Chemotherapeutic copolymers prepared via the RAFT polymerization of prodrug monomers

Reversible addition–fragmentation chain transfer (RAFT) polymerization was employed to prepare prodrug polymer carrier systems with the chemotherapeutic agent camptothecin (Cam) and the kinase inhibitor dasatinib (Dt).

Doxorubicin-loaded biodegradable self-assembly zein nanoparticle and its anti-cancer effect: Preparation, in vitro evaluation, and cellular uptake

Cancer is one top leading cause of the deaths worldwide. Various anticancer drugs, which can effectively kill cancer cells, have been developed in the last decade. However, the problem is still about the low therapeutic index of the drugs, which means that the effective dose of drugs will cause cytotoxicity to normal cells. A strategy based on drug nano-encapsulation is applied to achieve an effective anti-cancer therapy. In this study, we use zein, which is an amphiphilic protein, to make the anti-cancer drug nano-encapsulation. Doxorubicin (DOX), a popular anti-cancer drug, is selected as the core drug. The results show that DOX could be successfully encapsulated into zein to form spherical nanoparticles. The encapsulation efficiency and loading efficiency could reach as high as 90.06% and 15.01 mg/g, respectively. The cumulative release result showed a desired pH-responsible release behavior: DOX could be released faster in acidic buffer solutions (pH 5.0 and 6.5) than neutral one (pH 7.4). The effects of the nano-encapsulation on the anti-proliferation of HeLa cells were also examined. It indicated that, compared with free DOX, the DOX-loaded zein nanoparticles (DOX-zein-NPs) had a better effect on cancer cell killing at low DOX concentrations. We also investigated the cellular uptake of DOX-zein-NPs using confocal laser scanning microscopy (CLSM), flow cytometry, and transmission electron microscopy (TEM). And the endocytosis mechanism of DOX-zein-NPs entering into HeLa cells was studied using various endocytosis pathway inhibitors.

Synergistic antitumor activity of camptothecin-doxorubicin combinations and their conjugates with hyaluronic acid

Combinations of topoisomerase inhibitors I and II have been found to synergistically inhibit cancer cell growth in vitro, yet clinical studies of these types of combinations have not progressed beyond phase II trials. The results of clinical combinations of topoisomerase (top) I and II inhibitors typically fall within one of two categories: little to no improvement in therapeutic efficacy, or augmented toxicity compared to the single drug counterparts. Hence, despite the promising activity of top I and II inhibitor combinations in vitro, their clinical applicability has not been realized. Here, we report the use of polymer-drug conjugates as a means to co-deliver synergistic doses of top I and II inhibitors camptothecin (CPT) and doxorubicin (DOX) to tumors in vivo in a 4T1 breast cancer model. At specific molar ratios, DOX and CPT were found to be among the most synergistic combinations reported to date, with combination indices between 0.01 and 0.1. The identified optimal ratios were controllably conjugated to hyaluronic acid, and elicited significant tumor reduction of murine 4T1 breast cancer model when administered intravenously. This study elucidates a method to identify synergistic drug combinations and translate them to in vivo by preserving the synergistic ratio via conjugation to a carrier polymer, thus opening a promising approach to translate drug combinations to clinically viable treatment regimens.

Self-assembled amphotericin B-loaded polyglutamic acid nanoparticles: preparation, characterization and in vitro potential against Candida albicans

In the present study, we developed a self-assembled biodegradable polyglutamic acid (PGA)-based formulation of amphotericin B (AmB) and evaluated its in vitro antifungal potential against Candida albicans. The AmB-loaded PGA nanoparticles were prepared in-house and had a mean size dimension of around 98±2 nm with a zeta potential of -35.2±7.3 mV. Spectroscopic studies revealed that the drug predominantly acquires an aggregated form inside the formulation with an aggregation ratio above 2. The PGA-based AmB formulation was shown to be highly stable in phosphate-buffered saline as well as in serum (only 10%-20% of the drug was released after 10 days). The AmB-PGA nanoparticles were less toxic to red blood cells (<15% lysis at an AmB concentration of 100 μg/mL after 24 hours) when compared with Fungizone(®), a commercial antifungal product. An MTT assay showed that the viability of mammalian cells (KB and RAW 264.7) was negligibly affected at AmB concentrations as high as 200 μg/mL. Histopathological examination of mouse kidney revealed no signs of tissue necrosis. The AmB-PGA formulation showed potent antimicrobial activity similar to that of Fungizone against C. albicans. Interestingly, AmB-bearing PGA nanoparticles were found to inhibit biofilm formation to a considerable extent. In summary, AmB-PGA nanoparticles showed highly attenuated toxicity when compared with Fungizone, while retaining equivalent active antifungal properties. This study indicates that the AmB-PGA preparation could be a promising treatment for various fungal infections.

Curcumin conjugated with PLGA potentiates sustainability, anti-proliferative activity and apoptosis in human colon carcinoma cells

Curcumin, an ingredient of turmeric, exhibits a variety of biological activities such as anti-inflammatory, anti-atherosclerotic, anti-proliferative, anti-oxidant, anti-cancer and anti-metastatic. It is a highly pleiotropic molecule that inhibits cell proliferation and induces apoptosis in cancer cells. Despite its imperative biological activities, chemical instability, photo-instability and poor bioavailability limits its utilization as an effective therapeutic agent. Therefore, enhancing the bioavailability of curcumin may improve its therapeutic index for clinical setting. In the present study, we have conjugated curcumin with a biodegradable polymer Poly (D, L-lactic-co-glycolic acid) and evaluated its apoptotic potential in human colon carcinoma cells (HCT 116). The results show that curcumin-PLGA conjugate efficiently inhibits cell proliferation and cell survival in human colon carcinoma cells as compared to native curcumin. Additionally, curcumin conjugated with PLGA shows improved cellular uptake and exhibits controlled release at physiological pH as compared to native curcumin. The curcumin-PLGA conjugate efficiently activates the cascade of caspases and promotes intrinsic apoptotic signaling. Thus, the results suggest that conjugation potentiates the sustainability, anti-proliferative and apoptotic activity of curcumin. This approach could be a promising strategy to improve the therapeutic index of cancer therapy.

High-molecular weight star conjugates containing docetaxel with high anti-tumor activity and low systemic toxicity in vivo

The star polymer-docetaxel conjugates exert a much higher therapeutic activity and yet a lower systemic toxicity than free DTX.

Nanopharmacology in translational hematology and oncology

Nanoparticles have displayed considerable promise for safely delivering therapeutic agents with miscellaneous therapeutic properties. Current progress in nanotechnology has put forward, in the last few years, several therapeutic strategies that could be integrated into clinical use by using constructs for molecular diagnosis, disease detection, cytostatic drug delivery, and nanoscale immunotherapy. In the hope of bringing the concept of nanopharmacology toward a viable and feasible clinical reality in a cancer center, the present report attempts to present the grounds for the use of cell-free nanoscale structures for molecular therapy in experimental hematology and oncology.

Temperature-sensitive magnetic drug carriers for concurrent gemcitabine chemohyperthermia

To improve the efficacy of gemcitabine (GEM) for the treatment of advanced pancreatic cancer via local hyperthermia potentiated via a multi-functional nanoplatform permitting both in vivo heating and drug delivery is the goal of this study. Here, a chemohyperthermia approach to synergistically achieve high intra-tumoral drug concentrations, while permitting concurrent hyperthermia for more effective tumor cell kill and growth inhibition, is proposed. Drug delivery and hyperthermia are achieved using a hydroxypropyl cellulose (HPC)-grafted porous magnetic drug carrier that is MRI visible to permit in vivo visualization of the biodistribution. These synthesized magnetic drug carriers produce strong T2 -weighted image contrast and permit efficient heating using low-magnetic-field intensities. The thermomechanical response of HPC permits triggered GEM release confirmed during in vitro drug release studies. During in vitro studies, pancreatic cancer cell growth is significantly inhibited (≈82% reduction) with chemohyperthermia compared to chemotherapy or hyperthermia alone. Using PANC-1 xenografts in nude mice, the delivery of injected GEM-loaded magnetic carriers (GEM-magnetic carriers) is visualized with both MRI and fluorescent imaging techniques. Chemohyperthermia with intra-tumoral injections of GEM-magnetic carriers (followed by heating) results in significant increases in apoptotic cell death compared to tumors treated with GEM-magnetic carriers injections alone. Chemohyperthermia with GEM-magnetic carriers offers the potential to significantly improve the therapeutic efficacy of GEM for the treatment of pancreatic cancer. In vivo delivery confirmation with non-invasive imaging techniques could permit patient-specific adjustments therapeutic regimens for improve longitudinal outcomes.

Classification of stimuli-responsive polymers as anticancer drug delivery systems

Although several anticancer drugs have been introduced as chemotherapeutic agents, the effective treatment of cancer remains a challenge. Major limitations in the application of anticancer drugs include their nonspecificity, wide biodistribution, short half-life, low concentration in tumor tissue and systemic toxicity. Drug delivery to the tumor site has become feasible in recent years, and recent advances in the development of new drug delivery systems for controlled drug release in tumor tissues with reduced side effects show great promise. In this field, the use of biodegradable polymers as drug carriers has attracted the most attention. However, drug release is still difficult to control even when a polymeric drug carrier is used. The design of pharmaceutical polymers that respond to external stimuli (known as stimuli-responsive polymers) such as temperature, pH, electric or magnetic field, enzymes, ultrasound waves, etc. appears to be a successful approach. In these systems, drug release is triggered by different stimuli. The purpose of this review is to summarize different types of polymeric drug carriers and stimuli, in addition to the combination use of stimuli in order to achieve a better controlled drug release, and it discusses their potential strengths and applications. A survey of the recent literature on various stimuli-responsive drug delivery systems is also provided and perspectives on possible future developments in controlled drug release at tumor site have been discussed.

Exploiting nanotechnology to overcome tumor drug resistance: Challenges and opportunities

Tumor cells develop resistance to chemotherapeutic drugs through multiple mechanisms. Overexpression of efflux transporters is an important source of drug resistance. Efflux transporters such as P-glycoprotein reduce intracellular drug accumulation and compromise drug efficacy. Various nanoparticle-based approaches have been investigated to overcome efflux-mediated resistance. These include the use of formulation excipients that inhibit transporter activity and co-delivery of the anticancer drug with a specific inhibitor of transporter function or expression. However, the effectiveness of nanoparticles can be diminished by poor transport in the tumor tissue. Hence, adjunct therapies that improve the intratumoral distribution of nanoparticles may be vital to the successful application of nanotechnology to overcome tumor drug resistance. This review discusses the mechanisms of tumor drug resistance and highlights the opportunities and challenges in the use of nanoparticles to improve the efficacy of anticancer drugs against resistant tumors.