Water-soluble heparin–PTX conjugates for cancer targeting

Hydrogen sulfide-releasing polyurethane/gelatin/keratin-TA conjugate mats for wound healing

Hydrogen sulfide (H₂S) has indispensable effects on wound healing promotion, such as anti-inflammatory, cell proliferation enhancement, and angiogenesis improvement. However, small-molecular donors have drawbacks of burst release and low biocompatibility. In this study, a novel bio-macromolecular donor of H₂S based on a keratin-thiobenzoic acid conjugate (KTC) was first synthesized by a thiol-disulfide exchange reaction. Then, the KTC was incorporated into polyurethane and gelatin to fabricate nanofibrous mats by electrospinning. Interestingly, both the KTC donor and biocomposite mats were capable of releasing H₂S triggered by glutathione (GSH) under physiological conditions. These mats had excellent water absorption capacity, demonstrating their great ability to absorb tissue exudate. In addition, these mats possessed a notable antioxidant ability, thereby protecting cell membranes from oxidation. Cell assays in vitro demonstrated that these mats could promote cell proliferation and migration. Furthermore, the in vivo full-thickness defect model verified that these H₂S-releasing wound dressing mats could accelerate granulation tissue formation, enhance collagen deposition, and promote angiogenesis. Based on these advantages, these wound dressing mats had great potential applications for wound healing.

Natural and Synthetic Micelles for Delivery of Small Molecule Drugs, Imaging Agents and Nucleic Acids

The poor solubility, lack of targetability, quick renal clearance, and degradability of many therapeutic and imaging agents strongly limit their applications inside the human body. Amphiphilic copolymers having self-assembling properties can form core-shell structures called micelles, a promising nanocarrier for hydrophobic drugs, plasmid DNA, oligonucleotides, small interfering RNAs (siRNAs) and imaging agents. Fabrication of micelles loaded with different pharmaceutical agents provides numerous advantages including therapeutic efficacy, diagnostic sensitivity, and controlled release to the desired tissues. Moreover, due to their smaller particle size (10-100 nm) and modified surfaces with different functional groups (such as ligands) help them to accumulate easily in the target location, enhancing cellular uptake and reducing unwanted side effects. Furthermore, the release of the encapsulated agents may also be triggered from stimuli-sensitive micelles at different physiological conditions or by an external stimulus. In this review article, we discuss the recent advancement in formulating and targeting different natural and synthetic micelles including block copolymer micelles, cationic micelles, and dendrimers-, polysaccharide- and protein-based micelles for the delivery of different therapeutic and diagnostic agents. Finally, their applications, outcomes, and future perspectives have been summarized.

Smart Carriers and Nanohealers: A Nanomedical Insight on Natural Polymers

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer biodegradable systems are a promising arena of research for targeted and site-specific controlled drug delivery, for developing artificial limbs, 3D porous scaffolds for cellular regeneration or tissue engineering and biosensing applications. Several natural polymers have been identified, blended, functionalized and applied for designing nanoscaffolds and drug carriers as a prerequisite for enumerable bionano technological applications. Apart from these, natural polymers have been well studied and are widely used in material science and industrial fields. The present review explains the prominent features of commonly used natural polymers (polysaccharides and proteins) in various nanomedical applications and reveals the current status of the polymer research in bionanotechnology and science sectors.

Trimethyl chitosan based conjugates for oral and intravenous delivery of paclitaxel

Paclitaxel (PTX) conjugated trimethyl chitosan (TMC-PTX) and folic acid (FA) modified TMC-PTX (FA-TMC-PTX) were developed as polymer-drug conjugates for oral and intravenous delivery of PTX. As amphiphilic conjugates, TMC-PTX and FA-TMC-PTX containing approximately 11wt% PTX could self-assemble into spherical nanoparticles with average sizes of 170 and 187nm, respectively. The conjugates presented a sustained release of PTX and the release rate was positively correlated with the pH value of medium ranging from 1.2 to 7.4. TMC-PTX and FA-TMC-PTX possessed enhanced mucoadhesion compared with trimethyl chitosan, and promoted ex vivo intestinal transport of PTX in comparison to PTX solution by 15.5 and 18.8 folds, respectively. Hemolysis assessment confirmed the safety of TMC-PTX and FA-TMC-PTX, and FA modification alleviated protein adsorption of the conjugates. Prolonged blood retention and increased PTX accumulation in the tumor were achieved for orally and intravenously administered conjugates. In H22 tumor-bearing mice, TMC-PTX delivered via oral or intravenous route showed superior tumor retardation and survival rate compared with intravenously injected PTX, and FA-TMC-PTX further enhanced the antitumor efficacy. Overall, the trimethyl chitosan based drug conjugates may have potential applications as a promising candidate for cancer therapy.

STATEMENT OF SIGNIFICANCE

In the current study, PTX conjugated trimethyl chitosan (TMC-PTX) and folic acid (FA) modified TMC-PTX (FA-TMC-PTX) were developed as the polymer-drug conjugates for oral and intravenous delivery of PTX. By exploiting advantages with respect to improved solubility of drugs, controlled release behavior of covalently linked drugs, and enhanced targeting effect towards tumors, improved tumor growth inhibition efficacy and prolonged survival time were achieved for TMC-PTX as compared with free PTX, and FA modification further enhanced the in vivo antitumor efficacy. Overall, the self-assembled nanoplatform of trimethyl chitosan based drug conjugates may have potential applications as a promising candidate for tumor therapy via different administration routes.

Redox-sensitive self-assembled nanoparticles based on alpha-tocopherol succinate-modified heparin for intracellular delivery of paclitaxel

To remedy the problems riddled in cancer chemotherapy, such as poor solubility, low selectivity, and insufficient intra-cellular release of drugs, novel heparin-based redox-sensitive polymeric nanoparticles were developed. The amphiphilic polymer, heparin-alpha-tocopherol succinate (Hep-cys-TOS) was synthesized by grafting hydrophobic TOS to heparin using cystamine as the redox-sensitive linker, which could self-assemble into nanoparticles in phosphate buffer saline (PBS) with low critical aggregation concentration (CAC) values ranging from 0.026 to 0.093mg/mL. Paclitaxel (PTX)-loaded Hep-cys-TOS nanoparticles were prepared via a dialysis method, exhibiting a high drug-loading efficiency of 18.99%. Physicochemical properties of the optimized formulation were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM) and differential scanning calorimetry (DSC). Subsequently, the redox-sensitivity of Hep-cys-TOS nanoparticles was confirmed by the changes in size distribution, morphology and appearance after dithiothreitol (DTT) treatment. Besides, the in vitro release of PTX from Hep-cys-TOS nanoparticles also exhibited a redox-triggered profile. Also, the uptake behavior and pathways of coumarin 6-loaded Hep-cys-TOS nanoparticles were investigated, suggesting the nanoparticles could be taken into MCF-7 cells in energy-dependent, caveolae-mediated and cholesterol-dependent endocytosis manners. Later, MTT assays of different PTX-free and PTX-loaded formulations revealed the desirable safety of PTX-free nanoparticles and the enhanced anti-cancer activity of PTX-loaded Hep-cys-TOS nanoparticles (IC₅₀=0.79μg/mL). Apoptosis study indicated the redox-sensitive formulation could induce more apoptosis of MCF-7 cells than insensitive one (55.2% vs. 41.7%), showing the importance of intracellular burst release of PTX. Subsequently, the hemolytic toxicity confirmed the safety of the nanoparticles for intravenous administration. The results indicated the developed redox-sensitive nanoparticles were promising as intracellular drug delivery vehicles for cancer treatment.

Design, synthesis, and evaluation of water-soluble morpholino-decorated paclitaxel prodrugs with remarkably decreased toxicity

Novel water-soluble paclitaxel prodrugs were designed and synthesized by introducing morpholino groups through different linkers. These derivatives showed 400-20,000-times greater water solubility than paclitaxel as well as comparable activity in MCF-7 and HeLa cell lines. The prodrug PM4 was tested in the S-180 tumor mouse model, with paclitaxel as the positive control. The results showed that PM4 had comparable antitumor activity as paclitaxel, with tumor inhibition of 54% versus 56%, and remarkably decreased toxicity. The survival rate of treated mice was 8/8 in the PM4 group, compared to 3/8 in the paclitaxel group.

Recent progress in the development of polysaccharide conjugates of docetaxel and paclitaxel

Taxanes are one of the most potent and broadest spectrum chemotherapeutics used clinically, but also induce significant side effects. Different strategies have been developed to produce a safer taxane formulation. Development of polysaccharide drug conjugates has increased in the recent years because of the demonstrated biocompatibility, biodegradability, safety, and low cost of the biopolymers. This review focuses on polysaccharide-taxane conjugates and provides an overview on various conjugation strategies and their effect on the efficacy. Detailed analyses on the designing factors of an effective polysaccharide-drug conjugate are provided with a discussion on the future direction of this field. For further resources related to this article, please visit the WIREs website.

CONFLICT OF INTEREST

The authors have declared no conflicts of interest for this article.

Folate-mediated and doxorubicin-conjugated poly(ε-caprolactone)-g-chondroitin sulfate copolymers for enhanced intracellular drug delivery

The aim of this study was to conjugate an anticancer drug, doxorubicin (DOX) and a folate targeting moiety, folic acid (FA), to self-assembled polycaprolactone (PCL)-graft-chondroitin sulfate (CS) copolymers for enhanced chemotherapy.

Paclitaxel-loaded PCL-TPGS nanoparticles: in vitro and in vivo performance compared with Abraxane®

The purpose of this work was to develop Cremophor(®) EL-free nanoparticles (NPs) loaded with Paclitaxel (PTX) in order to improve the drug i.v. pharmacokinetic profile and to evaluate its activity against commercially available formulations such as Taxol(®) and Abraxane(®). PTX-loaded poly(ε-caprolactone)-alpha tocopheryl polyethylene glycol 1000 succinate (PCL-TPGS) NPs were prepared using three different techniques: (i) by nanoprecipitation (NPr-method), (ii) by emulsion-solvent evaporation homogenized with an Ultra-Turrax(®) (UT-method) and (iii) by emulsion-solvent evaporation homogenized with an ultrasonicator (US-method). The NPs prepared by US-method showed the smallest size and the highest drug content. The NPs exhibited a slow and continuous release of PTX. The in vitro anti-tumoral activity was assessed using two human breast cancer cell lines (MCF-7 and MDA-MB-231) with the WTS assay. Cytotoxicity studies with both cell lines showed that PTX-loaded PCL-TPGS NPs exhibited better anti-cancer activity compared to PTX solution and the commercial formulation Abraxane(®) at different concentrations. Importantly, in the case of triple negative MDA-MB-231 breast cancer cells, the IC50 value for PTX-loaded PCL-TPGS NPs was 7.8 times lower than Abraxane(®). Finally, in vivo studies demonstrated that PTX-loaded PCL-TPGS NPs exhibited longer systemic circulation time and slower plasma elimination rate than Taxol(®) and Abraxane(®). Therefore, the novel NPs investigated might be an alternative nanotechnological platform for PTX delivery system in cancer chemotherapy.

Polysaccharide-based micelles for drug delivery

Delivery of hydrophobic molecules and proteins has been an issue due to poor bioavailability following administration. Thus, micelle carrier systems are being investigated to improve drug solubility and stability. Due to problems with toxicity and immunogenicity, natural polysaccharides are being explored as substitutes for synthetic polymers in the development of new micelle systems. By grafting hydrophobic moieties to the polysaccharide backbone, self-assembled micelles can be readily formed in aqueous solution. Many polysaccharides also possess inherent bioactivity that can facilitate mucoadhesion, enhanced targeting of specific tissues, and a reduction in the inflammatory response. Furthermore, the hydrophilic nature of some polysaccharides can be exploited to enhance circulatory stability. This review will highlight the advantages of polysaccharide use in the development of drug delivery systems and will provide an overview of the polysaccharide-based micelles that have been developed to date.

Oral delivery of taurocholic acid linked heparin-docetaxel conjugates for cancer therapy

We have synthesized taurocholic acid (TCA) linked heparin-docetaxel (DTX) conjugates for oral delivery of anticancer drug. The ternary biomolecular conjugates formed self-assembly nanoparticles where docetaxel was located inside the core and taurocholic acid was located on the surface of the nanoparticles. The coupled taurocholic acid in the nanoparticles had enhanced oral absorption, presumably through the stimulation of a bile acid transporter of the small intestine. The oral absorption profile demonstrated that the concentration of the conjugates in plasma is about 6 fold higher than heparin alone. An anti-tumor study in MDA-MB231 and KB tumor bearing mice showed significant tumor growth inhibition activity by the ternary biomolecular conjugates. Ki-67 histology study also showed evidence of anticancer activity of the nanoparticles. Finally, noninvasive imaging using a Kodak Molecular Imaging System demonstrated that the nanoparticles were accumulated efficiently in tumors. Thus, this approach for oral delivery using taurocholic acid in the ternary biomolecular conjugates is promising for treatment of various types of cancer.

Dendronized heparin-doxorubicin conjugate based nanoparticle as pH-responsive drug delivery system for cancer therapy

Heparin drug conjugates are currently investigated as excellent candidates for drug delivery vehicles. In this study, we report the preparation and characterization of dendronized heparin-doxorubicin (heparin-DOX) conjugate as pH-sensitive drug delivery vehicle by combination of the features of dendrimer and heparin. Dynamic light scattering (DLS) and transmission electron microscope (TEM) studies demonstrated the dendronized heparin-DOX conjugate self-assembled into compact nanoparticles with negatively charged surface. The nanoparticles with 9.0 wt% (weight percent) of doxorubicin (DOX) showed pH-sensitive property due to the faster drug release rate at pH 5.0 and slow release rate at pH 7.4 aqueous. The nanoparticles were shown to effectively kill cancer cells in vitro. Notablely, the nanoparticles resulted in strong antitumor activity, high antiangiogenesis effects and induced apoptosis on the 4T1 breast tumor model due to the evidences from mice weight shifts, tumor weights, tumor growth curves, immunohistochemical assessment and histological analysis. It's also noteworthy that dendronized heparin and its nanoparticle with drug demonstrated no significant toxicity to healthy organs of both tumor-bearing and healthy mice, which was confirmed by histological analysis compared with free drug DOX. The dendronized heparin-DOX conjugate based nanopatilce with high antitumor activity and low side effects may be therefore a potential nanoscale drug delivery vehicle for breast cancer therapy.