Tumor microenvironment-responsive micelles for pinpointed intracellular release of doxorubicin and enhanced anti-cancer efficiency

Enzyme-responsive nano-drug delivery system for combined antitumor therapy

Efficient drug loading, tumor targeting, intratumoral penetration, and cellular uptake are the main factors affecting the effectiveness of drug delivery systems in oncotherapy. Based on the tumor microenvironment, we proposed to develop Curcumin (Cur)-loaded matrix metalloproteinase (MMP)-responsive nanoparticles (Cur-P-NPs) by static electricity, to enhance tumor targeting, cellular uptake, and drug loading efficiency. These nanoparticles combine the properties of both PEG-peptides (cleaved peptide + penetrating peptide) and star-shaped polyester (DPE-PCL) nanoparticles. Cur-P-NPs displayed good entrapment efficiency, drug loading and biocompatibility. Additionally, they showed an enhanced release rate, cellular uptake, and anti-proliferative activity by activating peptides under the simulated tumor microenvironment. Furthermore, intraperitoneal injection of losartan (LST) successfully enhanced intratumoral drug penetration by collagen I degradation. In vivo studies based on the systematic administration of the synergistic LST + Cur-P-NPs combination to mice confirmed that combined antitumor therapy with LST and Cur-P-NPs could further improve intratumor distribution, enhance anticancer efficacy, and reduce the toxicity and side effects. Therefore, LST + Cur-P-NPs represent a new and efficient system for clinical oncotherapy.

Chemical Modification of Chitosan for Developing Cancer Nanotheranostics

Cancer is a worldwide public health issue that has not been conquered. Theranostics, the combination of a therapeutic drug and imaging agent in one formulation using nanomaterials, has been developed to better cure cancer in recent years. Although diverse biomaterials have been applied in cancer theranostics, chitosan (CS), a natural polysaccharide bearing easy modification sites with excellent biocompatibility and biodegradability, shows great potential for developing cancer nanotheranostics. In this review, we seek to describe the chemical functionalities of CS used in cancer theranostics and their synthesis methods. We also present recent discoveries and research progresses on how the CS functionalization could improve the delivery efficiency of CS-based nanotheranostics. Finally, we report several case studies about the application of CS-based nanotheranostics. This paper focuses on the strategies to construct CS-based theranostics systems via chemical routes and highlights their applications in cancer treatment, which can provide useful references for further studies.

Discovery of Imaging and Therapeutic Integration Bifunctional Molecules Based on Bio-Orthogonal Reaction and Releasable Disulfide Bond

The application of conventional fluorescent probes in living cells has been limited by excess fluorescence interference, reduced selectivity, and poor permeability. Herein, we describe a convenient solution for overcoming the above limitations based on bio-orthogonal reactions and releasable linkers that provide bifunctional molecules for imaging and therapeutic integration. To reduce the interference of excess fluorescent moieties, a bio-orthogonal reaction was applied to activate the fluorescence of the active parent drugs without fluorophores. Moreover, disulfide bonds were incorporated as releasable linkers. After imaging the target protein, the newly yielded fluorophore could be released from the active drugs based on the highly reducing conditions of the tumor. Thus, these bifunctional molecules are comparable in therapeutic activity to the parent drug. These novel imaging and therapeutic integration molecules could be used to realize imaging-aided diagnosis and perform efficient real-time monitoring of cancer cells. Our findings are expected to enable efficient and specific imaging and real-time in vivo prognostic monitoring in the clinic.

Drug Delivery Based on Stimuli-Responsive Injectable Hydrogels for Breast Cancer Therapy: A Review

Breast cancer is the most common and biggest health threat for women. There is an urgent need to develop novel breast cancer therapies to overcome the shortcomings of conventional surgery and chemotherapy, which include poor drug efficiency, damage to normal tissues, and increased side effects. Drug delivery systems based on injectable hydrogels have recently gained remarkable attention, as they offer encouraging solutions for localized, targeted, and controlled drug release to the tumor site. Such systems have great potential for improving drug efficiency and reducing the side effects caused by long-term exposure to chemotherapy. The present review aims to provide a critical analysis of the latest developments in the application of drug delivery systems using stimuli-responsive injectable hydrogels for breast cancer treatment. The focus is on discussing how such hydrogel systems enhance treatment efficacy and incorporate multiple breast cancer therapies into one system, in response to multiple stimuli, including temperature, pH, photo-, magnetic field, and glutathione. The present work also features a brief outline of the recent progress in the use of tough hydrogels. As the breast undergoes significant physical stress and movement during sporting and daily activities, it is important for drug delivery hydrogels to have sufficient mechanical toughness to maintain structural integrity for a desired period of time.

CD44-targeted pH-responsive micelles for enhanced cellular internalization and intracellular on-demand release of doxorubicin

Poor cellular uptake and slow intracellular drug release remain the main barriers for the efficient application of micellar delivery system. Taking advantage of the overexpressed CD44 receptor and mild acidic microenvironment of tumour cells, CD44-targeted pH-responsive micelles based on the self-assembly of histidine-hyaluronic acid-dodecylamine (His-HA-DA) were prepared for the delivery of doxorubicin (DOX). These micelles exhibited pH-responsive behaviour with increased particle size, decreased encapsulation efficiency (EE%) of DOX and rapid release of DOX triggered by low pH. Compared with free DOX, DOX/HHD exhibited relatively high cellular uptake mainly via the CD44-mediated endocytosis. The on-demand intracellular release of DOX from DOX/HHD led to improved cytotoxicity. DOX/HHD also showed great penetration efficiency in 3D tumour spheres in vitro. Moreover, these micelles with suitable particle size gained excellent tumour-targeting effects, as well as improved anti-tumour effects and reduced side effects in vivo. In conclusion, these micelles with CD44 targeted and pH-responsive behaviours provide a promising strategy for the efficient delivery of anti-tumour drugs in vivo.

A Novel Folic Acid Receptor-Targeted Drug Delivery System Based on Curcumin-Loaded β-Cyclodextrin Nanoparticles for Cancer Treatment

Purpose

A novel folate receptor-targeted β-cyclodextrin (β-CD) drug delivery vehicle was constructed to improve the bioavailability, biosafety, and drug loading capacity of curcumin. Controlled release and targeted delivery was achieved by modifying the nanoparticles with folic acid (FA).

Methods

Folate-conjugated β-CD-polycaprolactone block copolymers were synthesized and characterized. Curcumin-loaded nanoparticles (FA-Cur-NPs) were structured by self-assembly. The physicochemical properties, stability, release behavior and tumor-targeting ability of the fabricated nanoparticles were studied.

Results

The average particle size and drug loading of FA-Cur-NPs was 151.8 nm and 20.27%, respectively. Moreover, the FA-Cur-NPs exhibited good stability in vitro for 72 h. The drug release profiles showed that curcumin from FA-Cur-NPs was released significantly faster in a pH 6.4 phosphate buffered solution (PBS) than in pH 7.4, indicating that curcumin can be enriched around the tumor site compared with normal cells. Additionally, the internalization of FA-Cur-NPs was aided by FA receptor-mediated endocytosis, and its cytotoxicity was proportional to the cellular uptake efficiency. Furthermore, in vivo studies confirmed that FA-Cur-NPs exhibited marked accumulation in the tumor site and excellent antitumor activity.

Conclusion

These findings suggest that FA-Cur-NPs are a promising approach for improving cancer therapy through active targeting and controllable release.

Collagenase IV and clusterin-modified polycaprolactone-polyethylene glycol nanoparticles for penetrating dense tumor tissues

Purpose: Novel collagenase IV (ColIV) and clusterin (CLU)-modified polycaprolactone-polyethylene glycol (PCL-PEG) nanoparticles that load doxorubicin (DOX) were designed and fully evaluated in vitro and in vivo. Methods: PCL-PEG-ColIV was synthesized by linking PCL-PEG and ColIV through a carbodiimide method. DOX-loaded nanoparticles (DOX-PCL-PEG-ColIV) were self-assembly prepared, followed by noncovalently adsorbing CLU on the DOX-PCL-PEG-ColIV surface to obtain DOX-PCL-PEG-ColIV /CLU nanoparticles, which can penetrate through the tumor extracellular matrix (ECM) and inhibit phagocytosis by macrophage. The physicochemical properties of nanoparticles were characterized. The cellular uptake and antiphagocytosis ability of nanoparticles in MCF-7 tumor cells and RAW264.7 cells were investigated. The penetration ability of nanoparticles was individually evaluated in the two-dimensional (2D) and three-dimensional (3D) ECM models. The tissue distribution and antitumor effect of nanoparticles were evaluated in MCF-7 cell-bearing nude mice. Results: Compared with DOX-PCL-PEG-COOH nanoparticles, DOX-PCL-PEG-ColIV/CLU nanoparticles could effectively overcome the phagocytosis by RAW264.7 and showed excellent cellular uptake in MCF-7 cells. In addition, they showed remarkable penetration ability through the 2D and 3D ECM models. DOX-PCL-PEG-ColIV/CLU nanoparticles significantly reduced the drug distribution in the liver and spleen and enhanced the drug accumulation in tumor tissue compared with DOX-PCL-PEG-COOH or DOX-PCL-PEG-ColIV nanoparticles. DOX-PCL-PEG-ColIV/CLU nanoparticles showed remarkable antitumor effect but did not cause severe pathological damages in the main tissues, including the heart, liver, spleen, lung, and kidney. Conclusion: Novel ColIV and CLU-modified PCL-PEG nanoparticles showed excellent cellular uptake, ECM penetration, antiphagocytosis, and antitumor effects both in vitro and in vivo.

Matrix metalloprotein-triggered, cell penetrating peptide-modified star-shaped nanoparticles for tumor targeting and cancer therapy

Background

Specific targeting ability and good cell penetration are two critical requirements of tumor-targeted delivery systems. In the present work, we developed a novel matrix metalloprotein-triggered, cell-penetrating, peptide-modified, star-shaped nanoparticle (NP) based on a functionalized copolymer (MePEG-Peptide-Tri-CL), with the peptide composed of GPLGIAG (matrix metalloprotein-triggered peptide for targeted delivery) and r9 (cell-penetrating peptide for penetration improvement) to enhance its biological specificity and therapeutic effect.

Results

Based on the in vitro release study, a sustained release profile was achieved for curcumin (Cur) release from the Cur-P-NPs at pH 7.4. Furthermore, the release rate of Cur was accelerated in the enzymatic reaction. MTT assay results indicated that the biocompatibility of polymer NPs (P-NPs) was inversely related to the NP concentration, while the efficiency toward tumor cell inhibition was positively related to the Cur-P-NP concentration. In addition, Cur-P-NPs showed higher fluorescence intensity than Cur-NPs in tumor cells, indicating improved penetration of tumor cells. An in vivo biodistribution study further demonstrated that Cur-P-NPs exhibited stronger targeting to A549 xenografts than to normal tissue. Furthermore, the strongest tumor growth inhibition (76.95%) was observed in Cur-P-NP-treated A549 tumor xenograft nude mice, with slight pulmonary toxicity.

Conclusion

All results demonstrated that Cur-P-NP is a promising drug delivery system that possesses specific enzyme responsiveness for use in anti-tumor therapy.

H2O2-responsive nano-prodrug for podophyllotoxin delivery

The tumor microenvironment is different from that of normal tissue; therefore, the development of a prodrug that retains its efficacy in the tumor microenvironment can be useful in enhancing the anticancer properties of podophyllotoxin. An innovative podophyllotoxin prodrug (POD-PEG) was designed by linking podophyllotoxin to poly(ethylene glycol)(n) monomethacrylate with a H2O2-responsive oxalate ester bond. POD-PEG can self-assemble into stable nanoparticles (POD-PEG NPs). In vitro experiments demonstrated that the POD-PEG NPs can be activated by hydrogen peroxide resulting in podophyllotoxin release and are highly toxic against colon carcinoma CT26 cells. In vivo biodistribution studies demonstrate that PEGylated POD-PEG NPs are capable of prolonging blood circulation. Intravenous injection of POD-PEG NPs into CT26 tumor-bearing Balb/c mice resulted in a significantly enhanced therapeutic efficacy against tumors, with no significant systemic toxicity. Therefore, this H2O2-responsive prodrug delivery system exhibits good biosafety and provides a novel strategy for the development of drug delivery systems.

Inhibiting PI3 kinase-γ in both myeloid and plasma cells remodels the suppressive tumor microenvironment in desmoplastic tumors

Phosphoinositide-3-kinases (PI3Ks) are part of signal transducing enzymes that mediate key cellular functions in cancer and immunity. PI3K-γ is crucial for cellular activation and migration in response to certain chemokines. PI3K-γ is highly expressed in myeloid cells and promotes their migration and the production of inflammatory mediators. We found that PI3K-γ was also highly expressed in tumor-associated B cells. IPI-549, the only PI3K-γ inhibitor in clinical development, offers a unique approach to enhance the anti-tumor immune response. We encapsulated IPI-549 in targeted polymeric nanoparticles (NP) and tested its activity in both murine pancreatic cancer and melanoma models. IPI-549 NP significantly decreased tumor growth and prolonged host survival in both models. Importantly, IPI-549 NP treatment reduced the suppressive tumor microenvironment by decreasing both suppressive myeloid and plasma cells in the tumor. We concluded that IPI-549 NP delivery could be a promising method for treating pancreatic cancer and other immune-suppressive tumors.

PEGylated self-assembled enzyme-responsive nanoparticles for effective targeted therapy against lung tumors

Background

Matrix-metalloproteinases, which are overexpressed in many types of cancer, can be applied to improve the bioavailability of chemotherapeutic drugs and guide therapeutic targeting. Thus, we aimed to develop enzyme-responsive nanoparticles based on a functionalized copolymer (mPEG-Peptide-PCL), which was sensitive to matrix metalloproteinase, as smart drug vesicles for enhanced biological specificity and reduced side effects.

Results

The rate of in vitro curcumin (Cur) release from Cur-P-NPs was not markedly accelerated in weakly acidic tumor microenvironment, indicating a stable intracellular concentration and a consistent therapeutic effect. Meanwhile, P-NPs and Cur-P-NPs displayed prominent biocompatibility, biostability, and inhibition efficiency in tumor cells. In addition, Cur-P-NPs showed higher fluorescence intensity than Cur-NPs in tumor cells, implying enhanced cell permeability and targeting ability. Moreover, the internalization and intracellular transport of Cur-P-NPs were mainly via macropinocytosis. Studies of pharmacodynamics and cellular uptake in vitro and biodistribution in vivo demonstrated that Cur-P-NPs had stronger target efficiency and therapeutic effect than Cur-DMSO and Cur-NPs in tumor tissue.

Conclusion

Results indicate that Cur-P-NPs can be employed for active targeted drug delivery in cancer treatment and other biomedical applications.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0384-8) contains supplementary material, which is available to authorized users.

Multifunctional redox-responsive and CD44 receptor targeting polymer-drug nanomedicine based curcumin and alendronate: synthesis, characterization and in vitro evaluation

The traditional therapy of cancer has systemic side effects, and many cancers, such as human breast cancer and lung cancer easily metastasize to bones, leading to the formation of secondary tumours. This study was aimed at enhancing the anti-tumour effect of curcumin (CUR) and preventing tumour spread to the bone. A novel multifunctional redox-responsive and CD44 receptor targeting polymer-drug, poly alendronate-hyaluronan-S-S-curcumin copolymer (ALN-oHA-S-S-CUR) based CUR and alendronate (ALN) were synthesized successfully with the disulphide bond linker. The structure of ALN-oHA-S-S-CUR was characterized by ¹H-NMR. The nanomedicine had natural anti-tumour drugs (CUR) as the hydrophobic kernel, and targeting CD44 receptor oligosaccharides of hyaluronan (oHA) and other anti-tumour drugs (ALN) as hydrophilic shell, named ALN-oHA-S-S-CUR conjugates, which could self-assemble into micelle-like nano-spheres in water via a dialysis method with hydrodynamic diameters of 179 ± 23 nm. Interestingly, the cur-loaded ALN-oHA-S-S-CUR micelles were stable in PBS but were capable of releasing the drug under the reducing environment. The rate of drug release was proportional to the GSH concentration. The uptake and cytotoxicity of micelles were higher in MDA-MB-231 cells than in MCF-7 cells because of a higher expression of the CD44 receptor in the former cell line. And compared to the cur-loaded oHA-CUR micelles, the cur-loaded ALN-oHA-S-S-CUR micelles had a good cellular uptake in 2D cancer cell and penetrability in 3D cancer cell spheroids. These results indicated the active targeting redox-sensitive micelles were promising as intracellular drug delivery systems for cancer treatment.

Effective improvement of the neuroprotective activity after spinal cord injury by synergistic effect of glucocorticoid with biodegradable amphipathic nanomicelles

Dexamethasone acetate (DA) produces neuroprotective effects by inhibiting lipid peroxidation and inflammation by reducing cytokine release and expression. However, its clinical application is limited by its hydrophobicity, low biocompatibility and numerous side effects when using large dosage. Therefore, improving DA's water solubility, biocompatibility and reducing its side effects are important goals that will improve its clinical utility. The objective of this study is to use a biodegradable polymer as the delivery vehicle for DA to achieve the synergism between inhibiting lipid peroxidation and inflammation effects of the hydrophobic-loaded drugs and the amphipathic delivery vehicle. We successfully prepared DA-loaded polymeric micelles (DA/MPEG-PCL micelles) with monodispersed and approximately 25 nm in diameter, and released DA over an extended period in vitro. Additionally, in the hemisection spinal cord injury (SCI) model, DA micelles were more effective in promoting hindlimb functional recover, reducing glial scar and cyst formation in injured site, decreasing neuron lose and promoting axon regeneration. Therefore, our data suggest that DA/MPEG-PCL micelles have the potential to be applied clinically in SCI therapy.

Shear-responsive injectable supramolecular hydrogel releasing doxorubicin loaded micelles with pH-sensitivity for local tumor chemotherapy

In this study, glycol chitosan-Pluronic F127 conjugate (GC-PF127), produced by an amidation reaction between terminal-carboxylated PF127 and glycol chitosan (GC), was used to prepare doxorubicin (DOX)-loaded micelles. The DOX/GC-PF127 micelles produced at optimal conditions had sizes of about 150nm and pH-sensitive surface charges. DOX/GC-PF127 hydrogel formed after addition of α-cyclodextrin into DOX/GC-PF127 micelle solution. The hydrogel had good shear-responsive, injectable and rapid recovery properties. In vitro release experiment confirmed that the hydrogel could sustainedly release DOX/GC-PF127 micelles via the dissociation of the hydrogel. After peritumoral injection into H22 tumor-bearing mice, the hydrogel could greatly increase DOX accumulation in tumor tissue and synchronously avoid DOX accumulation in normal tissues including heart. At similar total DOX dose administrated, the tumors of free DOX treatment group grew slowly after thrice intravenous injections, the tumors of the micelle group did not grow after twice intravenous injections, and the tumors of the hydrogel group disappeared almost after once peritumoral injection. This study demonstrates that injectable DOX/GC-PF127 hydrogel, which can sustainedly release DOX-loaded micelles with tumor-targeting function, is a promising system for local tumor chemotherapy.

Development of drug-loaded chitosan hollow nanoparticles for delivery of paclitaxel to human lung cancer A549 cells

In this study, biodegradable chitosan hollow nanospheres (CHN) were fabricated using polystyrene nanospheres (PS) as templates. CHN were applied to increase the solubility of poorly water-soluble drugs. The lung cancer drug paclitaxel (PTX), which is used as a model drug, was loaded into CHN by the adsorption equilibrium method. The drug-loaded sample (PTX-CHN) offered sustained PTX release and good bioavailability. The state characterization of PTX by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that the PTX absorbed into CHN existed in an amorphous state. An in vitro toxicity experiment indicated that CHN were nontoxic as carriers of poorly water-soluble drugs. The PTX-CHN produced a marked inhibition of lung cancer A549 cells proliferation and encouraged apoptosis. A cell uptake experiment indicated that PTX-CHN was successfully taken up by lung cancer A549 cells. Furthermore, a degradation experiment revealed that CHN were readily biodegradable. These findings state clearly that CHN can be regarded as promising biomaterials for lung cancer treatment.

Low-density lipoprotein-coupled micelles with reduction and pH dual sensitivity for intelligent co-delivery of paclitaxel and siRNA to breast tumor

Multidrug resistance (MDR) is a major obstacle for the clinical therapy of malignant human cancers. The discovery of RNA interference provides efficient gene silencing within tumor cells for reversing MDR. In this study, a new “binary polymer” low-density lipoprotein–N-succinyl chitosan–cystamine–urocanic acid (LDL–NSC–SS–UA) with dual pH/redox sensitivity and targeting effect was synthesized for the co-delivery of breast cancer resistance protein small interfering RNA (siRNA) and paclitaxel (PTX). In vivo, the co-delivering micelles can accumulate in tumor tissue via the enhanced permeability and retention effect and the specific recognition and combination of LDL and LDL receptor, which is overexpressed on the surface of tumor cell membranes. The siRNA–PTX-loaded micelles inhibited gene and drug release under physiological conditions while promoting fast release in an acid microenvironment or in the presence of glutathione. The micelles escaped from the lysosome through the proton sponge effect. Additionally, the micelles exhibited superior antitumor activity and downregulated the protein and mRNA expression levels of breast cancer resistance protein in MCF-7/Taxol cells. The biodistribution and antitumor studies proved that the siRNA–PTX-loaded micelles possessed prolonged circulation time with a remarkable tumor-targeting effect and effectively inhibited tumor growth. Therefore, the novel dual pH/redox-sensitive polymers co-delivering siRNA and PTX with excellent biocompatibility and effective reversal of MDR demonstrate a considerable potential in cancer therapy.

Zonisamide-loaded triblock copolymer nanomicelles as a novel drug delivery system for the treatment of acute spinal cord injury

Spinal cord injury (SCI) commonly leads to lifelong disability due to the limited regenerative capacity of the adult central nervous system. Nanomicelles can be used as therapeutic systems to provide effective treatments for SCI. In this study, a novel triblock monomethyl poly(ethylene glycol)-poly(l-lactide)-poly(trimethylene carbonate) copolymer was successfully synthesized. Next, polymeric nanomicelles loaded with zonisamide (ZNS), a Food and Drug Administration-approved antiepileptic drug, were prepared and characterized. The ZNS-loaded micelles (ZNS-M) were further utilized for the treatment of SCI in vitro and in vivo. The obtained ZNS-M were ~50 nm in diameter with good solubility and dispersibility. Additionally, these controlled-release micelles showed significant antioxidative and neuron-protective effects in vitro. Finally, our results indicated that ZNS-M treatment could promote motor function recovery and could increase neuron and axon density in a hemisection SCI model. In summary, these results may provide an experimental basis for the use of ZNS-M as a clinically applicable therapeutic drug for the treatment of SCI in the future.

A shell-crosslinked polymeric micelle system for pH/redox dual stimuli-triggered DOX on-demand release and enhanced antitumor activity

Based on targeted amphiphilic block copolymer N-acetyl glucosamine-poly (styrene-alt-maleic anhydride)₅₈-b-polystyrene₁₃₀ (NAG-P(St-alt-MA)₅₈-b-PSt₁₃₀), a pH/redox dual-triggered shell-crosslinked polymeric micelle system was constructed. The shell-crosslinked micelles (CLM) were prepared by post-crosslinking method to regulate drug release kinetics using cystamine as linkers between carboxy groups of the shell. Compared with non-crosslinked micelles (NCLM), CLM showed spherical shapes with little increased mean diameter of 102.40±0.54nm, low polydispersity index (PDI) of 0.19±0.36, enlarged zeta potential value from -41.46±0.99 to -9.31±0.50mV, indicating the successful modification of disulfide bonds in shell. In vitro drug release study clearly exhibited a pH and redox dual-sensitive drug release profile with significantly accelerated drug release under pH 5.0 and 10mM GSH conditions (46.84% in 96h) without burst release. Both CLM and NCLM showed quite different release profiles between physiological (pH 7.4) and tumoral microenvironment (pH 5.0), effectively avoiding the premature drug leakage and realizing on-demand drug release. The MTT assay implied that CLM presented a time- and concentration-dependent manner to inhibit proliferation of A549 and MCF-7 cells and much lower IC₅₀ values in comparison with that of NCLM after 72h incubation. Both FCM and CLSM results showed that CLM displayed much higher cellular uptake efficiency and anti-tumor activities than NCLM and free DOX. CLM and NCLM could be internalized by energy-dependent endocytosis mechanism due to similar surface properties. Overall, this dual-stimuli triggered micelle system provided a promising tumor-responsive platform for cancer therapy.