Fluorescent Block Copolymer Micelles That Can Self-Report on Their Assembly and Small Molecule Encapsulation

Förster resonance energy transfer within single chain nanoparticles

Single chain nanoparticles (SCNPs) are a highly versatile polymer architecture consisting of single polymer chains that are intramolecularly crosslinked. Currently, SCNPs are discussed as powerful macromolecular architectures for catalysis, delivery and sensors. Herein, we introduce a methodology based on Förster Resonance Energy Transfer (FRET) to evidence the folding of single polymer chains into SCNPs via fluorescence readout. We initially introduce a molecular FRET pair based on a bimane and nitrobenzoxadiazole (NBD) moiety and study its fluorescence properties in different solvents. We subsequently construct a low dispersity polymer chain carrying NBD units, while exploiting the bimane units for intramolecular chain collapse. Upon chain collapse and SCNP formation - thus bringing bimane and NBD units into close proximity - the SCNPs report their folded state by a strong and unambiguous FRET fluorescence signal. The herein introduced reporting of the folding state of SCNPs solely relies on an optical readout, opening avenues to monitoring SCNP folding without recourse to complex analytical methodologies.

Structural Determinants of Stimuli-Responsiveness in Amphiphilic Macromolecular Nano-assemblies

Stimuli-responsive nano-assemblies from amphiphilic macromolecules could undergo controlled structural transformations and generate diverse macroscopic phenomenon under stimuli. Due to the controllable responsiveness, they have been applied for broad material and biomedical applications, such as biologics delivery, sensing, imaging, and catalysis. Understanding the mechanisms of the assembly-disassembly processes and structural determinants behind the responsive properties is fundamentally important for designing the next generation of nano-assemblies with programmable responsiveness. In this review, we focus on structural determinants of assemblies from amphiphilic macromolecules and their macromolecular level alterations under stimuli, such as the disruption of hydrophilic-lipophilic balance (HLB), depolymerization, decrosslinking, and changes of molecular packing in assemblies, which eventually lead to a series of macroscopic phenomenon for practical purposes. Applications of stimuli-responsive nano-assemblies in delivery, sensing and imaging were also summarized based on their structural features. We expect this review could provide readers an overview of the structural considerations in the design and applications of nanoassemblies and incentivize more explorations in stimuli-responsive soft matters.

Fluorescence-readout as a powerful macromolecular characterisation tool

The last few decades have witnessed significant progress in synthetic macromolecular chemistry, which can provide access to diverse macromolecules with varying structural complexities, topology and functionalities, bringing us closer to the aim of controlling soft matter material properties with molecular precision. To reach this goal, the development of advanced analytical techniques, allowing for micro-, molecular level and real-time investigation, is essential. Due to their appealing features, including high sensitivity, large contrast, fast and real-time response, as well as non-invasive characteristics, fluorescence-based techniques have emerged as a powerful tool for macromolecular characterisation to provide detailed information and give new and deep insights beyond those offered by commonly applied analytical methods. Herein, we critically examine how fluorescence phenomena, principles and techniques can be effectively exploited to characterise macromolecules and soft matter materials and to further unravel their constitution, by highlighting representative examples of recent advances across major areas of polymer and materials science, ranging from polymer molecular weight and conversion, architecture, conformation to polymer self-assembly to surfaces, gels and 3D printing. Finally, we discuss the opportunities for fluorescence-readout to further advance the development of macromolecules, leading to the design of polymers and soft matter materials with pre-determined and adaptable properties.

Surfactant Micellar and Vesicle Microenvironments and Structures under Synthetic Organic Conditions

Fluorescence lifetime imaging microscopy (FLIM) reveals vesicle sizes, structures, microenvironments, reagent partitioning, and system evolution with two chemical reactions for widely used surfactant-water systems under conditions relevant to organic synthesis, including during steps of Negishi cross-coupling reactions. In contrast to previous investigations, the present experiments characterize surfactant systems with representative organohalide substrates at high concentrations (0.5 M) that are reflective of the preparative-scale organic reactions performed and reported in water. In the presence of representative organic substrates, 2-iodoethylbenzene and 2-bromo-6-methoxypyridine, micelles swell into emulsion droplets that are up to 20 μm in diameter, which is 3-4 orders of magnitude larger than previously measured in the absence of an organic substrate (5-200 nm). The partitioning of reagents in these systems is imaged through FLIM─demonstrated here with nonpolar, amphiphilic, organic, basic, and oxidative-addition reactive compounds, a reactive zinc metal powder, and a palladium catalyst. FLIM characterizes the chemical species and/or provides microenvironment information inside micelles and vesicles. These data show that surfactants cause surfactant-dictated microenvironments inside smaller micelles (<200 nm) but that addition of a representative organic substrate produces internal microenvironments dictated primarily by the substrate rather than by the surfactant, concurrent with swelling. Addition of a palladium catalyst causes the internal environments to differ between vesicles─information that is not available through nor predicted from prior analytical techniques. Together, these data provide immediately actionable information for revising reaction models of surfactant-water systems that underpin the development of sustainable organic chemistry in water.

Imaging Block-Selective Copolymer Solvation

Understanding individual-block solvation in self-assembled block copolymer systems is experimentally difficult, but this solvation underpins the assembly and disassembly observed at the bulk scale. Here, covalently attached viscosity-sensitive molecular rotors for fluorescence lifetime imaging microscopy uncover and quantitatively elucidate previously undisclosed differential block-selective responses toward solvation changes upon addition of DMSO and THF to self-assembled ROMP-based amphiphilic block copolymers. The sensitivity of this method provides unique information on block-selective solvent-triggered assembly and disassembly mechanisms, revealing behaviors invisible to or with superior sensitivity to traditional ¹H NMR spectroscopy. These experiments demonstrate an analytical method and provide a granular mechanistic understanding, both suitable for fine tuning block copolymer assembly and disassembly processes.

Fluorescence Resonance Energy Transfer Measurements in Polymer Science: A Review

Fluorescence resonance energy transfer (FRET) is a non-invasive characterization method for studying molecular structures and dynamics, providing high spatial resolution at nanometer scale. Over the past decades, FRET-based measurements are developed and widely implemented in synthetic polymer systems for understanding and detecting a variety of nanoscale phenomena, enabling significant advances in polymer science. In this review, the basic principles of fluorescence and FRET are briefly discussed. Several representative research areas are highlighted, where FRET spectroscopy and imaging can be employed to reveal polymer morphology and kinetics. These examples include understanding polymer micelle formation and stability, detecting guest molecule release from polymer host, characterizing supramolecular assembly, imaging composite interfaces, and determining polymer chain conformations and their diffusion kinetics. Finally, a perspective on the opportunities of FRET-based measurements is provided for further allowing their greater contributions in this exciting area.

Kinetically stable sub-50 nm fluorescent block copolymer nanoparticles via photomediated RAFT dispersion polymerization for cellular imaging

Self-assembled block copolymer nanoparticles (NPs) have emerged as major potential nanoscale vehicles for fluorescence bioimaging. The preparation of NPs with high yields possessing high kinetic stability to prevent the leakage of fluorophore molecules is crucial to their practical implementation. Here, we report a photomediated RAFT polymerization-induced self-assembly (PISA) yielding uniform and nanosized poly((oligo(ethylene glycol) acrylate)-block-poly(benzyl acrylate) particles (POEGA-b-PBzA) with a concentration of 22 wt%, over 20 times more than with micellization and nanoprecipitation. The spherical diblock copolymer nanoparticles have an average size of 10-50 nm controllable through the degree of polymerization of the stabilizing POEGA block. Subsequent dialysis against water and swelling with Nile red solution led to highly stable fluorescent NPs able to withstand the changes in concentration, ionic strength, pH or temperature. A PBzA/water interfacial tension of 48.6 mN m^-1 hinders the exchange between copolymer chains, resulting in the trapping of NPs in a "kinetically frozen" state responsible for high stability. A spectroscopic study combining fluorescence and UV-vis absorption agrees with a preferential distribution of fluorophores in the outer POEGEA shell despite its hydrophobic nature. Nile red-doped POEGA-b-PBzA micelles without initiator residues and unimers but with high structural stability turn out to be noncytotoxic, and can be used for the optical imaging of cells. Real-time confocal fluorescence microscopy shows a fast cellular uptake using C2C12 cell lines in minutes, and a preferential localization in the perinuclear region, in particular in the vesicles.

Chemical design and synthesis of macromolecular profluorescent nitroxide systems as self-reporting probes

The objective of this mini-review article is to highlight the importance of the chemical design towards the synthesis of polymeric profluorescent nitroxides applicable as self-reporting probes.

Prevent or Cure-The Unprecedented Need for Self-Reporting Materials

Self-reporting smart materials are highly relevant in modern soft matter materials science, as they allow for the autonomous detection of changes in synthetic polymers, materials, and composites. Despite critical advantages of such materials, for example, prolonged lifetime or prevention of disastrous material failures, they have gained much less attention than self-healing materials. However, as diagnosis is critical for any therapy, it is of the utmost importance to report the existence of system changes and their exact location to prevent them from spreading. Thus, we herein critically review the chemistry of self-reporting soft matter materials systems and highlight how current challenges and limitations may be overcome by successfully transferring self-reporting research concepts from the laboratory to the real world. Especially in the space of diagnostic self-reporting systems, the recent SARS-CoV-2 (COVID-19) pandemic indicates an urgent need for such concepts that may be able to detect the presence of viruses or bacteria on and within materials in a self-reporting fashion.

In situ conversion from crew-cut to hairy micelles by surface-initiated polymerization

Whether spherical micelles of block copolymers have short or long coronas is intrinsically determined by the molecular weight of the corona-forming block with respect to that of the core block before the micelles are assembled. Because of the inherent conditions of packing copolymer chains into a micelle, the core diameter is altered when we assemble a micelle from a block copolymer having a long corona block, compared to that having a short corona block with the same length of the core block. However, micelles with the same core diameter but having various corona lengths can be guaranteed when the corona is extended upon surface-initiated polymerization on the micelles. Herein, we demonstrated in situ conversion from crew-cut to hairy micelles by selectively extending a corona block while maintaining the spherical shape of block copolymer micelles. We first synthesized block copolymers having a chain transfer agent (CTA) positioned at the end of the corona block and then assembled them into a crew-cut micelle. Employing this micelle as an assembly of macro-CTAs, we conducted surface-initiated polymerization on the micelle by photo-induced energy/electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Since PET-RAFT enables the polymerization at room temperature, the corona block was selectively extended with preservation of the core diameter, thereby converting a crew-cut micelle to a hairy one. In addition, by applying the same polymerization protocol to a worm-like micelle, we could selectively extend the coronas, leading to the formation of a worm-like micelle with a long corona. If such copolymer chains were assembled into a micelle, we would obtain a spherical micelle instead of a worm-like micelle having a hairy corona, which is difficult to assess because of the inherent packing problem.

Injectable Thermogel Generated by the "Block Blend" Strategy as a Biomaterial for Endoscopic Submucosal Dissection

Endoscopic submucosal dissection is an established method for the removal of early cancers and large lesions from the gastrointestinal tract but is faced with the risk of perforation. To decrease this risk, a submucosal fluid cushion (SFC) is needed clinically by submucosal injection of saline and so on to lift and separate the lesion from the muscular layer. Some materials have been tried as the SFC so far with disadvantages. Here, we proposed a thermogel generated by the "block blend" strategy as an SFC. This system was composed of two amphiphilic block copolymers in water, so it was called a "block blend". We synthesized two non-thermogellable copolymers poly(d,l-lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) and blended them in water to achieve a sol-gel transition upon heating in both pure water and physiological saline. We explored the internal structure of the resultant thermogel with transmission electron microscopy, three-dimensional light scattering, ¹³C NMR, fluorescence resonance energy transfer, and rheological measurements, which indicated a percolated micelle network. The biosafety of the synthesized copolymer was preliminarily confirmed in vitro. The main necessary functions as an SFC, namely, injectability of a sol and the maintained mucosal elevation as a gel after injection, were verified ex vivo. This study has revealed the internal structure of the block blend thermogel and illustrated its potential application as a biomaterial. This work might be stimulating for investigations and applications of intelligent materials with both injectability and thermogellability of tunable phase-transition temperatures.

Design of an LCST-UCST-Like Thermoresponsive Zwitterionic Copolymer

Thermoresponsive polymers that possess both UCST- and LCST-like behaviors have generally been designed using diblock copolymers that are mostly composed of an LCST-like polymer and a UCST polymer. Herein, we prepared an LCST-UCST-type polymer composed of UCST-like thermoresponsive zwitterionic sulfabetaine methacrylate and nonthermoresponsive PEG methacrylate, ZB-PEG, by reversible addition-fragmentation chain transfer (RAFT) copolymerization. By adjusting the PEG composition, ZB-PEG formed a mesoglobule, a microglobule, and the dissociated states in phosphate-buffered saline (PBS). These states were found to be reversible via temperature control. Moreover, this behavior showed high reversibility and succeeded in stabilizing horseradish peroxidase (HRP) in the dilute condition. Such thermoresponsive ZB-PEG can be applied over a wide range of applications in biotechnology and other fields.

An AIE-driven fluorescent polysaccharide polymersome as an enzyme-responsive FRET nanoprobe to study the real-time delivery aspects in live cells

An enzyme-responsive FRET nanoprobe was designed and developed based on AIE-driven fluorescent polysaccharide polymersomes to study the real-time delivery aspects in the intracellular compartments in live cancer cells.

Zero-Overlap Fluorophores for Fluorescent Studies at Any Concentration

Fluorophores are powerful tools for the study of chemistry, biology, and physics. However, fluorescence is severely impaired when concentrations climb above 5 μM as a result of effects like self-absorption and chromatic shifts in the emitted light. Herein, we report the creation of a charge-transfer (CT) fluorophore and the discovery that its emission color seen at low concentrations is unchanged even at 5 mM, some 3 orders of magnitude beyond typical limits. The fluorophore is composed of a triphenylamine-substituted cyanostar macrocycle, and it exhibits a remarkable Stokes shift of 15 000 cm^-1 to generate emission at 633 nm. Crucial to the performance of this fluorophore is the observation that its emission spectrum shows near-zero overlap with the absorption band at 325 nm. We propose that reducing the spectral overlap to zero is a key to achieving full fluorescence across all concentrations. The triphenylamine donor and five cyanostilbene acceptor units of the macrocycle generate an emissive CT state. Unlike closely related donor-acceptor control compounds showing dual emission, the cyanostar framework inhibited emission from the second state to create a zero-overlap fluorophore. We demonstrated the use of emission spectroscopy for characterization of host-guest complexation at millimolar concentrations, which are typically the exclusive domain of NMR spectroscopy. The binding of the PF₆^- anion generates a 2:1 sandwich complex with blue-shifted emission. Distinct from twisted intramolecular charge-transfer (TICT) states, experiment-supported density functional theory shows a 67° twist inside an acceptor unit in the CT state instead of displaying a twist between the donor and acceptor; it is TICT-like. Inspired by the findings, we uncovered similar concentration-independent behavior from a control compound, strongly suggesting this behavior may be latent to other large Stokes-shift fluorophores. We discuss strategies capable of generating zero-overlap fluorophores to enable accurate fluorescence characterization of processes across all practical concentrations.

Triblock-Diblock Composite Nanoassemblies with Sequentially Addressable Host-Guest Properties for Hydrophobics and Hydrophilics

Noncovalent encapsulation of multiple guest molecules with distinct physiochemical properties, especially hydrophilic and hydrophobic guests, into a single polymeric nanoassembly is challenging, but would be profoundly beneficial to combination therapeutic delivery strategies. Here, we report a nanocomposite co-assembled by coating a layer of an amphiphilic block copolymer onto surface of a crosslinked inverse micelle driven by hydrophobic interactions. The hydrophobic coating layer and water-filled inverse micelles were utilized to encapsulate hydrophobic and hydrophilic cargos respectively. Rationally introducing the pH and redox responsive moieties into coating polymer and inverse micelles, allows sequentially addressing triggered release of the encapsulated cargos.

Manipulating the fluorescence lifetime at the sub-cellular scale via photo-switchable barcoding

Fluorescent barcoding is a pivotal technique for the investigation of the microscale world, from information storage to the monitoring of dynamic biochemical processes. Using fluorescence lifetime as the readout modality offers more reproducible and quantitative outputs compared to conventional fluorescent barcoding, being independent of sample concentration and measurement methods. However, the use of fluorescence lifetime in this area has been limited by the lack of strategies that provide spatiotemporal manipulation of the coding process. In this study, we design a two-component photo-switchable nanogel that exhibits variable fluorescence lifetime upon photoisomerization-induced energy transfer processes through light irradiation. This remotely manipulated fluorescence lifetime property could be visually mapped using fluorescence lifetime imaging microscopy (FLIM), allowing selective storage and display of information at the microscale. Most importantly, the reversibility of this system further provides a strategy for minimizing the background influence in fluorescence lifetime imaging of live cells and sub-cellular organelles.

A ratiometric fluorescence sensor based on enzymatically activatable micellization of TPE derivatives for quantitative detection of alkaline phosphatase activity in serum

A novel ratiometric fluorescence assay via enzymatically activatable micellization in aqueous solution was devised for quantitative detection of alkaline phosphatase (ALP) activity. We demonstrated that the dephosphorylation of the water-soluble, phosphate-functionalized, fluorophore monomer P-TPE-TG, induced by an enzymatic reaction of ALP, leads to micelle formation in aqueous solution because its water-soluble functionality is reduced. The dephosphorylation-induced micellization of P-TPE-TG exhibited a ratiometric sensing response for various ALP concentrations (10–200 mU mL⁻¹) and provided a suitable sensing platform for naked eye detection with increased fluorescence quantum yield (Φ = 3.2%), even compared to a typical TPE-based sensor (Φ = 1.0%), where ALP can be sensed with a detection limit of 0.034 mU mL⁻¹. In addition, P-TPE-TG displayed excellent sensing performance at concentrations from 0 to 50 mU mL⁻¹ in diluted human serum (10%), which offers the capability to exploit ratiometric responses for bioactive substances under practical conditions.

A novel ratiometric fluorescence assay via enzymatically activatable micellization in aqueous solution was devised for quantitative detection of alkaline phosphatase (ALP) activity.

Tuning H2S Release by Controlling Mobility in a Micelle Core

Drug delivery from polymer micelles has been widely studied, but methods to precisely tune rates of drug release from micelles are limited. Here, the mobility of hydrophobic micelle cores was varied to tune the rate at which a covalently bound drug was released. This concept was applied to cysteine-triggered release of hydrogen sulfide (H2S), a signaling gas with therapeutic potential. In this system, thiol-triggered H2S donor molecules were covalently linked to the hydrophobic blocks of self-assembled polymer amphiphiles. Because release of H2S is triggered by cysteine, diffusion of cysteine into the hydrophobic micelle core was hypothesized to control the rate of release. We confirmed this hypothesis by carrying out release experiments from H2S-releasing micelles in varying compositions of EtOH/H2O. Higher EtOH concentrations caused the micelles to swell, facilitating diffusion in and out of their hydrophobic cores and leading to faster H2S release from the micelles. To achieve a similar effect without addition of organic solvent, we prepared micelles with varying core mobility via incorporation of a plasticizing co-monomer in the core-forming block. The glass transition temperature (Tg) of the core block could therefore be precisely varied by changing the amount of the plasticizing co-monomer in the polymer. In aqueous solution under identical conditions, the release rate of H2S varied over 20-fold (t½ = 0.18 - 4.2 h), with the lowest Tg hydrophobic block resulting in the fastest H2S release. This method of modulating release kinetics from polymer micelles by tuning core mobility may be applicable to many types of physically encapsulated and covalently linked small molecules in a variety of drug delivery systems.

Fluorescence Resonance Energy Transfer (FRET): A Powerful Tool for Probing Amphiphilic Polymer Aggregates and Supramolecular Polymers

This Review Article highlights the utility of the fluorescence resonance energy transfer (FRET) to probe the dynamics and related issues in amphiphilic polymeric aggregates and supramolecular polymers. Amphiphilic polymers are more attractive compared to their small molecule analogues because they exhibit significantly lower critical aggregation concentration, relatively larger particle size (suitable for the enhanced permeation and retention effect), and a much slower dynamics of exchange between the unimer and the aggregate. Representative examples of exchange dynamics in amphiphilic polymer aggregates and their noncovalent encapsulation stability as a function of the structure of the macromolecule, cross-linking, environmental parameters, and biological conditions, as probed by FRET studies, have been included in this article. Further, related observations on the utility of FRET in studying the exchange dynamics in supramolecular polymers, particularly in aqueous medium, have been discussed at length, revealing a strong impact of chirality, side chain polarity, and other parameters. Overall, this Review Article brings out the strength of this technique to probe dynamics of aggregates and assembled systems, mostly in water medium, which has a paramount importance in designing future biomaterials.

Coordination-induced assemblies of quantum dots in amphiphilic thermo-responsive block copolymer micelles: morphologies, optical properties and applications

Thermo-responsive dual-emitting QD/BCP assemblies with QDs located in the core (CDMs), shell (SDMs) and the interface (IDMs) between the core and the shell of micelles were constructed via coordination-driven assemblies for the selective detection of TNP and Hg²⁺ ions.

Fluorescent ROMP Monomers and Copolymers for Biomedical Applications

The synthesis and characterization of a series of green, blue and red-fluorescent exo-oxanorbornene acid and imide monomers carrying nitrobenzofurazan, coumarin, and Rhodamin B, respectively, as fluorophores is presented. These monomers carry oxanorbornene as polymerizable unit, and were readily copolymerized with bioactive functional oxanorbornene monomers by ring-opening metathesis polymerization (ROMP), as demonstrated by gel permeation chromatography and NMR spectroscopy. Due to the ease of synthesis of these monomers, and their cost-effectiveness compared many to other fluorescent probes, they are useful for biomaterials applications.

Energy-Transfer Phenomena in Thermoresponsive and pH- Switchable Fluorescent Diblock Copolymer Vesicles

We describe the development of a polymeric vesicle that not only selectively fluoresces at low pH, a condition prevailing in cancer cells, but also can potentially monitor the thermoresponsive release of a drug even if the drug is nonfluorescent. The developed fluorescence resonance energy transfer (FRET)-based thermoresponsive vesicular nanocarriers are composed of a new poly(PEGMA)-b-poly(NIPA-r-R6GMED) block copolymer, which undergoes pH-switchable superior turn on-off fluorescence characteristics. The block copolymer was synthesized using the RAFT technique, and its solution properties and self-assembly behavior were investigated by turbidity measurements, fluorescence spectroscopy, ¹H NMR, dynamic light scattering, and transmission electron microscopy. The block copolymer self-assembled to form nanostructured vesicles above the critical aggregation temperature under physiologically relevant conditions. Steady-state and time-resolved fluorescence spectroscopy were utilized to study the FRET process between encapsulated hydrophobic guest C-153 (donor) and polymer-bound R6GMED units (acceptor) in the thermoresponsive vesicles. The FRET rate and efficiency were found to vary as a result of the pH-dependent changes in the quantum yield of the acceptor molecules. The occurrence of a highly efficient FRET in this polymeric vesicular nanocarrier at acidic pH, a condition similar to the cytoplasm and cell nucleus in leukemic tissues, and the ability to encapsulate hydrophilic and hydrophobic molecules and their temperature-controlled release make it potentially useful in imaging guided real-time monitoring of drug-delivery vehicles.

Anionic Polymer and Quantum Dot Excipients to Facilitate siRNA Release and Self-Reporting of Disassembly in Stimuli-Responsive Nanocarrier Formulations

The incorporation of anionic excipients into polyplexes is a promising strategy for modulating siRNA binding versus release and integrating diagnostic capabilities; however, specific design criteria and structure-function relationships are needed to facilitate the development of nanocarrier-based theranostics. Herein, we incorporated poly(acrylic acid) (PAA) and quantum dot (QD) excipients into photolabile siRNA polyplexes to increase gene silencing efficiencies by up to 100% and enable self-reporting of nanocarrier disassembly. Our systematic approach identified the functional relationships between gene silencing and key parameters such as excipient loading fractions and molecular weights that facilitated the establishment of design rules for optimization of nanocarrier efficacy. For example, we found that PAA molecular weights ∼10-20× greater than that of the coencapsulated siRNA exhibited the most efficient release and silencing. Furthermore, siRNA release assays and RNAi modeling allowed us to generate a PAA "heat map" that predicted gene silencing a priori as a function of PAA molecular weight and loading fraction. QDs further promoted selective siRNA release and provided visual as well as Förster resonance energy transfer (FRET)-based monitoring of the dynamic changes in nanostructure in situ. Moreover, even with the addition of anionic components, our formulations exhibited substantially improved stability and shelf life relative to typical formulations, with complete stability after a week of storage and full activity in the presence of serum. Taken together, this study enabled synergistic improvements in siRNA release and diagnostic capabilities, along with the development of mechanistic insights that are critical for advancing the translation of nucleic acid theranostics into the clinic.

Reduction-responsive dithiomaleimide-based polymeric micelles for controlled anti-cancer drug delivery and bioimaging

The biocompatible amphiphilic block copolymers and the CPT model drug were self-assembled into micelles with bright fluorescence and taken up by tumor cells. Then, the disulfide bonds in the micelles were cleaved to release CPT at a high GSH concentration.