Self-assembly strategy for the preparation of polymer-based nanoparticles for drug and gene delivery

Development, Validation, and Applications of Nonbonded Interaction Parameters between Coarse-Grained Amino Acid and Water Models

Interactions between amino acids and water play an important role in determining the stability and folding/unfolding, in aqueous solution, of many biological macromolecules, which affects their function. Thus, understanding the molecular-level interactions between water and amino acids is crucial to tune their function in aqueous solutions. Herein, we have developed nonbonded interaction parameters between the coarse-grained (CG) models of 20 amino acids and the one-site CG water model. The nonbonded parameters, represented using the 12-6 Lennard Jones (LJ) potential form, have been optimized using an artificial neural network (ANN)-assisted particle swarm optimization (PSO) (ANN-assisted PSO) method. All-atom (AA) molecular dynamics (MD) simulations of dipeptides in TIP3P water molecules were performed to calculate the Gibbs hydration free energies. The nonbonded force-field (FF) parameters between CG amino acids and the one-site CG water model were developed to accurately reproduce these energies. Furthermore, to test the transferability of these newly developed parameters, we calculated the hydration free energies of the analogues of the amino acid side chains, which showed good agreement with reported experimental data. Additionally, we show the applicability of these models by performing self-assembly simulations of peptide amphiphiles. Overall, these models are transferable and can be used to study the self-assembly of various biomaterials and biomolecules to develop a mechanistic understanding of these processes.

Caffeic Acid Phenethyl Ester Loaded PEG-PLGA Nanoparticles Enhance Wound Healing in Diabetic Rats

Delayed wound healing is a serious complication of diabetes and a main reason for foot amputation. Caffeic acid phenethyl ester (CAPE) is a main active constituent of honeybee propolis with reported appealing pharmacological activities. In the current study, CAPE was loaded onto PEG-PLGA nanoparticles and showed a particle size of 198 ± 7.3 nm and polydispersity index of 0.43 ± 0.04. An in vivo study was performed to appraise the wound-healing activity of CAPE-loaded PEG-PLGA nanoparticles (CAPE-NPs) in diabetic rats. Wound closure was significantly accelerated in rats treated with CAPE-NPs. This was confirmed via histological examinations of skin tissues that indicated expedited healing and enhanced collagen deposition. This was accompanied by observed antioxidant activity as evidenced by the prevention of lipid peroxidation and the exhaustion of superoxide dismutase (SOD) and catalase (CAT) activities. In addition, CAPE-NPs showed superior anti-inflammatory activity as compared with the regular formula of CAPE, as they prevented the expression of interleukin-6 (IL-6) as well as tumor necrosis-alpha (TNF-α). The pro-collagen actions of CAPE-NPs were highlighted by the enhanced hyroxyproline content and up-regulation of Col 1A1 mRNA expression. Furthermore, the immunohistochemial assessment of skin tissues indicated that CAPE-NPs enhance proliferation and angiogenesis, as shown by the increased expression of transforming growth factor β1 (TGF-β1) and platelet-derived growth factor subunit B (PDGF-B). In conclusion, CAPE-loaded PEG-PLGA nanoparticles possess potent healing effects in diabetic wounds. This is mediated, at least partially, by its antioxidant, anti-inflammatory, and pro-collagen as well as angiogenic activities.

Amitriptyline-Based Biodegradable PEG-PLGA Self-Assembled Nanoparticles Accelerate Cutaneous Wound Healing in Diabetic Rats

The aim of this work was to study the healing activity of amitriptyline (Amitrip) in rat diabetic wounds. A nanoformula of the drug was prepared as Amitrip-based biodegradable PEG-PLGA self-assembled nanoparticles (Amitrip-NPs) with a mean particle size of 67.4 nm. An in vivo investigation was conducted to evaluate the wound-healing process of Amitrip-NPs in streptozotocin-induced diabetic rats. Wound contraction was accelerated in rats treated with Amitrip-NPs. Histological examinations confirmed these findings, with expedited remodeling and collagen deposition in the NPs-treated animals. The formula showed anti-inflammatory activities as demonstrated by inhibition of interleukin-6 (IL-6) expression and tumor necrosis factor-α (TNF-α) expression, as well as enhanced expression of interleukin-10 (IL-10). In addition, Amitrip-NPs protected against malondialdehyde (MDA) buildup and superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic exhaustion. The pro-collagen activity of Amitrip-NPs was confirmed by the observed enhancement of hydroxyproline wounded skin content, upregulation of Col 1A1 mRNA expression and immune expression of collagen type IV expression. Further, Amitrip-NPs significantly increased expression transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor-A (VEGF-A), platelet-derived growth factor-B (PDGF-B) and cluster of differentiation 31 (CD31). In conclusion, the developed Amitrip-NPs expedited wound healing in diabetic rats. This involves anti-inflammatory, antioxidant, pro-collagen and angiogenic activities of the prepared NPs. This opens the gate for evaluating the usefulness of other structurally related tricyclic antidepressants in diabetic wounds.

Preparation of anisotropic multiscale micro-hydrogels via two-photon continuous flow lithography

HYPOTHESIS

Polymeric anisotropic soft microparticles show interesting behavior in biological environments and hold promise for drug delivery and biomedical applications. However, self-assembly and substrate-based lithographic techniques are limited by low resolution, batch operation or specific particle geometry and deformability. Two-photon polymerization in microfluidic channels may offer the required resolution to continuously fabricate anisotropic micro-hydrogels in sub-10 µm size-range.

EXPERIMENTS

Here, a pulsed laser source is used to perform two-photon polymerization under microfluidic flow of a poly(ethylene glycol) diacrylate (PEGDA) solution with the objective of realizing anisotropic micro-hydrogels carrying payloads of various nature, including small molecules and nanoparticles. The fabrication process is described via a reactive-convective-diffusion system of equations, whose solution under proper auxiliary conditions is used to corroborate the experimental observations and sample the configuration space.

FINDINGS

By tuning the flow velocity, exposure time and pre-polymer composition, anisotropic PEGDA micro-hydrogels are obtained in the 1-10 μm size-range and exhibit an aspect ratio varying from 1 to 5. Furthermore, 200 nm curcumin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles and 100 nm ssRNA-encapsulating lipid nanoparticles were entrapped within square PEGDA micro-hydrogels. The proposed approach could support the fabrication of micro-hydrogels of well-defined morphology, stiffness, and surface properties for the sustained release of therapeutic agents.

Formulation of tunable size PLGA-PEG nanoparticles for drug delivery using microfluidic technology

Amphiphilic block co-polymer nanoparticles are interesting candidates for drug delivery as a result of their unique properties such as the size, modularity, biocompatibility and drug loading capacity. They can be rapidly formulated in a nanoprecipitation process based on self-assembly, resulting in kinetically locked nanostructures. The control over this step allows us to obtain nanoparticles with tailor-made properties without modification of the co-polymer building blocks. Furthermore, a reproducible and controlled formulation supports better predictability of a batch effectiveness in preclinical tests. Herein, we compared the formulation of PLGA-PEG nanoparticles using the typical manual bulk mixing and a microfluidic chip-assisted nanoprecipitation. The particle size tunability and controllability in a hydrodynamic flow focusing device was demonstrated to be greater than in the manual dropwise addition method. We also analyzed particle size and encapsulation of fluorescent compounds, using the common bulk analysis and advanced microscopy techniques: Transmission Electron Microscopy and Total Internal Reflection Microscopy, to reveal the heterogeneities occurred in the formulated nanoparticles. Finally, we performed in vitro evaluation of obtained NPs using MCF-7 cell line. Our results show how the microfluidic formulation improves the fine control over the resulting nanoparticles, without compromising any appealing property of PLGA nanoparticle. The combination of microfluidic formulation with advanced analysis methods, looking at the single particle level, can improve the understanding of the NP properties, heterogeneities and performance.

Recent Advances in Asialoglycoprotein Receptor and Glycyrrhetinic Acid Receptor-Mediated and/or pH-Responsive Hepatocellular Carcinoma- Targeted Drug Delivery

BACKGROUND

Hepatocellular carcinoma (HCC) seriously affects human health, especially, it easily develops multi-drug resistance (MDR) which results in treatment failure. There is an urgent need to develop highly effective and low-toxicity therapeutic agents to treat HCC and to overcome its MDR. Targeted drug delivery systems (DDS) for cancer therapy, including nanoparticles, lipids, micelles and liposomes, have been studied for decades. Recently, more attention has been paid to multifunctional DDS containing various ligands such as polymer moieties, targeting moieties, and acid-labile linkages. The polymer moieties such as poly(ethylene glycol) (PEG), chitosan (CTS), hyaluronic acid, pullulan, poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) protect DDS from degradation. Asialoglycoprotein receptor (ASGPR) and glycyrrhetinic acid receptor (GAR) are most often used as the targeting moieties, which are overexpressed on hepatocytes. Acid-labile linkage, catering for the pH difference between tumor cells and normal tissue, has been utilized to release drugs at tumor tissue.

OBJECTIVES

This review provides a summary of the recent progress in ASGPR and GAR-mediated and/or pH-responsive HCC-targeted drug delivery.

CONCLUSION

The multifunctional DDS may prolong systemic circulation, continuously release drugs, increase the accumulation of drugs at the targeted site, enhance the anticancer effect, and reduce side effects both in vitro and in vivo. But it is rarely used to investigate MDR of HCC; therefore, it needs to be further studied before going into clinical trials.

Stereocomplex micelle loaded with paclitaxel for enhanced therapy of breast cancer in an orthotopic mouse model

Micelles are promising a nano drug carrier for cancer therapy. However, their application is often limited due to the instability of them in vivo. Herein, we reported the development of stereocomplex micelle (SCM) based on amphiphilic dextran-block-polylactide (Dex-b-PLA) that could improve the stability of micelles, reduce the early release of loaded drugs and target the breast cancer through the enhanced permeability and retention (EPR) effect for enhanced breast cancer therapy. The SCM were fabricated from the equimolar mixture of the enantiomeric Dex-b-PLA copolymers. Paclitaxel (PTX) as a model anti breast cancer drug was loaded in the SCM, noted as SCM/PTX. Transmission electron microscopy (TEM) and dynamic laser scattering (DLS) showed the diameter of SCM/PTX was below100 nm, which was suitable sizes for the EPR effect. The release kinetics of SCM/PTX exhibited that the release of PTX was obviously slow down and showed constant release. In the in vitro antitumor test, the SCM/PTX could effectively suppress the viability of 4T1 cells, which was demonstrated by the MTT assay. Moreover, the SCM/PTX could reduce the distribution of PTX at normal organs and obviously increase the accumulation of PTX at tumor sites. The circulation time of SCM/PTX was also obviously enhanced compared to free PTX. In the in vivo antitumor test, the SCM/PTX effectively inhibited the progression of 4T1 breast cancer in the orthotopic mouse model, as demonstrated by decreased tumor growth and increased apoptosis and necrosis areas within tumor tissues. In addition, the toxic side effects of PTX was also alleviated in the SCM/PTX group. This study introduced a stable micelle system that passive targeted the tumor for enhanced breast cancer therapy.

Molecular Self-Assembly Strategy for Encapsulation of an Amphipathic α-Helical Antimicrobial Peptide into the Different Polymeric and Copolymeric Nanoparticles

Encapsulation of peptide and protein-based drugs in polymeric nanoparticles is one of the fundamental fields in controlled-release drug delivery systems. The molecular mechanisms of absorption of peptides to the polymeric nanoparticles are still unknown, and there is no precise molecular data on the encapsulation process of peptide and protein-based drugs. Herein, the self-assembly of different polymers and block copolymers with combinations of the various molecular weight of blocks and the effects of resultant polymer and copolymer nanomicelles on the stability of magainin2, an α-helical antimicrobial peptide, were investigated by means of all-atom molecular dynamics (MD) simulation. The micelle forming, morphology of micellar aggregations and changes in the first hydration shell of the micelles during micelles formation were explored as well. The results showed that the peptide binds to the polymer and copolymer micelles and never detaches during the MD simulation time. In general, all polymers and copolymers simultaneously encapsulated the peptide during micelles formation and had the ability to maintain the helical structure of the peptide, whereas the first hydration shell of the peptide remained unchanged. Among the micelles, the polyethylene glycol (PEG) micelles completely encapsulated magainin2 and, surprisingly, the NMR structure of the peptide was perfectly kept during the encapsulation process. The MD results also indicated that the aromatic and basic residues of the peptide strongly interact with polymers/copolymers and play important roles in the encapsulation mechanism. This research will provide a good opportunity in the design of polymer surfaces for drug delivery applications such as controlled-release peptide delivery systems.

Controlled Drug Delivery by Polylactide Stereocomplex Micelle for Cervical Cancer Chemotherapy

A stable doxorubicin (DOX)-loaded stereocomplex micelle drug delivery system was developed via the stereocomplex interaction between enantiomeric 4-armed poly(ethylene glycol)-poly(D-lactide) and poly(ethylene glycol)-poly(L-lactide) to realize control drug release and improve tumor cell uptake for efficient cervical carcinoma therapy. All these DOX-loaded micelles including poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) exhibited appropriate sizes of ∼100 nm for the enhanced permeability and retention (EPR) effect. In addition, compared to PDM/DOX and PLM/DOX, SCM/DOX exhibited the slowest DOX releaser, highest tumor cell uptake and the most efficient tumor cell suppression in vitro. Moreover, the excellent tumor inhibiting rates of the DOX-loaded micelles, especially SCM/DOX, were verified in the U14 cervical carcinoma mouse model. Increased tumorous apoptosis and necrosis areas were observed in the DOX-loaded micelles treatment groups, especially the SCM/DOX group. In addition, all these DOX-loaded micelles obviously alleviated the systemic toxicity of DOX. As a result, SCM can be a promising drug delivery system for the future therapy of cervical carcinoma.

Synthesis and Evaluation of Chloroquine-Containing DMAEMA Copolymers as Efficient Anti-miRNA Delivery Vectors with Improved Endosomal Escape and Antimigratory Activity in Cancer Cells

Chloroquine-containing 2-(dimethylamino)ethyl methacrylate copolymers (PDCs) are synthesized by reversible addition-fragmentation chain-transfer polymerization. Systematic evaluation is performed to test the hypothesis that presence of chloroquine (CQ) in the PDC structure will improve miRNA delivery due to enhanced endosomal escape while simultaneously contribute to anticancer activity of PDC/miRNA polyplexes through inhibition of cancer cell migration. The results show that miRNA delivery efficiency is dependent both on the molecular weight and CQ. The best performing PDC/miRNA polyplexes show effective endosomal escape of miRNA. PDC polyplexes with therapeutic miR-210 show promising anticancer activity in human breast cancer cells. PDC/miRNA polyplexes show excellent ability to inhibit migration of cancer cells. Overall, this study supports the use of PDC as a promising polymeric drug platform for use in combination anti-metastatic and anticancer miRNA therapeutic strategies.

Vesicles from Amphiphilic Dumbbells and Janus Dendrimers: Bioinspired Self-Assembled Structures for Biomedical Applications

The current review focuses on vesicles obtained from the self-assembly of two types of dendritic macromolecules, namely amphiphilic Janus dendrimers (forming dendrimersomes) and amphiphilic dumbbells. In the first part, we will present some synthetic strategies and the various building blocks that can be used to obtain dendritic-based macromolecules, thereby showing their structural versatility. We put our focus on amphiphilic Janus dendrimers and amphiphilic dumbbells that form vesicles in water but we also encompass vesicles formed thereof in organic solvents. The second part of this review deals with the production methods of these vesicles at the nanoscale but also at the microscale. Furthermore, the influence of various parameters (intrinsic to the amphiphilic JD and extrinsic-from the environment) on the type of vesicle formed will be discussed. In the third part, we will review the numerous biomedical applications of these vesicles of nano- or micron-size.

ZnO nanorods assembled with different porphyrins – size-tunable hybrid particles

We present a fundamental study on ZnO nanorod–porphyrin assembly formation in solution, providing the key to novel tunable hybrid assemblies with potential in solar energy conversion.

High throughput microencapsulation of Bacillus subtilis in semi-permeable biodegradable polymersomes for selenium remediation

Encapsulating bacteria within constrained microenvironments can promote the manifestation of specialized behaviors. Using double-emulsion droplet-generating microfluidic synthesis, live Bacillus subtilis bacteria were encapsulated in a semi-permeable membrane composed of poly(ethylene glycol)-b-poly(D,L-lactic acid) (mPEG-PDLLA). This polymer membrane was sufficiently permeable to permit exponential bacterial growth, metabolite-induced gene expression, and rapid biofilm growth. The biodegradable microparticles retained structural integrity for several days and could be successfully degraded with time or sustained bacterial activity. Microencapsulated B. subtilis successfully captured and contained sodium selenite added outside the polymersomes, converting the selenite into elemental selenium nanoparticles that were selectively retained inside the polymer membrane. This remediation of selenium using polymersomes has high potential for reducing the toxicity of environmental selenium contamination, as well as allowing selenium to be harvested from areas not amenable to conventional waste or water treatment.

Intracellular plasmid DNA delivery by self-assembled nanoparticles of amphiphilic PHML-b-PLLA-b-PHML copolymers and the endocytosis pathway analysis

This work presents a new series of polycationic nanoparticles of (l-)-lysine conjugated amphiphilic triblock copolymer poly(hydroxyletheyl methacrylate-L-lysine)-b-poly(L-lactide)-b-poly(hydroxyletheyl methacrylate-L-lysine)s (PHML-b-PLLA-b-PHML) as potent low cytotoxic vectors for intracellular plasmid DNA delivery. First, the triblock PHML-b-PLLA-b-PHML copolymers were prepared via a combination of metal-free controlled ring opening polymerization and successive atom transfer radical polymerization. Then the cationic PHML-b-PLLA-b-PHML nanoparticles were further prepared by solution self-assembly. The particle size, zeta potential and morphology of as-prepared PHML-b-PLLA-b-PHML nanoparticles were characterized by dynamic light scattering and atomic force microscopy, respectively. The plasmid DNA binding affinities and polyplex stabilities were separately explored by agarose gel retardation and DNase I degradation assays. Then in vitro cytotoxicity and gene transfection efficiency of the PHML-b-PLLA-b-PHML nanoparticles vectors as well as relevant polyplex endocytosis pathway were investigated with H1299 cells. It was revealed that the PHML-b-PLLA-b-PHML nanoparticles exhibited low cytotoxicity, strong plasmid DNA binding affinity, high polyplex stability and efficient plasmid DNA transfection even under serum conditions (10% FBS). Moreover, the endocytosis analysis results disclosed that the PHML₃₀-b-PLLA-b-PHML₃₀ nanoparticle/plasmid DNA polyplexes were predominantly involved in lipid-raft-mediated endocytosis pathway, similar to that of SV40 virus-based vectors.

Shaping the future of nanomedicine: anisotropy in polymeric nanoparticle design

Nanofabrication and biomedical applications of polymeric nanoparticles have become important areas of research. Biocompatible polymeric nanoparticles have been investigated for their use as delivery vehicles for therapeutic and diagnostic agents. Although polymeric nanoconstructs have traditionally been fabricated as isotropic spheres, anisotropic, nonspherical nanoparticles have gained interest in the biomaterials community owing to their unique interactions with biological systems. Polymeric nanoparticles with different forms of anisotropy have been manufactured using a variety of novel methods in recent years. In addition, they have enhanced physical, chemical, and biological properties compared with spherical nanoparticles, including increased targeting avidity and decreased nonspecific in vivo clearance. With these desirable properties, anisotropic nanoparticles have been successfully utilized in many biomedical settings and have performed superiorly to analogous spherical nanoparticles. We summarize the current state-of-the-art fabrication methods for anisotropic polymeric nanoparticles including top-down, bottom-up, and microfluidic design approaches. We also summarize the current and potential future applications of these nanoparticles, including drug delivery, biological targeting, immunoengineering, and tissue engineering. Ongoing research into the properties and utility of anisotropic polymeric nanoparticles will prove critical to realizing their potential in nanomedicine.

A novel type of self-assembled nanoparticles as targeted gene carriers: an application for plasmid DNA and antimicroRNA oligonucleotide delivery

In this study, a new type of amphiphilic cetylated polyethyleneimine (PEI) was synthesized, and then polylactic-co-glycolic acid (PLGA)/cetylated PEI/hyaluronic acid nanoparticles (PCPH NPs) were developed by self-assembly as a novel type of gene-delivering vehicle. The PCPH NPs showed good DNA-condensation ability by forming polyplexes with small particle size and positive zeta potential. The transfection efficiency and cytotoxicity of PCPH NPs were evaluated as plasmid DNA vectors to transfect HepG2 in vitro. PCPH NPs exhibited much lower cytotoxicity and higher gene-transfection efficiency than PEI (25,000) and commercial transfection reagents. Furthermore, PCPH NPs were used as an anti-miR-221 vector for transfecting HepG2 cells, and anti-miR-221 was effectively transfected into cells and produced a greater inhibitory effect on cancer-cell growth by PCPH NPs. These results demonstrate that PCPH NPs can be a promising nonviral vector for gene-delivery systems.

Crystalline Oligo(ethylene sulfide) Domains Define Highly Stable Supramolecular Block Copolymer Assemblies

With proper control over copolymer design and solvation conditions, self-assembled materials display impressive morphological variety that encompasses nanoscale colloids as well as bulk three-dimensional architectures. Here we take advantage of both hydrophobicity and crystallinity to mediate supramolecular self-assembly of spherical micellar, linear fibrillar, or hydrogel structures by a family of highly asymmetric poly(ethylene glycol)-b-oligo(ethylene sulfide) (PEG-OES) copolymers. Assembly structural polymorphism was achieved with modification of PEG-OES topology (linear versus multiarm) and with precise, monomer-by-monomer control of OES length. Notably, all three morphologies were accessed utilizing OES oligomers with degrees of polymerization as short as three. These exceptionally small assembly forming blocks represent the first application of ethylene sulfide oligomers in supramolecular materials. While the assemblies demonstrated robust aqueous stability over time, oxidation by hydrogen peroxide progressively converted ethylene sulfide residues to increasingly hydrophilic and amorphous sulfoxides and sulfones, causing morphological changes and permanent disassembly. We utilized complementary microscopic and spectroscopic techniques to confirm this chemical stimulus-responsive behavior in self-assembled PEG-OES colloidal dispersions and physical gels. In addition to inherent stimulus-responsive behavior, fibrillar assemblies demonstrated biologically relevant molecular delivery, as confirmed by the dose-dependent activation of murine bone marrow-derived dendritic cells following fibril-mediated delivery of the immunological adjuvant monophosphoryl lipid A. In physical gels composed of either linear or multiarm PEG-OES precursors, rheologic analysis also identified mechanical stimulus-responsive shear thinning behavior. Thanks to the facile preparation, user-defined morphology, aqueous stability, carrier functionality, and stimuli-responsive behaviors of PEG-OES supramolecular assemblies, our findings support a future role for these materials as injectable or implantable biomaterials.

Mesoscopic simulation of the self-assembly of the weak polyelectrolyte poly(ethylene oxide)-block-poly(methyl methacrylate) diblock copolymers

We designed twelve types of weak polyelectrolytes (i.e., PEO-b-PMMA copolymers (BCP) in multi-arm structures, where six include EO blocks as joint points and the other six have MMA blocks as joint points). All of the BCPs with EO as the joint points form disordered phases with the exception of long-chained and four-armed BCP. The main mesophases of all of the BCPs with MMA as joint points are micelle-like and bicontinuous phases. In particular, the short-chained BCP with four-arms and EO segments outside form a new phase type (i.e., crossed lamellar phase). Using MesoDyn, we provide a comprehensive representation of the micelle and crossed lamellar phase formation mechanisms based on both thermodynamic and dynamic analyses. A shear force on a micelle-like phase could promote a hexagonal columnar phase, which is a good technique for generating an ordered arrangement of nanotube arrays. Blending homopolymers with the same constituents could promote uniformity of the micelle size and decrease the polydispersity, especially for blends with a high BCP concentration, which may provide a new approach for regulating the properties of materials.

Polyhydroxyalkanoate-based amphiphilic diblock copolymers as original biocompatible nanovectors

Nanoparticles derived from poly(β-malic acid)-b-poly(3-hydroxybutyrate) (PMLA-b-PHB) copolymers revealed no cytotoxicity towards HepaRG and SK-MEL-28 cells.

Stealth Amphotericin B nanoparticles for oral drug delivery: In vitro optimization

Purpose

Amphotericin B (AmB) is an effective anti-fungal and anti-leishmanial agent. However, AmB has low oral bioavailability (0.3%) and adverse effects (e.g., nephrotoxicity). The objectives of this study were to improve the oral bioavailability by entrapping AmB in pegylated (PEG) poly lactide co glycolide copolymer (PLGA–PEG) nanoparticles (NPs). The feasibility of different surfactants and stabilizers on the mean particle size (MPS) and entrapment efficiency were also investigated.

Materials and methods

NPs of AmB were prepared by a modified emulsification diffusion method employing a vitamin E derivative as a stabilizer. Physicochemical properties and particle size characterization were evaluated using Fourier Transform Infra-Red spectroscopy (FTIR), differential scanning calorimetry, scanning electron microscopy and transmission electron microscopy. Moreover, in vitro dissolution profiles were performed for all formulated AmB NPs.

Results

MPS of the prepared spherical particles of AmB ranged from 26.4 ± 2.9 to 1068 ± 489.8 nm. An increased stirring rate favored AmB NPs with a smaller MPS. There was a significant reduction in MPS, drug content and drug release, when AmB NPs were prepared using the diblock polymer PLGA–PEG with 15% PEG. Addition of three emulsifying agents poly vinyl pyrrolidone (PVP), Vitamin E (TPGS) and pluronic F-68 to AmB formulations led to a significant reduction in particle size and increase in drug entrapment efficiency (DEE) compared to addition of PVP alone. FTIR spectroscopy demonstrated a successful loading of AmB to pegylated PLGA–PEG copolymers. PLGA–PEG copolymer entrapment efficiency of AmB was increased up to 56.7%, with 92.7% drug yield. After a slow initial release, between 20% and 54% of AmB was released in vitro within 24 h phosphate buffer containing 2% sodium deoxycholate and were best fit Korsmeyer–Peppas model. In conclusion, PLGA–PEG diblock copolymer with 15% PEG produced a significant reduction (>70%) in MPS with highest drug content. The percentage of PEG in the copolymer and the surfactant/stabilizer used had a direct effect on AmB release in vitro, entrapment efficiency and MPS. These developed formulations are feasible, effective and improved alternatives to other carriers for oral delivery of AmB.

Self-assembly of amido-ended hyperbranched polyester films with a highly ordered dendritic structure

Self-assemblies fabricated from dendrimers and amphiphilic polymers have demonstrated remarkable performances and a wide range of applications. Direct self-assembly of hyperbranched polymers into highly ordered macrostructures with heat-resistance remains a big challenge due to the weak amphiphilicity of the polymers. Here, we report the self-assembly of amphiphilic amido-ended hyperbranched polyester (HTDA-2) into millimeter-size dendritic films using combined hydrogen bond interaction and solvent induction. The self-assembly process and mechanism have been studied. Hydrogen bond interaction between amido-ended groups assists the aggregation of inner and outer chains of the HTDA-2, resulting in phase separation and micelle formation. Some micelles attach to and grow on the glass substrate like seedlings. Other micelles move to the seedlings and connect with their branches via solvent induction and hydrogen bond interaction, leading to the fabrication of highly ordered crystalline dendritic films that show high heat-resistance. HTDA-2 can further self-assemble into sheet crystals on the dendritic films.

Synthesis and self-assembly of amphiphilic poly(acrylicacid)–poly(ɛ-caprolactone)–poly(acrylicacid) block copolymer as novel carrier for 7-ethyl-10-hydroxy camptothecin

The process of molecular self-assembly plays a crucial role in formulation of polymeric nanoparticulated drug delivery carriers as it creates the possibility for enhanced drug encapsulation and carrier surface engineering. This study aimed to develop a novel self-assembled polymeric micelles for targeted delivery in tumor cells in order to overcome not only various drawbacks of 7-ethyl-10-hydroxy camptothecin (SN-38) but also various reported limitations of other drug delivery systems, especially low drug loading and premature release. Custom synthesized amphiphilic triblock copolymer poly(acrylic acid)–poly(ɛ-caprolactone)–poly(acrylic acid) (PAA13–PCL35–PAA13) was used to prepare kinetically stable micelles by nanoprecipitation and modified nanoprecipitation procedure. Core-shell micelles with diameter of 120–140 nm, negative zeta potential and satisfactory drug loading were produced. The prepared formulations were stable in pH range of 3–12 and in media with NaCl concentration <1 mol/l. Screening mixed level factorial 3 × 22 design identified that the process temperature as well as the type of organic solvent has influence upon the efficacy of encapsulation, particle size, dissolution rate and burst release. Fourier transform infrared and differential scanning calorimetry analyses confirmed the entrapment of the active substance into the micelles. The kinetic analysis of dissolution studies revealed that the main mechanism of drug release from the prepared formulations is Fickian diffusion. Growth inhibition studies as well as DNA fragmentation assay performed on SW-480 cell lines clearly demonstrated increased growth inhibition effect and presence of fragmented DNA in cells treated with loaded micelles compared to SN-38 solution. Altogether, these results point out to potential biomedical and clinical application of PAA–PCL–PAA systems in the future.

Cryogelation of chitosan using noble-metal ions: in situ formation of nanoparticles

One of the purposes of the project was to develop the method of preparation of 3D macroporous hydrogel with a structure of interconnected pores by the use of noncovalent interactions. The combination of chitosan and noble-metal complexes was investigated as cross-linking agents for the preparation of ionic cryogels (ICs). Furthermore, the treatment of the ICs containing gold complex by glutaraldehyde results in spontaneous formation of gold nanoparticles (AuNPs) and chemical cross-linking of the cryogel. The characterization of prepared macroporous materials was carried out by the use of FTIR, SEM, TEM techniques, and texture analyzer. A new strategy for control of size distribution of AuNPs was suggested. The size distribution of obtained AuNPs and their population inside of walls of cryogels was estimated. A method for quantifying unreacted chloroauric acid in the presence of acetic acid was proposed. The possibility of use of prepared cryogels with immobilized AuNPs as a catalytic flow through reactor is shown.

Biodegradable nanoparticles composed of enantiomeric poly(γ-glutamic acid)-graft-poly(lactide) copolymers as vaccine carriers for dominant induction of cellular immunity

Stereocomplex nanoparticles composed of enantiomeric poly(γ-glutamic acid)-graft-poly(lactide) copolymers are excellent vaccine delivery carriers that can elicit potent cellular immunity.

Materials innovation for co-delivery of diverse therapeutic cargos

Co-delivery is a rapidly growing sector of drug delivery that aspires to enhance therapeutic efficacy through controlled delivery of diverse therapeutic cargoes with synergistic activities. It requires the design of carriers capable of simultaneously transporting to and releasing multiple therapeutics at a disease site. Co-delivery has arisen from the emerging trend of combination therapy, where treatment with two or more therapeutics at the same time can succeed where single therapeutics fail. However, conventional combination therapy offers little control over achieving an optimized therapeutic ratio at the target site. Co-delivery via inclusion of multiple therapeutic cargos within the same carrier addresses this issue by not only ensuring delivery of both therapeutics to the same cell, but also offering a platform for control of the delivery process, from loading to release. Co-delivery systems have been formulated using a number of carriers previously developed for single-therapeutic delivery. Liposomes, polymeric micelles, PLGA nanoparticles, and dendrimers have all been adapted for co-delivery. Much of the effort focuses on dealing with drugs having dissimilar properties, increasing loading efficiencies, and controlling loading and release ratios. In this review, we highlight the innovations in carrier designs and formulations to deliver combination cargoes of drug/drug, drug/siRNA, and drug/pDNA toward disease therapy. With rapid advances in mechanistic understanding of interrelating molecular pathways and development of molecular medicine, the future of co-delivery will become increasingly promising and prominent.

Biodegradable stereocomplex micelles based on dextran-block-polylactide as efficient drug deliveries

Biodegradable stereocomplex micelles (SCMs) based on amphiphilic dextran-block-polylactide (Dex-b-PLA) were designed and used for efficient intracellular drug deliveries. The Dex-b-PLA copolymers were successfully synthesized by click reaction. The structures of the resultant copolymers were verified by (1)H NMR and FT-IR spectra. The formation of stable micelles through self-assembly driven by the stereocomplexation between enantiomeric l- and d-PLA blocks was characterized by transmission electron microscopy (TEM), dynamic laser scattering (DLS), and fluorescence techniques. It was interesting to observe that the SCMs showed lower critical micelle concentration values (CMCs) because of the stereocomplex interaction between PLLA and PDLA. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis provided information on the thermal and crystal properties of the copolymers and SCMs. The improved stability of SCMs should be attractive for intracellular drug delivery. Thus, a model anticancer drug doxorubicin (DOX) was loaded into micelles, and the in vitro drug release in was also studied. The release kinetics of DOX showed DOX-loaded SCMs exhibited slower DOX release. Confocal laser scanning microscopy (CLSM) and flow cytometry studies also showed that the DOX-loaded SCMs exhibited a slower drug release behavior. Meanwhile, the MTT assay demonstrated that DOX-loaded SCMs show lower cellular proliferation inhibition against HepG2. In sum, the micelles through self-assembly driven by stereocomplex interaction would have great potential to be used as stable delivery vehicles for pharmaceutical and biomedical applications.

Cell penetrating peptide conjugated polymeric micelles as a high performance versatile nonviral gene carrier

The major goal of this study is to design, synthesize, and evaluate linoleic acid and penetratin dual-functionalized chitosan (CS-Lin-Pen) as a nonviral gene carrier. The amphiphilic CS-Lin-Pen self-assembles to form cationic micelles in an aqueous environment. These polymeric micelles exhibited excellent hemocompatibility and cell viability, as evaluated by in vitro hemolysis and MTT assay, respectively. When CS-Lin-Pen micelles were added to plasmid DNA (pDNA) solution, the electrostatic interaction between the cationic micelles and anionic pDNA led to the formation of stable CS-Lin-Pen/pDNA polyplexes with ~100 nm in size. The resultant polyplexes demonstrated ~5-fold higher cellular uptake as compared to unmodified chitosan. Furthermore, CS-Lin-Pen micelles showed efficient protection of pDNA from DNase I attack and exhibited ~34-40-fold higher transfection in comparison with unmodified chitosan in HEK 293, CHO, and HeLa cells. These findings illustrate that the CS-Lin-Pen micelles could be exploited as a potential nonviral vector for efficient gene therapy.

Block copolymers containing a hydrophobic domain of membrane-lytic peptides form micellar structures and are effective gene delivery agents

Endosomal release peptides have been incorporated in synthetic gene delivery formulations to increase transfection efficiencies. In this work, cationic copolymers containing sHGP, a membrane-lytic peptide derived from HIV gp41, were synthesized and evaluated. Diblock, with sHGP displayed on one block, and statistical, with sHGP randomly displayed, copolymers were prepared via RAFT polymerization. While the statistical copolymer existed as unimers in solution, amphiphilic diblock copolymers self-assembled into cationic micelles in aqueous solution as evidenced by TEM and dynamic light scattering analyses. This self-assembly sequestered the lytic domain and significantly reduced the cytotoxicity of the materials. However, when complexed with plasmid DNA, both the diblock and statistical copolymers of sHGP showed higher gene delivery efficacy compared to the copolymers without the membrane lytic motif. The ability of amphiphilic, diblock copolymers containing endosomal release motifs to self-assemble and sequester lytic domains is a promising feature for the nucleic acid delivery.

Multifunctional polyelectrolyte microparticles for oral insulin delivery

Multicomponent insulin-containing microparticles are prepared by layer-by-layer assembly of dextran sulfate and chitosan on the core of protein-polyanion complex with or without protease inhibitors. Oral bioavailability of the encapsulated insulin is improved due to the cumulative effect of each component. A physico-chemical study shows that the particle design allows adjustment of the pH-dependent profile of the insulin release, as well as mucoadhesive properties and Ca(2+) binding ability of the microparticles. Supplementing the microparticles with 2-3% protease inhibitors fully prevents proteolysis of human insulin. The pharmacological effect of microencapsulated insulin in doses 50-100 IU kg(-1) is demonstrated in chronic experiments after oral administration to diabetic rats fed ad libitum.

Hyaluronic acid nanohydrogels as a useful tool for BSAO immobilization in the treatment of melanoma cancer cells

An alternative anticancer therapy based on the use of bovine serum amine oxidase (BSAO), an enzyme that converts polyamines over-expressed in malignant cells, into hydrogen peroxide and aldehyde(s), thus inducing high cytotoxicity in cancer cells, was recently proposed. With the aim of improving the system efficacy by exploiting a nanotechnology approach, BSAO is covalently immobilized onto injectable nanohydrogels (NHs) based on cholesterol-graft-hyaluronic acid (HA-CH), a biocompatible conjugate that spontaneously leads to self-assembled structures in aqueous solutions. In this study, the physicochemical properties of the HA-CH-based NHs and the NHs cytocompatibility are reported. The properties of the NHs-BSAO system are also studied in terms of protein residual activity, both in vitro and on a model melanoma cell line.

Controlled Delivery of Functionalized Gold Nanoparticles by pH-Sensitive Polymersomes

The present study reports on the development of composite gold nanoparticles (AuNPs)/polymersome formulations, based on pH-responsive biocompatible polymer vesicles integrating prefunctionalized AuNPs, doped with a hydrophobic model probe for improved multimodal drug delivery. The polymer vesicles were prepared from an amphiphilic pentablock terpolymer poly(ε-caprolactone)-b-poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide)-b-poly(ε-caprolactone) (PCL-PEO-P2VP-PEO-PCL), consisting of a pH-sensitive and biodegradable P2VP/PCL membrane, surrounded by neutral hydrophilic PEO looping chains. Additionally, partial quaternization of the P2VP block has been performed to introduce cationic moieties. Water-dispersible AuNPs carrying a hydrophobic molecule were encapsulated in the hydrophilic aqueous lumen of the vesicles, and the release was monitored at pH conditions simulating physiological and tumor environments. The complex delivery of the cargos from these vesicles showed improved and controlled kinetics relative to the individual nanocarriers, which could be further tuned by pH and chemical modification of the membrane forming block.

Biopolymer-based nanoparticles for drug/gene delivery and tissue engineering

There has been a great interest in application of nanoparticles as biomaterials for delivery of therapeutic molecules such as drugs and genes, and for tissue engineering. In particular, biopolymers are suitable materials as nanoparticles for clinical application due to their versatile traits, including biocompatibility, biodegradability and low immunogenicity. Biopolymers are polymers that are produced from living organisms, which are classified in three groups: polysaccharides, proteins and nucleic acids. It is important to control particle size, charge, morphology of surface and release rate of loaded molecules to use biopolymer-based nanoparticles as drug/gene delivery carriers. To obtain a nano-carrier for therapeutic purposes, a variety of materials and preparation process has been attempted. This review focuses on fabrication of biocompatible nanoparticles consisting of biopolymers such as protein (silk, collagen, gelatin, β-casein, zein and albumin), protein-mimicked polypeptides and polysaccharides (chitosan, alginate, pullulan, starch and heparin). The effects of the nature of the materials and the fabrication process on the characteristics of the nanoparticles are described. In addition, their application as delivery carriers of therapeutic drugs and genes and biomaterials for tissue engineering are also reviewed.