Self-assembled polyethylenimine-graft-poly(epsilon-caprolactone) micelles as potential dual carriers of genes and anticancer drugs

Polymersomes for Therapeutic Protein and Peptide Delivery: Towards Better Loading Properties

Therapeutics based on proteins and peptides have profoundly transformed the landscape of treatment for diseases, from diabetes mellitus to cancers, yet the short half-life and low bioavailability of therapeutic proteins and peptides hinder their wide applications. To break through this bottleneck, biomolecules-loaded polymersomes with strong adjustability and versatility have attracted more and more attentions recently. Loading proteins or peptides into polymersomes is the first but extremely important step towards developing high-quality formulation products. However, increasing protein and peptide loading content is quite challenging due to the inherent nature of self-assembled vesicle formation mechanism and physiochemical characteristics of biomacromolecules. This review highlights the potential of polymersomes as the next-generation therapeutic proteins and peptides carrier and emphatically introduces novel approaches and recent progress to achieve satisfactory encapsulation capability of polymersomes for proteins and peptides. On the one hand, with the help of intermolecular interactions, such as electrostatic, lipid-protein, and hydrophobic interactions, the drug loading could be significantly improved. On the other hand, loading improvement could be attained through innovation of preparation methods, ranging from modified traditional film hydration techniques to the novel phase-guided assembly method.

Drug Encapsulation via Peptide-Based Polyelectrolyte Complexes

Peptide-based polyelectrolyte complexes are biocompatible materials that can encapsulate molecules with different polarities due to their ability to be precisely designed. Here we use UV-Vis spectroscopy, fluorescence microscopy, and infrared spectroscopy to investigate the encapsulation of model drugs, doxorubicin (DOX) and methylene blue (MB) using a series of rationally designed polypeptides. For both drugs, we find an overall higher encapsulation efficiency with sequences that have higher charge density, highlighting the importance of ionic interactions between the small molecules and the peptides. However, comparing molecules with the same charge density, illustrated that the most hydrophobic sequence pairs had the highest encapsulation of both DOX and MB molecules. The phase behavior and stability of DOX-containing complexes did not change compared to the complexes without drugs. However, MB encapsulation caused changes in the stabilities of the complexes. The sequence pair with the highest charge density and hydrophobicity had the most dramatic increase in stability, which coincided with a phase change from liquid to solid. This study illustrates how multiple types of molecular interactions are required for efficient encapsulation of poorly soluble drugs and provides insights into the molecular design of delivery carriers.

Redox responsive polymeric micelles of gellan gum/abietic acid for targeted delivery of ribociclib

In most breast tumors level of glutathione reductase is much higher than in healthy tissues. In the current study, a redox-glutathione sensitive micelle based on Abietic acid-Cystamine-Gellan gum (AB-ss-GG) was designed for targeted delivery of Ribociclib (RIB) to breast cancer cells. AB is a monocarboxylic acid and a diterpenoid abietane with anti-tumor effects. Successful synthesis of the conjugate was confirmed by FT-IR and ¹HNMR spectroscopy. Critical micelle concentration (CMC) was measured by pyrene as a fluorescent probe. Micelles of AB-GG and AB-ss-GG were loaded with different RIB/polymer ratios, and their redox-sensitivity was measured in the presence and absence of dithiothreitol (DTT) by determining the particle size and RIB release efficiency. Cell cytotoxicity and cellular uptake were assessed by MTT assay and flow-cytometry method on MCF-7 cells. CMC of AB-ss-GG and AB-GG micelles were estimated to be 40.15 and 37.33 mg/mL, respectively. In the presence of DTT, the particle size and release efficiency of AB-ss-GG micelles increased specially at a 1:1 drug/polymer ratio. AB-ss-GG micelles containing RIB showed higher cytotoxicity (IC₅₀ = 47.86 μmol/L) and cellular uptake than AB-GG micelles (IC₅₀ = 190.25 μmol/L) and free RIB (IC₅₀ = 75.26 μmol/L) at 48 h. AB-ss-GG micelles showed a promising redox-sensitive polymeric carrier for RIB delivery.

Recent advances in the self-assembly of sparsely grafted amphiphilic copolymers in aqueous solution

This review describes the self-assembly of sparsely grafted amphiphilic copolymers and highlights the effects of structural factors and solvents on their self-assembly behaviour.

Synthesis, Morphology, and Rheological Evaluation of HPMA (N-2-Hydroxypropyl Methacrylamide)-PCL (Polycaprolactone) Conjugates

The design, synthesis, and physicochemical characterization of conjugates are arduous and tedious processes. Several synthetic pathways for polymeric conjugation have been reported; however, conjugation through monomers with suitable reaction conditions can be a simple and robust approach. In the present study, three different conjugates of hydrophilic N-2-hydroxypropyl methacrylamide (HPMA) and hydrophobic polycaprolactone (PCL) were synthesized. The followed synthetic pathway not only was simple and robust but also reduced the overall synthetic steps as well as harsh reaction conditions significantly. In a nutshell, three conjugates, i.e., N-2-hydroxypropyl methacrylamide and polycaprolactone (HP-PCL), n-butanol-polycaprolactone-N-2-hydroxypropyl methacrylamide (nBu-PCL-HP), and isoamyl alcohol-polycaprolactone-N-2-hydroxypropyl methacrylamide (ISAL-PCL-HP), were synthesized through this simple synthetic strategy following the monomer conjugation approach along with exhaustive spectroscopic and rheological characterization. The conjugates HP-PCL, nBu-PCL-HP, and ISAL-PCL-HP were characterized by Fourier transform infrared (FT-IR) and NMR (¹³C and ¹H) spectroscopies. The size and ζ potential of conjugates were determined through the dynamic light scattering (DLS) method. The nBu-PCL-HP conjugate displayed a hexagonal-like shape, as evidenced by scanning electron microscopy (SEM) with an obtained size of 237.9 ± 0.21 nm. X-ray diffraction (XRD) analysis proved the crystalline nature of nBu-PCL-HP conjugates. The results of smartly synthesized conjugates intrigued us to study their flow properties in detail. Rheological evaluation resulted in their non-Newtonian type of flow with the best-fit behavior for all of the conjugates followed as per the Herschel-Bulkley and power-law models applied herein. Conclusively, the synthesized HPMA and PCL conjugates may have applications in the preparation of blends, fibers, etc. in the future. The study portrayed that the explored synthetic scheme using monomers and initiators could be a suitable approach for the synthesis of HPMA and PCL conjugates.

Programmable Assembly of π-Conjugated Polymers

π-Conjugated polymers have numerous applications due to their advantageous optoelectronic and mechanical properties. These properties depend intrinsically on polymer ordering, including crystallinity, orientation, morphology, domain size, and π-π interactions. Programming, or deliberately controlling the composition and ordering of π-conjugated polymers by well-defined inputs, is a key facet in the development of organic electronics. Here, π-conjugated programming is described at each stage of material development, stressing the links between each programming mode. Covalent programming is performed during polymer synthesis such that complex architectures can be constructed, which direct polymer assembly by governing polymer orientation, π-π interactions, and morphological length-scales. Solution programming is performed in a solvated state as polymers dissolve, aggregate, crystallize, or react in solution. Solid-state programming occurs in the solid state and is governed by polymer crystallization, domain segregation, or gelation. Recent progress in programming across these stages is examined, highlighting order-dependent features and assembly techniques that are unique to π-conjugated polymers. This should serve as a guide for delineating the many ways of directing π-conjugated polymer assembly to control ordering, structure, and function, enabling the further development of organic electronics.

Development of poly(ethyleneimine) grafted amphiphilic copolymers: Evaluation of their cytotoxicity and ability to complex DNA

Poly(ethyleneimine) (PEI) is one of the most widely used cationic polymers for gene delivery. The high molecular weight polymer, which is commercially available, is highly efficient but also very cytotoxic. The reduction in charge density by using nonlinear architectures based on low molecular weight (LMW) PEI is a promising approach to produce safer DNA-vectors. Herein, a group of cationic graft copolymers with different composition containing a hydrophobic biocompatible backbone and LMW linear PEI (lPEI) grafts obtained by ring opening polymerization and click chemistry was studied. The self-assembly and DNA complexation behavior of these materials was analyzed by the gel retardation assay, zeta potential measurements, and dynamic light scattering. The copolymers formed positively charged particles in water with average sizes between 270 and 377 nm. After they were added to DNA in serum-free medium, these particles acquired negative/near-neutral charges and increased in size depending on the N/P ratio. All copolymers showed reduced cytotoxicity compared to the 25 kDa lPEI used as reference, but the transfection efficiency was reduced. This result suggested that the cationic segments were too small to fully condense the DNA and promote cellular uptake, even with the use of several grafts and the introduction of hydrophobic domains. The trends found in this research showed that a higher degree of hydrophobicity and a higher grafting density can enhance the interaction between the copolymers and DNA. These trends could direct further structural modifications in the search for effective and safe vectors based on this polycation.

Electromagnetic Field-Programmed Magnetic Vortex Nanodelivery System for Efficacious Cancer Therapy

Effective delivery of anticancer drugs into the nucleus for pharmacological action is impeded by a series of intratumoral transport barriers. Despite the significant potential of magnetic nanovehicles in electromagnetic field (EF)-activated drug delivery, modularizing a tandem magnetoresponsive activity in a one-nanoparticle system to meet different requirements at both tissue and cellular levels remain highly challenging. Herein, a strategy is described by employing sequential EF frequencies in inducing a succession of magnetoresponses in the magnetic nanovehicles that aims to realize cascaded tissue penetration and nuclear accumulation. This nanovehicle features ferrimagnetic vortex-domain iron oxide nanorings coated with a thermo-responsive polyethylenimine copolymer (PI/FVIOs). It is shown that the programmed cascading of low frequency (Lf)-EF-induced magnetophoresis and medium frequency (Mf)-EF-stimulated magneto-thermia can steer the Doxorubicin (DOX)-PI/FVIOs to the deep tissue and subsequently trigger intracellular burst release of DOX for successful nuclear entry. By programming the order of different EF frequencies, it is demonstrated that first-stage Lf-EF and subsequent Mf-EF operation enables DOX-PI/FVIOs to effectively deliver 86.2% drug into the nucleus in vivo. This nanodelivery system empowers potent antitumoral activity in various models of intractable tumors, including DOX-resistant MCF-7 breast cancer cells, triple-negative MDA-MB-231 breast cancer cells, and BxPC-3 pancreatic cancer cells with poor permeability.

Combinatorial Effect of DCA and Let-7a on Triple-Negative MDA-MB-231 Cells: A Metabolic Approach of Treatment

Dichloroacetate (DCA) is a metabolic modulator that inhibits pyruvate dehydrogenase activity and promotes the influx of pyruvate into the tricarboxylic acid cycle for complete oxidation of glucose. DCA stimulates oxidative phosphorylation (OXPHOS) more than glycolysis by altering the morphology of the mitochondria and supports mitochondrial apoptosis. As a consequence, DCA induces apoptosis in cancer cells and inhibits the proliferation of cancer cells. Recently, the role of miRNAs has been reported in regulating gene expression at the transcriptional level and also in reprogramming energy metabolism. In this article, we indicate that DCA treatment leads to the upregulation of let-7a expression, but DCA-induced cancer cell death is independent of let-7a. We observed that the combined effect of DCA and let-7a induces apoptosis, reduces reactive oxygen species generation and autophagy, and stimulates mitochondrial biogenesis. This was later accompanied by stimulation of OXPHOS in combined treatment and was thus involved in metabolic reprogramming of MDA-MB-231 cells.

Amphiphilic Double-Brush Copolymers with a Polyurethane Backbone: A Bespoke Macromolecular Emulsifier for Ionic Liquid-in-Oil Emulsion

The study on ionic liquid (IL)-based emulsions is very interesting due to the "green" quality and potential wide applications of ILs, whereas the emulsifiers for the formation of IL-based emulsions are extremely limited and mainly centered on low molecular weight surfactants. In this work, synthesis of amphiphilic double-brush copolymers (DBCs) and their application as bespoke macromolecular emulsifiers for the formation of IL-containing non-aqueous emulsions are described. DBCs consisted of a polyurethane (PU) backbone and poly(N,N-dimethyl acrylamide) (PDMA) and poly(methyl methacrylate) (PMMA) chains that were grafted simultaneously at the same reactive site along the PU backbone (PU-g-PDMA/PMMA), which were synthesized through the combination of polyaddition and the reversible-deactivation radical polymerization reactions. Highly stable [Bmim][PF₆]-in-benzene emulsions could be gained by adopting PU-g-PDMA/PMMA DBCs as macromolecular emulsifiers at a low content, such as 0.025 wt %. On the basis of the stability and the size of emulsion droplets, PU-g-PDMA/PMMA DBCs exhibited much better emulsifying performances than their analogues, including PU-g-PDMA, PU-g-PMMA, and PDMA-b-PMMA copolymers. Such excellent emulsifying performances of PU-g-PDMA/PMMA DBCs were due to high interfacial activities. PU-g-PDMA/PMMA DBCs exhibited higher capabilities in lowering the interfacial tension of the [Bmim][PF₆]-benzene interface than their analogues. A large energy barrier to desorption of adsorbed PU-g-PDMA/PMMA DBCs from the interface contributed to high stability of the [Bmim][PF₆]-in-benzene emulsion.

Cationic nanoparticles self-assembled from amphiphilic chitosan derivatives containing poly(amidoamine) dendrons and deoxycholic acid as a vector for co-delivery of doxorubicin and gene

Combination treatment through the co-delivery of drugs and genes by nanoformulations may achieve a synergistic effect. In our previous study, poly(amidoamine) dendronized chitosan derivative (PAMAM-Cs) showed good gene transfection efficiency and low cytotoxicity. Here, we incorporated hydrophobic deoxycholic acid (DCA) onto the chitosan backbone of PAMAM-Cs to obtain an amphiphilic derivative-PAMAM-Cs-DCA, which could self-assemble into cationic nanoparticles (NPs). The resulting NPs with diameters of 140-220 nm can encapsulate the hydrophobic anticancer drug doxorubicin (DOX) in the core while bind pDNA via the positively charged PAMAM shell. PAMAM-Cs-DCA NPs could completely complex with pDNA at a ratio of nitrogen to phosphorous (N/P) low as 1 and the complexes achieved a transfection efficiency up to 74 % at N/P 20. Moreover, low-dose co-delivered DOX could enhance the transgene expression, showing a synergistic effect. These results suggest that PAMAM-Cs-DCA NPs hold great promise to co-deliver chemotherapeutics and nucleic acid drugs.

Aptamers used for biosensors and targeted therapy

Aptamers are single-stranded nucleic acid sequences that can bind to target molecules with high selectivity and affinity. Most aptamers are screened in vitro by a combinatorial biology technique called systematic evolution of ligands by exponential enrichment (SELEX). Since aptamers were discovered in the 1990s, they have attracted considerable attention and have been widely used in many fields owing to their unique advantages. In this review, we present an overview of the advancements made in aptamers used for biosensors and targeted therapy. For the former, we will discuss multiple aptamer-based biosensors with different principles detected by various signaling methods. For the latter, we will focus on aptamer-based targeted therapy using aptamers as both biotechnological tools for targeted drug delivery and as targeted therapeutic agents. Finally, challenges and new perspectives associated with these two regions were further discussed. We hope that this review will help researchers interested in aptamer-related biosensing and targeted therapy research.

A library of aminoglycoside-derived lipopolymer nanoparticles for delivery of small molecules and nucleic acids

Simultaneous delivery of small molecules and nucleic acids using a single vehicle can lead to novel combination treatments and multifunctional carriers for a variety of diseases. In this study, we report a novel library of aminoglycoside-derived lipopolymers nanoparticles (LPNs) for the simultaneous delivery of different molecular cargoes including nucleic acids and small-molecules. The LPN library was screened for transgene expression efficacy following delivery of plasmid DNA, and lead LPNs that showed high transgene expression efficacies were characterized using hydrodynamic size, zeta potential, 1H NMR and FT-IR spectroscopy, and transmission electron microscopy. LPNs demonstrated significantly higher efficacies for transgene expression than 25 kDa polyethyleneamine (PEI) and lipofectamine, including in presence of serum. Self-assembly of these cationic lipopolymers into nanoparticles also facilitated the delivery of small molecule drugs (e.g. doxorubicin) to cancer cells. LPNs were also employed for the simultaneous delivery of the small-molecule histone deacetylase (HDAC) inhibitor AR-42 together with plasmid DNA to cancer cells as a combination treatment approach for enhancing transgene expression. Taken together, our results indicate that aminoglycoside-derived LPNs are attractive vehicles for simultaneous delivery of imaging agents or chemotherapeutic drugs together with nucleic acids for different applications in medicine and biotechnology.

6-Aminocaproic acid as a linker to improve near-infrared fluorescence imaging and photothermal cancer therapy of PEGylated indocyanine green

Clinical extensive application of indocyanine green (ICG) is limited by several drawbacks such as poor bioenvironmental stability, aggregate propensity, and rapid elimination from the body, etc. In this study, we construct a novel amphiphilic mPEG-ACA-ICG conjugate by modifying synthetic heptamethine cyanine derivative ICG-COOH with a hydrophobic linker 6-aminocaproic acid (ACA) and amino-terminal poly(ethylene glycol) (mPEG-NH₂). The as-prepared mPEG-ACA-ICG conjugate has the ability to self-assemble into micellar aggregates in an aqueous solution with a lower CMC value than mPEG-ICG conjugate without ACA linker. More importantly, compared with free ICG and mPEG-ICG conjugate, mPEG-ACA-ICG nanomicelles exhibited better stability and higher photothermal conversion efficiency upon near-infrared light irradiation due to the intramolecular introduction of a hydrophobic ACA segment. In our in vivo experiment, mPEG-ACA-ICG nanomicelles ensured the formidable effect on tumor photothermal therapy (PTT) and the maximum tumor inhibition rate reached 72.6 %. In addition, real-time determination ability for fluorescence image-guided surgery (FIGS) of mPEG-ACA-ICG nanomicelles was also confirmed on tumor xenograft mice model. Taken together, mPEG-ACA-ICG conjugate may hold great promise for non-invasive cancer theranostics.

Co-delivery of gemcitabine prodrug along with anti NF-κB siRNA by tri-layer micelles can increase cytotoxicity, uptake and accumulation of the system in the cancers

Combination treatment based on gene and chemotherapy is a promising strategy for effective cancer treatment due to the limited therapeutic efficacy of anticancer drugs. Dual functional polymeric micelles (PMs) have been emerged as potent nanocarriers for combinational cancer therapy. In the present study, the potential of tri-layer PMs loaded with anti-nuclear factor-κB (NF-κB) siRNA and 4-(N)-stearoyl gemcitabine (GemC18) has been investigated for cancer treatment. PMs with different core hydrophobicity were prepared by using poly(ε-caprolactone), polyethyleneimine and polyethylene glycol (PCL-PEI-PEG) copolymers and evaluated. The results revealed that GemC18-loaded PMs were significantly more cytotoxic than free drug on breast and pancreatic cancer cells. However, the cytotoxicity of drug loaded micelles was decreased by increasing the micellar core hydrophobicity because of decreasing drug release rate. Moreover, siRNA loaded PMs could considerably inhibit NF-κB expression. PMs loaded with both GemC18 and siRNA exhibited higher capability to induce apoptosis and inhibit migration of both cells. PMs with the most hydrophobic core indicated higher tumor accumulation efficiency via in-vivo imaging study. In conclusion, the prepared PMs hold a promise as an attractive dual functional delivery system for an effective cancer therapy.

Intraperitoneal administration of biocompatible hyaluronic acid hydrogel containing multi-chemotherapeutic agents for treatment of colorectal peritoneal carcinomatosis

Colorectal peritoneal carcinomatosis (CRPC) is an advanced stage of colorectal cancer (CRC), which significantly decreases patient survival and quality of life. Here, the naturally occurring polysaccharide hyaluronic acid (HA) was used to prepare an injectable hydrogel and simultaneously deliver 5-fluorouracil (5-FU), cisplatin (DDP) and paclitaxel (PTX) microspheres for intraperitoneal CRPC chemotherapy. The drug-loaded HA hydrogel released the drugs in a sustained manner, and showed low toxicity both in vitro and in a mouse model of CRPC. Furthermore, direct injection of the drug-loaded HA hydrogel in the abdominal cavity of tumor-bearing mice significantly decreased tumor growth and liver/lung metastasis, along with decreasing the volume of ascites and inhibiting local intestinal infiltration of the tumor cells. Therefore, this novel multi-drug hydrogel delivery system may effectively clear CRPC tumors without any adverse effects when used in intraperitoneal chemotherapy.

Polymeric Co-Delivery Systems in Cancer Treatment: An Overview on Component Drugs' Dosage Ratio Effect

Multiple factors are involved in the development of cancers and their effects on survival rate. Many are related to chemo-resistance of tumor cells. Thus, treatment with a single therapeutic agent is often inadequate for successful cancer therapy. Ideally, combination therapy inhibits tumor growth through multiple pathways by enhancing the performance of each individual therapy, often resulting in a synergistic effect. Polymeric nanoparticles prepared from block co-polymers have been a popular platform for co-delivery of combinations of drugs associated with the multiple functional compartments within such nanoparticles. Various polymeric nanoparticles have been applied to achieve enhanced therapeutic efficacy in cancer therapy. However, reported drug ratios used in such systems often vary widely. Thus, the same combination of drugs may result in very different therapeutic outcomes. In this review, we investigated polymeric co-delivery systems used in cancer treatment and the drug combinations used in these systems for synergistic anti-cancer effect. Development of polymeric co-delivery systems for a maximized therapeutic effect requires a deeper understanding of the optimal ratio among therapeutic agents and the natural heterogenicity of tumors.

Tuning the Potential of Electron Extraction from Microbes with Ferrocene-Containing Conjugated Oligoelectrolytes

Synthetic systems that facilitate electron transport across cellular membranes are of interest in bio-electrochemical technologies such as bio-electrosynthesis, waste water remediation, and microbial fuel cells. The design of second generation redox-active conjugated oligoelectrolytes (COEs) bearing terminal cationic groups and a π-delocalized core capped by two ferrocene units is reported. The two COEs, DVFBO and F₄ -DVFBO, have similar membrane affinity, but fluorination of the core results in a higher oxidation potential (422 ± 5 mV compared to 365 ± 4 mV vs Ag/AgCl for the neutral precursors in chloroform). Concentration-dependent aggregation is suggested by zeta potential measurements and confirmed by cryogenic transmission electron microscopy. When the working electrode potential (E_CA ) is poised below the oxidation potential of the COEs (E_CA = 200 mV) in three-electrode electrochemical cells containing Shewanella oneidensis MR-1, addition of DVFBO and F₄ -DVFBO produces negligible biocurrent enhancement over controls. At E_CA = 365 mV, DVFBO increases steady-state biocurrent by 67 ± 12% relative to controls, while the increase with F₄ -DVFBO is 30 ± 5%. Cyclic voltammetry supports that DVFBO increases catalytic biocurrent and that F₄ -DVFBO has less impact, consistent with their oxidation potentials. Overall, electron transfer from microbial species is modulated via tailoring of the COE redox properties.

A Polycationic Brush Mediated Co-Delivery of Doxorubicin and Gene for Combination Therapy

The combination of drug and gene strategies for cancer therapy, has exhibited greater effectiveness than drug or gene therapy alone. In this paper, a coil-comb shaped polycationic brush was used as a multifunctional carrier for co-delivery of drug and gene. The side chains of the comb block of the brush were composed of cyclodextrin (CD)-containing cationic star polymers, with a super-high density of positive charge. Doxorubicin (DOX) could be loaded into the cavity of CD polymers to form DOX-loaded nanoparticles (DOX-NPs) and the p53 gene could be subsequently condensed by DOX-NPs. The obtained DOX-NPs/pDNA complexes were less than 150 nm in size, and so could transport DOX and the gene into the same cell. The complexes performed well with regards to their transfection efficiency on MCF-7 cancer cells. As a result, enhanced cell growth inhibition, with decreased DOX dosage was achieved due to the synergistic effect of co-delivery of DOX and the p53 gene. This finding provides an efficient approach for the development of a co-delivery system in combination therapy.

Novel hyaluronic acid coated hydrophobically modified chitosan polyelectrolyte complex for the delivery of doxorubicin

The aim of this work was to examine the formation and properties of a novel polyelectrolyte complex of drug carrier system for the delivery of doxorubicin (DOX), which consists of hyaluronic acid (HA) coated hydrophobically modified chitosan (CS). Various batches of polyelectrolyte complexes with the molar ratio of deoxycholic acid (DCA) and chitosan (CS) of 0.1, 0.2, 0.3 were prepared, and were termed as CS-DCA₁₀, CS-DCA₂₀, and CS-DCA₃₀ respectively. The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM), nuclear magnetic resonance hydrogen spectrum (¹H NMR) and dynamic light scattering (DLS). Particle sizes of synthesized polyelectrolyte complex nanoparticles (PCNs) were found to be in the range of 280-310 nm, larger than those of uncoated nanoparticles (~150 nm). The PCNs have large zeta potentials (about 26 mV) which make them stable and no sizes' change was determined. DOX could be easily incorporated into the PCNs with encapsulation efficiency (56%) and kept a sustained release manner without burst effect when exposed to PBS (pH 7.4) at 37 °C. Overall, these findings confirmed the potential of these PCNs for drug carrier and prolonged and sustained delivery in the bloodstream.

Advancements and Challenges in Multidomain Multicargo Delivery Vehicles

Reparative and regenerative processes are well-orchestrated temporal and spatial events that are governed by multiple cells, molecules, signaling pathways, and interactions thereof. Yet again, currently available implantable devices fail largely to recapitulate nature's complexity and sophistication in this regard. Herein, success stories and challenges in the field of layer-by-layer, composite, self-assembly, and core-shell technologies are discussed for the development of multidomain/multicargo delivery vehicles.

Development of cholate conjugated hybrid polymeric micelles for FXR receptor mediated effective site-specific delivery of paclitaxel

The aim of the present study was to explore the tumor targeting potential of a cholic acid (CA) conjugated polymeric micelle system for the effective delivery of paclitaxel (PTX).

Core/Shell Gene Carriers with Different Lengths of PLGA Chains to Transfect Endothelial Cells

In order to improve the transfection efficiency and reduce the cytotoxicity of gene carriers, many strategies have been used to develop novel gene carriers. In this study, five complex micelles (MSP(2 k), MSP(4 k), MSP(6 k), MSP(8 k), and MSP(10 k)) were prepared from methoxy-poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) (mPEG-b-PLGA) and sorbitol-poly(d,l-lactide-co-glycolide)-graft-PEI (sorbitol-PLGA-g-PEI, where the designed molecular weights of PLGA chains were 2 kDa, 4 kDa, 6 kDa, 8 kDa, and 10 kDa, respectively) copolymers by a self-assembly method, and the mass ratio of mPEG-b-PLGA to sorbitol-PLGA-g-PEI was 1/3. These complex micelles and their gene complexes had appropriate sizes and zeta potentials, and pEGFP-ZNF580 (pDNA) could be efficiently internalized into EA.hy926 cells by their gene complexes (MSP(2 k)/pDNA, MSP(4 k)/pDNA, MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA). The MTT assay results demonstrated that the gene complexes had low cytotoxicity in vitro. When the hydrophobic PLGA chain increased above 6 kDa, the gene complexes showed higher performance than that prepared from short hydrophobic chains. Moreover, the relative ZNF580 protein expression levels in MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA) groups were 79.6%, 71.2%, and 73%, respectively. These gene complexes could promote the transfection of endothelial cells, while providing important information and insight for the design of new and effective gene carriers to promote the proliferation and migration of endothelial cells.

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl comonomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over 2 orders of magnitude (0.36 M^-1 s^-1 < k_homo < 82 M^-1 s^-1). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(d,l-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by nonlinear least-squares fitting of the instantaneous comonomer concentrations according to the Mayo-Lewis terminal model. In-depth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r₁/r₂ < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo- and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

Polymeric micelles: Basic research to clinical practice

Rapidly developing polymeric micelles as potential targeting carriers has intensified the need for better understanding of the underlying principles related to the selection of suitable delivery materials for designing, characterizing, drug loading, improving stability, targetability, biosafety and efficacy. The emergence of advanced analytical tools such as fluorescence resonance energy transfer and dissipative particle dynamics has identified new dimensions of these nanostructures and their behavior in much greater details. This review summarizes recent efforts in the development of polymeric micelles with respect to their architecture, formulation strategy and targeting possibilities along with their preclinical and clinical aspects. Literature of the past decade is discussed critically with special reference to the chemistry involved in the formation and clinical applications of these versatile materials. Thus, our main objective is to provide a timely update on the current status of polymeric micelles highlighting their applications and the important parameters that have led to successful delivery of drugs to the site of action.

pH-sensitive micelles self-assembled from polymer brush (PAE-g-cholesterol)-b-PEG-b-(PAE-g-cholesterol) for anticancer drug delivery and controlled release

A novel amphiphilic pH-sensitive triblock polymer brush (poly(β-amino esters)-g-cholesterol)-b-poly(ethylene glycol)-b-(poly(β-amino esters)-g-cholesterol) ((PAE-g-Chol)-b-PEG-b-(PAE-g-Chol)) was designed and synthesized successfully through a three-step reaction, and their self-assembled polymeric micelles were used as hydrophobic anticancer drug delivery carriers to realize effectively controlled release. The critical micelle concentrations were 6.8 μg/mL, 12.6 μg/mL, 17.4 μg/mL, and 26.6 μg/mL at pH values of 7.4, 6.5, 6.0, and 5.0, respectively. The trend of critical micelle concentrations indicated that the polymer had high stability that could prolong the circulation time in the body. The hydrodynamic diameter and zeta potential of the polymeric micelles were influenced significantly by the pH values. As pH decreased from 7.4 to 5.0, the particle size and zeta potential increased from 205.4 nm to 285.7 nm and from +12.7 mV to +47.0 mV, respectively. The pK_b of the polymer was confirmed to be approximately 6.5 by the acid–base titration method. The results showed that the polymer had sharp pH-sensitivity because of the protonation of the amino groups, resulting in transformation of the PAE segment from hydrophobic to hydrophilic. Doxorubicin-loaded polymeric micelles were prepared with a high loading content (20%) and entrapment efficiency (60%) using the dialysis method. The in vitro results demonstrated that drug release rate and cumulative release were obviously dependent on pH values. Furthermore, the drug release mechanism was also controlled by the pH values. The polymer had barely any cytotoxicity, whereas the doxorubicin-loaded system showed high toxicity for HepG2 cells as free drugs. All the results proved that the pH-sensitive triblock polymer brush and its self-assembled micelle might be a potential delivery carrier for anticancer drugs with sustained release.

Supramolecular Amphiphilic Polymer-Based Micelles with Seven-Armed Polyoxazoline Coating for Drug Delivery

Supramolecular polymer micelles composed of seven-armed poly(2-methy-2-oxazoline) as the coating and linear poly(dl-lactide) as the core were prepared through synthesizing β-cyclodextrin-terminated poly(2-methy-2-oxazoline) and adamantine-terminated linear poly(dl-lactide), followed by host-guest interaction between β-cyclodextrin and adamantine groups in two polymers and self-assembly in aqueous solution. Dynamic light-scattering measurement showed that the micelles based on supramolecular amphiphilic polymers have the size of 119 nm and were highly stable in salt solution. When the micelles were used as the carrier of cabazitaxel, an antitumor agent for drug-resistant cancers, satisfactory drug loading content and encapsulation efficacy were obtained. In vitro cellular cytotoxicity assays found that cabazitaxel-loaded micelles presented obvious cytotoxicity against taxane-sensitive and -resistant cancer cells. Further in vivo antitumor activity evaluation showed that cabazitaxel-loaded micelles have significantly superior efficacy in inhibiting tumor growth and prolonging survival in tumor-bearing mice compared to that of free paclitaxel and free cabazitaxel.

Novel PEI/Poly-γ-Gutamic Acid Nanoparticles for High Efficient siRNA and Plasmid DNA Co-Delivery

The efficient delivery of sufficient amounts of nucleic acids into target cells is critical for successful gene therapy and gene knockdown. The DNA/siRNA co-delivery system has been considered a promising approach for cancer therapy to simultaneously express and inhibit tumor suppressor genes and overexpressed oncogenes, respectively, triggering synergistic anti-cancer effects. Polyethylenimine (PEI) has been identified as an efficient non-viral vector for transgene expression. In this study, we created a very high efficient DNA/siRNA co-delivery system by incorporating a negatively-charged poly-γ-glutamic acid (γ-PGA) into PEI/nucleic acid complexes. Spherical nanoparticles with about 200 nm diameter were formed by mixing PEI/plasmid DNA/siRNA/γ-PGA (dual delivery nanoparticles; DDNPs) with specific ratio (N/P/C ratio) and the particles present positive surface charge under all manufacturing conditions. The gel retardation assay shows both nucleic acids were effectively condensed by PEI, even at low N/P ratios. The PEI-based DDNPs reveal excellent DNA/siRNA transfection efficiency in the human hepatoma cell line (Hep 3B) by simultaneously providing high transgene expression efficiency and high siRNA silencing effect. The results indicated that DDNP can be an effective tool for gene therapy against hepatoma.

The effect of micelles with random pH-sensitive/hydrophobic structure on the workability, hydration process and microstructure of cement paste

In this study, micelles with pH sensitive/hydrophobic structure efficiently affected the workability, hydration and microstructure of cement paste. The mechanisms are related to the nucleation effect, molecular structure and adsorption of micelles.