Nanoparticle encapsulation in vesicles formed by amphiphilic diblock copolymers

Co-assembly of Amphiphilic Triblock Copolymers with Nanodrugs and Drug Release Kinetics in Solution

Polymeric vesicles present great potential in disease treatment as they can be featured as a structurally stable and easily functionalized drug carrier that can simultaneously encapsulate multiple drugs and release them on-demand. Based on the dissipative particle dynamics (DPD) simulation, the drug-loaded vesicles were designed by the co-assembly process of linear amphiphilic triblock copolymers and hydrophobic nanodrugs in solvents, and most importantly, the drug release behavior of drug-loaded vesicles were intensively investigated. The drug-loaded aggregates, such as vesicles, spherical micelles, and disk-like micelles, were observed by varying the size and concentration of nanodrugs and the length of the hydrophobic block. The distribution of nanodrugs in the vesicles was intensively analyzed. As the size of the nanodrugs increases, the localization of nanodrugs change from being unable to fully wrap in the vesicle wall to the uniform distribution and finally to the aggregation in the vesicles at the fixed concentration of nanodrugs. The membrane thickness of the drug-loaded polymeric vesicle can be increased, and the nanodrugs localized closer to the center of the vesicle by increasing the length of the hydrophobic block. The nanodrugs will be released from vesicles by varying the interactions between the nanodrug and the solvent or the hydrophobic block and the solvent, respectively. We found that the release kinetics conforms to the first-order kinetic model, which can be used to fit the cumulative release rate of nanodrugs over time. The results showed that increasing the size of nanodrugs, the length of hydrophobic block, and the interaction parameters between the hydrophobic block and the solvent will slow down the release rate of the nanodrug and change the drug release process from monophasic to biphasic release model.

In Situ and Ex Situ Studies of Ring-Like Assembly of Silica Nanoparticles in the Presence of Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers

Block copolymer-mediated self-assembly of colloidal nanoparticles has attracted great attention for fabricating various nanoparticle arrays. We have previously shown that silica nanoparticles (SNPs) assemble into ring-like nanostructures in the presence of temperature-responsive block copolymers poly[(2-ethoxyethyl vinyl ether)-block-(2-methoxyethyl vinyl ether)] (PEOVE-PMOVE) in an aqueous phase. The ring-like nanostructures formed within an aggregate of PEOVE-PMOVE when the temperature was increased to 45 °C, at which the polymer is amphiphilic. Herein, we report that SNPs assemble into ring-like nanostructures even with a different temperature-responsive, amphiphilic block copolymer poly(propylene oxide)-block-poly(ethylene oxide) (PPO-PEO) at 45 °C. Field-emission scanning electron microscopy for SNP assemblies that were spin-coated on a substrate indicated that SNP first assembled into chain-like nanostructures and then bent into closed loops over several days. In contrast, in situ small-angle X-ray diffraction measurements revealed the formation of SNP nanorings within 75 s at 45 °C in the liquid phase. These results indicated that ring-like assembly of SNPs occurs quickly in the liquid phase, but the slow formation of Si-O-Si bonds between SNPs leads to their structure being destroyed by spin-coating. Intriguingly, SNPs with a diameter of 15 nm form a well-defined nanoring structure, with five SNPs located at the vertex points of a regular pentagon. Additionally, small-angle neutron scattering, where the contrast of the solvent (a mixture of H2O and D2O) matches that of SNPs, clarified that SNPs are contained within the spherical micelle formed from PPO-PEO. This work offers a facile and versatile approach to preparing ring-like arrays from inorganic colloidal nanoparticles, leading to applications including sensing, catalysis, and nanoelectronics.

Insight into carbon quantum dot-vesicles interactions: role of functional groups

Understanding carbon quantum dot–cell membrane interaction is essential for designing an effective nanoparticle-based drug delivery system. In this study, an attempt has been made to study the interaction involving phosphatidylcholine vesicles (PHOS VES, as model cell membrane) and four different carbon quantum dots bearing different functional groups (–COOH, –NH₂, –OH, and protein bovine serum albumin coated) using various tools such as PL behavior, surface charge on vesicles, QCM, ITC, TEM, LSV, and FTIR. From the above studies, it was observed that the –NH₂ terminating carbon dots were capable of binding strongly with the vesicles whereas other functional groups bearing carbon dots were not significantly interacting. This observation was also supported by direct visual evidence as shown by transmission electron microscopy, which shows that the polyethyleneimine carbon dot (PEICD) bearing –NH₂ functionality has greater affinity towards PHOS VES. The mechanistic insight presented in the paper indicates greater possibility of higher H-bonding, signifying better interaction between –NH₂ functionalized carbon dots and PHOS VES supported by FTIR, QCM, ITC and TEM. Moreover, the transport of neurotransmitters (which are generally amine compound) in neurons for cellular communication through synapse is only possible through vesicular platforms, showing that in our body, such interactions are already present. Such studies on the nano–bio interface will help biomedical researchers design efficient carbon-based nanomaterial as drug/gene delivery vehicles.

An interaction study at the nano–bio interface involving phosphatidylcholine vesicles (as a model cell membrane) and four different carbon dots bearing different functional groups (–COOH, –NH₂, –OH, and BSA-coated).

Dissipative particle dynamics simulations in colloid and Interface science: a review

Dissipative particle dynamics (DPD) is one of the most efficient mesoscale coarse-grained methodologies for modeling soft matter systems. Here, we comprehensively review the progress in theoretical formulations, parametrization strategies, and applications of DPD over the last two decades. DPD bridges the gap between the microscopic atomistic and macroscopic continuum length and time scales. Numerous efforts have been performed to improve the computational efficiency and to develop advanced versions and modifications of the original DPD framework. The progress in the parametrization techniques that can reproduce the engineering properties of experimental systems attracted a lot of interest from the industrial community longing to use DPD to characterize, help design and optimize the practical products. While there are still areas for improvements, DPD has been efficiently applied to numerous colloidal and interfacial phenomena involving phase separations, self-assembly, and transport in polymeric, surfactant, nanoparticle, and biomolecules systems.

Aptamer-Conjugated Multifunctional Polymeric Nanoparticles as Cancer-Targeted, MRI-Ultrasensitive Drug Delivery Systems for Treatment of Castration-Resistant Prostate Cancer

Nanoscopic therapeutic systems that incorporate therapeutic agents, molecular targeting, and imaging capabilities have gained momentum and exhibited significant therapeutic potential. In this study, multifunctional polymeric nanoparticles with controlled drug delivery, cancer-targeted capability, and efficient magnetic resonance imaging (MRI) contrast characteristics were formulated and applied in the treatment of castration-resistant prostate cancer (CRPC). The "core-shell" targeted nanoparticles (NPs) were synthesized by the self-assembly of a prefunctionalized amphiphilic triblock copolymer composed of poly(lactic-co-glycolic-acid) (PLGA), polyethylene glycol (PEG), and the Wy5a aptamer (Apt), which have been screened for targeting the CRPC cell line PC-3 by cell-SELEX technique as described in our previous study. Docetaxel (Dtxl) and a cluster of hydrophobic superparamagnetic iron oxide (SPIO) nanoparticles were simultaneously encapsulated into the targeted nanoparticles. The targeted NPs showed a controlled drug release and an increased contrast-enhanced MRI capability. The presence of Wy5a on the nanoparticle surface resulted in the cancer-targeted delivery to PC-3 cells in vitro and in vivo. In vitro MRI and cytotoxicity studies demonstrated the ultrasensitive MRI and increased cytotoxicity of these targeted NPs. In vivo studies revealed that the targeted NPs exhibited a more efficacious antitumor capability without significant systemic toxicity. Our data suggested that these targeted NPs may be a promising drug delivery system for the efficacious treatment of CRPC.

Encapsulation and release of drug nanoparticles in functional polymeric vesicles

We investigated the co-assembly of amphiphilic diblock copolymers in solutions containing drugs and functional nanoparticles using the dissipative particle dynamics (DPD) method. By controlling the size and the concentration of the functional nanoparticles, the length of the hydrophobic blocks, and the interaction parameters between the hydrophobic block/solvent and the functional nanoparticles, we obtained the desired aggregates to load drugs. The aggregates loaded with drugs can be disk-like micelles, sphere-like micelles and vesicles with functional nanoparticles on the surface. When the solvent environment changes, the drugs loaded in the functional vesicles can release into the solvent. The release content is critically dependent on the repulsive interaction between the drugs and the solvent. The dynamic curve of drug release is obtained. The result is in agreement with the experiments about drug release. Our studies showed that we can precisely control the formation of functional vesicles to load and release drugs. Loading drugs in the process of self-assembly and controlling the release have broad potential in the field of clinical medicine and adding functional nanoparticles can be of great help in drug delivery and medical diagnosis.

Self-Assembly of Polymer Blends and Nanoparticles through Rapid Solvent Exchange

Molecular dynamics simulations were performed to study the fabrication of polymeric colloids containing inorganic nanoparticles (NPs) via the flash nanoprecipitation (FNP) technique. During this process, a binary polymer blend, initially in a good solvent for the polymers, is rapidly mixed with NPs and a poor solvent for the polymers that is miscible with the good solvent. The simulations reveal that the polymers formed Janus particles with NPs distributed either on the surface of the aggregates, throughout their interior, or aligned at the interface between the two polymer domains, depending on the NP-polymer and NP-solvent interactions. The loading and surface density of NPs can be controlled by the polymer feed concentration, the NP feed concentration, and their ratio in the feed streams. Selective localization of NPs by incorporating electrostatic interactions between polymers and NPs has also been investigated, and was shown to be an effective way to enhance NP loading and surface density as compared to the case with only van der Waals attractions. This work demonstrates that the FNP process is promising for the production of structured and hybrid nanocolloids in a continuous and scalable way, with independent control over particle properties such as size, NP location, loading, and surface density. Our results provide useful guidelines for experimental fabrication of such hybrid nanoparticles.

Evaluation of Conditions Affecting Properties of Gac (Momordica Cocochinensis Spreng) Oil-Loaded Solid Lipid Nanoparticles (SLNs) Synthesized Using High-Speed Homogenization Process

In this study, we attempted the preparation of gac oil-loaded solid lipid nanoparticles (SLNs) by the high-speed homogenization method using Naterol SE solid lipid, a cosmetic self-emulsifying base, and surfactant and investigated the effects of different conditions on the characteristics of the resulting nanoparticles. The suspensions containing 5% active agents (gac-oil, w/w) were dispersed in a surfactant concentration of 5% (w/w) (Span 80:Tween 80 ratio of 28:72 w/w) and 2.5% (w/w) of solid lipid (Naterol SE) concentration. Suitable conditions for hot homogenization were 13,000 rpm, 60 min and 60 °C for speed, time and temperature, respectively. The suitable conditions for the subsequent cold homogenization were 25 min of homogenization time and 5 °C of temperature. The results showed that the mean size of SLNs-gac oil was 107 nm (measured by laser diffraction spectrometry, LDS), and dried size of SLNs-gac oil ranged from 50 to 80 nm (measured by transmission electron microscope, TEM). In addition, the study investigated the impact of gac oil content on the particle size of SLNs-gac oil and its stability under different storage conditions of UV radiation and storage temperature. At high storage temperatures, the color changes (ΔE) of the samples were more profound in comparison to that at the low storage temperature. The ΔE value of the blank sample (SLN-FREE gac-oil) was higher than that of the Gac oil-loaded SLNs samples (SLN-gac oil).

Dissipative Particle Dynamics Simulation on Vesicles Self-Assembly Controlled by Terminal Groups

Block copolymer vesicles have been widely used in the field of drug delivery, microreactors, and cell membrane mimetics. Introducing terminal groups to the block copolymer can control the structures of vesicles, which is important for improving the application of vesicles. In this paper, the effects of terminal groups on the structure of vesicles were studied by dissipative particle dynamics simulation. We considered different locations, hydrophobicity, and numbers of terminal groups. When the terminal group located at the end of a hydrophobic block, the increase of wall thickness and the decrease of cavity size of vesicles were observed with the hydrophobicity of the terminal group increasing. In contrast, when the terminal group located at the end of the hydrophilic block, with the hydrophobicity of terminal groups increasing, the vesicular cavity size increased but the wall thickness of vesicles remained nearly unchanged. Finally, increasing the number of terminal groups lead to a decrease of cavity size and an increase of wall thickness of vesicles. The hydrophobic changes of polymer molecules are regarded as the origin of the structural changes of vesicles. This simulation study supplies a potential approach that controls the structures of vesicles and is expected to facilitate its further applications.

Ring-Like Assembly of Silica Nanospheres in the Presence of Amphiphilic Block Copolymer: Effects of Particle Size

Block copolymer-mediated self-assembly of colloidal nanoparticles has attracted great attention for the fabrication of a wide variety of nanoparticle arrays. We have previously shown that silica nanospheres (SNSs) 15 nm in diameter assemble into ring-like nanostructures in the presence of amphiphilic block copolymers poly[(2-ethoxyethyl vinyl ether)- block-(2-methoxyethyl vinyl ether)] (EOVE-MOVE) in an aqueous phase. Here, the effects of particle size of SNSs on this polymer-mediated self-assembly are studied systematically using scanning electron microscopy to observe SNSs of seven different sizes between 13 to 42 nm. SNSs of 13, 16, 19, and 21 nm in diameter assemble into nanorings in the presence of EOVE-MOVE. In contrast, larger SNSs of 26, 34, and 42 nm aggregate heavily, form chain-like networks, and remain dispersed, respectively, instead of forming ring-like nanostructures. The assembly trend for 26-42 nm-SNSs agrees with that expected from the increased colloidal stability for larger particles. Time-course observation for the assembled morphology of 16 nm-SNSs reveals that the nanorings, once formed, assemble further into network-like structures, as if the nanorings behave as building units for higher-order assembly. This indicates that the ring-like assembly is a fast process that can proceed onto random colloidal aggregation. Detailed analysis of nanoring structures revealed that the average number of SNSs comprising one ring decreased from 5.0 to 3.1 with increasing the SNS size from 13 to 21 nm. A change in the number of ring members was also observed when the length of EOVE-MOVE varied while the size of SNSs was fixed. Dynamic light scattering measurements and atomic force microscopy confirmed the SNSs/polymer composite structures. We hypothesize that a stable composite morphology may exist that is influenced by both the size of SNSs and the polymer molecular structures.