pH-responsive Micelles Research Articles

PH-Responsive Micelles Containing Quinine Functionalities Enhance Intracellular Gene Delivery and Expression.

Quinine is a promising building block for creating polymer carriers for intracellular nucleic acid delivery. This is due to its ability to bind to genetic material through intercalation and electrostatic interactions and the balance of hydrophobicity and hydrophilicity dependent on the pH/charge state. Yet, studies utilizing cinchona alkaloid natural products in gene delivery are limited. Herein, we present the incorporation of a quinine functionalized monomer (Q) into block polymer architectures to form self-assembled micelles for highly efficient gene delivery. Q was incorporated into the core and/or the shell of the micelles to introduce the unique advantages of quinine to the system. We found that incorporation of Q into the core of the micelle resulted in acid-induced disassembly of the micelle and a boost in transfection efficiency by promoting endosomal escape. This effect was especially evident in the cancerous cell line, A549, which has a more acidic intracellular environment. Incorporation of Q into the shell of the micelles resulted in intercalative binding to the genetic payload as well as larger micelle-DNA complexes (micelleplexes) from the hydrophobicity of Q in the shell. These factors enable the micelleplexes to be more resistant to serum and have more persistent protein expression post-transfection. Overall, this study is the first to demonstrate the benefits of including quinine functionalities into self-assembled micelles for highly efficient gene delivery and presents a platform for inclusion of other natural products with similar properties into micellar systems.

A Smart CA IX-Targeting and pH-Responsive Nano-Mixed Micelles for Delivery of FB15 with Superior Anti-Breast Cancer Efficacy.

Breast cancer treatment has been a global puzzle, and targeted strategies based on the hypoxic tumor microenvironment (TME) have attracted extensive attention. As a signature transcription factor overexpressed in hypoxia tumor, hypoxia-inducible factor-1 (HIF-1) contribute to cancer progression. Compound 7-(3-(2-chloro-1H-benzo[d]1midazole-1-yl) propoxy)-2-(3,4,5-trime-thoxyphenyl)-4H-chromen-4-one, synthesized and named FB15 in our earlier research, a potential inhibitor of HIF-1α signaling pathway, has been proved a promising drug candidate for many kinds of cancer chemotherapy. However, the poor solubility and undesirable pharmacokinetics of FB15 leads to limited treatment efficacy of tumor, which ultimately restricts its potential clinical applications. Carbonic anhydrase IX (CAIX), a tumor cell transmembrane protein, was overexpressed in hypoxia tumor site. Acetazolamide (AZA), a highly selective ligand targeting CAIX, can be utilized to delivery FB15 to hypoxia tumor site. In this study, we prepared and characterized FB15 loaded nano-mixed micelles with the AZA conjugated poloxamer 188 (AZA-P188) and D-a-Tocopherol Polyethylene 1000 Glycol Succinate (TPGS), denoted as, AZA-P188/TPGS@FB15. Its delivery efficiency in vitro and in vivo was assessed by in vitro drug release, cytotoxicity assay, cellular uptake, and in vivo pharmacokinetics and fluorescence imaging. Finally, therapeutic effect of AZA-P188/TPGS@FB15 was investigated using a preclinical breast cancer subcutaneous graft model in vivo. In vitro studies revealed that AZA-P188/TPGS@FB15 could efficiently target breast cancer cells mediated by CAIX receptor, trigger FB15 release in response to acidic condition, and enhance cellular uptake and cytotoxicity against breast cancer cells. The pharmacokinetic studies showed that FB15-loaded AZA-functionalized micelles exhibited significantly increased AUC0-t over free FB15. In vivo imaging demonstrated that AZA-functionalized micelles significantly increased the drug distribution in the tumor site. In vivo experiments confirmed that AZA-P188/TPGS@FB15 exhibited superior inhibition of tumor growth in nude mice with good biosafety. AZA-P188/TPGS@FB15 hold promise as a potentially effective therapeutic way for breast cancer. Its targeted delivery system utilizing AZA as a carrier shows potential for improving the efficacy of FB15 in cancer therapy.

PH-Responsive Block Copolymer Micelles of Temsirolimus: Preparation, Characterization and Antitumor Activity Evaluation.

Renal cell carcinoma (RCC) is the most common and lethal type of urogenital cancer, with one-third of new cases presenting as metastatic RCC (mRCC), which, being the seventh most common cancer in men and the ninth in women, poses a significant challenge. For patients with poor prognosis, temsirolimus (TEM) has been approved for first-line therapy, possessing pharmacodynamic activities that block cancer cell growth and inhibit proliferation-associated proteins. However, TEM suffers from poor water solubility, low bioavailability, and systemic side effects. This study aims to develop a novel drug formulation for the treatment of RCC. In this study, amphiphilic block copolymer (poly(ethylene glycol) monomethyl ether-poly(beta-amino ester)) (mPEG-PBAE) was utilized as a drug delivery vehicle and TEM-loaded micelles were prepared by thin-film hydration method by loading TEM inside the nanoparticles. Then, the molecular weight of mPEG-PBAE was controlled to make it realize hydrophobic-hydrophilic transition in the corresponding pH range thereby constructing pH-responsive TEM-loaded micelles. Characterization of pH-responsive TEM-loaded nanomicelles particle size, potential and micromorphology while its determination of drug-loading properties, in vitro release properties. Finally, pharmacodynamics and hepatorenal toxicity were further evaluated. TEM loading in mPEG-PBAE increased the solubility of TEM in water from 2.6μg/mL to more than 5 mg/mL. The pH-responsive TEM-loaded nanomicelles were in the form of spheres or spheroidal shapes with an average particle size of 43.83 nm and a Zeta potential of 1.79 mV. The entrapment efficiency (EE) of pH-responsive TEM nanomicelles with 12.5% drug loading reached 95.27%. Under the environment of pH 6.7, the TEM was released rapidly within 12h, and the release rate could reach 73.12% with significant pH-dependent characteristics. In vitro experiments showed that mPEG-PBAE preparation of TEM-loaded micelles had non-hemolytic properties and had significant inhibitory effects on cancer cells. In vivo experiments demonstrated that pH-responsive TEM-loaded micelles had excellent antitumor effects with significantly reduced liver and kidney toxicity. In conclusion, we successfully prepared pH-responsive TEM-loaded micelles. The results showed that pH-responsive TEM-loaded micelles can achieve passive tumor targeting of TEM, and take advantage of the acidic conditions in tumor tissues to achieve rapid drug release.

Preparation and biochemical evaluation of daily-thiosulfinate/polyoxyethylene conjugated pH-responsive micelle with enhanced stability, hydrosolubility and antibacterial properties

Preparation and biochemical evaluation of daily-thiosulfinate/polyoxyethylene conjugated pH-responsive micelle with enhanced stability, hydrosolubility and antibacterial properties

Oligoelectrolyte-mediated, pH-triggered release of hydrophobic drugs from non-responsive micelles: Influence of oligo(2-vinyl pyridine)-loading on drug-loading, release and cytotoxicity

pH-responsive polymeric micelles have been extensively studied for nanomedicine and take advantage of pH differentials in tissues for the delivery of large doses of cytotoxic drugs at specific target sites. Despite significant advances in this area, there is a lack of versatile and adaptable strategies to render micelles pH-responsive that could be widely applied to different payloads and applications. To address this deficiency, we introduce the concept of oligoelectrolyte-mediated, pH-triggered release of hydrophobic drugs from non-responsive polymeric micelles as a highly effective approach with broad scope. Herein, we investigate the influence of the oligoelectrolyte, oligo(2-vinyl pyridine) (OVP), loading and polymer molecular weight on the pH-sensitivity, drug loading/release and cytotoxicity of poly(ethylene glycol-b-ε-caprolactone) (PEG-b-PCL) micelles using copolymers with either short or long hydrophobic blocks (PEG4PCL4 and PEG10PCL10, respectively). The micelles were characterized as a function of pH (7.4 to 3.5). Dynamic light scattering (DLS) revealed narrow particle size distributions (PSDs) for both the blank and OVP-loaded micelles at pH 7.4. While OVP encapsulation resulted in an increase in the hydrodynamic diameter (Dh) (cf. blank micelles), a decrease in the pH below 6.5 led to a decrease in the Dh consistent with the ionization and release of OVP and core collapse, which were further supported by proton nuclear magnetic resonance (1H NMR) spectroscopy and UV–visible (UV–vis) spectrophotometry. The change in zeta potential (ζ) with pH for the OVP-loaded PEG4PCL4 and PEG10PCL10 micelles was different, suggesting that the location/distribution of OVP in the micelles is influenced by the polymer molecular weight. In general, co-encapsulation of drugs (doxorubicin (DOX), gossypol (GP), paclitaxel (PX) or 7-ethyl-10-hydroxycamptothecin (SN38)) and OVP in the micelles proceeded efficiently with high encapsulation efficiency percentages (EE%). In vitro release studies revealed the rapid, pH-triggered release of drugs from OVP-loaded PEG10PCL10 micelles within hours, with higher OVP loadings providing faster and more complete release. In comparison, no triggered release was observed for the OVP-loaded PEG4PCL4 micelles, implying a strong molecular weight dependency. In metabolic assays the drug- and OVP-loaded PEG10PCL10 micelles were found to result in significant enhancement of the cytotoxicity compared to drug-loaded micelles (no OVP) or other controls. Importantly, micelles with low OVP loadings were found to be nearly as effective as those with high OVP loadings. These results provide key insights into the tunability of the oligoelectrolyte-mediated approach for the effective formulation of pH-responsive micelles and pH-triggered drug release.

Hydrophilically-modified poly(ε-caprolactone) with zwitterionic sulfobetaine/tertiary amine and their self-assemblies in water

To achieve hydrophilic modification of poly(ε-caprolactone) (PCL), a series of amphiphilic copolymers, poly(ε-caprolactone)-b-poly(N,N-dimethylaminoethyl methacrylate-co-sulfobetaine methacrylate) (PCDSs), were synthesized with varying sulfobetaine compositions using a three-step synthetic strategy. Firstly, the hydroxyl-terminated polymer, PDMAEMA-OH was synthesized through free radical polymerization using AIBN as an initiator and 2-mercaptoethanol as a chain transfer agent. Subsequently, the block copolymer poly(ε-caprolactone)-b- poly(N,N-dimethylamino ethylmethacrylate) (PCD) was prepared through ring-opening polymerization of PDMAEMA-OH and ε-caprolactone employing Sn(OCt)2 as the catalyst. Finally, zwitterionization of the tertiary amine groups in PCD was achieved by treating it with 1,3-propane sultone (1,3-PS) in THF to obtain the desired PCDSs copolymers. The chemical compositions and the structures of PCDSs were confirmed by 1H nuclear magnetic resonance (1H NMR) spectroscopy and gel permeation chromatography (GPC). Additionally, self-assembly behavior in water was systematically investigated for both PCD and PCDSs copolymers. The results showed that these copolymers could form stable, pH-responsive micelles with diameters less than 150 nm via solvent evaporation method while also exhibiting efficient loading and release capabilities for the anti-tumor drug doxorubicin (DOX). Furthermore, cytotoxicity assay revealed low cell cytotoxicity of PCDS micelles towards L929, HeLa, and MCF-7 cells; however DOX-loaded PCDS micelles (PCDS/DOX), particularly those composed of 47% sulfobetaine content exhibited significant inhibitory effects on HeLa and MCF-7 cells along with enhanced cellular uptake efficiency. These findings highlight that pH-responsive zwitterionic sulfobetaine-based polymeric micelles derived from the PCDSs hold great promise for effective DOX delivery.

Pharmacokinetic-Pharmacodynamic Analysis of pH-Responsive Doxorubicin-Releasing Micelles with Anticancer Activity.

This study aimed to investigate the effect of in vivo pH-responsive doxorubicin (DOX) release and the targetability of pilot molecules in folic acid (FA)-modified micelles using a pharmacokinetic-pharmacodynamic (PK-PD) model. The time profiles of intratumoral DOX concentrations in Walker256 tumor-bearing rats were monitored using a microdialysis probe, followed by compartmental analysis, to evaluate intratumoral tissue pharmacokinetics. Maximal DOX was released from micelles 350 min after the administration of pH-responsive DOX-releasing micelles. However, FA modification of the micelles shortened the time to peak drug concentration to 150 min. Additionally, FA modification resulted in a 27-fold increase in the tumor inflow rate constant. Walker256 tumor-bearing rats were subsequently treated with DOX, pH-responsive DOX-releasing micelles, and pH-responsive DOX-releasing FA-modified micelles to monitor the tumor growth-time profiles. An intratumoral threshold concentration of DOX (55-64 ng/g tumor) was introduced into the drug efficacy compartment to construct a PD model, followed by PK-PD analysis of the tumor growth-time profiles. Similar results of threshold concentration and drug potency of DOX were obtained across all three formulations. Cell proliferation was delayed as the drug delivery ability of DOX was improved. The PK model, which was developed using the microdialysis method, revealed the intratumoral pH-responsive DOX distribution profiles. This facilitated the estimation of intratumoral PK parameters. The PD model with threshold concentrations contributed to the estimation of PD parameters in the three formulations, with consistent mechanisms observed. We believe that our PK-PD model can objectively assess the contributions of pH-responsive release ability and pilot molecule targetability to pharmacological effects.

Efficient Strategy to Synthesize Tunable pH-Responsive Hybrid Micelles Based on Iron Oxide and Gold Nanoparticles.

The preparation of multifunctional nanomaterials based on inorganic nanoparticles with organic materials has emerged as a promising strategy for the development of new nanomedicines for in vitro and in vivo biomedical applications. Here, we synthesized pH-responsive hybrid inorganic micelles by combining a novel pH-responsive amphiphilic molecule with hydrophobic payloads. This amphiphile was synthesized in a one-pot reaction and self-assembled readily into micelles under acidic pH conditions. In the presence of hydrophobic NP payloads such as AuNPs or IONPs, the amphiphile self-organized around them through hydrophobic interactions, resulting in the formation of colloidally stable hybrid micelles. The size of the hydrophobic NPs determined the pH-response of the inorganic hybrid micelles, which is tuned from pH 7 to 11 for our pH-responsive amphiphilic molecule. This achievement represents a novel approach for the synthesis of tunable pH-responsive hybrid micelles based on inorganic NPs for biomedical imaging, hyperthermia treatment, and also drug delivery nanosystems.

Rheological modulation of a pH-responsive wormlike micelle driven by charge and cosurfactant

Responsive wormlike micelles are intriguing systems capable of transitioning their viscosity from that of water to a gel-like state in response to external stimuli such as pH changes. Referred to as “smart wormlike micelles”, these structures offer the unique ability to adapt their viscosity for specific applications. In this study, we explored the rheological behavior of smart wormlike micelles formed by combining a cationic surfactant, Cetyltrimethylammonium bromide (C16TAB) with phthalic acid. The aromatic nature of phthalic acid, featuring two pKas at 2.9 and 4.5, provides control over the system's pH, enabling adjustments in the fraction of neutral, anionic, or dianionic species and thereby modulating the micellar rheology. The partitioning of phthalic acid between the micelle palisade and bulk solution plays a crucial role in inducing the formation of wormlike micelles by influencing curvature changes of the aggregate. This partitioning behavior is intricately governed by the balance between charge and hydrophobicity of the aromatic molecule. The investigation spanned a wide pH range, encompassing various concentrations of C16TAB and phthalic acid. Cryo-TEM imaging allowed direct characterization of distinct aggregate types formed at different pH levels. Additionally, to minimize electrostatic repulsion between cationic micellar heads in wormlike micelles, long alkyl alcohols were introduced as cosurfactants, enabling the exploration of synergistic effects at the micelle interface.

Molecular origin for pH-responsive wormlike micelles of zwitterionic surfactants triggered by aromatic acid derivatives

Introduction of aromatic acid derivatives (AADs) into zwitterionic surfactants is an efficient method to prepare wormlike micelles with pH-controllable viscosity; however, the coincident molecular origin of AAD/zwitterionic surfactant binary mixtures remains unclear. Herein, the self-assembly of hydroxyl derivatives of benzoic acid (BA) and cetyldimethyl betaine (BS-16) mixtures in water was systematically assessed, and various factors, such as the molecular structure, molar ratio of AAD and BS-16, and solution pH, were investigated. The structure–property relationship of AAD/BS-16 binary mixtures was established, which provided the molecular origin for the effect of AAD on micellar microstructures and the pH-induced morphological transitions. The ortho-substituted hydroxyl moiety in the BA molecule facilitated the formation of larger wormlike micelles, whereas the effect of the meta-substituted moiety was less significant. The para-substituted hydroxyl moiety in BA did not favor micellar growth. This moiety exhibited similar characteristics to the increasing hydroxyl moiety number in the AAD molecules or solution pH where the negative effects of steric hindrance and electrostatic interactions of molecules in micelles are dominant.

Preparation of pH-responsive polyurethane nano micelles and their antibacterial application

Considering the differences in pH between bacterial infection microenvironment and normal tissues, a series of pH-responsive drug-release amphiphilic polyurethane copolymers (DPU-g-PEG) have been prepared in this work. Fourier transform infrared (FT-IR) spectroscopy and 1H NMR was selected to detect the structure of the condensed polymers. The DPU-g-PEG amphiphilic copolymers could form stable micelles with a hydrophilic shell of polyethylene glycol (PEG) and a hydrophobic core of polylactic acid (PLA). We loaded a model drug called triclosan onto DPU-g-PEG micelles and studied how pH affects their particle size, Zeta potential, and drug release performance. The results revealed that when exposed to acidic conditions, the surface potential of DPU-g-PEG micelles changed, the micelles’ particle size increased, and the drug release performance was significantly enhanced. These results suggested that the micelles prepared in this study can release more antibacterial substances at sites of bacterial infection. Meanwhile, we also investigated the impact of different ratios of soft and hard segments on the properties of micelles, and the results showed that the pH responsiveness of micelles was strongest when the ratio of soft segments (PLLA diol + PEG 2000): 1,6-hexamethylene diisocyanate (HDI): 2,6-Bis-(2-hydroxy-ethyl)-pyrrolo[3,4-f]isoindole-1,3,5,7-tetraone (DMA) = 1: 1.2: 0.2. Furthermore, the results of inhibition zone test, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) all confirmed the antibacterial activity of triclosan-load DPU-g-PEG micelles. In conclusion, the DPU-g-PEG micelles produced in this study have the potential to be used as intelligent drug delivery systems in the biomedical field.

Effect of zwitterionic sulfobetaine incorporation on blood behaviours, phagocytosis, and in vivo biodistribution of pH-responsive micelles with positive charges.

pH-responsive micelles with positive charges are challenged by their significant effect on the cells/proteins and compromise their final fate due to electrostatic interactions. As one of the promising strategies, zwitterion incorporation in micelles has attracted considerable attention and displayed improved protein adsorption and blood circulation performances. However, previous reports in this field have been mostly limited in hemolysis for studying blood behaviour and lack a comprehensive understanding of their interactions with blood components. Herein, we present a prelimilary study on the effect of zwitterionic sulfobetaine incorporation on blood behaviour, phagocytosis, and in vivo biodistribution of pH-responsive micelles with positive charges. Amphiphilic triblock copolymers, namely poly(ε-caprolactone)-b-poly(N,N-diethylaminoethyl methacrylate)-(N-(3-sulfopropyl-N-methacryloxyethy-N,N-diethylammonium betaine)) (PCL-PDEAPSx, x = 2, 6, 10), containing different numbers of sulfobetaine groups were synthesized through four steps to prepare the pH-responsive micelles with positive charges. The effect of the sulfobetaine incorporation displayed different profiles, e.g., the micelles had no effect on RBC aggregation, thrombin time (TT), and platelet aggregation, while the cytotoxicity, hemolysis, RBC deformability, activated partial thromboplastin time (APTT), prothrombin time (PT), platelet activation, protein (albumin, fibrinogen, plasma) adsorption, phagocytosis, and in vivo biodistribution decreased with the increase in the sulfobetaine number, in which the transition mainly occurred at a sulfobetaine/tertiary amine group ratio of 3/7-1/1 compared to that of the mPEG control. In addition, the micelles displayed a strong inhibitory effect on the intrinsic coagulation pathway, which was associated with a significant decrease in the coagulation factor activity. Based on these findings, the related mechanism is discussed and proposed, which can aid the rational design of pH-responsive micelles for improved therapeutics.

Therapeutic effect and metabolic fingerprinting of triple-negative breast cancer cells following exposure to a novel pH-responsive, gambogic acid-loaded micelle

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis and lacks effective therapeutic targets. The use of gambogic acid (GA), a class of active ingredients in traditional Chinese medicine with anti-tumour potential, is limited in tumour therapy owing to its drawbacks and unclear organ toxicity. In this study, we used the pH-responsive amphiphilic block copolymer, PEOz-PCL, to create nanodrugs for GA delivery to MDA-MB-231 cells. The pH-responsive GA-loaded micelles were prepared through nanoprecipitation with a more homogeneous size. The average particle size was 42.29 ± 1.74 nm, and the zeta potential value was 9.88 ± 0.17 mV. The encapsulation rate was 85.06%, and the drug loading rate was 10.63%. The process was reproducible, and sustained release reached 80% in 96 h at acid pH 5.0. Furthermore, cellular tests using CCK-8, TUNEL, and flow cytometry revealed that pH-responsive GA-loaded micelles killed MDA-MB-231 cells more effectively and had much higher activity and targeting compared with free drugs. Metabolomic analysis of the changes in differential metabolites revealed that pH-responsive GA-loaded micelles may inhibit TNBC cells by causing amino acid anabolism, nucleotide metabolism, and glucose metabolism, as well as by affecting their energy sources. The study outcomes will help understand the mechanism of action and the therapeutic efficacy of pH-responsive GA-loaded micelles in vivo.

Co-delivering irinotecan and imiquimod by pH-responsive micelle amplifies anti-tumor immunity against colorectal cancer

Irinotecan (IRT), a classic clinical chemotherapeutic agent for treating colorectal cancer, has been found to induce immunogenic cell death (ICD) while exerting cytotoxicity in tumor cells. This effect is likely to be amplified in combination with immune modulators. Unfortunately, free drugs without targeting capacity would receive poor outcomes and strong side effects. To address these issues, in this work, an acid-sensitive micelle based on an amphiphilic poly(β-amino ester) derivative was constructed to co-deliver IRT and the immune adjuvant imiquimod (IMQ), termed PII. PII kept stable under normal physiological conditions. After internalization by tumor cells, PII dissociated in acidic lysosomes and released IRT and IMQ rapidly. In the CT26 tumor mouse model, PII increased the intra-tumoral SN38 (the active metabolite of IRT) and IMQ concentrations by up to 9.39 and 3.44 times compared with the free drug solution. The tumor inhibition rate of PII achieved 87.29%. This might profit from that IRT induced ICD, which promoted dendritic cells (DCs) maturation and intra-tumoral infiltration of CD8+ T cells. In addition, IMQ enhanced the antigen presenting ability of DCs and stimulated tumor associated macrophages to secrete tumor-killing cytokines. PII provided an effective strategy to combat colorectal cancer by synergy of chemotherapy and immunoregulation.

A novel pH-responsive wormlike micelles combinated sodium dodecyl sulfate (SDS) and diethylenetriamine (DETA) based on noncovalent electrostatic interaction

pH-Responsive wormlike micelles (WLMs) have attracted lots of attention due to their abundant advantages, for example, ease of adjustment and strong reversibility. We have learned that the degree of protonation of diethylenetriamine (DETA) varies with pH, and the anionic sodium dodecyl sulfate (SDS) can connect with cationic groups. Inspired by this, a novel pH-responsive WLMs was prepared based on noncovalent electrostatic interaction with sodium dodecyl sulfate (SDS) and DETA at a molar ratio of 3:1. Properties of the SDS/DETA system were assessed from the aspects of rheology, macro-morphology, aggregates diameter, and micro-morphology. When the pH decreased from 9.98 to 6.80, the SDS/DETA system represented as a weak gel with the viscosity increasing from 7.6 mPa s to 1.4 × 103 mPa·s and the average hydrodynamic radius increasing from 5.6 to 91.3 nm. The phenomenon is attributed to the protonation of DETA when reducing the pH and the formation of WLMs based on electrostatic interaction between DETA and SDS. However, when pH was further reduced by adding HCl, the SDS/DETA system would reach its isoelectric point, thus the solution became turbid with low viscosity. The SDS/DETA solution represents excellent reversibility (at least three cycles) in viscoelasticity by adjusting the pH value, and such pH-responsive WLM holds significant potential for broader applications in biomedical, oilfield chemistry, and other fields.

PH-responsive intermediary layer cross-linked micelles from zwitterionic triblock copolymers and investigation of their drug-release behaviors.

ABC-type triblock copolymers, namely poly[(ethylene glycol)methyl ether]-block-poly(tert-butyl methacrylate)-block-poly[2-N-(diisopropylamino)ethyl methacrylate] (MPEG-b-PBuMA-b-PDPA), were first synthesized and then the middle blocks were successfully converted into poly(methacrylic acid) to obtain MPEG-b-PMAA-b-PDPA zwitterionic triblock copolymers. These block copolymers were soluble in water and formed micellar aggregates with complex cores via hydrogen bonding interactions between MPEG and PMAA blocks below pH 4.0. When the pH was between 5.0 and 7.0, due to charge compensation between partially protonated PDPA and partially ionized PMAA blocks, micelles with polyion complex cores were observed. If the solution pH was above 8.0, deprotonation of tertiary amine groups provided a hydrophobic character to the PDPA block, which resulted in the formation of PDPA-core micelles while MPEG/anionic PMAA hybrid blocks formed hydrated coronas. Intermediary layer cross-linked (ILCL) micelles from PDPA-core micelles were also prepared by cross-linking the inner PMAA shell. The hydrophobic drug dipyridamole (DIP) was used to investigate the release profile of ILCL micelles. DIP can be loaded to the PDPA cores of the micelles in basic aqueous media. An increase in the degree of cross-linking causes slower release for the model drug. It was concluded that the more complex matrix formation in the intermediary layer of the micelles via cross-linking retards the drug release from the core.

PH-responsive wormlike micelles formed by an anionic surfactant derived from erucic acid

An erucic acid-based anionic surfactant, AdEr, was synthesized by a simple neutralization reaction, and AdEr constructed a novel pH-responsive wormlike micellar viscoelastic system in the presence of potassium chloride (KCl). The viscoelasticity and pH-responsiveness of the pH-responsive wormlike micelles have been investigated using rheology, and its corresponding mechanism has been analyzed by Fourier transform infrared (FT-IR) spectra. The zero-shear viscosity (η0) of the AdEr/KCl system dramatically increases by 5 orders of magnitude as the pH increases from 6 to 10. The viscoelastic fluids and dispersion system with white precipitate can be converted by tuning the pH between 10.46 and 6.03, and the corresponding aggregates also transform between wormlike micelles and spherical micelles. Furthermore, by directly adding acid and alkali, the AdEr/KCl system can be precisely reversibly controlled in the pH range 6–10, and the viscosity stays unchanged after three reversible cycles, exhibiting strong pH reversibility. The pH-responsive behavior can be attributed to the manipulation of carboxylic acid protonation. This study promotes new applications of erucic acid resources in smart viscoelastic solutions.

Schiff-linked prodrugs of pH-responsive nanoparticles to facilitate drug delivery

Endosomal pH-responsive micelle nanoparticles were prepared by self-assembly of amphiphilic polyethylene glycol Schiff-doxorubicin (PEG-Schiff-DOX) precursor drugs. The free DOX could be encapsulated in the hydrophobic core of the nanoparticles. These nanoparticles exhibited decompose rapidly in weakly acidic environments, but can keep excellent storage stability under normal conditions. Due to the differences in drug release mechanisms and rates between encapsulated DOX and linked DOX, programmed drug release behavior was observed, which may result in higher intracellular drug concentrations and longer duration of action.CCK-8 analysis showed that the nanoparticles showed better antitumor activity than free DOX. These nanomedicines based on precursor drugs have great potential for the development of transformational DOX agents for cancer therapy.

PH-Sensitive Polymeric Nanoparticles for Effective Delivery of Doxorubicin

pH-responsive micelles beam nanoparticles were created using the self-assembly of PEG-Shiff-DOX medication. Under normal circumstances, these nanoparticles have great storage stability for more than a week, however they will degrade fast in a weak acidic environment. We saw a process-dependent drug release behaviour. This could lead to higher intracellular drug concentrations and a more sustained effect. The anti-tumor efficacy of nanoparticles on HeLa cells is superior to that of free DOX, according to the CCK-8 analysis. The potential for creating conversion DOX formulations for the treatment of cancer with these pre-drug-based nano-drugs is enormous.

PH-responsive polyzwitterion covered nanocarriers for DNA delivery

The success of gene therapy relies on gene nanocarriers to achieve therapeutic effects in vivo. Surface shielding of poly(ethylene glycol) (PEG), known as PEGylation, onto gene delivery carriers is a predominant strategy for extending blood circulation and improving therapeutic outcomes in vivo. Nevertheless, PEGylation frequently compromises the transfection efficiency by decreasing the interactions with the cellular membrane of the targeted cells, thereby preventing the cellular uptake and the subsequent endosomal escape. Herein, we developed a stepwise pH-responsive polyplex micelle for the plasmid DNA delivery with the surface covered by ethylenediamine-based polycarboxybetaines. This polyplex micelle switched its surface charge from neutral at pH 7.4 to positive at tumorous and endo−/lysosomal pH (i.e., pH 6.5 and 5.5, respectively), thus enhancing the cellular uptake and facilitating the endosomal escape toward efficient gene transfection. Additionally, the polyplex micelle demonstrated prolonged blood circulation as well as enhanced tumor accumulation, leading to highly effective tumor growth suppression by delivering an antiangiogenic gene. These results suggest the usefulness of a pH-responsive charge-switchable shell polymer on the surface of the polyplex micelle for the efficient nucleic acid delivery.