Poly(l-aspartic acid) nanogels for lysosome-selective antitumor drug delivery

Nanogel: A versatile drug delivery system for the treatment of various diseases and their future perspective

Nanogel (NG) drug delivery systems have emerged as promising tools for targeted and controlled drug release, revolutionizing treatment approaches across various diseases. Their unique physicochemical properties, such as nano size, high surface area, biocompatibility, stability, and tunable drug release, make them ideal carriers for a wide range of therapeutic agents. Nanogels (NGs), characterized by their 3D network of crosslinked polymers, offer unique edges like high drug loading capacity, controlled release, and targeted delivery. Additionally, the diverse applications of NGs in medical therapeutics highlight their versatility and potential impact on improving patient outcomes. Their application spans cancer treatment, infectious diseases, and chronic conditions, allowing for precise drug delivery to specific tissues or cells, minimizing side effects, and enhancing therapeutic efficacy. Despite their potential, challenges such as scalability, manufacturing reproducibility, and regulatory hurdles must be addressed. Achieving clinical translation requires overcoming these obstacles to ensure therapeutic payloads' safe and efficient delivery. Strategies such as surface modification and incorporating stimuli-responsive elements enhanced NG performance and addressed specific therapeutic challenges. Advances in nanotechnology, biomaterials, and targeted drug design offer opportunities to improve the performance of NGs and address current limitations. Tailoring NGs for exploring combination therapies and integrating diagnostics for real-time monitoring represent promising avenues for future research. In conclusion, NG drug delivery systems have demonstrated tremendous potential in diverse disease applications. Overcoming challenges and leveraging emerging technologies will pave the way for their widespread clinical implementation, ushering in a new era of precision medicine and improved patient care.

Biodegradable Nanogels for Dermal Applications: An Insight

Abstract:

Biodegradable nanogels in the biomedical field are emerging vehicles comprising dispersions of hydrogel nanoparticles having 3D crosslinked polymeric networks. Nanogels show distinguished characteristics including their homogeneity, adjustable size, low toxicity, stability in serum, stimuli-responsiveness (pH, temperature, enzymes, light, etc.), and relatively good drug encapsulation capability. Due to these characteristics, nanogels are referred to as nextgeneration drug delivery systems and are suggested as promising carriers for dermal applications. The site-specific delivery of drugs with effective therapeutic effects is crucial in transdermal drug delivery. The nanogels made from biodegradable polymers can show external stimuliresponsiveness which results in a change in gel volume, water content, colloidal stability, mechanical strength, and other physical and chemical properties, thus improving the site-specific topical drug delivery. This review provides insight into the advances in development, limitations, and therapeutic significance of nanogels formulations. It also highlights the process of release of drugs in response to external stimuli, various biodegradable polymers in the formulation of the nanogels, and dermal applications of nanogels and their role in imaging, anti‐inflammatory therapy, antifungal and antimicrobial therapy, anti‐psoriatic therapy, and ocular and protein/peptide drug delivery.

Exploring the feasibility of carbamoylethyl pullulan-g-palmitic acid polymeric micelles for the effective targeting of raloxifene to breast tumor: Optimization and preclinical evaluation

Carbamoylethyl pullulan-grafted palmitic acid (CP-g-PA), a novel self-assembled polymer was synthesized and examined for its efficacy in delivering the raloxifene (RA) to mammary carcinoma. The synthesized CP-g-PA was confirmed by evaluating through various spectral and morphological attributes. Further, the central composite design-response surface methodology with two factors at three levels was utilized to obtain the optimized and stable polymeric micelles. The optimized formulation was subjected to in vitro and in vivo evaluation. RA loaded polymeric micelles (RA-PMs) were spherical in shape with particle size less than 100 nm and high entrapment efficiency (77.02%). The developed formulation exhibited pH-dependent release profile of RA when loaded in polymeric micelles and provides substantial compatibility to erythrocytes. In vivo pharmacokinetic study demonstrates that RA-PMs offers higher mean residence time and volume of distribution as compared to pure RA. Besides, the biodistribution study manifested enhanced drug concentration in tumor and decreased concentration in other tissue as compared to pure drug. The treatment with RA-PMs also increases the median survival time, tumor inhibition rate and % increase in life span of the tumor bearing rats. Overall, the results pointed towards the overwhelming response of RA when loaded into micelles made from CP-g-PA.

An On-Demand pH-Sensitive Nanocluster for Cancer Treatment by Combining Photothermal Therapy and Chemotherapy

Combination therapy is considered to be a promising strategy for improving the therapeutic efficiency of cancer treatment. In this study, an on-demand pH-sensitive nanocluster (NC) system was prepared by the encapsulation of gold nanorods (AuNR) and doxorubicin (DOX) by a pH-sensitive polymer, poly(aspartic acid-graft-imidazole)-PEG, to enhance the therapeutic effect of chemotherapy and photothermal therapy. At pH 6.5, the NC systems formed aggregated structures and released higher drug amounts while sustaining a stable nano-assembly, structured with less systemic toxicity at pH 7.4. The NC could also increase antitumor efficacy as a result of improved accumulation and release of DOX from the NC system at pHex and pHen with locally applied near-infrared light. Therefore, an NC system would be a potent strategy for on-demand combination treatment to target tumors with less systemic toxicity and an improved therapeutic effect.

Stimulus-responsive polymeric nanogels as smart drug delivery systems

Nanogels are three-dimensional nanoscale networks formed by physically or chemically cross-linking polymers. Nanogels have been explored as drug delivery systems due to their advantageous properties, such as biocompatibility, high stability, tunable particle size, drug loading capacity, and possible modification of the surface for active targeting by attaching ligands that recognize cognate receptors on the target cells or tissues. Nanogels can be designed to be stimulus responsive, and react to internal or external stimuli such as pH, temperature, light and redox, thus resulting in the controlled release of loaded drugs. This "smart" targeting ability prevents drug accumulation in non-target tissues and minimizes the side effects of the drug. This review aims to provide an introduction to nanogels, their preparation methods, and to discuss the design of various stimulus-responsive nanogels that are able to provide controlled drug release in response to particular stimuli. STATEMENT OF SIGNIFICANCE: Smart and stimulus-responsive drug delivery is a rapidly growing area of biomaterial research. The explosive rise in nanotechnology and nanomedicine, has provided a host of nanoparticles and nanovehicles which may bewilder the uninitiated reader. This review will lay out the evidence that polymeric nanogels have an important role to play in the design of innovative drug delivery vehicles that respond to internal and external stimuli such as temperature, pH, redox, and light.

A nano-sized blending system comprising identical triblock copolymers with different hydrophobicity for fabrication of an anticancer drug nanovehicle with high stability and solubilizing capacity

Background: A very common and simple method (known as the blending method) to formulate drug delivery systems with required properties is to physically mix amphiphilic block copolymers with different hydrophobicity. In addition to its simplicity, this blending strategy could help avoid the time and effort involved in the synthesis of block copolymers with the desired structure required for specific drug formulations. Purpose: We used the blending strategy to design a system that could overcome the problem of high hydrophobicity and be a good candidate for drug product development using PEG-PLA-PEG triblock copolymers. Methods: Two types of PEG-PLA-PEG triblock copolymers with similar (long) PLA molecular weights (MWs) and different PEG MWs were synthesized. The micellar formulations were prepared by blending the two block copolymers in various ratios. The size and stability of the blending systems were subsequently investigated to optimize the formulations for further studies. The loading properties of doxorubicin or paclitaxel into the optimized blending system were compared to that in mono systems (systems composed of only a single type of triblock copolymer). In vitro and in vivo anti-cancer effects of the preparations were evaluated to assess the use of the blending system as an optimal nanomedicine platform for insoluble anticancer agents. Results: The blending system (B20 system) with an optimized ratio of the triblock copolymers overcame the drawbacks of mono systems. Drug uptake from the drug-loaded B20 system and its anticancer effects against KB cells were superior compared to those of free drugs (doxorubicin hydrochloride and free paclitaxel). In particular, doxorubicin-loaded B20 resulted in extensive doxorubicin accumulation in tumor tissues and significantly higher in vivo anti-cancer effects compared to free doxorubicin. Conclusion: The blending system reported here could be a potential nanoplatform for drug delivery due to its simplicity and efficiency for pharmaceutical application.

Amphiphilic Block Copolymer Poly (Acrylic Acid)-B-Polycaprolactone as a Novel pH-sensitive Nanocarrier for Anti-Cancer Drugs Delivery: In-vitro and In-vivo Evaluation

Gambogenic acid (GNA) has been demonstrated with outstanding antitumor activity as a potential antitumor drug in recent years. However, the low solubility and deficient bioavailability of GNA seriously hinder its practical application in the clinic area. In this study, a novel amphiphilic block copolymer, poly (acrylic acid)-b-polycaprolactone (PAA-b-PCL) is prepared and assembled into pH-responsive polymeric micelles (PMs) as one mold of drug delivery system (DDS) with unique properties. Relevant investigation on PMs exhibits excellent carrying potential and pH-dependent release performance for GNA. The drug loading capacity (DLC) and drug loading efficiency (DLE) for GNA-loaded PMs can be achieved as high as 15.20 ± 0.07% and 83.67 ± 0.49%, respectively. The in vitro experiments indicate that the GNA releasing time, cytotoxicity, and cellular uptake are significantly enhanced. Especially, the peak concentration (Cmax) and area under the curve (AUC) are promoted sharply in the GNA-loaded PMs concentration-time curve. This study not only provides a novel way to widen the application of anticancer GNA in the future, but also extends the potential of stimuli-responsive copolymers to biomedical applications.

Development of a docetaxel micellar formulation using poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG) with successful reconstitution for tumor targeted drug delivery

Docetaxel (DTX)-loaded polymeric micelles (DTBM) were formulated using the triblock copolymer, poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG), to comprehensively study their pharmaceutical application as anticancer nanomedicine. DTBM showed a stable formulation of anticancer nanomedicine that could be reconstituted after lyophilization (DTBM-R) in the presence of PEG 2000 and D-mannitol (Man) as surfactant and protectant, respectively. DTBM-R showed a particle size less than 150 nm and greater than 90% of DTX recovery after reconstitution. The robustly formed micelles might minimize systemic toxicity due to their sustained drug release and also maximize antitumor efficacy through increased accumulation and release of DTX from the micelles. From the pharmaceutical development point of view, DTBM-R showing successful reconstitution could be considered as a potent nanomedicine for tumor treatment.

pH-Responsive hyaluronated liposomes for docetaxel delivery

In this study, we report pH-responsive liposomes consisting of hydrogenated soy phosphatidylcholine (HSPC) as a lipid, hyaluronic acid (HA) grafted with functional 3-diethylaminopropyl (DEAP) groups (hereafter denoted as HA-g-DEAP) as a pH-responsive polymer, and docetaxel (DTX) as an antitumor drug. DTX-loaded HSPC liposomes were prepared via a conventional liposome manufacturing procedure and then were decorated with HA-g-DEAP (HA-g-DEAP0.15, HA-g-DEAP0.25, and HA-g-DEAP0.40, according to the molar conjugate ratio of DEAP to HA) in an aqueous solution (pH 7.4), by sonication. The liposomes with HA-g-DEAP0.40 allowed the efficient release of the encapsulated DTX content when the pH of the solution decreased to 6.5 (i.e., endosomal pH), owing to the acidic pH-induced protonation of the DEAP anchored to the vesicular lipid bilayers. These hyaluronated liposomes were effective at entering the human colon carcinoma HCT-116 cells with a CD44 receptor overexpression. In an in vitro tumor cell cytotoxicity test, the DTX-loaded liposomes caused a significant increase in HCT-116 tumor cell death, revealing their pharmaceutical potential in tumor therapy.

Synergistic photodynamic therapeutic effect of indole-3-acetic acid using a pH sensitive nano-carrier based on poly(aspartic acid-graft-imidazole)-poly(ethylene glycol)

Poly(aspartic acid-graft-imidazole)-poly(ethylene glycol) (P(Asp-g-Im)-PEG) was utilized as a pH-sensitive nanocarrier of the photosensitizer indole-3-acetic acid (IAA) for the treatment of skin cancer. IAA loaded micelles (ILMs) exhibited the formation of ca. 140 nm spherical particles at pH 7.4. The micelles disintegrated at acidic pHs, resulting in pH-dependent IAA release and cytotoxicity. Treatment of ILMs with visible light at a wavelength of 480 nm caused pH dependent synergistic cell damage in both in vitro and in vivo models using the B16F10 melanoma cell line. Interestingly, ILMs synergistically produced reactive oxygen species (ROS) at an acidic pH of 6.5 with visible light irradiation by proton coupled electron transfer (PCET). The pH sensitive ILMs could be considered a potent nanomedicine used to exert synergistic photodynamic therapeutic effects to treat cancers.

A charge-reversible nanocarrier using PEG-PLL (-g-Ce6, DMA)-PLA for photodynamic therapy

A polyelectrolyte nanoparticle composed of PEG-PLL(-g-Ce6, DMA)-PLA was developed for nanomedicinal application in photodynamic therapy. These nanoparticles formed stable aggregates through the hydrophobic interaction of poly(lactic acid) and demonstrated pH-dependent behaviors such as surface charge conversion and enhanced cellular uptake at acidic pH, resulting in improved phototoxicity. In vivo animal imaging revealed that the prepared PEG-PLL(-g-Ce6, DMA)-PLA nanoparticles effectively accumulated at the targeted tumor site through enhanced permeability and retention effects. Reversible surface charge for PEG-PLL (-g-Ce6, DMA)-PLA nanoparticles allows the nanoparticles to escape the immune system and concentrate on the tumor tissue. Tumor growth in the nude mice treated with the nanoparticles decreased significantly and the hydrophobic interaction in the poly(lactic acid) block could allow the incorporation of multiple drugs. Therefore, the PEG-PLL(-g-Ce6, DMA)-PLA nanoparticles could have considerable potential as a nanomedicinal platform for photodynamic therapy.

Spontaneous Vesiculation and pH-Induced Disassembly of a Lysosomotropic Detergent: Impacts on Lysosomotropism and Lysosomal Delivery

Lysosomotropic detergents (LDs) selectively rupture lysosomal membranes through mechanisms that have yet to be characterized. A consensus view, currently, holds that LDs, which are weakly basic, diffuse across cellular membranes as monomers in an uncharged state, and via protonation in the acidic lysosomal compartment, they become trapped, accumulate, and subsequently solubilize the membrane and induce lysosomal membrane permeabilization. Here we demonstrate that the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) spontaneously assembles into vesicles at, and above, cytosolic pH, and that the vesicles disassemble as the pH reaches 6.4 or lower. The aggregation commences at concentrations below the range of those used in cell studies. Assembly and disassembly of the vesicles was studied via dynamic light scattering, zeta potential measurements, cryo-TEM, and fluorescence correlation spectroscopy and was found to be reversible via control of the pH. Aggregation of MSDH into closed vesicles under cytosolic conditions is at variance with the commonly held view of LD behavior, and we propose that endocytotic pathways should be considered as possible routes of LD entry into lysosomes. We further demonstrate that MSDH vesicles can be loaded with fluorophores via a solution transition from low to high pH, for subsequent release when the pH is lowered again. The ability to encapsulate molecular cargo into MSDH vesicles together with its ability to disaggregate at low pH and to permeabilize the lysosomal membrane presents an intriguing possibility to use MSDH as a delivery system.

Structure-biocompatibility and transfection activity relationships of cationic polyaspartamides with (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups

A series of 14 cationic derivatives of poly(aspartic acid) i.e. cationic polyaspartamides with different (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups was synthesized by nucleophilic addition on polysuccinimide. The resulting polyaspartamides have moderate amphiphilic properties. Relationships between the structure and ratio of side groups and in vitro properties of polyaspartamides, including their cytotoxic and membrane-damaging activity towards human cell lines, primary skin fibroblasts and erythrocytes, were established and discussed. Cationic polyaspartamides vary in their DNA-binding, condensing and nuclease-protecting characteristics depending on the concentration ratio of (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups. Effective cell transfection was achieved upon polyaspartamide-mediated plasmid DNA delivery in serum-free medium in the presence of chloroquine. Effect of serum proteins adsorption onto polyaspartamide based polyplexes, and the role of concentration of polyplexes in culture medium in their colloidal stability and transfection process were demonstrated. Synthesized polyaspartamides are biocompatible and long-acting gene carriers, which are applied to cells after dilution and without washing, thus providing transfection level comparable to that of commercial transfection reagent.

Development of pH-responsive starch–glycol chitosan nanogels for proapoptotic (KLAKLAK)2 peptide delivery

In this study, we report pH-responsive polysaccharidic nanogels for cytosolic peptide delivery. We conjugated starch to water-soluble glycol chitosan and pH-responsive 3-diethylaminopropylamine (starch–(glycol chitosan–3-diethylaminopropylamine)). Starch–(glycol chitosan–3-diethylaminopropylamine) self-organizes in aqueous solution, with the glycol chitosan blocks on the hydrophilic outer shell and starch and 3-diethylaminopropylamine blocks in the hydrogel inner core. The experimental results demonstrated that the protonation of 3-diethylaminopropylamine at pH 6.0 (endosomal pH) allowed for accelerated release of the encapsulated D-(KLAKLAK)2 proapoptotic peptide from the nanogels as a result of electrostatic repulsion between D-(KLAKLAK)2 and 3-diethylaminopropylamine. A hemolysis test using red blood cell membranes (as an endosomal membrane model) revealed the excellent endosomolytic activity of these nanogels, which likely stems from the proton-sponge effect of 3-diethylaminopropylamine at pH 6.0. As a result, these nanogels resulted in increased KB tumor cell ablation.

Highly Versatile Polyelectrolyte Complexes for Improving the Enzyme Replacement Therapy of Lysosomal Storage Disorders

Lysosomal storage disorders are currently treated by enzyme replacement therapy (ERT) through the direct administration of the unprotected recombinant protein to the patients. Herein we present an ionically cross-linked polyelectrolyte complex (PEC) composed of trimethyl chitosan (TMC) and α-galactosidase A (GLA), the defective enzyme in Fabry disease, with the capability of directly targeting endothelial cells by incorporating peptide ligands containing the RGD sequence. We assessed the physicochemical properties, cytotoxicity, and hemocompatibility of RGD-targeted and untargeted PECs, the uptake by endothelial cells and the intracellular activity of PECs in cell culture models of Fabry disease. Moreover, we also explored the effect of different freeze-drying procedures in the overall activity of the PECs. Our results indicate that the use of integrin-binding RGD moiety within the PEC increases their uptake and the efficacy of the GLA enzyme, while the freeze-drying allows the activity of the therapeutic protein to remain intact. Overall, these results highlight the potential of TMC-based PECs as a highly versatile and feasible drug delivery system for improving the ERT of lysosomal storage disorders.

pH-Responsive globular poly(ethylene glycol) for photodynamic tumor therapy

In this study, we report the development of extremely small-sized globular poly(ethylene glycol) (gPEG) that can specifically recognize tumor acidic pH. gPEG coupled with chlorin e6 (Ce6, a photosensitizing drug) and 2,3-dimethylmaleic acid (DMA, as a pH-responsive moiety) (gPEG-Ce6-DMA, particle size: 3-4nm in diameter) was easily dispersed in phosphate buffered saline (PBS) without any of the nanoparticle fabrication steps. We observed that gPEG-Ce6-DMA displayed pH-dependent zeta-potential changes due to coupling (at pH 7.4) or decoupling (at pH 6.8-6.0) of DMA. As a result, the uptake of gPEG-Ce6-DMA was significantly increased in tumors at acidic pH, likely due to the decoupling of DMA (backing cationic primary amines). As a result, the preferential cellular uptake of gPEG-Ce6-DMA at acidic pH allowed for a significant enhancement of in vitro/in vivo photodynamic tumor cell ablation under light illumination.

Preparation of iron oxide nanoparticles functionalized with Y-shaped ligands for brain tumor targeting

In this study, we developed functionalized iron oxide nanoparticles for brain tumor targeting. The iron oxide (Fe₃O₄) particles were stabilized with pluronic F127 and coupled with dopamine-terminated Y-shaped ligands (Tat peptide and transferrin) as a result of the noncovalent conjugation of dopamine (of Y-shaped ligands) and the iron oxide nanoparticles. Here, the hydrophobic domain of pluronic F127 coated on the iron oxide nanoparticles enabled the absorption of a model photosensitizing antitumor drug (chlorin e6) in the core/shell interface of the nanoparticles. The experimental results demonstrated that the Y-shaped ligands on the nanoparticles enabled a significant enhancement of in vitro/in vivo cellular uptake for human primary glioblastoma U87-MG cells as a result of multivalent endocytosis by Y-shaped ligands (transferrin receptor-mediated endocytosis and the following Tat peptide-mediated cellular interaction). Furthermore, the Ce6-loaded nanoparticles showed significant enhancement of in vitro/in vivo photodynamic U87-MG cell ablation under light illumination.

GNeosomes: Highly Lysosomotropic Nanoassemblies for Lysosomal Delivery

GNeosomes, lysosomotropic lipid vesicles decorated with guanidinoneomycin, can encapsulate and facilitate the cellular internalization and lysosomal delivery of cargo ranging from small molecules to high molecular weight proteins, in a process that is exclusively dependent on cell surface glycosaminoglycans. Their cellular uptake mechanism and co-localization with lysosomes, as well as the delivery, release, and activity of internalized cargo, are quantified. GNeosomes are proposed as a universal platform for lysosomal delivery with potential as a basic research tool and a therapeutic vehicle.

Enhanced anti-tumor effect of pH-responsive dextrin nanogels delivering doxorubicin on colorectal cancer

Efficacy of doxorubicin (DOX) in colorectal cancer treatment is limited by undesirable side-effects, which are partially due to nonspecific delivery DOX to the tumor target site. This study aimed to develop pH-responsive dextrin nanogels (DNGs) as anticancer drug carriers with pH-controlled drug release. DNGs prepared with formaldehyde as a cross-linker (FDNGs) exhibited smaller size, compared to that using glyoxal (GDNGs). Both DNGs showed pH-dependent drug release properties; drug release was slow at neutral pH but increased significantly in acidic medium. The cytotoxicity of empty and DOX-loaded FDNGs was lower than free DOX and GDNGs, against two commonly used colorectal cancer cells. Intracellular uptake studies indicated that the DOX-loaded FDNGs could efficiently deliver DOX into the nuclei. In vivo, DOX-loaded FDNGs substantially enhanced anti-tumor efficacy, compared to free DOX, exhibiting much higher effects on inhibiting proliferation and inducing apoptosis, as confirmed by mice weight shifts, tumor weight, tumor volume and histological assessment. Therefore, FDNGs are promising as a potential drug delivery vehicle for colorectal cancer therapy.

Photodynamic tumor therapy of nanoparticles with chlorin e6 sown in poly(ethylene glycol) forester

We developed novel photosensitizing drug-carrying nanoparticles with poly(ethylene glycol) (PEG) forester.

Hyaluronic acid-conjugated apoferritin nanocages for lung cancer targeted drug delivery

In this paper, we proposed a naturally derived protein cage based pH-responsive delivery system for intracellular prodrug controlled release.

pH-sensitive short worm-like micelles targeting tumors based on the extracellular pH

We developed novel photosensitizing drug-carrying worm-like micelles using a pH-sensitive AB₂ miktoarm block copolymer consisting of one methoxy-poly(ethylene glycol) (mPEG) block (A) and two 3-diethylaminopropylated poly(l-lysine) [poly(Lys-DEAP)] blocks (B₂).