Versatile Polymer-Initiating Biomineralization for Tumor Blockade Therapy.

Tumor blockade therapy is a promising penetration-independent antitumor modality, which effectively inhibits the exchange of nutrients, oxygen, and information between the tumor and surrounding microenvironments. However, the current blockade therapy strategies have limited antitumor efficacy due to defects of inadequate tumor obstruction, possible side effects, and short duration. For these reasons, a facilely synthesized versatile polymer 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol)-alendronate (DSPE-PEG-ALN, DPA) is developed to initiate the formation of biomineral shell around osteosarcoma as a potent physical barrier. The DSPE moiety shares a similar chemical structure with the cytomembrane, allowing the membrane insertion of DPA. The bisphosphonic acid groups in ALN attract ions to realize biomineralization around cells. After injection in the invasive osteosarcoma tissue, DPA inserts into the cytomembrane, induces continuous mineral deposition, and ultimately builds a physical barrier around the tumor. Meanwhile, ALN in DPA alleviates bone destruction by suppressing the activity of osteoclasts. Through hindering the exchange of necessary substances, the biomineralization coating inhibits the growth of primary osteosarcoma and pulmonary metastasis simultaneously. Therefore, the multifunctional polymer-initiating blockade therapy provides a promising modality for tumor inhibition in clinics with high efficacy and negligible side effects.

3D-printing magnesium-polycaprolactone loaded with melatonin inhibits the development of osteosarcoma by regulating cell-in-cell structures.

Melatonin has been proposed as a potent anticarcinogen presents a short half-life for osteosarcoma (OS). Cell-in-cell (CIC) structures play a role in the development of malignant tumors by changing the tumor cell energy metabolism. This study developed a melatonin-loaded 3D printed magnesium-polycaprolactone (Mg-PCL) scaffold and investigated its effect and molecular mechanism on CIC in OS. Mg-PCL scaffold was prepared by 3D-printing and its characteristic was determined. The effect and molecular mechanism of Mg-PCL scaffold as well as melatonin-loaded Mg-PCL on OS growth and progression were investigated in vivo and in vitro. We found that melatonin receptor 1 (MT1) and CIC expressions were increased in OS tissues and cells. Melatonin treatment inhibit the key CIC pathway, Rho/ROCK, through the cAMP/PKA signaling pathway, interfering with the mitochondrial physiology of OS cells, and thus playing an anti-invasion and anti-metastasis role in OS. The Mg-PCL-MT could significantly inhibit distant organ metastasis of OS in the in vivo model. Our results showed that melatonin-loaded Mg-PCL scaffolds inhibited the proliferation, invasion and metastasis of OS cells through the CIC pathway. The Mg-PCL-MT could be a potential therapeutics for OS.

Poly(l-glutamic acid)-cisplatin nanoformulations with detachable PEGylation for prolonged circulation half-life and enhanced cell internalization.

PEGylation has been widely applied to prolong the circulation times of nanomedicines via the steric shielding effect, which consequently improves the intratumoral accumulation. However, cell uptake of PEGylated nanoformulations is always blocked by the steric repulsion of PEG, which limits their therapeutic effect. To this end, we designed and prepared two kinds of poly(l-glutamic acid)-cisplatin (PLG-CDDP) nanoformulations with detachable PEG, which is responsive to specific tumor tissue microenvironments for prolonged circulation time and enhanced cell internalization. The extracellular pH (pHe)-responsive cleavage 2-propionic-3-methylmaleic anhydride (CDM)-derived amide bond and matrix metalloproteinases-2/9 (MMP-2/9)-sensitive degradable peptide PLGLAG were utilized to link PLG and PEG, yielding pHe-responsive PEG-pH e-PLG and MMP-sensitive PEG-MMP-PLG. The corresponding smart nanoformulations PEG-pH e-PLG-Pt and PEG-MMP-PLG-Pt were then prepared by the complexation of polypeptides and cisplatin (CDDP). The circulation half-lives of PEG-pH e-PLG-Pt and PEG-MMP-PLG-Pt were about 4.6 and 4.2 times higher than that of the control PLG-Pt, respectively. Upon reaching tumor tissue, PEG on the surface of nanomedicines was detached as triggered by pHe or MMP, which increased intratumoral CDDP retention, enhanced cell uptake, and improved antitumor efficacy toward a fatal high-grade serous ovarian cancer (HGSOC) mouse model, indicating the promising prospects for clinical application of detachable PEGylated nanoformulations.

Mesenchymal stem cells for cartilage regeneration.

Cartilage injuries are typically caused by trauma, chronic overload, and autoimmune diseases. Owing to the avascular structure and low metabolic activities of chondrocytes, cartilage generally does not self-repair following an injury. Currently, clinical interventions for cartilage injuries include chondrocyte implantation, microfracture, and osteochondral transplantation. However, rather than restoring cartilage integrity, these methods only postpone further cartilage deterioration. Stem cell therapies, especially mesenchymal stem cell (MSCs) therapies, were found to be a feasible strategy in the treatment of cartilage injuries. MSCs can easily be isolated from mesenchymal tissue and be differentiated into chondrocytes with the support of chondrogenic factors or scaffolds to repair damaged cartilage tissue. In this review, we highlighted the full success of cartilage repair using MSCs, or MSCs in combination with chondrogenic factors and scaffolds, and predicted their pros and cons for prospective translation to clinical practice.

Spatiotemporally Targeted Nanomedicine Overcomes Hypoxia-Induced Drug Resistance of Tumor Cells after Disrupting Neovasculature.

Vascular disrupting agents (VDAs) are emerging anticancer agents, which show rising demand for combination with cytostatic drugs (CSDs), owing to inadequate tumor inhibition when applied singly. Nevertheless, the combination remains a challenge due to the different working sites of VDAs and CSDs and hypoxia-induced drug resistance after disrupting neovasculature by VDAs. Herein, we developed a shell-stacked nanoparticle (SNP) for coencapsulation of a VDA combretastatin A-4 phosphate (CA4P) and a proteasome inhibitor bortezomib (BTZ). The SNP could spatiotemporally deliver CA4P to tumor neovasculature and BTZ to tumor cells mediated by the site-specific stimuli-activated drug release. Moreover, the SNP also reversed the drug resistance caused by the overexpressed ABCG2 under CA4P-induced hypoxic conditions. The spatiotemporally targeted combination therapy significantly inhibited the growth of both the human A549 pulmonary adenocarcinoma xenograft model and patient-derived xenograft (PDX) model of colon cancer in mice, providing a promising strategy for treating advanced cancers.

Polymer-Mediated Penetration-Independent Cancer Therapy.

The development of polymer-based drug delivery systems provides efficient modalities for cancer therapy. Most of the polymer pharmaceuticals target cancer cells directly, but the insufficient penetration always results in unsatisfactory anticancer efficacy. To break the above bottleneck, strategies of penetration-independent cancer therapy have been developed as advanced treatments for various cancers in the past decade. In this Perspective, we discussed the pros and cons of polymer-mediated biological and physical penetration-independent approaches for cancer therapy and highlighted their further prospects from bench to bedsides.

Chiral Polypeptide Thermogels Induce Controlled Inflammatory Response as Potential Immunoadjuvants.

The in vivo implanted biomaterials are known to induce inflammatory response and recruit immune cells, which could be used as robust adjuvants for immunotherapy. However, the degree of inflammatory response induced by the implanted biomaterials is hard to control. In this work, we reported the application of three kinds of thermogels from the polypeptide methoxy poly(ethylene glycol)-polyalanine (mPEG-PAla) with various chiralities to regulate the levels of inflammatory responses in vivo. The mPEG-PLAla (EG45LA28) and mPEG-PDAal (EG45DA27) thermogels exhibited comparable storage modulus ( G') and loss modulus ( G″), both of which were about two times higher than the values of the racemic mPEG-PAla (EG45RA) thermogel. The component d-alanine in the polypeptide thermogels led to controlled tissue inflammation after subcutaneous injection, and the content of d-alanine could adjust the level of inflammation. The expression of tumor necrosis factor (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) in subcutaneous tissue around the injected thermogel EG45DA27 were 3.62, 1.52, and 4.55 times the levels of those after EG45RA thermogel injection and 4.52, 7.38, and 7.96 times the levels of those after EG45LA28 injection, respectively. The results indicated that the chiral polypeptide thermogels could induce a controllable inflammatory response in vivo and exhibit great potential as an efficient adjuvant for immunotherapy.

Gradiently degraded electrospun polyester scaffolds with cytostatic for urothelial carcinoma therapy.

Kidney-sparing surgery is the preferred treatment strategy for low-risk upper tract urothelial carcinoma (UTUC). However, after this procedure, prevention of the carcinoma recurrence in the ureter and supporting the ureter with a ureteral stent are necessary. Biodegradable drug-loaded ureteral scaffolds are able to maintain their long-term effective drug concentrations in the lesion sites without the defects of traditional ureteral stents, which may address both issues simultaneously. The purpose of this study was to reveal the possibility of the controlled delivery of epirubicin (EPI) via gradiently degraded electrospun poly(ε-caprolactone) (PCL)/poly(lactide-co-glycolide) (PLGA) scaffolds to evaluate their antitumor activity against UTUC. The degradable PCL/PLGA scaffolds containing 15.0 and 25.0 wt% PCL and loading of 0, 5.0, and 10.0 wt% EPI were successfully fabricated via electrospinning. In addition, the PCL/PLGA scaffolds showed sustained and controlled degradation and drug release kinetics, that is, their degradation and drug release rates slowed with an increase in the ratio of PCL. The EPI-loaded PCL/PLGA scaffolds showed excellent antitumor activities both in vitro and in vivo without apparent systemic toxicity. Overall, the gradiently-degraded EPI-loaded electrospun polyester scaffolds are potential ureteral stent tubes for the local inhibition of the recurrence of UTUC, where the continued release of EPI can prevent the subsequent proliferation of residual tumor cells, and the gradient degradation is consistent with the repair of the ureter.

Receptor and Microenvironment Dual-Recognizable Nanogel for Targeted Chemotherapy of Highly Metastatic Malignancy.

Targeted delivery of chemotherapeutic drugs to the desired lesion sites is the main objective in malignancy treatment, especially in highly metastatic malignancies. However, extensive studies around the world on traditional targeting strategies of recognizing either overexpressed receptors or microenvironments in tumors show great limitations, owing to the off-target effect and tumor homogeneity. Integration of both receptor-mediated targeting (RMT) and environment-mediated targeting (EMT) enhances the tumor accumulation and subsequent cell uptake at the same time, which may avoid these limitations. Herein, a dual targeting nanogel of PMNG engineered with both phenylboronic acid (PBA) and morpholine (MP) was reported for not only RMT via specific recognition of sialyl (SA) epitopes but also EMT toward extracellular acidity. Further engineering the nanoparticles via loading doxorubicin (DOX) brought a novel dual targeting system, that is, PMNG/DOX. PMNG/DOX demonstrated a greater targeting effect to both primary and metastatic B16F10 melanoma than the single PBA-modified nanogel (PNG) with only RMT in vitro and in vivo. Moreover, PMNG/DOX was also proved to be highly potent on inhibiting primary tumor growth as well as tumor metastasis on B16F10 melanoma-grafted mouse model. The results demonstrated the dual targeting design as a translational approach for drug delivery to highly metastatic tumor.

Sequentially Responsive Shell-Stacked Nanoparticles for Deep Penetration into Solid Tumors.

Nanomedicine to overcome both systemic and tumor tissue barriers ideally should have a transformable size and surface, maintaining a certain size and negative surface charge for prolonged circulation, while reducing to a smaller size and switching to a positive surface charge for efficient penetration to and retention in the interstitial space throughout the tumor tissue. However, the design of such size and charge dual-transformable nanomedicine is rarely reported. Here, the design of a shell-stacked nanoparticle (SNP) is reported, which can undergo remarkable size reduction from about 145 to 40 nm, and surface charge reversal from -7.4 to 8.2 mV at acidic tumor tissue, for enhanced tumor penetration and uptake by cells in deep tumor tissue. The disulfide-cross-linked core maintains the stability of the particle and prevents undesired premature drug release until the shedding of the shell, which accelerates the cleavage of more exposed disulfide bond sand intracellular drug release. SNP penetrates about 1 mm into xenografted A549 lung carcinoma, which is about four times penetration depth of the nontransformable one. The doxorubicin (DOX)-loaded SNP (SNP/DOX) shows significant antitumor efficacy and nearly eradicates the tumor, substantiating the importance of the design of size and charge dual-transformable nanomedicine.

Schiff base bond-linked polysaccharide-doxorubicin conjugate for upregulated cancer therapy.

The pH-responsive polymer prodrugs were designed to maintain sufficient stability in the bloodstream and promptly release the active drugs when entering the acidic microenvironments, such as tumor tissue and cells. This kind of polymer-drug conjugates has become increasingly intriguing given the specific advantages over traditional drug delivery system. In our work, dextran (Dex) was oxidized into aldehyde-functionalized Dex-CHO before conjugating with doxorubicin (DOX) via efficient Schiff base reaction. The amphiphilic product Dex-DOX aggregated into uniform spherical nanoparticle in aqueous condition. The imine bond in Dex-DOX stayed tough in neutral solution yet quickly fractured when pH was lowered, in which way DOX was locally released and functioned in tumor cells. Our findings proved that the newly-constructed Dex-DOX could obviously promote the pH-dependent drug release, highlight the cell uptake efficiency, and strengthen the antitumor ability toward mouse B16F10 melanoma. In addition, it also largely averted the adverse effects to vital organs, which guaranteed higher level of security. Therefore, Dex-DOX held great potential of becoming a qualified chemotherapeutic drug delivery system.

Core cross-linked poly(ethylene glycol)-graft-Dextran nanoparticles for reduction and pH dual responsive intracellular drug delivery.

A kind of core cross-linked poly(ethylene glycol)-graft-Dextran nanoparticles (CPD NPs) was prepared by a simple chemical cross-linking method for reduction and pH dual response drug delivery. The resultant CPD NPs are of homogeneous spherical structure with sizes from 69±11 to 107±18nm. Doxorubicin (DOX) was then loaded into the CPD NPs in high efficiency, and showing typical reduction and pH dual responsive release profiles. The flow cytometric analysis and confocal laser scanning microscopy (CLSM) confirmed that the DOX-loaded CPD NPs could be internalized into cancer cell efficiently and release DOX in intracellular environment. Furthermore, cell cytotoxicity assays indicated that the CPD NPs had good biocompatibility toward both cancerous and normal cells, while the Dox-loaded CPD NPs exhibited significant inhibition of cell proliferation in various cancer cells. Therefore, this biocompatible CPD NP may have great potential for intracellular drug delivery in clinical cancer therapy.

Scavenger Receptor-Mediated Targeted Treatment of Collagen-Induced Arthritis by Dextran Sulfate-Methotrexate Prodrug.

Rheumatoid arthritis (RA) is a chronic autoimmune disorder implicated in multiple joint affection and even disability. The activated macrophages perform a predominant role in onset and persistence of RA. Scavenger receptor (SR), one of several receptors overexpressed on the activated macrophages, is a specific biomarker for targeted therapy of numerous chronic inflammation diseases like RA. In this work, dextran sulfate-graft-methotrexate conjugate (DS-g-MTX) is synthesized and characterized, which exhibits excellent targetability to SR on the activated RAW 264.7 cells. Additionally, the enhanced accumulation and potent inflammatory inhibition are observed in the affected joint after intravenous injection of DS-g-MTX, compared to the treatment with dextran-graft-methotrexate (Dex-g-MTX), as is confirmed by the detection of histopathology and pro-inflammatory cytokines. Our work highlights DS-g-MTX as a potential therapeutic option for RA aiming the SR-expressed activated macrophages.

A comparative study of linear, Y-shaped and linear-dendritic methoxy poly(ethylene glycol)-block-polyamidoamine-block-poly(l-glutamic acid) block copolymers for doxorubicin delivery in vitro and in vivo.

UNLABELLED: The linear, Y-shaped, and linear-dendritic block copolymers of methoxy poly(ethylene glycol)-block-polyamidoamine-block-poly(l-glutamic acid) (MPEG-b-PAMAM-b-PGA) with one, two, four, and eight PGA arms but similar MPEG/PGA weight ratios (W/W) (named as P1PA, P2PA, P4PA and P8PA, respectively) were synthesized and comparatively investigated for doxorubicin hydrochloride (DOX) delivery. All the obtained block copolymers were highly biocompatible and could efficiently load DOX into nanoparticles (NPs) through electrostatic interaction. The NPs formed by linear (P1PA) or Y-shaped (P2PA) block copolymers and DOX were spherically shaped with smaller sizes, while the NPs formed from linear-dendritic block copolymers (P4PA and P8PA) were irregular in shape and larger in size. The P1PA/DOX and P2PA/DOX NPs exhibited better DOX protection and slower DOX release profile. However, cell cytotoxicity assays indicated that all the DOX-loaded NPs exhibited similar cytotoxicities with free DOX, indicating effective DOX release after cellular uptake. The NPs from linear and Y-shaped block copolymers greatly extended the blood circulation time, and displayed more accumulation in tumor site and less accumulation in the liver and kidney compared with the linear-dendritic counterparts. In addition, the P1PA/DOX and P2PA/DOX NPs also exhibited higher anti-tumor efficacy and less toxicity than the other DOX formulations. All these results indicated that the linear and Y-shaped MPEG-b-PAMAM-b-PGA block copolymers displayed better DOX delivery ability in anti-tumor treatment than the linear-dendritic copolymers. STATEMENT OF SIGNIFICANCE: Polymeric NPs derived from block copolymers have emerged as effective vehicles for drug delivery. However, the majority of the researches in this field have involved simple linear block copolymers and there are very few comparative studies on the self-assembly, in vitro, and in vivo drug delivery by the block copolymers with similar composition but different architectures. In this study, a series of linear, Y-shaped, and linear-dendritic polypeptide-based block copolymers were prepared and thoroughly investigated for DOX delivery. These block polymers loaded DOX into NPs with different sizes and morphologies, and exhibited different anti-tumor capabilities both in vitro and in vivo. The results indicated that the architecture of the block copolymers played an important role in their drug delivery behaviors.

One-Step "Click Chemistry"-Synthesized Cross-Linked Prodrug Nanogel for Highly Selective Intracellular Drug Delivery and Upregulated Antitumor Efficacy.

Polymeric prodrugs formed by the conjugation of drugs onto polymers have shown great promise in cancer therapy because of the enhancement of water solubility, elimination of premature drug release, and the improvement of pharmacokinetics. To integrate the two advantages of upregulated stability during circulation and selective release of drug in cancer cells, a pH and reduction dual-sensitive prodrug nanogel (CLP) was synthesized via a simple one step "click chemistry". CLP was spherically shaped with a uniform diameter of 60.6 ± 13.7 nm and exhibited great stability in size against large volume dilution, high salt concentration, and long-time incubation in phosphate-buffered saline. Owing to the presence of hydrazone-bonded doxorubicin (DOX) and disulfide cross-linker, CLP released minimal amount (7.8%) of drug under normal physiological pH (i.e., 7.4) condition. But it released 85.5% of the loaded DOX at endosomal pH (i.e., 5.5) plus the presence of 5.0 mM GSH in 120 h. CLP could be effectively internalized by tumor cells and subsequently release DOX in the intracellular environment, resulting in effective proliferation inhibition of HeLa and MCF-7 cells. Furthermore, compared with free DOX and non-cross-linked prodrug micelle (NCLP), CLP accumulated more in tumor site but less in the normal organs, so that CLP performed the enhanced antitumor efficiency and reduced side-toxicities toward the MCF-7 human breast cancer xenograft nude mouse model. With convenient fabrication, favorable stability, controlled release properties, optimized biodistribution, and enhanced suppression of tumor growth, CLP held great potential for optimal antitumor therapy.

Mesomeric configuration makes polyleucine micelle an optimal nanocarrier.

Micelle with mesomeric polyleucine (PDLLeu) core demonstrated the most uniform morphology, the smallest diameter and the highest drug loading capability compared to those with dextrorotatory (PDLeu), levorotatory (PLLeu) and racemic PLeu (PD/LLeu) cores. In addition, the modification with c(RGDfC) endowed the optimal PDLLeu micelle with enhanced intracellular drug release and cytotoxicity, indicating its great potential for targeted drug delivery.

Drug binding rate regulates the properties of polysaccharide prodrugs.

Three intracellular acid-degradable hydroxyethyl starch-doxorubicin (HES[double bond, length as m-dash]DOX) prodrugs with different drug binding rates (DBRs) were synthesized through the conjugation of oxidized HES and DOX with a pH-responsive Schiff base bond. The DBRs of HES[double bond, length as m-dash]DOX conjugates were determined to be 1.7, 3.3, and 5.9%, which could be facilely adjusted by the feeding molar amount of DOX. All HES[double bond, length as m-dash]DOX conjugates could spontaneously self-assemble into spherical micellar nanoparticles in phosphate-buffered saline. The hydrodynamic diameter decreased from 73.4 ± 5.3, 63.9 ± 5.5, to 51.9 ± 8.5 nm with the increase of the DBR from 1.7, 3.3, to 5.9%. The DOX release from HES[double bond, length as m-dash]DOX could be accelerated by the decrease of pH and the DBR, attributed to the acid-sensitive Schiff base bond and the loose core, respectively. Furthermore, the HES[double bond, length as m-dash]DOX micelle selectively released DOX in the endosome and/or lysosome after cellular uptake, and exhibited excellent proliferation inhibition toward murine melanoma B16F10 cells in vitro and in vivo. Furthermore, the antitumor efficacy was upregulated by the increase of the DBR, benefiting from the selective acidity-triggered DOX release in tumor cells. These results indicated that HES[double bond, length as m-dash]DOX exhibited great potential in the precise chemotherapy of malignancy.