Polyphenolic Polymersomes of Temperature-Sensitive Poly(N-vinylcaprolactam)-block-Poly(N-vinylpyrrolidone) for Anticancer Therapy

Hypoxia-Responsive Polymersomes for Stemness Reduction in Patient-Derived Solid Tumor Spheroids

Aggressive solid tumors are associated with rapid growth, early hypoxia, a lack of targeted therapies, and a poor prognosis. The hypoxic niches within the rapidly growing solid tumors give rise to a stem-cell-like phenotype with higher metastasis and drug resistance. To overcome the drug resistance of these regions, we used hypoxia-responsive polymersomes with an encapsulated anticancer drug (doxorubicin, Dox) and a stemness modulator (all-trans retinoic acid, ATRA). Reductase enzymes overexpressed in hypoxia reduce the azobenzene linker of the polymers, disrupt the bilayer structure of the polymersomes, and release the encapsulated drugs. We used triple-negative breast cancer (TNBC) as a representative of aggressive and hypoxic solid tumors. We observed that ATRA synergistically enhanced the efficacy of Dox in killing cancer cells. A synergistic combination of the two drug-encapsulated polymersomes reduced the volumes of patient-derived TNBC spheroids by 90%. In contrast, Dox alone decreased the spheroid volumes by 70% and encapsulated ATRA by 19%. Mechanistic studies revealed that ATRA inhibited efflux pumps, leading to a higher concentration of doxorubicin within TNBC cells. In addition, the combination of encapsulated Dox and ATRA significantly decreased stemness expression of the TNBC cells in hypoxia compared to that of Dox alone.

Polymersome Membrane Engineering with Active Targeting or Controlled Permeability for Responsive Drug Delivery

Polymersomes have been extensively investigated for drug delivery as nanocarriers for two decades due to a series of advantages including high stability under physiological conditions, simultaneous encapsulation of hydrophilic and hydrophobic drugs inside inner cavities and membranes, respectively, and facile adjustment of membrane and surface properties, as well as controlled drug release through incorporation of stimuli-responsive components. Despite these features, polymersome nanocarriers frequently suffer from nontargeting delivery and poor membrane permeability. In recent years, polymersomes have been functionalized for more efficient drug delivery. The surface shells were explored to be modified with diverse active targeting groups to improve disease-targeting delivery. The membrane permeability of the polymersomes was adjusted by incorporation of the stimuli-responsive components for smart controlled transportation of the encapsulated drugs. Therefore, being the polymersome-biointerface, tailorable properties can be introduced by its carefully modulated engineering. This review elaborates on the role of polymersome membranes as a platform to incorporate versatile features. First, we discuss how surface functionalization facilitates the directional journey to the targeting sites toward specific diseases, cells, or intracellular organelles via active targeting. Moreover, recent advances in the past decade related to membrane permeability to control drug release are also summarized. We finally discuss future development to promote polymersomes as in vivo drug delivery nanocarriers.

Advanced liposome and polymersome-based drug delivery systems: Considerations for physicochemical properties, targeting strategies and stimuli-sensitive approaches

Liposomes and polymersomes are colloidal vesicles that are self-assembled from lipids and amphiphilic polymers, respectively. Because of their ability to encapsulate both hydrophilic and hydrophobic therapeutics, they are of great interest in drug delivery research. Today, the applications of liposomes and polymersomes have expanded to a wide variety of complex therapeutic molecules, including nucleic acids, proteins and enzymes. Thanks to their chemical versatility, they can be tailored to different drug delivery applications to achieve maximum therapeutic index. This review article evaluates liposomes and polymersomes from a perspective that takes into account the physical and biological barriers that reduce the efficiency of the drug delivery process. In this context, the design approaches of liposomes and polymersomes are discussed with representative examples in terms of their physicochemical properties (size, shape, charge, mechanical), targeting strategies (passive and active) and response to different stimuli (pH, redox, enzyme, temperature, light, magnetic field, ultrasound). Finally, the challenges limiting the transition from laboratory to practice, recent clinical developments, and future perspectives are addressed.

Direct Radiolabeling of Trastuzumab-Targeting Triblock Copolymer Vesicles with 89Zr for Positron Emission Tomography Imaging

Radiolabeled drug nanocarriers that can be easily imaged via positron emission tomography (PET) are highly significant as their in vivo outcome can be quantitatively PET-traced with high sensitivity. However, typical radiolabeling of most PET-guided theranostic vehicles utilizes modification with chelator ligands, which presents various challenges. In addition, unlike passive tumor targeting, specific targeting of drug delivery vehicles via binding affinity to overexpressed cancer cell receptors is crucial to improve the theranostic delivery to tumors. Herein, we developed 89Zr-labeled triblock copolymer polymersomes of 60 nm size through chelator-free radiolabeling. The polymersomes are assembled from poly(N-vinylpyrrolidone)5-b-poly(dimethylsiloxane)30-b-poly(N-vinylpyrrolidone)5 (PVPON5-PDMS30-PVPON5) triblock copolymers followed by adsorption of a degradable tannin, tannic acid (TA), on the polymersome surface through hydrogen bonding. TA serves as an anchoring layer for both 89Zr radionuclide and targeting recombinant humanized monoclonal antibody, trastuzumab (Tmab). Unlike bare PVPON5-PDMS30-PVPON5 polymersomes, TA- and Tmab-modified polymersomes demonstrated a high radiochemical yield of more than 95%. Excellent retention of 89Zr by the vesicle membrane for up to 7 days was confirmed by PET in vivo imaging. Animal biodistribution using healthy BALB/c mice confirmed the clearance of 89Zr-labeled polymersomes through the spleen and liver without their accumulation in bone, unlike the free nonbound 89Zr radiotracer. The 89Zr-radiolabeled polymersomes were found to specifically target BT474 HER2-positive breast cancer cells via the Tmab-TA complex on the vesicle surface. The noncovalent Tmab anchoring to the polymersome membrane can be highly advantageous for nanoparticle modification compared to currently developed covalent methods, as it allows easy and quick integration of a broad range of targeting proteins. Given the ability of these polymersomes to encapsulate and release anticancer therapeutics, they can be further expanded as precision-targeted therapeutic carriers for advancing human health through highly effective drug delivery strategies.

Polymersome-based protein drug delivery - quo vadis?

Protein-based therapeutics are an attractive alternative to established therapeutic approaches and represent one of the fastest growing families of drugs. While many of these proteins can be delivered using established formulations, the intrinsic sensitivity of proteins to denaturation sometimes calls for a protective carrier to allow administration. Historically, lipid-based self-assembled structures, notably liposomes, have performed this function. After the discovery of polymersome-based targeted drug-delivery systems, which offer manifold advantages over lipid-based structures, the scientific community expected that such systems would take the therapeutic world by storm. However, no polymersome formulations have been commercialised. In this review article, we discuss key obstacles for the sluggish translation of polymersome-based protein nanocarriers into approved pharmaceuticals, which include limitations imparted by the use of non-degradable polymers, the intricacies of polymersome production methods, and the complexity of the in vivo journey of polymersomes across various biological barriers. Considering this complex subject from a polymer chemist's point of view, we highlight key areas that are worthy to explore in order to advance polymersomes to a level at which clinical trials become worthwhile and translation into pharmaceutical and nanomedical applications is realistic.

Assembly of Celastrol to Zeolitic Imidazolate Framework-8 by Coordination as a Novel Drug Delivery Strategy for Cancer Therapy

Celastrol (Cel), a compound derived from traditional Chinese medicine Tripterygium wilfordii Hook. F, has attracted considerable attention as an anticancer drug. However, its clinical application is limited due to its low bioavailability and potential toxicity. With the advancement of nanoscale metal organic frameworks (MOF), the nano-delivery of drugs can effectively improve those disadvantages. Nevertheless, hydrophobic drugs apparently cannot be encapsulated by the hydrophilic channels of MOF-based drug delivery systems. To address these issues, a new assembly strategy for hydrophobic Cel was developed by coordinating the deprotonated Cel to zeolitic imidazolate framework-8 (ZIF-8) with the assistance of triethylamine (Cel-ZIF-8). This strategy greatly elevates the assembly efficiency of Cel from less than 1% to ca. 80%. The resulted Cel-ZIF-8 remains stable in the physiological condition while dissociating and releasing Cel after a 45-minute incubation in an acidic tumor microenvironment (pH 5.5). Furthermore, Cel-ZIF-8 is proved to be easily taken up by cancer cells and exhibits a better therapeutic effect on tumor cells than free Cel. Overall, the Cel-ZIF-8 provides a novel assembly strategy for hydrophobic drugs, and the findings are envisaged to facilitate the application of Cel in cancer therapies.

Poly(N-vinylcaprolactam) containing solid lipid polymer hybrid nanoparticles for controlled delivery of a hydrophilic drug gemcitabine hydrochloride

Folic acid tagged and hydrophilic polymer containing solid lipid nanoparticles (SLNs) were formulated for the controlled and targeted delivery of gemcitabine, a hydrophilic drug. Drug loaded SLNs were prepared by double emulsion method and optimized by 32 level factorial design. Then, a hydrophilic polymer, namely, poly(N-vinylcaprolactam) (PVCL) was incorporated in the optimized SLN batch in the first aqueous phase (W1) to obtain solid lipid polymer hybrid nanoparticles (SLPHNs) that were further decorated with folic acid (F-SLPHNs). TEM analysis of SLNs and SLPHNs revealed the spherical shape with no aggregation while SLPHNs showed higher % EE. SLPHNs exhibited limited burst release of gemcitabine compared to SLNs as well as lower overall % release. All the formulations showed good cytocompatibility against MDA-MB-231 cell lines and folic acid-tagged hybrid particles (F-SLPHNs) showed remarkably higher cellular uptake.

Dually Responsive Poly(N-vinylcaprolactam)-b-poly(dimethylsiloxane)-b-poly(N-vinylcaprolactam) Polymersomes for Controlled Delivery

Limited tissue selectivity and targeting of anticancer therapeutics in systemic administration can produce harmful side effects in the body. Various polymer nano-vehicles have been developed to encapsulate therapeutics and prevent premature drug release. Dually responsive polymeric vesicles (polymersomes) assembled from temperature-/pH-sensitive block copolymers are particularly interesting for the delivery of encapsulated therapeutics to targeted tumors and inflamed tissues. We have previously demonstrated that temperature-responsive poly(N-vinylcaprolactam) (PVCL)-b-poly(dimethylsiloxane) (PDMS)-b-PVCL polymersomes exhibit high loading efficiency of anticancer therapeutics in physiological conditions. However, the in-vivo toxicity of these polymersomes as biocompatible materials has not yet been explored. Nevertheless, developing an advanced therapeutic nanocarrier must provide the knowledge of possible risks from the material’s toxicity to support its future clinical research in humans. Herein, we studied pH-induced degradation of PVCL₁₀-b-PDMS₆₅-b-PVCL₁₀ vesicles in-situ and their dually (pH- and temperature-) responsive release of the anticancer drug, doxorubicin, using NMR, DLS, TEM, and absorbance spectroscopy. The toxic potential of the polymersomes was evaluated in-vivo by intravenous injection (40 mg kg⁻¹ single dose) of PVCL₁₀-PDMS₆₅-PVCL₁₀ vesicles to mice. The sub-acute toxicity study (14 days) included gravimetric, histological, and hematological analyses and provided evidence for good biocompatibility and non-toxicity of the biomaterial. These results show the potential of these vesicles to be used in clinical research.

Poly(N-vinylpyrrolidone)-block-Poly(dimethylsiloxane)-block-Poly(N-vinylpyrrolidone) Triblock Copolymer Polymersomes for Delivery of PARP1 siRNA to Breast Cancers

Nearly 20% of HER2-positive breast cancers develop resistance to HER2-targeted therapies requiring the use of advanced therapies. Silencing RNA therapy may be a powerful modality for treating resistant HER2 cancers due to its high specificity and low toxicity. However, the systemic administration of siRNAs requires a safe and efficient delivery platform because of siRNA's low stability in physiological fluids, inefficient cellular uptake, immunoreactivity, and rapid clearance. We have developed theranostic polymeric vesicles to overcome these hurdles for encapsulation and delivery of small functional molecules and PARP1 siRNA for in vivo delivery to breast cancer tumors. The 100 nm polymer vesicles were assembled from biodegradable and non-ionic poly(N-vinylpyrrolidone)₁₄-block-poly(dimethylsiloxane)₄₇-block-poly(N-vinylpyrrolidone)₁₄ triblock copolymer PVPON₁₄-PDMS₄₇-PVPON₁₄ using nanoprecipitation and thin-film hydration. We demonstrated that the vesicles assembled from the copolymer covalently tagged with the Cy5.5 fluorescent dye for in vivo imaging could also encapsulate the model drug with high loading efficiency (40%). The dye-loaded vesicles were accumulated in tumors after 18 h circulation in 4TR breast tumor-bearing mice via passive targeting. We found that PARP1 siRNA encapsulated into the vesicles was released intact (13%) into solution by the therapeutic ultrasound treatment as quantified by gel electrophoresis. The PARP1 siRNA-loaded polymersomes inhibited the proliferation of MDA-MB-361TR cells by 34% after 6 days of treatment by suppressing the NF-kB signaling pathway, unlike their scrambled siRNA-loaded counterparts. Finally, the treatment by PARP1 siRNA-loaded vesicles prolonged the survival of the mice bearing 4T1 breast cancer xenografts, with the 4-fold survival increase, unlike the untreated mice after 3 weeks following the treatment. These biodegradable, non-ionic PVPON₁₄-PDMS₄₇-PVPON₁₄ polymeric nanovesicles capable of the efficient encapsulation and delivery of PARP1 siRNA to successfully knock down PARP1 in vivo can provide an advanced platform for the development of precision-targeted therapeutic carriers, which could help develop highly effective drug delivery nanovehicles for breast cancer gene therapy.

Multi-responsive γ-methylene-γ-butyrolactone/N-vinyl caprolactam copolymers involving pH-dependent reversible lactonization

Copolymerization of γ-methylene-γ-butyrolactone with N-vinyl caprolactam leads to a peculiar multi-responsive NVCL-based system involving a unique reversible pH-dependent ring opening/closure of the pendant lactones.

Multifaceted role of phyto-derived polyphenols in nanodrug delivery systems

As naturally occurring bioactive products, several lines of evidence have shown the potential of polyphenols in the medical intervention of various diseases, including tumors, inflammatory diseases, and cardiovascular diseases. Notably, owing to the particular molecular structure, polyphenols can combine with proteins, metal ions, polymers, and nucleic acids providing better strategies for polyphenol-delivery strategies. This contributes to the inherent advantages of polyphenols as important functional components for other drug delivery strategies, e.g., protecting nanodrugs from oxidation as a protective layer, improving the physicochemical properties of carbohydrate polymer carriers, or being used to synthesize innovative functional delivery vehicles. Polyphenols have emerged as a multifaceted player in novel drug delivery systems, both as therapeutic agents delivered to intervene in disease progression and as essential components of drug carriers. Although an increasing number of studies have focused on polyphenol-based nanodrug delivery including epigallocatechin-3-gallate, curcumin, resveratrol, tannic acid, and polyphenol-related innovative preparations, these molecules are not without inherent shortcomings. The active biochemical characteristics of polyphenols constitute a prerequisite to their high-frequency use in drug delivery systems and likewise to provoke new challenges for the design and development of novel polyphenol drug delivery systems of improved efficacies. In this review, we focus on both the targeted delivery of polyphenols and the application of polyphenols as components of drug delivery carriers, and comprehensively elaborate on the application of polyphenols in new types of drug delivery systems. According to the different roles played by polyphenols in innovative drug delivery strategies, potential limitations and risks are discussed in detail including the influences on the physical and chemical properties of nanodrug delivery systems, and their influence on normal physiological functions inside the organism.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Dual-responsive polymersomes as anticancer drug carriers for the co-delivery of doxorubicin and paclitaxel

Multi stimuli-responsive polymersomes are in high demand as smart drug carriers, particularly for the treatment of complex cancers. However, most polymersomes have multi-responsiveness that does not affect each other and focus on single drug loading. Here, we have designed photo-crosslinked temperature and pH dual-responsive polymersomes by the self-assembly of a triblock polymer of methoxyl poly(ethylene glycol)-b-poly(N-isopropylacrylamide)-b-poly[2-(diethylamino)ethyl methacrylate-co-2-hydroxy-4-(methacryloyloxy)benzophenone] (mPEG-b-PNIPAM-b-P(DEAEMA-co-BMA)) synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). The dual-responsive polymersomes had a layered membrane, resulting in tunable permeability. Importantly, the polymersomes were proved to have a pH-controlled temperature-responsiveness. A hydrophilic-hydrophobic drug pair (doxorubicin hydrochloride, DOX, and paclitaxel, PTX) could be co-encapsulated in the fabricated polymersomes. The membrane permeability based on its layered structure was triggered by the change in temperature and pH to permit the separate control on the release of DOX and PTX. In a simulated tumor microenvironment, DOX and PTX encapsulated in the polymersomes could take effect for a relatively longer period and could work synergistically. Thus, the photo-crosslinked and dual-responsive polymersomes can be considered as promising drug carriers in the field of tumor combination chemotherapy.

Multilayer Microcapsules with Shell-Chelated 89Zr for PET Imaging and Controlled Delivery

Radionuclide-functionalized drug delivery vehicles capable of being imaged via positron emission tomography (PET) are of increasing interest in the biomedical field as they can reveal the in vivo behavior of encapsulated therapeutics with high sensitivity. However, the majority of current PET-guided theranostic agents suffer from poor retention of radiometal over time, low drug loading capacities, and time-limited PET imaging capability. To overcome these challenges, we have developed hollow microcapsules with a thin (<100 nm) multilayer shell as advanced theranostic delivery systems for multiday PET tracking in vivo. The 3 μm capsules were fabricated via the aqueous multilayer assembly of a natural antioxidant, tannic acid (TA), and a poly(N-vinylpyrrolidone) (PVPON) copolymer containing monomer units functionalized with deferoxamine (DFO) to chelate the ⁸⁹Zr radionuclide, which has a half-life of 3.3 days. We have found using radiochromatography that (TA/PVPON-DFO)₆ capsules retained on average 17% more ⁸⁹Zr than their (TA/PVPON)₆ counterparts, which suggests that the covalent attachment of the DFO to PVPON provides stable ⁸⁹Zr chelation. In vivo PET imaging studies performed in mice demonstrated that excellent stability and imaging contrast were still present 7 days postinjection. Animal biodistribution analyses showed that capsules primarily accumulated in the spleen, liver, and lungs with negligible accumulation in the femur, with the latter confirming the stable binding of the radiotracer to the capsule walls. The application of therapeutic ultrasound (US) (60 s of 20 kHz US at 120 W cm^-2) to Zr-functionalized capsules could release the hydrophilic anticancer drug doxorubicin from the capsules in the therapeutic amounts. Polymeric capsules with the capability of extended in vivo PET-based tracking and US-induced drug release provide an advanced platform for development of precision-targeted therapeutic carriers and could aid in the development of more effective drug delivery systems.

Targeted polymeric nanoparticles for drug delivery to hypoxic, triple-negative breast tumors

High recurrence and metastasis to vital organs are the major characteristics of triple-negative breast cancer (TNBC). Low vascular oxygen tension promotes resistance to chemo- and radiation therapy. Neuropilin-1 (NRP-1) receptor is highly expressed on TNBC cells. The tumor-penetrating iRGD peptide interacts with the NRP-1 receptor, triggers endocytosis and transcytosis, and facilitates penetration. Herein, we synthesized a hypoxia-responsive diblock PLA-diazobenzene-PEG copolymer and prepared self-assembled hypoxia-responsive polymersomes (Ps) in an aqueous buffer. The iRGD peptide was incorporated into the polymersome structure to make hypoxia-responsive iRGD-conjugated polymersomes (iPs). Doxorubicin (DOX) was encapsulated in the polymersomes to prepare both targeted and non-targeted hypoxia-responsive polymersomes (DOX-iPs and DOX-Ps, respectively). The polymeric nanoparticles released less than 30% of their encapsulated DOX within 12 hours under normoxic conditions (21% oxygen), whereas under hypoxia (2% Oxygen), doxorubicin release remarkably increased to over 95%. The targeted polymersomes significantly decreased TNBC cells' viability in monolayer and spheroid cultures under hypoxia compared to normoxia. Animal studies displayed that targeted polymersomes significantly diminished tumor growth in xenograft nude mice. Overall, the targeted polymersomes exhibited potent anti-tumor activity in monolayer, spheroid, and animal models of TNBC. With further developments, the targeted nanocarriers discussed here might have the translational potential as drug carriers for the treatment of TNBC.

Synthesis and characterization of biodegradable and antioxidant phosphazene-tannic acid nanospheres and their utilization as drug carrier material

In this study, hexachlorocyclotriphosphazene (HCCP) and tannic acid (TA) were used at different stoichiometric ratios to synthesize cyclomatrix-type polymeric materials with different surface features and dimensions. Using different reactive ratios, the structure and surface functional groups of the synthesized polymeric particles were explained using Fourier-Transform Infrared Spectroscopic (FTIR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric (TG) analysis techniques. With morphologically fully spherical structure and mean 234.82 ± 49.37 nm dimensions, Phz-TA (4:1) nanospheres were researched for in vitro biodegradability, antioxidant features, and usability as a drug release system. In vitro biodegradability of Phz-TA (4:1) nanospheres was investigated at pH = 7.0 and pH = 1.2. Determined to degrade in 8-10 h at these pH values, nanospheres were used for releasing of Rhodamine 6G as a model drug. Due to the rich phenolic structure of the contained tannic acid units, nanospheres were determined to simultaneously have antioxidant features. Thus, this study determined that Phz-TA nanospheres with in vitro biodegradability and antioxidant features are promising polymeric materials for use as a potential drug-carrier in the future.

A Review on Chitosan's Uses as Biomaterial: Tissue Engineering, Drug Delivery Systems and Cancer Treatment

Chitosan, derived from chitin, is a biopolymer consisting of arbitrarily distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine that exhibits outstanding properties- biocompatibility, biodegradability, non-toxicity, antibacterial activity, the capacity to form films, and chelating of metal ions. Most of these peculiar properties are attributed to the presence of free protonable amino groups along the chitosan backbone, which also gives it solubility in acidic conditions. Moreover, this biopolymer can also be physically modified, thereby presenting a variety of forms to be developed. Consequently, this polysaccharide is used in various fields, such as tissue engineering, drug delivery systems, and cancer treatment. In this sense, this review aims to gather the state-of-the-art concerning this polysaccharide when used as a biomaterial, providing information about its characteristics, chemical modifications, and applications. We present the most relevant and new information about this polysaccharide-based biomaterial's applications in distinct fields and also the ability of chitosan and its various derivatives to selectively permeate through the cancer cell membranes and exhibit anticancer activity, and the possibility of adding several therapeutic metal ions as a strategy to improve the therapeutic potential of this polymer.

Polymer Nanocontainers for Intracellular Delivery

Carriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture.

Temperature-Responsive Polymersomes of Poly(3-methyl-N-vinylcaprolactam)-block-poly(N-vinylpyrrolidone) To Decrease Doxorubicin-Induced Cardiotoxicity

Despite being one of the most potent chemotherapeutics, doxorubicin (DOX) facilitates cardiac toxicity by irreversibly damaging the cardiac muscle as well as severely dysregulating the immune system and impairing the resolution of cardiac inflammation. Herein, we report synthesis and aqueous self-assembly of nanosized polymersomes from temperature-responsive poly(3-methyl-N-vinylcaprolactam)-block-poly(N-vinylpyrrolidone) (PMVC-PVPON) diblock copolymers and demonstrate their potential to minimize DOX cardiotoxicity compared to liposomal DOX. RAFT polymerization of vinylpyrrolidone and 3-methyl-N-vinylcaprolactam, which are structurally similar monomers but have drastically different hydrophobicity, allows decreasing the cloud point of PMVC_m-PVPON_n copolymers below 20 °C. The lower critical solution temperature (LCST) of the PMVC₅₈-PVPON_n copolymer varied from 19.2 to 18.6 and to 15.2 °C by decreasing the length of the hydrophilic PVPON_n block from n = 98 to n = 65 and to n = 20, respectively. The copolymers assembled into stable vesicles at room temperature when PVPON polymerization degrees were 65 and 98. Anticancer drug DOX was entrapped with high efficiency into the aqueous PMVC₅₈-PVPON₆₅ polymersomal core surrounded by the hydrophobic temperature-sensitive PMVC shell and the hydrophilic PVPON corona. Unlike many liposomal, micellar, or synthetic drug delivery systems, these polymersomes exhibit an exceptionally high loading capacity of DOX (49%) and encapsulation efficiency (95%) due to spontaneous loading of the drug at room temperature from aqueous DOX solution. We also show that C57BL/6J mice injected with the lethal dose of DOX at 15 mg kg^-1 did not survive the 14 day treatment, resulting in 100% mortality. The DOX-loaded PMVC₅₈-PVPON₆₅ polymersomes did not cause any mortality in mice indicating that they can be used for successful DOX encapsulation. The gravimetric analyses of the animal organs from mice treated with liposome-encapsulated DOX (Lipo-DOX) and PMVC₅₈-PVPON₆₅ polymersomes (Poly-DOX) revealed that the Lipo-DOX injection caused some toxicity manifesting as decreased body weight compared to Poly-DOX and saline control. Masses of the left ventricle of the heart, lung, and spleen reduced in the Lipo-DOX-treated mice compared to the nontoxic saline control, while no significant decrease of those masses was observed for the Poly-DOX-treated mice. Our results provide evidence for superior stability of synthetic polymersomes in vivo and show promise for the development of next-generation drug carriers with minimal side effects.

A chitosan-based cascade-responsive drug delivery system for triple-negative breast cancer therapy

BACKGROUND

It is extremely difficult to develop targeted treatments for triple-negative breast (TNB) cancer, because these cells do not express any of the key biomarkers usually exploited for this goal.

RESULTS

In this work, we develop a solution in the form of a cascade responsive nanoplatform based on thermo-sensitive poly(N-vinylcaprolactam) (PNVCL)-chitosan (CS) nanoparticles (NPs). These are further modified with the cell penetrating peptide (CPP) and loaded with the chemotherapeutic drug doxorubicin (DOX). The base copolymer was optimized to undergo a phase change at the elevated temperatures of the tumor microenvironment. The acid-responsive properties of CS provide a second trigger for drug release, and the inclusion of CPP should ensure the formulations accumulate in cancerous tissue. The resultant CPP-CS-co-PNVCL NPs could self-assemble in aqueous media into spherical NPs of size < 200 nm and with low polydispersity. They are able to accommodate a high DOX loading (14.8% w/w). The NPs are found to be selectively taken up by cancerous cells both in vitro and in vivo, and result in less off-target cytotoxicity than treatment with DOX alone. In vivo experiments employing a TNB xenograft mouse model demonstrated a significant reduction in tumor volume and prolonging of life span, with no obvious systemic toxicity.

CONCLUSIONS

The system developed in this work has the potential to provide new therapies for hard-to-treat cancers.

Temperature and pH-responsive nano-hydrogel drug delivery system based on lysine-modified poly (vinylcaprolactam)

BACKGROUND

Smart materials capable of responding to external stimuli are noteworthy candidates in designing drug delivery systems. In many of the recent research, temperature and pH have been recognized as the main stimulating factors in designing systems for anti-cancer drugs delivery systems.

PURPOSE

In this study, thermo and pH-responsive character of a nano-carrier drug delivery platform based on lysine modified poly (vinylcaprolactam) hydrogel conjugated with doxorubicin was assessed.

METHODS

Poly (vinylcaprolactam) cross-linked with poly (ethyleneglycol) diacrylate was prepared via RAFT polymerization, and the prepared structure was linked with lysine through ring-opening. The anti-cancer drug doxorubicin, was linked to lysine moiety of the prepared structure via Schiff-base reaction. The prepared platform was characterized by 1HNMR and FT-IR, while molecular weight characterization was performed by size exclusion chromatography. The temperature-responsive activity was evaluated using differential scanning calorimetry and dynamic light scattering. In vitro release pattern in simulated physiologic pH at 37°C was compared with acidic pH attributed to tumor site and elevated temperature. The anticancer efficiency of the drug-conjugated structure was evaluated in breast cancer cell line MCF-7 in 24 and 48 h, and cell uptake assay was performed on the same cell line.

CONCLUSION

According to the results, well-structure defined smart pH and temperature responsive nano-hydrogel was prepared. The enhanced release rates are observed at acidic pH and elevated temperature. We have concluded that the doxorubicin-conjugated nanoparticle results in higher cellular uptakes and more cytotoxicity.

Stimulus-responsive vesicular polymer nano-integrators for drug and gene delivery

Over the past two decades, nano-sized biosystems have increasingly been utilized to deliver various pharmaceutical agents to a specific region, organ or tissue for controllable precision therapy. Whether solid nanohydrogel, nanosphere, nanoparticle, nanosheet, micelles and lipoproteins, or "hollow" nanobubble, liposome, nanocapsule, and nanovesicle, all of them can exhibit outstanding loading and releasing capability as a drug vehicle - in particular polymeric nanovesicle, a microscopic hollow sphere that encloses a water core with a thin polymer membrane. Besides excellent stability, toughness and liposome-like compatibility, polymeric nanovesicles offer considerable scope for tailoring properties by changing their chemical structure, block lengths, stimulus-responsiveness and even conjugation with biomolecules. In this review, we summarize the latest advances in stimulus-responsive polymeric nanovesicles for biomedical applications. Different functionalized polymers are in development to construct more complex multiple responsive nanovesicles in delivery systems, medical imaging, biosensors and so on.

Polyphenol-Based Particles for Theranostics

Polyphenols, due to their high biocompatibility and wide occurrence in nature, have attracted increasing attention in the engineering of functional materials ranging from films, particles, to bulk hydrogels. Colloidal particles, such as nanogels, hollow capsules, mesoporous particles and core-shell structures, have been fabricated from polyphenols or their derivatives with a series of polymeric or biomolecular compounds through various covalent and non-covalent interactions. These particles can be designed with specific properties or functionalities, including multi-responsiveness, radical scavenging capabilities, and targeting abilities. Moreover, a range of cargos (e.g., imaging agents, anticancer drugs, therapeutic peptides or proteins, and nucleic acid fragments) can be incorporated into these particles. These cargo-loaded carriers have shown their advantages in the diagnosis and treatment of diseases, especially of cancer. In this review, we summarize the assembly of polyphenol-based particles, including polydopamine (PDA) particles, metal-phenolic network (MPN)-based particles, and polymer-phenol particles, and their potential biomedical applications in various diagnostic and therapeutic applications.

Rapid conjugation of nanoparticles, proteins and siRNAs to microbubbles by strain-promoted click chemistry for ultrasound imaging and drug delivery

A new strategy using catalyst-free strain-promoted alkyne-azide cycloaddition (SPAAC) "click" chemistry for the ligation of anti-cancer drug-loaded nanoparticles, functionalized proteins, and siRNA conjugated micelles to microbubbles (MB) was established. The results showed fast ligation within 5 min without sacrificing microbubble size and density. The ultrasound test showed good imaging abilities of the microbubbles after functionalization. This microbubble-therapeutic SPAAC "click" conjugation developed in the current study involves no toxic catalyst or initiator, has ultra-fast reaction speed, and is versatile for the ligation of various anti-cancer or therapeutic agents to microbubbles. These advantages render the SPAAC click strategy promising for broad applications in ultrasound-guided imaging and therapeutic delivery.

Stimuli-Responsive Poly( N-Vinyllactams) with Glycidyl Side Groups: Synthesis, Characterization, and Conjugation with Enzymes

Herein we report the synthesis of new reactive stimuli-responsive polymers by RAFT copolymerization of glycidyl methacrylate and three cyclic N-vinyllactam derivatives. The copolymerization process was thoroughly investigated and the influence of the steric hindrance originating from the monomer structure of cyclic N-vinyllactams on the polymerization process and the properties of obtained copolymers were studied. A series of water-soluble copolymers with variable chemical composition, controlled molecular weight and narrow dispersity ( Đ) were synthesized and their properties are systematically investigated. Experimentally determined cloud points for different copolymers in aqueous solutions indicate shift of lower critical solution temperature (LCST) to lower values with the increase of GMA content in copolymers and increase of the lactam ring size. The obtained reactive stimuli-responsive copolymers can be efficiently used for encapsulation of cellulase in water-in-oil emulsions forming biohybrid nanogels. The enzymes entrapped in nanogels demonstrated significantly improved resistance against harsh store conditions, chaotropic agents, and organic solvents.

The emulsion polymerization induced self-assembly of a thermoresponsive polymer poly(N-vinylcaprolactam)

A thermoresponsive polymer, poly(N-vinylcaprolactam) (PNVCL), was synthesized in an emulsion above its thermal transition temperature to produce particles via polymerization induced self-assembly (PISA).

Physical stimuli-responsive vesicles in drug delivery: Beyond liposomes and polymersomes

Over the past few decades, a range of vesicle-based drug delivery systems have entered clinical practice and several others are in various stages of clinical translation. While most of these vesicle constructs are lipid-based (liposomes), or polymer-based (polymersomes), recently new classes of vesicles have emerged that defy easy classification. Examples include assemblies with small molecule amphiphiles, biologically derived membranes, hybrid vesicles with two or more classes of amphiphiles, or more complex hierarchical structures such as vesicles incorporating gas bubbles or nanoparticulates in the lumen or membrane. In this review, we explore these recent advances and emerging trends at the edge and just beyond the research fields of conventional liposomes and polymersomes. A focus of this review is the distinct behaviors observed for these classes of vesicles when exposed to physical stimuli - such as ultrasound, heat, light and mechanical triggers - and we discuss the resulting potential for new types of drug delivery, with a special emphasis on current challenges and opportunities.

A facile synthesis of pH stimuli biocompatible block copolymer poly(methacrylic acid)-block-poly(N-vinylpyrrolidone) utilizing switchable RAFT agents

Synthesis of block copolymer PMAA-b-PNVP utilizing switchable RAFT agents and its self-assembly.

Multilayer Hydrogel Capsules of Interpenetrated Network for Encapsulation of Small Molecules

We report on a facile capsule-based platform for efficient encapsulation of a broad spectrum of hydrophilic compounds with molecular weight less than 1000 g mol^-1. The encapsulated compounds extend from low-molecular-weight anionic Alexa Fluor 532 dye and cationic anticancer drug doxorubicin (DOX) to fluorescein isothiocyanate-dextrans with M_w ranging from 4000 to 40 000 g mol^-1. The pH-sensitive hydrogel capsules with an interpenetrated network shell are synthesized by layer-by-layer assembly of poly(methacrylic acid) (PMAA, M_w = 150 000 g mol^-1) and poly( N-vinylpyrrolidone) (PVPON, M_w = 1 300 000 g mol^-1) on 5 μm silica microparticles followed by chemical cross-linking of the PMAA multilayers. Following core dissolution, the result is a hollow microcapsule with PVPON interpenetrated in the PMAA network. The capsules exhibit a reversible change in the diameter with a swelling ratio of 1.5 upon pH variation from 7.5 to 5.5. Capsules cross-linked for 4 h display high permeability toward molecules with molecular weight under 1000 g mol^-1 at pH = 7.5 but exclude dextran molecules with M_w ≥ 40 000 g mol^-1. Encapsulation of small molecules was achieved at pH = 7.5 followed by sealing the capsule wall with 40 000 g mol^-1 dextran at pH = 5.5. This approach results in negatively charged molecules such as Alexa Fluor being entrapped within the capsule cavity, whereas positively charged molecules such as DOX are encapsulated within the negatively charged capsule shell. Considering the simple postloading approach, the ability to entrap both anionic and cationic small molecules, and the pH-responsiveness of the interpenetrated network in the physiologically relevant range, these capsules offer a versatile method for controlled delivery of multiple hydrophilic compounds.

Translatable High Drug Loading Drug Delivery Systems Based on Biocompatible Polymer Nanocarriers

Most nanocarriers possess low drug loading, resulting in frequently repeated administration and thereby high cost and increased side effects. Furthermore, the characteristics of nanocarrier materials, especially the drug loading capacity, plays a vital role in the drug delivery efficacy. In this review, we focus on the readily translatable polymeric drug delivery systems with high drug loading, which are comprised of biocompatible polymers such as poly(ethylene glycol), poly( N-vinylpyrrolidone), polyoxazoline, natural proteins like albumin and casein, non-natural proteins such as recombinant elastin-like polypeptides, as well as nucleic acids. At the end of this review, applications of these polymeric nanocarriers on the delivery of proteins and gene drugs are also briefly discussed.