pH responsive micelles based on copolymers mPEG-PCL-PDEA: The relationship between composition and properties

PH-sensitive BSA-modified resveratrol micelles targeting macrophages alleviate symptoms of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, leading to severe inflammatory infiltration and joint damage, accompanied by a decrease in pH of joint microenvironment. Macrophages play an important role in the pathogenesis of RA, with high expression of bovine serum albumin (BSA) receptors on the surface of macrophages. Resveratrol (Res) has strong anti-inflammatory effects, but its application is limited due to its poor water solubility and low bioavailability. Therefore, we constructed pH-sensitive micelles by encapsulating Res and modifying BSA on the surface of the micelles (BSA-Res@Ms), thereby greatly improving the therapeutic effect of RA. Our research results indicated that BSA-Res@Ms had a smooth and uniform appearance, small particle size, high drug encapsulation efficiency, good stability, and pH-sensitive properties. In vitro, BSA-Res@Ms increased the uptake of Res by RAW264.7 cells, reduced the levels of pro-inflammatory cytokines and cleared excess ROS produced by activated RAW264.7 cells, and inhibited the generation of osteoclasts. In vivo, BSA-Res@Ms could target inflamed joint sites, significantly alleviate joint inflammation symptoms, inhibit activated macrophages, improve synovial hyperplasia and inflammatory cell infiltration, and protect cartilage. BSA-Res@Ms provide a very promising method for the treatment of RA, which can effectively improve the inflammatory manifestations of RA.

Nanoparticle-based inhibition of vascular endothelial growth factor receptors alleviates osteoarthritis pain and cartilage damage

Osteoarthritis (OA) is characterized by cartilage damage, inflammation, and pain. Vascular endothelial growth factor receptors (VEGFRs) have been associated with OA severity, suggesting that inhibitors targeting these receptors alleviate pain (via VEGFR1) or cartilage degeneration (via VEGFR2). We have developed a nanoparticle-based formulation of pazopanib (Votrient), an FDA-approved anticancer drug that targets both VEGFR1 and VEGFR2 (Nano-PAZII). We demonstrate that a single intraarticular injection of Nano-PAZII can effectively reduce joint pain for a prolonged time without substantial side effects in two different preclinical OA rodent models involving either surgical (upon partial medial meniscectomy) or nonsurgical induction (with monoiodoacetate). The injection of Nano-PAZII blocks VEGFR1 and relieves OA pain by suppressing sensory neuronal ingrowth into the knee synovium and neuronal plasticity in the dorsal root ganglia and spinal cord. Simultaneously, the inhibition of VEGFR2 reduces cartilage degeneration. These findings provide a mechanism-based disease-modifying drug strategy that addresses both pain symptoms and cartilage loss in OA.

Preparation of reversible cross-linked amphiphilic polymeric micelles with pH-responsive behavior for smart drug delivery

A new type of reversible cross-linked and pH-responsive polymeric micelle (PM), poly[polyethylene glycol methacrylate-co-2-(acetoacetoxy)ethyl methacrylate]-b-poly [2-(dimethylamino)ethyl methacrylate] [P(PEGMA-co-AEMA)-b-PDMAEMA], was synthesized for targeted delivery of curcumin. After reversible cross-linking of the micellar shell, the PMs with a typical core-shell structure exhibited excellent stability against extensive dilution and good reversibility of pH-responsiveness in solutions with different pH values. P(PEGMA9-co-AEMA6)-b-PDMAEMA10 has the lowest critical micelle concentration (CMC) value (0.0041 mg mL-1), the highest loading capacity (13.86%) and entrapment efficiency (97.03%). A slow sustained drug release at pH 7.4 with 12.36% in 108 h, while a fast release (42.36%) was observed at pH 5.0. Furthermore, a dissipative particle dynamics (DPD) simulation method was employed to investigate the self-assembly process and pH-responsive behavior of PMs. The optimal drug-carrier ratio (2%) and fraction of water (92%) were confirmed by analyzing the drug distribution and morphology of micelles during the self-assembly process of the block copolymer. The simulation results were consistent with experimental results, indicating DPD simulation shows potential to study the structure properties of reversible cross-linked micelles. The present findings provide a new method for the development of SDDS with good structural stability and controlled drug release properties.

Exploring the Application of Micellar Drug Delivery Systems in Cancer Nanomedicine

Various formulations of polymeric micelles, tiny spherical structures made of polymeric materials, are currently being investigated in preclinical and clinical settings for their potential as nanomedicines. They target specific tissues and prolong circulation in the body, making them promising cancer treatment options. This review focuses on the different types of polymeric materials available to synthesize micelles, as well as the different ways that micelles can be tailored to be responsive to different stimuli. The selection of stimuli-sensitive polymers used in micelle preparation is based on the specific conditions found in the tumor microenvironment. Additionally, clinical trends in using micelles to treat cancer are presented, including what happens to micelles after they are administered. Finally, various cancer drug delivery applications involving micelles are discussed along with their regulatory aspects and future outlooks. As part of this discussion, we will examine current research and development in this field. The challenges and barriers they may have to overcome before they can be widely adopted in clinics will also be discussed.

Predicting nanoemulsion formulation and studying the synergism mechanism between surfactant and cosurfactant: A combined computational and experimental approach

Nanoemulsion (NE) is a dosage form widely used in pharmaceutical, food, agrochemical, cosmetics, and personal care industries. NE systems are usually formulated through trial and error via numerous semi-empirical experiments. Moreover, the complex interaction mechanisms between the formulation surfactant and cosurfactant are difficult to understand. Dissipative particle dynamics (DPD) may be helpful in solving these formulation problems. Silibinin is a flavonolignan isolated from milk thistle, which has demonstrated antioxidant and antimicrobial effects. For this project, silibinin-loaded nanoemulsion (SBNE) was formulated by DPD, including surfactant and cosurfactant screening, pseudo-ternary phase construction, and SBNE characterization, all of which were verified by experimentation. Most importantly, this work shows that DPD can be adopted to explore the synergetic mechanisms between the surfactant and cosurfactant, including emulsification efficiency, distance, angle, arrangement, and order parameter. Additional verification experiments on the antioxidant and antimicrobial applications of simulation-designed SBNE were also carried out and confirmed DPD-predicted results. As such, predicting NE formulation by DPD has been proven to be feasible. For SBNE, the addition of PEG400 cosurfactant stretches the Cremophor RH40 surfactant molecules and assists in a more orderly arrangement. An enhanced interfacial thickness in SBNE could be attributed to the stretched hydrophilic head group and the decreased angle between the molecular axis and interface normal. These DPD and experimentally-verified results indicated that a proper cosurfactant will enhance the interfacial thickness, decrease the consumption of surfactant, and benefit NE formation. This new computationally applied knowledge should facilitate optimizing, designing, and understanding NE formulation more rationally and scientifically.

A review of stimuli-responsive polymeric micelles for tumor-targeted delivery of curcumin

Despite a potential drug with multiple pharmacological activities, curcumin has disadvantages of the poor water solubility, rapid metabolism, low bioavailability, which considerably limit its clinical application. Currently, polymeric micelles (PMs) have gained widespread concern due to their advantageous physical and chemical properties, easy preparation, and biocompatibility. They can be used to improve drug solubility, prolong blood circulation time, and allow passive targeted drug delivery to tumor through enhanced penetration and retention effect. Moreover, studies focused on tumor microenvironment offer alternatives to design stimulus-responsive smart PMs based on low pH, high levels of glutathione, altered enzyme expression, increased reactive oxygen species production, and hypoxia. There are various external stimuli, such as light, ultrasound, and temperature. These endogenous/exogenous stimuli can be used for the research of intelligent micelles. Intelligent PMs can effectively load curcumin with improved solubility, and intelligently respond to release the drug at a controlled rate at targeted sites such as tumors to avoid early release, which markedly improves the bioavailability of curcumin. The present review is aimed to discuss and summarize recent developments in research of curcumin-loaded intelligent PMs based on endogenous and exogenous stimuli, and facilitates the development of novel delivery systems for future research.

Charge-balanced terpolymer poly(diethylaminoethyl methacrylate-hydroxyethyl methacrylate-2-acrylamido-2-methyl-propanesulfonic acid) hydrogels and cryogels: scaling parameters and correlation with composition

The scaling laws relating the preparation conditions to the swelling degree, reduced modulus and effective crosslinking density of poly(diethylaminoethyl methacrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methyl-propanesulfonic acid), henceforth designated as PDHA, gels prepared by radical crosslinking copolymerization in a solvent mixture were reported. Charge-balanced terpolymer PDHA hydrogels and cryogels (PDHA-Hgs and Cgs) were prepared in different monomer feed compositions. The swelling dependence of the reduced modulus was described by a power law relationship G_r≈ (φ_V)^m with an exponent of m = -0.30 at low swelling degree, while in the high swelling region the scaling becomes 0.21, indicating the finite extensibility of the network chains. The scaling exponent for the swelling degree and terpolymer composition, φ_V≈ (Nν)^m, was found to be -0.13, indicating the increasing extent of the topological constraints arising from the trapped entanglements. By combining elasticity and swelling results, the scaling relationship between the apparent crosslink density and HEMA content used in the terpolymer feed was obtained as a cubic polynomial of the mol% of HEMA. In the HEMA-rich terpolymer PDHA Hgs and Cgs, the swelling degree was possibly controlled by the HEMA part of the terpolymer network, while the presence of DEAEM units in the network triggered the thermoresponsive swelling behavior. The dependence of interaction parameter χ on the volume fraction of the crosslinked terpolymer network in the swollen gel ν₂ was evaluated and the results revealed extremely strong concentration dependence of χ for all terpolymer samples. Because of their inherent properties, the resulting terpolymer gels might contribute to the improvement of the loading capacity of polymers used in anticancer drug delivery systems.

Molecular mechanism underlying the effects of temperature and pH on the size and surface charge of octenylsuccinated oat β-glucan aggregates

Environmental temperature and pH induced significant changes in the size and surface charge (ζ) of octenylsuccinated oat β-glucan aggregates. The underlying mechanisms were explored by using ¹H-NMR, fluorescence spectra, thermodynamic analysis, and SAXS. At pH 6.5, the size decreased with temperature while ζ continuously increased. With increasing pH at 293 K, parabolic and U-shaped trends were observed in the size and ζ, peaking at pH 8.5 and 6.5, respectively. At any tested pH, the size decreased with temperature. Overall, ζ significantly increased with temperature at each pH. As temperature increased, the compactness of hydrophobic-domains increased while the compactness of hydrophilic-domains decreased. In an acidic environment, both the compactness increased with decreasing pH, but in an alkaline environment, they decreased with pH. The compactness changes were co-driven by enthalpy and entropy and corresponded to changes in the hydrophobic interactions in hydrophobic-domains, hydrogen bonds in hydrophilic-domains and electrostatic repulsions among octenylsuccinate molecules.

pH/redox dual-responsive amphiphilic zwitterionic polymers with a precisely controlled structure as anti-cancer drug carriers

Responding to the tumor microenvironment, functional polymers can serve as preeminent drug carriers for targeted cancer therapy. Stimuli-responsive polymeric drug carriers are reported with diverse anti-tumor effects for various polymer structures. Thus, three pH/redox dual-responsive amphiphilic zwitterionic polymer 'isomers' with different locations of pH/redox responsive units were prepared to understand the relationship between polymer structure and anti-tumor effect. Containing poly(ε-caprolactone) (PCL), poly(N,N-diethylaminoethyl methacrylate) (PDEA) and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), polymers PCL-ss-P(DEA-r-MPC) (SDRM), PCL-ss-PDEA-b-PMPC (SDBM) and PCL-PDEA-ss-PMPC (DSM) with a precisely controlled structure were constructed and confirmed through NMR, FITR and EA. The formed micellar drug carriers were characterized by their morphology, loading capacity, acid/redox sensitivity, drug release, in vitro cytotoxicity and in vivo antitumor effects. Micelles with uniform spherical morphologies can effectively encapsulate anti-tumor drugs such as DOX. Among these micelles, DSM@DOX displays the most excellent drug encapsulation capacity (13.4%) with neutral surface charge (-1.02 mV) and good stability, and is different from SDRM@DOX with positive charge (+11.1 mV) and SDBM@DOX with poor stability. All micelles respond to acid and reducing environments and present fast drug release at mildly acidic pH and high concentrations of GSH, exhibiting low burst release under the physiological conditions of plasma. There is no significant difference between these micelles in tumor cell cytotoxicity against MCF-7 and 4T1 cells. Internalization of SDRM@DOX and DSM@DOX by the tumor cells is stronger than that of SDBM@DOX. Notably, DSM@DOX has longer blood circulation and more effective accumulation at the tumor site than the other two micelles. As a result, DSM@DOX shows enhanced antitumor efficacy in 4T1 tumor-bearing mice with reduced side toxicities. Overall, structures of the above polymers significantly influence the in vivo antitumor effects of the drug carriers through blood circulation and cellular uptake.

4/6-Herto-arm and 4/6-mikto-arm star-shaped block polymeric drug-loaded micelles and their pH-responsive controlled release properties: a dissipative particle dynamics simulation

Star-shaped polymers have received significant attention and have been widely developed for prospective applications in drug delivery owing to their topological structure and unique physiochemical characteristics.

UV-Responsive Behavior of Multistate and Multiscale Self-Assemblies Constructed by Gemini Surfactant 12-3-12·2Br- and trans- o-Methoxy-cinnamate

Photoresponsive systems with adjustable self-assembly morphologies and tunable rheological properties have aroused widespread concern of researchers in recent years because of their prospect applications in controlled release, microfluidics, sensors, and so forth. In this paper, we combine a cationic Gemini surfactant 12-3-12·2Br^- and trans-2-methoxy-cinnamate ( trans-OMCA) together to create a representative UV-responsive self-assembly system. The system displays abundant self-assembly behaviors, and the self-assemblies with different states and different scales including wormlike micelles, vesicles, and lyotropic liquid crystals (LCs) as well as an aqueous two-phase system (ATPS) are observed even at lower surfactant concentration. The UV-responsive behavior of the formed self-assemblies is investigated systematically. The results have shown that the photoisomerization of OMCA from trans form to cis form under UV light irradiation alters the hydrophobicity and steric hindrance effect of OMCA and thus affects the molecular packing at the micellar interface and further leads to the transformation of assembly morphologies. The long wormlike micelles can gradually transform into much shorter rodlike micelles under UV irradiation and companied by the decrease of solution viscosity by 2 orders of magnitude. In addition, the vesicles can evolve into multistate self-assembly structures including the ATPS, wormlike micelles, rod-like micelles, and small spherical micelles depending on the UV irradiation time. The ATPS and its adjacent anisotropic LC phase can respectively combine into a single phase and separate into ATPS under UV irradiation. The morphologies of assemblies in the 12-3-12·2Br^-/ trans-OMCA mixed system can be tailored by adjusting the system composition and duration of UV light irradiation on purpose. The photoresponsive system with abundant self-assembly behaviors and tunable rheological properties has wide application prospect in numerous fields such as drug delivery, materials science, smart fluids, and so forth, and the macroscopic phase separation and combination provide novel strategies for effective separation and purification of certain substances.

Fabrication of PDEAEMA-based pH-responsive mixed micelles for application in controlled doxorubicin release

Co-micellization of MPEG–PDEAEMA and MPEG–PCL was carried out to enhance the drug loading content and realize pH-responsive release.