pH Triggered Doxorubicin Delivery of PEGylated Glycolipid Conjugate Micelles for Tumor Targeting Therapy

Enzyme/pH dual stimuli-responsive nanoplatform co-deliver disulfiram and doxorubicin for effective treatment of breast cancer lung metastasis

OBJECTIVES

Metastasis is still one of the main obstacles in the treatment of breast cancer. This study aimed to develop disulfiram (DSF) and doxorubicin (DOX) co-loaded nanoparticles (DSF-DOX NPs) with enzyme/pH dual stimuli-responsive characteristics to inhibit breast cancer metastasis.

METHODS

DSF-DOX NPs were prepared using the amphiphilic poly(ε-caprolactone)-b-poly(L-glutamic acid)-g-methoxy poly(ethylene glycol) (PCL-b-PGlu-g-mPEG) copolymer by a classical dialysis method. In vitro release tests, in vitro cytotoxicity assay, and anti-metastasis studies were conducted to evaluate pH/enzyme sensitivity and therapeutic effect of DSF-DOX NPs.

RESULTS

The specific pH and enzyme stimuli-responsiveness of DSF-DO NPs can be attributed to the transformation of secondary structure and the degradation of amide bonds in the PGlu segment, respectively. This accelerated drug release significantly increased the cytotoxicity to 4T1 cells. Compared with the control group, the DSF-DOX NPs showed a strong inhibition of in vitro metastasis with a wound healing rate of 36.50% and a migration rate of 18.39%. Impressively, in vivo anti-metastasis results indicated that the metastasis of 4T1 cells was almost completely suppressed by DSF-DOX NPs.

CONCLUSION

DSF-DOX NPs with controllable tumor site delivery of DOX and DSF were a prospectively potential strategy for metastatic breast cancer treatment.

Combination of tumor vessel normalization and immune checkpoint blockade for breast cancer treatment via multifunctional nanocomplexes

Tumor vessel normalization can alleviate hypoxia, reduce the intratumoral infiltration of immunosuppressive cells and increase the intratumoral infiltration of immune effector cells (CD8⁺ T cells), further reversing the immunosuppressive microenvironment. Here, nanocomplexes (lipo/St@FA-COSA/BMS-202) which can accurately deliver drugs to tumor tissues and release different drugs at different sites with different rates were prepared to combine tumor vessel normalization with immune checkpoint blockade. The results of drug release in vitro showed that in a pH 6.5 release medium, lipo/St@FA-COSA/BMS-202 rapidly released the vascular normalizing drug (sunitinib, St) and slowly released the PD-1/PD-L1-blocking drug (BMS-202). The results of in vivo experiments showed that the rapidly released St normalized tumor vessels and formed an immunosupportive microenvironment which improved the anti-tumor efficacy of BMS-202. In conclusion, the drug delivery strategy significantly inhibited tumor growth and had excellent anti-tumor efficacy, which can provide a potential approach for effective tumor treatment.

A Novel Sprague-Dawley Rat Model Presents Improved NASH/NAFLD Symptoms with PEG Coated Vitexin Liposomes

Chronic liver disease (CLD) is a global threat to the human population, with manifestations resulting from alcohol-related liver disease (ALD) and non-alcohol fatty liver disease (NAFLD). NAFLD, if not treated, may progress to non-alcoholic steatohepatitis (NASH). Furthermore, inflammation leads to liver fibrosis, cirrhosis, and hepatocellular carcinoma. Vitexin, a natural flavonoid, has been recently reported for inhibiting NAFLD. It is a lipogenesis inhibitor and activates lipolysis and fatty acid oxidation. In addition, owing to its antioxidant properties, it appeared as a hepatoprotective candidate. However, it exhibits low bioavailability and low efficacy due to its hydrophobic nature. A novel rat model for liver cirrhosis was developed by CCL4/Urethane co-administration. Vitexin encapsulated liposomes were synthesized by the ‘thin-film hydration’ method. Polyethylene glycol (PEG) was coated on liposomes to enhance stability and stealth effect. The diseased rats were then treated with vitexin and PEGylated vitexin liposomes, administered intravenously and orally. Results ascertained the liposomal encapsulation of vitexin and subsequent PEG coating to be a substantial strategy for treating liver cirrhosis through oral drug delivery.

Size-Adjustable Nano-Drug Delivery Systems for Enhanced Tumor Retention and Penetration

Over the past decades, nano-drug delivery systems have shown great potential in improving tumor treatment. And the controllability and design flexibility of nanoparticles endow them a broad development space. The particle size is one of the most important factors affecting the potency of nano-drug delivery systems. Large-size (100–200 nm) nanoparticles are more conducive to long circulation and tumor retention, but have poor tumor penetration; small-size (<50 nm) nanoparticles can deeply penetrate tumor but are easily cleared. Most of the current fixed-size nanoparticles are difficult to balance the retention and penetration, while the proposal of size-adjustable nano-drug delivery systems offers a solution to this paradox. Many endogenous and exogenous stimuli, such as acidic pH, upregulated enzymes, temperature, light, catalysts, redox conditions, and reactive oxygen species, can trigger the in situ transformation of nanoparticles based on protonation, hydrolysis, click reaction, phase transition, photoisomerization, redox reaction, etc. In this review, we summarize the principles and applications of stimuli-responsive size-adjustable strategies, including size-enlargement strategies and size-shrinkage strategies. We also propose the challenges faced by size-adjustable nano-drug delivery systems, hoping to promote the development of this strategy.

Preparation and evaluation of dabrafenib-loaded, CD47-conjugated human serum albumin-based nanoconstructs for chemoimmunomodulation

The transmembrane proteins, CD47 and signal-regulatory protein α are overexpressed in cancer cells and macrophages, respectively, and facilitate the escape of cancer cells from macrophage-mediated phagocytosis. The immunomodulatory and targeting properties of CD47, the chemotherapeutic effects of dabrafenib (D), and the anti-programmed death-1 antibodies (PD-1) pave the way for effective chemoimmunomodulation-mediated anticancer combination therapy. In this study, CD47-conjugated, D-loaded human serum albumin (HSA) nanosystems were fabricated by modified nanoparticle albumin-bound technology. Cis-aconityl-PEG-maleimide (CA), an acid-labile linker, was used to conjugate D@HSA and CD47; the resultant CD47-CA@D@HSA exhibited tumor-specificity through receptor targeting, as well as preferential cleavage and drug release in the acidic tumor microenvironment (pH 5) compared to normal physiological pH conditions (pH 6.5, 7.4). The successful preparation of nanosized (∼220 nm), narrowly dispersed (∼0.13) CD47-CA@D@HSA was proven by physicochemical characterization. In vitro and in vivo internalization, accumulation, cytotoxicity, and apoptosis were observed to be higher with CD47-conjugated nanoconstructs, than with free D or non-targeted nanoconstructs. CD47-CA@D@HSA was found to promote the infiltration of cytotoxic T cells and tumor-associated macrophages into tumors and improve in vivo tumor inhibition. Administration in combination with PD-1 further improved antitumor efficacy by promoting immune responses that blocked the immune checkpoint. No signs of toxicity were seen in mice treated with the nanoconstructs; the formulation was, therefore, thought to be biocompatible and as having potential for clinical use. The targeted chemoimmunomodulation achieved by this combination therapy was found to combat major immunosuppressive facets, making it a viable candidate for use in the treatment of cancer.

Chitosan-Based Glycolipid Conjugated siRNA Delivery System for Improving Radiosensitivity of Laryngocarcinoma

Glucose Transporter-1 (GLUT-1) is considered to be a possible intrinsic marker of hypoxia in malignant tumors, which is an important factor in radioresistance of laryngocarcinoma. We speculated that the inhibition of GLUT-1 expression might improve the radiosensitivity of laryngocarcinoma. GLUT-1 siRNA was designed to inhibit the GLUT-1 expression, but the high molecular weight and difficult drug delivery limited the application. Herein, we constructed a glycolipid polymer chitosan oligosaccharide grafted stearic acid (CSSA) to conjugate siRNA via electrostatic interaction. The characteristics of CSSA and CSSA/siRNA were studied, as well as the radiosensitization effect of siRNA on human laryngocarcinoma epithelial (Hep-2) cells. Compared with the traditional commercial vector LipofectamineTM2000 (Lipo), CSSA exhibited lower cytotoxicity, more efficiently cellular uptake. Incubating with CSSA/siRNA, the survival rates of Hep-2 cells were significantly decreased comparing with either the group before transfection or Lipo/siRNA. CSSA is a promising carrier for efficient siRNA delivery and radiosensitization of laryngocarcinoma.

From Nanoparticles to Cancer Nanomedicine: Old Problems with New Solutions

Anticancer nanomedicines have been studied over 30 years, but fewer than 10 formulations have been approved for clinical therapy today. Despite abundant options of anticancer drugs, it remains challenging to have agents specifically target cancer cells while reducing collateral toxicity to healthy tissue. Nanocompartments that can be selective toward points deeply within malignant tissues are a promising concept, but the heterogeneity of tumor tissue, inefficiency of cargo loading and releasing, and low uniformity of manufacture required from preclinical to commercialization are major obstacles. Technological advances have been made in this field, creating engineered nanomaterials with improved uniformity, flexibility of cargo loading, diversity of surface modification, and less inducible immune responses. This review highlights the developmental process of approved nanomedicines and the opportunities for novel materials that combine insights of tumors and nanotechnology to develop a more effective nanomedicine for cancer patients.

Stimuli-Responsive Polymeric Nanoplatforms for Cancer Therapy

Polymeric nanoparticles have been widely used as carriers of drugs and bioimaging agents due to their excellent biocompatibility, biodegradability, and structural versatility. The principal application of polymeric nanoparticles in medicine is for cancer therapy, with increased tumor accumulation, precision delivery of anticancer drugs to target sites, higher solubility of pharmaceutical properties and lower systemic toxicity. Recently, the stimuli-responsive polymeric nanoplatforms attracted more and more attention because they can change their physicochemical properties responding to the stimuli conditions, such as low pH, enzyme, redox agents, hypoxia, light, temperature, magnetic field, ultrasound, and so on. Moreover, the unique properties of stimuli-responsive polymeric nanocarriers in target tissues may significantly improve the bioactivity of delivered agents for cancer treatment. This review introduces stimuli-responsive polymeric nanoparticles and their applications in tumor theranostics with the loading of chemical drugs, nucleic drugs and imaging molecules. In addition, we discuss the strategy for designing multifunctional polymeric nanocarriers and provide the perspective for the clinical applications of these stimuli-responsive polymeric nanoplatforms.

Hepatocyte-targeting and microenvironmentally responsive glycolipid-like polymer micelles for gene therapy of hepatitis B

Hepatitis B (HB) is a viral infectious disease that seriously endangers human health, and since there are no radical drugs to counter this, effective and safe therapies urgently need to be developed. HB virus (HBV) mainly infects hepatocytes (HCs), while the drugs are easily phagocytosed by Kupffer cells (KCs). In this study, the glutathione concentration difference between HCs and KCs was examined and utilized in an ideal drug-release strategy. Here, galactosylated chitosan-oligosaccharide-SS-octadecylamine (Gal-CSSO) was prepared to accurately deliver 10-23 DNAzyme DrzBC (blocking HBeAg expression) or DrzBS (blocking HBsAg expression) in targeted HB therapy. In vitro Gal-CSSO systems exhibited low cytotoxicity, endosomal escape, and glutathione responsiveness. The HBeAg and HBsAg secretion of HepG2.2.15 was significantly decreased by Gal-CSSO systems, and the maximum inhibition rates were 1.82-fold and 2.38-fold greater than those of commercial Lipofectamine 2000 (Lipo2000) systems. In vivo Gal-CSSO systems exhibited HC targeting and HC microenvironmental responsiveness without noticeable hepatotoxicity or systemic toxicity. The HBeAg and HBsAg titers of the HBV-infected mice were evidently decreased by Gal-CSSO systems, and the inhibition rates were 1.52-fold and 1.22-fold greater than those of Lipo2000 systems. This study presents a kind of glycolipid-like polymer micelles that promise efficient and safe gene therapy of HB.

Review of Curcumin Physicochemical Targeting Delivery System

Curcumin (CUR), as a traditional Chinese medicine monomer extracted from the rhizomes of some plants in Ginkgo and Araceae, has shown a wide range of therapeutic and pharmacological activities such as anti-tumor, anti-inflammatory, anti-oxidation, anti-virus, anti-liver fibrosis, anti-atherosclerosis, and anti-Alzheimer’s disease. However, some issues significantly affect its biological activity, such as low aqueous solubility, physico-chemical instability, poor bioavailability, and low targeting efficacy. In order to further improve its curative effect, numerous efficient drug delivery systems have been carried out. Among them, physicochemical targeting preparations could improve the properties, targeting ability, and biological activity of CUR. Therefore, in this review, CUR carrier systems are discussed that are driven by physicochemical characteristics of the microenvironment (eg, pH variation of tumorous tissues), affected by external influences like magnetic fields and vehicles formulated with thermo-sensitive materials.

Acid-Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5

PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring-opening copolymerization of ethylene oxide with 3,4-epoxy-1-butene (EPB) and subsequent modification to introduce acid-degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross-linking. Copolymers with different molar ratios of EPB, molecular weights (Mn ) up to 10 000 g mol-1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG-co-isoEPB)MA copolymer and the hydrogels showed pH-dependent, rapid hydrolysis at pH 5-6 and long-term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA-Alexa488 can be tailored from a few hours to several days (hydrolysis half-life time t1/2 at pH 5: 13 h to 51 h).

Novel cytokine-loaded PCL-PEG scaffold composites for spinal cord injury repair

Severe spinal cord injury (SCI) always leads to permanent sensory and motor dysfunction. However, the therapeutic effects of current treatment methods, including high dose methylprednisolone, surgical interventions and rehabilitative care, are far from satisfactory. In recent years, cellular, molecular, tissue engineering and rehabilitative training have shown promising results in animal models. Poly-ε-caprolacton (PCL) - based hydrogel composite system has been considered as a promising strategy to direct the axon growth and mimic the properties of natural extracellular matrix. In this study, we found the addition of the fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) to the hydrogel induces the production of axon growth-supportive substrates. The addition of the glial-derived neurotrophic factor (GDNF) to the hydrogel further induces axon directional growth. This "five-in-one" composite scaffold, referred to as PCL/PEG/FGF2/EGF/GDNF, improved the locomotor function in rats 8 weeks after spinal cord injury (SCI) after implantation in transected spinal cord. Furthermore, histological assessment indicated that the designed composite scaffold guided the neuronal regeneration and promoted the production of axon growth-supportive substrates, providing a favorable biological microenvironment. Our novel composite scaffold provides a promising therapeutic method for SCI.

Effects of PEGylation on capture of dextran-coated magnetic nanoparticles in microcirculation

BACKGROUND

Magnetic nanoparticles (MNPs) can be localized against hemodynamic forces in blood vessels with the application of an external magnetic field. In addition, PEGylation of nanoparticles may increase the half-life of nanocomposites in circulation. In this work, we examined the effect of PEGylation on the magnetic capture of MNPs in vivo.

METHODS

Laser speckle contrast imaging and capillaroscopy were used to assess the magnetic capture of dextran-coated MNPs and red blood cell (RBC) flow in cremaster microvessels of anesthetized rats. Magnetic capture of MNPs in serum flow was visualized with an in vitro circulating system. The effect of PEGylation on MNP-endothelial cell interaction was studied in cultured cells using an iron assay.

RESULTS

In microcirculation through cremaster muscle, magnet-induced retention of 250 nm MNPs was associated with a variable reduction in RBC flow, suggesting a dynamic coupling of hemodynamic and magnetic forces. After magnet removal, faster restoration of flow was observed in PEG(+) than PEG(-) group, which may be attributed to a reduced interaction with vascular endothelium. However, PEGylation appears to be required for magnetic capture of 50 nm MNPs in microvessels, which was associated with increased hydrodynamic diameter to 130±6 nm in serum, but independent of the ς-potential.

CONCLUSION

These results suggest that PEGylation may enhance magnetic capture of smaller MNPs and dispersion of larger MNPs after magnet removal, which may potentially affect the targeting, pharmacokinetics and therapeutic efficacy.

Redox-responsive chitosan oligosaccharide-SS-Octadecylamine polymeric carrier for efficient anti-Hepatitis B Virus gene therapy

DrzBC and DrzBS (10-23 DNAzyme) could block the expression of HBV e- and s- gene respectively. But the application of 10-23 DNAzyme was limited owing to the lack of appropriate delivery vehicles. Chitosan oligosaccharide-SS-Octadecylamine (CSSO), a redox-responsive nano-sized polymeric carrier, could self-aggregate and bind with DNA by electrostatic interaction at proper mass ratio. Compared with the traditional commercial carrier Lipo2000, CSSO exhibited lower cytotoxicity, efficient cellular uptake by targeting cells, and rapidly DNA released in cytoplasm after escaping from endosomes. Including the same DNA concentration, Lipo2000/(DrzBC or DrzBS) showed maximum inhibitory rate on HBeAg (47.29 ± 1.86%) and HBsAg (33.58 ± 0.72%) secretion after 48 h incubation, and then both decreased. In contrast, HBeAg secretion inhibition by CSSO/DrzBC and HBsAg secretion inhibition by CSSO/DrzBS were up to 73.86 ± 1.77% and 67.80 ± 2.51% at 48 h, and further increased to 83.83 ± 2.34% and 76.79 ± 2.18% at 72 h, respectively. CSSO is a promising redox-responsive polymeric carrier for efficient anti-Hepatitis B Virus gene therapy.

OFF–ON nanodiamond drug platform for targeted cancer imaging and therapy

The pH-responsive drug delivery system (NPGD) can act as a direct OFF–ON mechanism for activatable bioimaging and cancer therapy.

Immune Adjuvant Targeting Micelles Allow Efficient Dendritic Cell Migration to Lymph Nodes for Enhanced Cellular Immunity

Cellular immunity is essential for the effectiveness of vaccines against cancer. After capture of vaccines, dendritic cells (DCs) have to migrate to lymph nodes via chemokine receptor type 7 (CCR7). Subsequently, DCs present cytosolic antigens via major histocompatibility complex class I (MHC I) molecules to induce cellular immunity. However, various vaccines fail to induce potent cellular immunity due to insufficient MHC I-restricted antigen presentation and limitations of immune adjuvants. Hence, we constructed novel immune adjuvant targeting micelles (M-COSA) to targeted codeliver antigen ovalbumin (OVA) and plasmid DNA encoding CCR7 (CCR7 pDNA) to the cytosol of DCs, thus promoting DC migration to lymph nodes to boost MHC I-restricted antigen presentation. M-COSA exhibited adjuvant activity and demonstrated more efficient DC cellular uptake compared with COSA. M-COSA/OVA/pDNA increased costimulatory molecule expression and cytokine secretion, resulting in DC activation and maturation. Moreover, antigens and pDNA, which were encapsulated in micelles, escaped from the endosome into the cytoplasm to achieve MHC I-restricted antigen presentation and increase CCR7 expression. The number of CD8⁺ T cells, which was positively correlated with tumor rejection, was notably increased and tumor growth was dramatically suppressed after vaccination with M-COSA/OVA/pDNA. In summary, M-COSA/OVA/pDNA micelles, which allow DC targeting and efficient DC migration to lymph nodes to enhance cellular immunity, exhibit effective tumor inhibition and lay the foundation for novel vaccine design.

Recent Progress and Advances in Stimuli-Responsive Polymers for Cancer Therapy

The conventional chemotherapeutic agents, used for cancer chemotherapy, have major limitations including non-specificity, ubiquitous biodistribution, low concentration in tumor tissue, and systemic toxicity. In recent years, owing to their unique features, polymeric nanoparticles have been widely used for the target-specific delivery of drugs in the body. Although polymeric nanoparticles have addressed a number of important issues, the bioavailability of drugs at the disease site, and especially upon cellular internalization, remains a challenge. A polymer nanocarrier system with a stimuli-responsive property (e.g., pH, temperature, or redox potential), for example, would be amenable to address the intracellular delivery barriers by taking advantage of pH, temperature, or redox potentials. With a greater understanding of the difference between normal and pathological tissues, there is a highly promising role of stimuli-responsive nanocarriers for drug delivery in the future. In this review, we highlighted the recent advances in different types of stimuli-responsive polymers for drug delivery.

Co-delivery of Metformin and Paclitaxel Via Folate-Modified pH-Sensitive Micelles for Enhanced Anti-tumor Efficacy

Single chemotherapeutic agent like paclitaxel (PTX) has shown some limitations in anti-tumor treatment, such as undesirable side effects, multidrug resistance, and high toxicity. In order to reduce the toxicity of PTX and increase the anti-tumor effect, folate-modified amphiphilic and biodegradable biomaterial was developed to co-deliver PTX and metformin (MET) for exerting the synergistic effect. PTX was physically entrapped in the hydrophobic inner core of the amphiphilic block copolymer by a solvent evaporation method, whereas MET was chemically conjugated to the hydrophilic terminals of copolymer via a pH-sensitive cis-aconityl linkage (Cis). The in vitro release behaviors of the drugs were analyzed by high-performance liquid chromatography (HPLC), and the synergistic effect of the drugs was evaluated by a Q value method. Results showed that drug-loaded micelles with an average size about 100 nm were successfully constructed. In acidic environments, the chemically conjugated MET was rapidly released after the breakage of sensitive bond between drug and copolymer. In vitro anti-tumor studies demonstrated that MET and PTX had a synergistic effect and co-delivery micelles induced higher cytotoxicity and apoptosis against 4T1 breast cancer cells than free drugs. Furthermore, folate-targeted co-delivery micelles increased the cellular uptake of drugs and were found to be effective for the treatment of solid tumor in vivo. These findings indicated that co-delivery of MET and PTX through the polymeric micelles is a promising strategy for cancer therapy.

Self-assembly of bioactive peptides, peptide conjugates, and peptide mimetic materials

Molecular self-assembly is a multi-disciplinary field of research, with potential chemical and biological applications. One of the main driving forces of self-assembly is molecular amphiphilicity, which can drive formation of complex and stable nanostructures. Self-assembling peptide and peptide conjugates have attracted great attention due to their biocompatibility, biodegradability and biofunctionality. Understanding assembly enables the better design of peptide amphiphiles which may form useful and functional nanostructures. This review covers self-assembly of amphiphilic peptides and peptide mimetic materials, as well as their potential applications.

Nanomicelle drug with acid-triggered doxorubicin release and enhanced cellular uptake ability based on mPEG-graft-poly(N-(2-aminoethyl)-L-aspartamide)-hexahydrophthalic acid copolymers

In order to achieve the passive tumor targeting and acid-triggered drugs release in lysosomes, optimized delivery system for doxorubicin based on pH-sensitive complex nanomicelles with suitable particle size was developed in this research. Particularly, poly(L-succinimide) was thoroughly ring-opened by ethylenediamine to give the poly(N-(2-aminoethyl)-L-aspartamide). Then, graft copolymer mPEG-graft-poly(N-(2-aminoethyl)-L-aspartamide)-hexahydrophthalic acid (mPEG-g-P(ae-Asp)-Hap) was synthesized by grafting mPEG-2000 and hexahydrophthalic anhydride onto poly(N-(2-aminoethyl)-L-aspartamide). In vitro studies revealed that mPEG-g-P(ae-Asp)-Hap copolymer was stable in neutral solutions but tend to be hydrolyzed under acidic condition, which was attributed to the acid-sensitive properties of hexahydrophthalic amides (β-carboxylic amides). MPEG-g-P(ae-Asp)-Hap copolymer with critical aggregation concentration of 0.166 mg·mL^-1 could self-assemble into stable blank nanomicelles with an average particle hydrodynamic diameter of 98.1 nm, but the hydrodynamic diameter of doxorubicin-loaded nanomicelles (mPEG-g-P(ae-Asp)-Hap·Dox) was smaller and approximately 77.5 nm. MPEG-g-P(ae-Asp)-Hap·Dox nanomicelles showed sustained drug release profiles over 34 h, and the cumulative drug release showed a tendency to increase from 25% to 62% with the pH value decreasing from 7.4 to 5.0 due to the acid-triggered disassembly of nanomicelles. The cytotoxicity of mPEG-g-P(ae-Asp)-Hap·Dox nanomicelles against A549 treated with 40 mM NH₄Cl (lysosomotropic weak bases) was decreased significantly than that without NH₄Cl treatment, further confirmed the drug release from the nanomicelles was triggered by the low pH value of lysosome (pH 5.0). Compared with doxorubicin HCl, mPEG-g-P(ae-Asp)-Hap·Dox nanomicelle drug showed enhanced cellular uptake ability during 2 or 4 h of incubation due to the endocytosis mechanism of nanomicelle drug. In summary, the cleavage of pH-sensitive β-carboxylic amides bonds on the hydrophobic branch of mPEG-g-P(ae-Asp)-Hap copolymer triggered the disassembly of the nanomicelles and release of doxorubicin in the acidic lysosomal compartments of cancer cells. These nanomicelles exhibited excellent potential for drug delivery due to their smart properties-PEGylation, suitable size, and acid-triggered drug release.

In vitro and in vivo study of pH-sensitive and colon-targeting P(LE-IA-MEG) hydrogel microspheres used for ulcerative colitis therapy

Hydrocortisone sodium succinate (HSS) is an anti-inflammatory drug, but its application on ulcerative colitis (UC) treatment is limited by its associated side-effects. To solve this problem, a kind of pH-sensitive P(LE-IA-MEG) hydrogel microspheres (HMSs) were prepared as the drug carrier of hydrocortisone sodium succinate (HSS) for the treatment of UC. The P(LE-IA-MEG) HMSs were spherical in shape with good dispersion and the mean particle size was 34.87±0.90μm. HSS was successfully loaded into the P(LE-IA-MEG) HMSs. The in vitro release study of HSS-loaded HMSs (HSS-HMSs) revealed that the HSS-HMSs possessed desirable pH-sensitivity, the cumulative release rate was 4.07% and 94.64% in the solution with pH 1.2 and pH 7.4 solution during 12h, respectively. Furthermore, the study on pharmacokinetic, gastrointestinal drug residue and side-effects were conducted to evaluate the in vivo colon-targeting property of the HSS-HMSs. All the results showed that the HSS-HMSs could deliver HSS to the colon as well as reduce its premature absorption in the upper gastrointestinal tract. Finally, the HSS-HMSs showed better ameliorative effects and therapeutic effects on mice with experimental colitis as compared to HSS. In conclusion, the HSS-HMSs had great potential in the treatment of UC.

Galactose-Containing Polymer-DOX Conjugates for Targeting Drug Delivery

A novel multifunctional drug delivery system was fabricated by conjugating galactose-based polymer, methoxy-poly(ethylene glycol)-block-poly(6-O-methacryloyl-D-galactopyranose) (mPEG-b-PMAGP) with doxorubicin (DOX) via an acid-labile carbamate linkage. The mPEG-b-PMAGP-co-DOX nanoparticles were spherical in shape, and the diameter determined by dynamic light scattering (DLS) was 54.84 ± 0.58 nm, larger than that characterized by transmission electron microscopy (TEM). The in vitro drug release profiles were studied, and the release of DOX from the nanoparticles was pH-responsive. The cellular uptake behavior of free-DOX and mPEG-b-PMAGP-co-DOX nanoparticles by asialoglycoprotein (ASGP) receptor-positive cancer cell line (HepG2) and ASGP receptor-negative cancer cell lines (MCF-7 and A549 cells) was evaluated by confocal laser scanning microscopy (CLSM) and flow cytometry (FCM), respectively. The mPEG-b-PMAGP-co-DOX nanoparticles which contain galactose functional groups exhibited higher cellular uptake behavior via ASGP receptor-mediated endocytosis in HepG2 cells than in other two cancer cells. The in vitro cytotoxicity assay manifested that the mPEG-b-PMAGP-co-DOX nanoparticles exhibited higher anticancer efficacy against HepG2 cells than MCF-7 cells. These results indicated that the multifunctional mPEG-b-PMAGP-co-DOX nanoparticles possessing pH-responsible and hepatoma-targeting function have great potential to be used as a targeting drug delivery system for hepatoma therapy.

Advances in Bone-targeted Drug Delivery Systems for Neoadjuvant Chemotherapy for Osteosarcoma

Targeted therapy for osteosarcoma includes organ, cell and molecular biological targeting; of these, organ targeting is the most mature. Bone-targeted drug delivery systems are used to concentrate chemotherapeutic drugs in bone tissues, thus potentially resolving the problem of reaching the desired foci and minimizing the toxicity and adverse effects of neoadjuvant chemotherapy. Some progress has been made in bone-targeted drug delivery systems for treatment of osteosarcoma; however, most are still at an experimental stage and there is a long transitional period to clinical application. Therefore, determining how to combine new, polymolecular and multi-pathway targets is an important research aspect of designing new bone-targeted drug delivery systems in future studies. The purpose of this article was to review the status of research on targeted therapy for osteosarcoma and to summarize the progress made thus far in developing bone-targeted drug delivery systems for neoadjuvant chemotherapy for osteosarcoma with the aim of providing new ideas for highly effective therapeutic protocols with low toxicity for patients with osteosarcoma.

A54 Peptide Modified and Redox-Responsive Glucolipid Conjugate Micelles for Intracellular Delivery of Doxorubicin in Hepatocarcinoma Therapy

Redox-responsive nanomaterials applied in drug delivery systems (DDS) have attracted an increasing attention in pharmaceutical research as a carrier for antitumor therapy. However, there would be unwanted drug release from a redox-responsive DDS with no selection at nontarget sites, leading to undesirable toxicities in normal tissues and cells. Here, an A54 peptide modified and PEGylated reduction cleavable glucolipid conjugate (A54-PEG-CSO-ss-SA, abbreviated to APC_ssA) was designed for intracellular delivery of doxorubicin (DOX). The synthesized APC_ssA could be assembled via micellization self-assembly in aqueous water above the critical micelle concentration (54.9 μg/mL) and exhibited a high drug encapsulation efficiency (77.92%). The APC_ssA micelles showed an enhanced redox sensitivity in that the disulfide bond could be degraded quickly and the drug would be released from micelles in 10 mM levels of glutathione (GSH). The cellular uptake studies highlighted the affinity of APC_ssA micelles toward the hepatoma cells (BEL-7402) compared to that toward HepG2 cells. In contrast with the nonresponsive conjugate, the drug was released from APC_ssA micelles more quickly in 10 mM level of GSH concentration (tumor cells). Moreover, the DOX-loaded APC_ssA micelles displayed an increased cytotoxicity which was 1.6- to 2.0-fold that of unmodified and nonresponsive micelles. In vivo, the APC_ssA micelles had stronger distribution to liver and hepatoma tissue and prolonged the circulation and retention time, while the drug release only occurred in the tumor tissue. The APC_ssA/DOX showed the tumor inhibition rate equal to that of commercial doxorubicin hydrochloric without negative consequence. This study suggested that the APC_ssA/DOX showed promising potential to treat the tumor for its special tumor targeting, selective intracellular drug release, enhanced antitumor activity, and reduced toxicity on normal tissues.

Novel biodegradable nanocarriers for enhanced drug delivery

With the refinement of functional properties, the interest around biodegradable materials, in biorelated applications and, in particular, in their use as controlled drug-delivery systems, increased in the last decades. Biodegradable materials are an ideal platform to obtain nanoparticles for spatiotemporal controlled drug delivery for the in vivo administration, thanks to their biocompatibility, functionalizability, the control exerted on delivery rates and the complete degradation. Their application in systems for cancer treatment, brain and cardiovascular diseases is already a consolidated practice in research, while the bench-to-bedside translation is still late. This review aims at summarizing reported applications of biodegradable materials to obtain drug-delivery nanoparticles in the last few years, giving a complete overview of pros and cons related to degradable nanomedicaments.

Graphene oxide-incorporated pH-responsive folate-albumin-photosensitizer nanocomplex as image-guided dual therapeutics

The objective of this study was to develop an active-targeted, pH-responsive albumin-photosensitizer-incorporated graphene oxide nanocomplex as an image-guided theranostic agent for dual therapies. Herein, bovine serum albumin (BSA)-cis-aconityl pheophorbide-a (c-PheoA) conjugate was complexed with graphene oxide (GO) at ratios of 1:1, 1:0.5, and 1:0.1 with the mean hydrodynamic diameter of the resulting complex being 100-200nm. Further, with the 1:0.5 ratio, we developed a folate-BSA-c-PheoA conjugate:GO complex incorporated free PheoA (PheoA+GO:FA-BSA-c-PheoA NC) with a mean hydrodynamic diameter of 182.0±33.2nm. The release study showed that the photosensitizer from the nanocomplex was released rapidly at pH5.5 compared to that at pH7.4 when incubated for 24h. Cellular uptake results showed that the PheoA+GO:FA-BSA-c-PheoA NCs was readily taken up by B16F10 and MCF7 cancer cells. In vitro phototoxicity results showed that PheoA+GO:FA-BSA-c-PheoA NC has a higher efficacy against cancer cells than free PheoA, thereby demonstrating the synergistic effect of PS and GO in response to a single laser of 670nm. In vivo and ex vivo bioimaging results showed that fluorescence signals of higher intensity were observed in the tumor area of mice treated with PheoA+GO:FA-BSA-c-PheoA NC than those in the tumor of mice treated with free PheoA, thereby suggesting that the targeted nanocomplex selectively accumulated in the tumor area compared to free PheoA. Through antitumor study, PheoA+GO:FA-BSA-c-PheoA NC showed a synergistic effect in tumor-bearing mice by a single 671nm laser treatment. These results demonstrate that our prepared PheoA+GO:FA-BSA-c-PheoA NC can be used as a theranostic agent in phototherapies and for the photodiagnosis of cancer.

MMP2-Targeting and Redox-Responsive PEGylated Chlorin e6 Nanoparticles for Cancer Near-Infrared Imaging and Photodynamic Therapy

A unique matrix metalloproteinase 2-targeted photosensitizer delivery platform was developed in this study for tumor-targeting imaging and photodynamic therapy. The model photosensitizer therapeutic agent chlorin e6 (Ce6) was first covalently conjugated with matrix metalloproteinase 2-cleavable polypeptide and then modified with polyethylene glycol via a redox-responsive cleavable disulfide linker. The resultant matrix metalloproteinase 2-cleavable polypeptide modified PEGylated Ce6 (PEG-SS-Ce6-MMP2) nanoparticles, which formed via self-assembly, were observed to be monodisperse and significantly stable in aqueous solution. In addition, owing to their cellular redox-responsiveness at the cleavable disulfide linker, the PEG-SS-Ce6-MMP2 nanoparticles were able to release Ce6 rapidly. Despite displaying enhanced intracellular internalization, the synthesized PEG-SS-Ce6-MMP2 nanoparticles did not compromise their phototoxic effects toward A549 cancer cells when compared with free Ce6 and PEGylated Ce6 nanoparticles. In vivo experiments further revealed that, in contrast with the free Ce6 or with the PEGylated Ce6 nanoparticles, the PEG-SS-Ce6-MMP2 nanoparticles showed a remarkable increase in tumor-targeting ability and a significantly improved photodynamic therapeutic efficiency in A549 tumor-bearing mice. These results suggest that the PEG-SS-Ce6-MMP2 nanoparticles hold great potential for tumor-targeting imaging and photodynamic therapy.

The fluorescent interactions between amphiphilic chitosan derivatives and water-soluble quantum dots

The LCC-CdTe quantum dots (QDs) hybrid was fabricated by mixing the N-lauryl-N, O-carboxymethyl chitosan (LCC) micelle with water-soluble CdTe QDs in an aqueous solution via hydrophobic forces and the electronic attraction. The structures of LCC and LCC-CdTe QDs hybrid were determined by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The results showed that the lauryl and carboxymethyl were successfully grafted to chitosan oligosaccharide (CSO), and a number of CdTe QDs were encapsulated by LCC micelle to form a core/shell structure. The tested results of the fluorescent characteristics of LCC, CdTe QDs and LCC-CdTe QDs hybrid showed that there were some obvious fluorescent interactions between LCC and CdTe QDs. Meanwhile, with the change in LCC space structure, the fluorescent interactions between LCC and QDs showed different fluorescent characteristics. The QDs fluorescent (FL) intensity increased first and then decreased to almost quenching, while LCC FL intensity decreased continually.

pH-sensitive nanomedicine based on PEGylated nanodiamond for enhanced tumor therapy

pH-sensitive nanomedicine based on PEGylated nanodiamond with excellent dispersity, a slow and sustained drug release capability for enhanced tumor therapy.

pH and thermosensitive 5-fluorouracil loaded poly(NIPAM-co-AAc) nanogels for cancer therapy

The aim of the study was to develop 5-FU loaded pH and thermo-sensitive nanogels that could specifically respond to tumour endosomal pH and extracellular pH, while being dormant to physiological pH at physiological temperature.

Improved oral delivery of resveratrol from N-trimethyl chitosan-g-palmitic acid surface-modified solid lipid nanoparticles

Despite the therapeutic effects of resveratrol, its clinical application is restricted by its poor oral bioavailability, low water solubility, and instability. Solid lipid nanoparticles (SLNs)-based drug delivery systems have been shown to provide excellent support for the delivery of hydrophobic drugs. The poor stability and burst release behavior in stomach acidic pH conditions of SLNs result in increased aggregation of the particles in the gastrointestinal environment, limiting the success of these particles as an oral delivery system for hydrophobic drugs. N-trimethyl chitosan (TMC) graft palmitic acid (PA) (TMC-g-PA) mucoadhesive copolymer was hypothesized to be a promising candidate for the surface modification of PA-decorated resveratrol-loaded SLNs to stabilize SLNs and circumvent all the above mentioned obstacles. TMC and TMC-g-PA copolymers were therefore synthesized and characterized by (1)H-nuclear magnetic resonance ((1)H NMR) and Fourier-transformed infra-red (FT-IR) spectroscopy. Resveratrol-loaded SLNs (SLRNs) that comprised Precirol ATO 5, PA, Gelucire 50/13, Tween 80, and resveratrol as well as TMC-g-PA SLRNs were formulated and characterized in terms of physicochemical properties, stability, cytotoxicity, and in vitro and in vivo effects. The in vitro release studies of TMC-g-PA SLRNs demonstrated negligible release of resveratrol in simulated gastric and sustained release in simulated intestinal conditions and the relative bioavailability of resveratrol was furthermore found to be 3.8-fold higher from TMC-g-PA SLRNs than that from resveratrol suspension. Overall, the findings reported here indicate that TMC-g-PA SLRNs represent a potential oral drug delivery system for resveratrol.

Triazole-Linked Glycolipids Enhance the Susceptibility of MRSA to β-Lactam Antibiotics

We show here that a series of triazolyl glycolipid derivatives modularly synthesized by a "click" reaction have the ability to increase the susceptibility of a drug-resistant bacterium to β-lactam antibiotics. We determine that the glycolipids can suppress the minimal inhibitory concentration of a number of ineffective β-lactams, upward of 256-fold, for methicillin-resistant Staphylococuss aureus (MRSA). The mechanism of action has been preliminarily probed and discussed.

Matrix metalloproteinase triggered size-shrinkable gelatin-gold fabricated nanoparticles for tumor microenvironment sensitive penetration and diagnosis of glioma

To improve glioma targeting delivery efficiency and to monitor drug delivery and treatment outcome, a novel tumor microenvironment sensitive size-shrinkable theranostic system was constructed and evaluated. The G-AuNPs-DC-RRGD system was constructed by fabricating small sized gold nanoparticles (AuNPs) onto matrix metalloproteinase-2 (MMP-2) degradable gelatin nanoparticles (GNPs), doxorubicin (DOX) and Cy5.5 were decorated onto AuNPs through a hydrazone bond to enable the system with pH triggered cargoes release, and RRGD, a tandem peptide of RGD and octarginine was surface-modified onto the system to enable it with glioma active targeting ability. In vitro, the size of G-AuNPs-DC-RRGD could effectively shrink from 188.2 nm to 55.9 nm after incubation with MMP-2, while DOX and Cy5.5 were released in a pH dependent manner. Cellular uptake demonstrated that G-AuNPs-DC-RRGD could be effectively taken up by cells with higher intensity than G-AuNPs-DC-PEG. A study of tumor spheroids further demonstrated that the particles with smaller size showed better penetration ability, while RRGD modification could further improve permeability. In vivo, G-AuNPs-DC-RRGD displayed the best glioma targeting and accumulation efficiency, with good colocalization with neovessels. Cy5.5 also was colocalized well with DOX, indicating that Cy5.5 could be used for imaging of DOX delivery.

Emerging antitumor applications of extracellularly reengineered polymeric nanocarriers

Recently, polymeric nanocarriers with shielding surfaces, e.g., poly(ethylene glycol) and small molecules, have been widely applied in antitumor drug delivery mainly because of their stealth during blood circulation. However, the shielding shell greatly hinders the tumor penetration, drug release, and cell internalization of the nanocarriers, which leads to unsatisfactory therapeutic efficacy. To integrate the extended blood circulation time and the enhanced drug transmission in one platform, some extracellularly stimuli-mediated shell-sheddable polymeric nanocarriers have been exploited. The systems are stealthy and stable during blood circulation, and as soon as they reach tumor tissue, the shielding matrices are removed, which is triggered by extracellular endogenous stimuli (e.g., pH or enzymes) or exogenous excitations (e.g., light or voltage). This review mainly focuses on recent advances in the designs and emerging antitumor applications of extracellularly reengineered polymeric nanocarriers for directional drug delivery, as well as perspectives for future developments.

Selective redox-responsive drug release in tumor cells mediated by chitosan based glycolipid-like nanocarrier

The redox responsive nanocarriers have made a considerable progress in achieving triggered drug release by responding to the endogenous occurring difference between the extra- and intra- cellular redox environments. Despite the promises, this redox difference exists both in normal and tumor tissue. So a non-selective redox responsive drug delivery system may result in an undesired drug release in normal cells and relevant side-effects. To overcome these limitations, we have developed a chitosan based glycolipid-like nanocarrier (CSO-ss-SA) which selectively responded to the reducing environment in tumor cells. The CSO-ss-SA showed an improved reduction-sensitivity which only fast degraded and released drug in 10mM levels of glutathione (GSH). The CSO-ss-SA could transport the drug fast into the human ovarian cancer SKOV-3 cells and human normal liver L-02 cells by internalization, but only fast release drug in SKOV-3 cells. By regulating the intracellular GSH concentration in SKOV-3 cells, it indicated that the cellular inhibition of the PTX-loaded CSO-ss-SA showed a positive correlation with the GSH concentration. The CSO-ss-SA was mainly located in the liver, spleen and tumor in vivo, which evidenced the passive tumor targeting ability. Despite the high uptake of liver and spleen, drug release was mainly occurred in tumor. PTX-loaded CSO-ss-SA achieved a remarkable tumor growth inhibition effect with rather low dose of PTX. This study demonstrates that a smartly designed glycolipid-like nanocarrier with selective redox sensitivity could serve as an excellent platform to achieve minimal toxicity and rapid intracellular drug release in tumor cells.

Effect of anionic PEGylated polypeptide on gene transfection mediated by glycolipid conjugate micelles

To improve the gene transfection efficiency mediated by chitosan-g-stearic acid (CS) micelles, poly(ethylene glycol)-b-poly(γ-glutamic acid) (PG) was incorporated into a CS-based gene delivery system. CS/PG/pDNA complexes were prepared by ionic interaction. CS and PEGylated CS (PCS) micelles were introduced to prepare binary complexes for use as controls. CS/PG/pDNA complexes possessed similar sizes and presented as irregular spheroids in shape. The incorporation of PG into CS/pDNA complexes did not affect the ability of CS to compact pDNA and also showed a protective effect against DNase I based degradation of pDNA. Importantly, PG could increase gene transfection efficiency, which was also affected by the mixing methods used for the preparation of CS/PG/pDNA ternary complexes. The transfection efficiencies mediated by CS/PG/pDNA complexes against HEK293 and EC-1 cells reached up to 40.8% and 11.6%, respectively, which were much higher than those of CS/pDNA complexes (1.3% and 4.0%) and PCS/pDNA complexes (0.8% and 2.4%). In addition, the incorporation of PG into CS/pDNA complexes significantly enhanced cellular uptake in HEK293 and EC-1 cells and, additionally, improved endosomal escape and intracellular vector unpacking. However, the incorporation of PG reduced the cellular uptake of CS/PG/pDNA complexes in macrophages (RAW264.7 cells). It was further demonstrated that, in addition to a nonspecific charge-mediated binding to cell membranes, a γ-PGA-specific receptor-mediated pathway was involved in the internalization of CS/PG/pDNA complexes. These results indicated that PG played multiple important roles in enhancing the transfection efficiency of CS/PG/pDNA complexes.

In situ synthesis of multidentate PEGylated chitosan modified gold nanoparticles with good stability and biocompatibility

To realize desirable functions in the rather complex biological systems, a suitable surface coating is desirable for gold nanoparticles, which plays an important role in their colloidal stability and biocompatibility.

Active-targeted pH-responsive albumin–photosensitizer conjugate nanoparticles as theranostic agents

The objective of this study was to develop an active-targeted, pH-responsive albumin–photosensitizer conjugate as a theranostic agent.