Optimizing long-term stability of siRNA using thermoassemble ionizable reverse pluronic-Bcl2 micelleplexes

Thermosassemble Ionizable Reverse Pluronic (TIRP) platform stands out for its distinctive combination of thermoassemble and ionizable features, effectively overcoming challenges in previous siRNA delivery systems. This study opens up a formation for long-term stabilization, and high loading of siRNA, specifically crafted for targeting oncogenic pathways. TIRP-Bcl2 self-assembles into a unique micelle structure with a nanodiameter of 75.8 ± 5.7 nm, efficiently encapsulating Bcl2 siRNA while maintaining exceptional colloidal stability at 4 °C for 8 months, along with controlled release profiles lasting 180 h. The dual ionizable headgroup enhance the siRNA loading and the revers pluronic unique structural orientation enhance the stability of the siRNA. The thermoassemble of TIRP-Bcl2 facilitates flexi-rigid response to mild hyperthermia, enhancing deep tissue penetration and siRNA release in the tumor microenvironment. This responsive behavior improves intracellular uptake and gene silencing efficacy in cancer cells. TIRP, with its smaller particle size and reverse pluronic nature, efficiently transports siRNA across the blood-brain barrier, holding promise for revolutionizing glioblastoma (GBM) treatment. TIRP-Bcl2 shows significant potential for precise, personalized therapies, promising prolonged siRNA delivery and in vitro/in vivo stability. This research opens avenues for further exploration and clinical translation of this innovative nanocarrier system across different cancers.

FRET-based analysis on the structural stability of polymeric micelles: Another key attribute beyond PEG coverage and particle size affecting the blood clearance

Various attributes of micelles, such as PEG density and particle size, are considered to be related to blood clearance. The structural stability of micelles is another key attribute that will affect the in vivo fate. This study employed fluorescence resonance energy transfer (FRET) analysis to guide the preparation of polymeric micelles with different structural stability. Micelles prepared using copolymers with longer hydrophobic blocks showed higher structural stability; emulsification was a better method than nanoprecipitation to prepare stable micelles. The fast chain exchange kinetics and the high-water content of micellar cores explained the low structural stability of those micelles. Moreover, this study highlighted the importance of structural stability that affected blood clearance in concert with PEG length and particle size. One-third of the small and stable micelles were detected in the blood 24 h after injection. While unstable micelles would be cleared from the circulation within 4 h. Notably, there would be a threshold of structural stability. Micelles with structural stability below this threshold were quickly cleared even if they possessed a longer PEG length and a smaller size. In contrast, higher structural stability allowed polymeric micelles to maintain higher integrity in vivo and enhance tumor accumulation and anti-tumor efficacy. In conclusion, this study systematically analyzed the importance of the structural stability of micelles on the in vivo fate.

Determination of the critical micelle concentration of surfactants using fluorescence strategies

The increasing importance of surfactants in various fields has led to growing interest in the comprehensive characterization of surfactants. The critical micelle concentration (CMC), the most fundamental property of surfactants, is a parameter that must be measured. In particular, with the continuous expansion of the molecular structure of surfactants, numerous novel amphiphilic molecules have been developed that are capable of forming ordered aggregates in various solvent systems. Fluorescence spectroscopy, based on the differences in fluorescence intensity and wavelength of the fluorescent probe in the solvent phase and micellar phase, can sensitively detect the CMC of surfactants. This review aims to summarize the various fluorescence methods used to determine the CMC, including aggregation-induced emission (AIE), excimer formation, intramolecular charge transfer (ICT), and other miscellaneous strategies. The difficulties and limitations in the CMC determination process are also described. Further suggestions are provided to guide the existing fluorescence probes and the corresponding fluorescence methods to detect critical aggregation concentrations of amphiphilic molecules.

A Novel Study on the Self-Assembly Behavior of Poly(lactic-co-glycolic acid) Polymer Probed by Curcumin Fluorescence

Understanding the self-assembly behavior of block copolymers is of great importance due to their usefulness in a wide range of applications. In this work, the physical properties of poly(lactic-co-glycolic acid) (PLGA polymer) are studied for the first time in solution using the fluorescence technique and curcumin as a molecular probe. First, curcumin at a concentration of 2 μM was added to different concentrations of PLGA, and the fluorescence of curcumin was tracked. It was found that the critical micellar concentration (CMC) was equal to 0.31 g/L and the critical micellar temperature (CMT) was obtained to be 25 °C. Furthermore, an insight on the effect of NaCl salt on the CMC value of PLGA is assessed through curcumin probing. A decrease in the CMC has been observed with the increase in the concentration of NaCl, which could be due to the salting out effect. Moreover, in order to understand the aggregation behavior of PLGA in different solutions, CMC experiments were investigated using chloroform as a solvent. Results showed that the solvent does not affect the CMC value of the polymer; however, it only affects the shape of the obtained micelle forming a reversed micelle. Finally, fluorescence quenching of curcumin with hydrophobic cetyl-pyridinium bromide (CPB) and hydrophilic KI quenchers was established, where it was proved that curcumin is located near the hydrophobic pocket of the Stern layer of the PLGA micelle.

Fabrication of reversible pH-responsive aggregation-induced emission luminogens assisted by a block copolymer via a dynamic covalent bond

Aggregated induced emission (AIE) molecules with stimuli-responsive properties have attracted increasing attention for many applications.

CO2-Responsive Nano-Objects with Assembly-Related Aggregation-Induced Emission and Tunable Morphologies

CO₂-responsive polymeric nano-objects with assembly-related aggregation-induced emission (AIE) are obtained via polymerization-induced self-assembly (PISA) of 2-(dimethylamino)ethyl methacrylate (DMAEMA), 2-(4-formylphenoxy)ethyl methacrylate (MAEBA), and 4-(1,2,2-triphenylvinyl)phenyl methacrylate (TPEMA). These nano-objects exhibit, depending on the feed of MAEBA, a morphology evolution process from spherical micelles to vesicles. Due to the presence of DMAEMA units, CO₂ promotes morphology transformation of the nano-objects from spheres to a mixture of "jellyfish" and vesicles and vesicles to complex vesicles. Moreover, TPEMA endows the AIE feature to these nano-objects, offering a strategy to monitor the morphology evolution process in real time. Thus, this approach is significant for exploring the assembly mechanism of copolymer in polymerization-induced self-assembly and designing multistimuli-responsive polymeric nanomaterials with tunable morphologies and sizes.

Glutathione-Priming Nanoreactors Enable Fluorophore Core/Shell Transition for Precision Cancer Imaging

In an attempt to develop an imaging probe with ultra-high sensitivity for a broad range of tumors in vivo and inspired by the concept of chemical synthetic nanoreactors, we designed a type of glutathione-priming fluorescent nanoreactor (GPN) with an albumin-coating shell and hydrophobic polymer core containing disulfide bonds, protonatable blocks, and indocyanine green (ICG), a near-infrared fluorophore. The albumin played multiple roles including biocompatible carriers, hydrophilic stabilizer, "receptor" of the fluorophores, and even targeting molecules. The protonation of the hydrophobic core triggered the outside-to-core transport of acidic glutathione (GSH), as well as the core-to-shell transference of ICGs after the disulfide bond cleavage by GSH, which induced strong binding of fluorophores with albumins on the GPN shell, initiating intensive fluorescence signals. As a result, the GPNs demonstrated extremely high response sensitivity and imaging contrast, proper time window, and broad cancer specificity. In fact, an orthogonal activation pattern was found in vitro with an ON/OFF ratio up to 24.7-fold. Furthermore, the nanoprobes specifically amplified the tumor signals in five cancer-bearing mouse models and actualized tumor margin delineation with a contrast up to 20-fold, demonstrating much better imaging efficacy than the other four commercially available probes. Therefore, the GPNs provide a new paradigm in developing high-performance bioresponsive nanoprobes.

A Transformable Chimeric Peptide for Cell Encapsulation to Overcome Multidrug Resistance

Multidrug resistance (MDR) remains one of the biggest obstacles in chemotherapy of tumor mainly due to P-glycoprotein (P-gp)-mediated drug efflux. Here, a transformable chimeric peptide is designed to target and self-assemble on cell membrane for encapsulating cells and overcoming tumor MDR. This chimeric peptide (C₁₆ -K(TPE)-GGGH-GFLGK-PEG₈ , denoted as CTGP) with cathepsin B-responsive and cell membrane-targeting abilities can self-assemble into nanomicelles and further encapsulate the therapeutic agent doxorubicin (termed as CTGP@DOX). After the cleavage of the Gly-Phe-Leu-Gly (GFLG) sequence by pericellular overexpressed cathepsin B, CTGP@DOX is dissociated and transformed from spherical nanoparticles to nanofibers due to the hydrophilic-hydrophobic conversion and hydrogen bonding interactions. Thus obtained nanofibers with cell membrane-targeting 16-carbon alkyl chains can adhere firmly to the cell membrane for cell encapsulation and restricting DOX efflux. In comparison to free DOX, 45-time higher drug retention and 49-fold greater anti-MDR ability of CTGP@DOX to drug-resistant MCF-7R cells are achieved. This novel strategy to encapsulate cells and reverse tumor MDR via morphology transformation would open a new avenue towards chemotherapy of tumor.

A supramolecular fluorescent vesicle based on a coordinating aggregation induced emission amphiphile: insight into the role of electrical charge in cancer cell division

Binding of Zn²⁺ to the coordinating supramolecular vesicle based on an aggregation induced emission amphiphile TPE-BPA immediately triggers the formation of charged vesicles. This induces vesicle fission and fluorescence reduction, suggesting a looser molecular packing in the charged vesicle membrane. Since cancer cells are highly charged, this indicates that the quick fission of cancer cells may have electrical charge origin.

Aggregation enhanced excimer emission (AEEE) of benzo[ghi]perylene and coronene: multimode probes for facile monitoring and direct visualization of micelle transition

Excimer to monomer transition of multimode probes facilitating the accurate monitoring and direct visualization of monomer–micelle transition.

A novel aggregation-induced emission enhancement triggered by the assembly of a chiral gelator: from non-emissive nanofibers to emissive micro-loops

A novel aggregation-induced emission enhancement triggered by chiral self-assembled superstructures has been developed in this work.

Self-Assembly and Critical Aggregation Concentration Measurements of ABA Triblock Copolymers with Varying B Block Types: Model Development, Prediction, and Validation

The dissipative particle dynamics (DPD) simulation technique is a coarse-grained (CG) molecular dynamics-based approach that can effectively capture the hydrodynamics of complex systems while retaining essential information about the structural properties of the molecular species. An advantageous feature of DPD is that it utilizes soft repulsive interactions between the beads, which are CG representation of groups of atoms or molecules. In this study, we used the DPD simulation technique to study the aggregation characteristics of ABA triblock copolymers in aqueous medium. Pluronic polymers (PEG-PPO-PEG) were modeled as two segments of hydrophilic beads and one segment of hydrophobic beads. Tyrosine-derived PEG5K-b-oligo(desaminotyrosyl tyrosine octyl ester-suberate)-b-PEG5K (PEG5K-oligo(DTO-SA)-PEG5K) block copolymers possess alternate rigid and flexible components along the hydrophobic oligo(DTO-SA) chain, and were modeled as two segments of hydrophilic beads and one segment of hydrophobic, alternate soft and hard beads. The formation, structure, and morphology of the initial aggregation of the polymer molecules in aqueous medium were investigated by following the aggregation dynamics. The dimensions of the aggregates predicted by the computational approach were in good agreement with corresponding results from experiments, for the Pluronic and PEG5K-oligo(DTO-SA)-PEG5K block copolymers. In addition, DPD simulations were utilized to determine the critical aggregation concentration (CAC), which was compared with corresponding results from an experimental approach. For Pluronic polymers F68, F88, F108, and F127, the computational results agreed well with experimental measurements of the CAC measurements. For PEG5K-b-oligo(DTO-SA)-b-PEG5K block polymers, the complexity in polymer structure made it difficult to directly determine their CAC values via the CG scheme. Therefore, we determined CAC values of a series of triblock copolymers with 3-8 DTO-SA units using DPD simulations, and used these results to predict the CAC values of triblock copolymers with higher molecular weights by extrapolation. In parallel, a PEG5K-b-oligo(DTO-SA)-b-PEG5K block copolymer was synthesized, and the CAC value was determined experimentally using the pyrene method. The experimental CAC value agreed well with the CAC value predicted by simulation. These results validate our CG models, and demonstrate an avenue to simulate and predict aggregation characteristics of ABA amphiphilic triblock copolymers with complex structures.

Fabrication of amphiphilic fluorescent nanoparticles with an AIE feature via a one-pot clickable mercaptoacetic acid locking imine reaction: synthesis, self-assembly and bioimaging

Water dispersible and non-toxic AIE active fluorescent organic nanoparticles were fabricatedviaa one-pot clickable mercaptoacetic acid locking imine reaction.

Single-wavelength-controlled in situ dynamic super-resolution fluorescence imaging for block copolymer nanostructures via blue-light-switchable FRAP

A blue-light-switchable fluorophore enables single-wavelength controlledin situdynamic super-resolution imaging of block copolymers.

Manipulation of the aggregation and deaggregation of tetraphenylethylene and silole fluorophores by amphiphiles: emission modulation and sensing applications

In this Feature Article, we have summarized the recent advances in the fluorescence modulation of tetraphenylethylene and silole fluorophores by manipulating the respective aggregation/deaggregation with amphiphiles. These include (i) the assembly of neutral tetraphenylethylene analogues with the aid of an ionic amphiphile, (ii) the aggregation of ionic tetraphenylethylene and silole induced by amphiphiles, and (iii) bio/chemosensors based on the aggregation/deaggregation of AIE fluorophores tuned by ionic amphiphiles.