Growing polyion complex micelles: kinetics and mechanism of electrostatic template polymerization and assembly.

HYPOTHESIS: Electrostatic-templated polymerization (ETP) is a recently developed strategy for robust fabrication of stable polyion complex (PIC) micelles with regulated size and morphology, yet the kinetics and mechanism about this one pot process remain elusive. EXPERIMENTS: In ETP method, ionic monomers are polymerized in the presence of an oppositely charged ionic-neutral diblock copolymer as template. We investigate the monomer conversion and electrostatic assembly as a function of time, under different polymerization conditions of ionic strength, pH, template/monomer molar ratio and the presence of a cross-linker. FINDINGS: The template copolymer accelerates the monomer conversion and formation of PIC micelles dependent on ionic strength and pH. The process follows the "Pick-up" mechanism, where monomers first convert into oligomers which complex with template to induce further chain growth and electrostatic assembly. Introducing cross-linker hardly impacts the reaction kinetics and "Pick-up" route, while it creates PIC micelles containing cross-linked ionic network assembly with the template. Further removing the template by concentrated salt provides purified ionic nanogels. The disclosed findings not only provide a better understanding of the polymerization-assembly process, but also optimize the controls of electrostatic-templated polymerization for the rational design and fabrication of diverse PIC micelles and polyelectrolyte particles.

Photo-Triggered Fluorescence Polyelectrolyte Nanoassemblies: Manipulate and Boost Singlet Oxygen in Photodynamic Therapy.

Photodynamic therapy (PDT) is a clinically approved therapeutic modality that has shown great potential for cancer treatment. However, there exist two major problems hindering PDT applications: the nonspecific phototoxicity requiring patients to stay in dark post-PDT, and the limited photodynamic efficiency. Herein, we report a photo-triggered porphyrin polyelectrolyte nanoassembling (photo-triggered PPN) strategy, in which porphyrin photosensitizer and photoswitchable energy accepter are assembled into polyelectrolyte micelles by a combined force of charge interaction and metal-ligand coordination. The polyelectrolyte-based PPN exhibits good biocompatibility, and bestows a unique "confining isolated" inner microenvironment for fully overcoming the π-π stacking of porphyrins with significant photodynamic efficiency (123-fold enhancement). Due to the high Förster resonance energy transfer (FRET) (91.5%) between porphyrin and photoswitch in closed-form, we could use light as a specific trigger to modulate photoswitch between closed- and open-form, and manipulate the 1O2 generation in three stages: pre-PDT (quenching 1O2 generation), during PDT (activating 1O2 generation), and post-PDT (silencing 1O2 generation). This de novo strategy has for the first time realized remotely manipulating and boosting 1O2 generation in PDT, well resolving the critical and general challenges of limited photodynamic efficiency and side effects from nonspecific phototoxicity.

Rational design of diblock copolymer enables efficient cytosolic protein delivery.

Polymer-mediated cytosolic protein delivery demonstrates a promising strategy for the development of protein therapeutics. Here, we propose a new designed diblock copolymer which realizes efficient cytosolic protein delivery both in vitro and in vivo. The polymer contains one protein-binding block composed of phenylboronic acid (PBA) and N-(3-dimethylaminopropyl) (DMAP) pendant units for protein binding and endosomal escape, respectively, followed by the response to ATP enriched in the cytosol which triggers the protein release. The other block is PEG designed to improve particle size control and circulation in vivo. By optimizing the block composition, sequence and length of the copolymer, the optimal one (BP20) was identified with the binding block containing 20 units of both PBA and DMAP, randomly distributed along the chain. When mixed with proteins, the BP20 forms stable nanoparticles and mediates efficient cytosolic delivery of a wide range of proteins including enzymes, toxic proteins and CRISPR/Cas9 ribonucleoproteins (RNP), to various cell lines. The PEG block, especially when further modified with folic acid (FA), enables tumor-targeted delivery of Saporin in vivo, which significantly suppresses the tumor growth. Our results shall inspire the design of novel polymeric vehicles with robust capability for cytosolic protein delivery, which holds great potential for both biological research and therapeutic applications.

Robust Electrostatic-Templated Polymerization for Controllable Synthesis of Stable and Permeable Polyelectrolyte Vesicles.

Polymer vesicles are of profound interest for designing delivery vehicles and nanoreactors toward a variety of biomedical and catalytic applications, yet robust synthesis of stable and permeable vesicles remains challenging. Here, we propose an electrostatic-templated polymerization that enables fabrication of polyelectrolyte vesicles with simultaneously regulated stability and permeability. In our design, cationic monomers were copolymerized with cross-linkers in the presence of a polyanionic-neutral diblock copolymer as a template. By properly choosing the block length ratio of the template, we fabricated a type of polyion complex vesicle consisting of a cross-linked cationic membrane, electrostatically assembled with the template copolymer which can be removed by sequential dissociation and separation under concentrated salt. We finally obtained stable polyelectrolyte vesicles of regulated size, membrane permeability, and response properties by tuning the synthesis factors including ionic strength, cross-linker type, and fraction as well as different monomers and concentrations. As a proof-of-concept, lipase was loaded in the designed cationic vesicles, which exhibited enhanced enzyme stability and activity. Our study has developed a novel and robust strategy for controllable synthesis of a new class of stable and permeable polymer (polyelectrolyte) vesicles that feature great potential applications as functional delivery carriers and nanoreactors.

Magnesium Ions Promote the Induction of Immunosuppressive Bone Microenvironment and Bone Repair through HIF-1α-TGF-ß Axis in Dendritic Cells.

The effect of immunoinflammation on bone repair during the recovery process of bone defects needs to be further explored. It is reported that Mg2+ can promote bone repair with immunoregulatory effect, but the underlying mechanism on adaptive immunity is still unclear. Here, by using chitosan and hyaluronic acid-coated Mg2+ (CSHA-Mg) in bone-deficient mice, it is shown that Mg2+ can inhibit the activation of CD4+ T cells and increase regulatory T cell formation by inducing immunosuppressive dendritic cells (imDCs). Mechanistically, Mg2+ initiates the activation of the MAPK signaling pathway through TRPM7 channels on DCs. This process subsequently induces the downstream HIF-1α expression, a transcription factor that amplifies TGF-ß production and inhibits the effective T cell function. In vivo, knock-out of HIF-1α in DCs or using a HIF-1α inhibitor PX-478 reverses inhibition of bone inflammation and repair promotion upon Mg2+-treatment. Moreover, roxadustat, which stabilizes HIF-1α protein expression, can significantly promote immunosuppression and bone repair in synergism with CSHA-Mg. Thus, the findings identify a key mechanism for DCs and its HIF-1α-TGF-ß axis in the induction of immunosuppressive bone microenvironment, providing potential targets for bone regeneration.

Stable and permeable polyion complex vesicles designed as enzymatic nanoreactors.

Polymeric vesicles are perspective vehicles for fabricating enzymatic nanoreactors towards diverse biomedical and catalytic applications, yet the design of stable and permeable vesicles remains challenging. Herein, we developed polyion complex (PIC) vesicles featuring high stability and a permeable membrane for adequate enzyme loading and activation. Our design relies on co-assembly of an anionic diblock copolymer (PSS96-b-PEO113) with cationic branched poly(ethylenimine) (PEI). The polymer combination endows strong electrostatic interaction between the PSS and PEI building blocks, so their assembly can be implemented at a high salt concentration (500 mM NaCl), under which the charge interaction of the enzyme-polymer is inhibited. This control realizes the successful and safe loading of enzymes associated with the formation of stable PIC vesicles with an intrinsic permeable membrane that is favourable for enhancing enzymatic activity. The control factors for vesicle formation and enzyme loading were investigated, and the general application of loading different enzymes for cascade reaction was validated as well. Our study reveals that proper design and combination of polyelectrolytes is a facile strategy for fabricating stable and permeable polymeric PIC vesicles, which exhibit clear advantages for loading and activating enzymes, consequently boosting their diverse applications as enzymatic nanoreactors.

Effects of catechol grafting on chitosan-based coacervation and adhesion.

In this study, we investigated detailedly the contribution of catechol in tuning the formation and adhesive properties of coacervates. We have constructed a series of catechol-grafted Chitosan (Chitosan-C), and investigated their coacervation with gum arabic (GA) and the corresponding adhesion. We demonstrate that, increasing catechol grafting ratio from 0 %-44 % impacted the coacervation moderately, while enhanced the adhesion of the coacervate up to 438 % when the catechol faction was 37 %. Further increasing the grafting ratio to 55 % led to precipitated coacervates associated with a declined adhesion. Our findings identify the optimal grafting threshold for coacervation and adhesion, providing insights into the underlying mechanism of coacervate binding. Moreover, the catechol enhancement on adhesion of coacervates tolerates different substrates and diverse polyelectrolyte pairs. The revealed principles shall be helpful for designing adhesive coacervates and boosting their applications in various industrial and biomedical areas.

Electrostatically Mediated In Situ Polymerization for Enzyme Immobilization and Activation.

Enzyme immobilization in nanoparticles is of interest for boosting their catalytic applications, yet rational approaches to designs achieving both high enzyme loading and activation remain a challenge. Herein, we report an electrostatically mediated in situ polymerization strategy that simultaneously realizes enzyme immobilization and activation. This was achieved by copolymerizing cationic monomers with a cross-linker in the presence of the enzyme lipase (anionic) as the template, which produces enzyme-loaded nanogels. The effects of different control factors such as pH, lipase dosage, and cross-linker fraction on nanogel formation are investigated systematically, and optimal conditions for enzyme loading and activation have been determined. A central finding is that the cationic polymer network of the nanogel creates a favorable environment that not only protects the enzyme but also boosts enzymatic activity nearly 2-fold as compared to free lipase. The nanogels improve the stability of the lipase to tolerate a broader working range of pH (5.5-8.5) and temperature (25-70 °C) and allow recycling such that after six cycles of reaction, 70% of the initial activity is conserved. The established fabrication strategy can be applied generally to different cationic monomers, and most of these nanogels exhibit adequate immobilization and activation of lipase. Our study confirms that in situ polymerization based on electrostatic interaction provides a facile and robust strategy for enzyme immobilization and activation. The wide variety of ionic monomers, therefore, features great potential for developing functional platforms toward satisfying enzyme immobilization and demanding applications.

Nucleation-Supersaturation Dual-Drive Crystallization Strategy Enables Efficient Protein Crystallization.

A rational crystallization strategy is essential to obtain high-quality protein crystals, yet the established methods suffer from different limitations arising from the single regulation on either nucleation or supersaturation. Herein, a nucleation-supersaturation dual-driven crystallization (DDC) strategy that realizes synergistic regulation of heterogeneous nucleation sites and solution supersaturation based on dual surface and confinement effects for efficient protein crystallization is reported. This strategy relies on a p(PEGDA-co-DMAA) hydrogel template with pre-filled NaCl under designed concentrations. Once dropping hen egg white lysozyme (HEWL) protein solution on the hydrogel, the wrinkled surface provides numerous nucleation sites, while the internal structure regulates the solution supersaturation in the crystallization region through diffusion. Finally, DDC strategy can create high-quality HEWL crystals with large sizes (100-300 µm), well-defined morphologies (hexagon and tetragon), and a significantly accelerated nucleation time (9-12 times faster than that achieved using the conventional hanging drop method). It also performs well at wider protein concentrations (10-50 mg mL-1 ) and categories (e.g., achieving fast crystallization and large-size crystals of trypsin), therefore demonstrating clear advantages and great potential for efficiently fabricating protein crystals desirable for diverse applications.

Selective amide bond formation in redox-active coacervate protocells.

Coacervate droplets are promising protocell models because they sequester a wide range of guest molecules and may catalyze their conversion. However, it remains unclear how life's building blocks, including peptides, could be synthesized from primitive precursor molecules inside such protocells. Here, we develop a redox-active protocell model formed by phase separation of prebiotically relevant ferricyanide (Fe(CN)63-) molecules and cationic peptides. Their assembly into coacervates can be regulated by redox chemistry and the coacervates act as oxidizing hubs for sequestered metabolites, like NAD(P)H and gluthathione. Interestingly, the oxidizing potential of Fe(CN)63- inside coacervates can be harnessed to drive the formation of new amide bonds between prebiotically relevant amino acids and α-amidothioacids. Aminoacylation is enhanced in Fe(CN)63-/peptide coacervates and selective for amino acids that interact less strongly with the coacervates. We finally use Fe(CN)63--containing coacervates to spatially control assembly of fibrous networks inside and at the surface of coacervate protocells. These results provide an important step towards the prebiotically relevant integration of redox chemistry in primitive cell-like compartments.

Redox-responsive peptide-based complex coacervates as delivery vehicles with controlled release of proteinous drugs.

Proteinous drugs are highly promising therapeutics to treat various diseases. However, they suffer from limited circulation times and severe off-target side effects. Inspired by active membraneless organelles capable of dynamic recruitment and releasing of specific proteins, here, we present the design of coacervates as therapeutic protocells, made from small metabolites (anionic molecules) and simple arginine-rich peptides (cationic motif) through liquid-liquid phase separation. These complex coacervates demonstrate that their assembly and disassembly can be regulated by redox chemistry, which helps to control the release of the therapeutic protein. A model proteinous drugs, tissue plasminogen activator (tPA), can rapidly compartmentalize inside the complex coacervates, and the coacervates formed from peptides conjugated with arginine-glycine-aspartic acid (RGD) motif (a fibrinogen-derived peptide sequence), show selective binding to the thrombus site and thus enhance on-target efficacy of tPA. Furthermore, the burst release of tPA can be controlled by the redox-induced dissolution of the coacervates. Our proof-of-principle complex coacervate system provides insights into the sequestration and release of proteinous drugs from advanced drug delivery systems and represents a step toward the construction of synthetic therapeutic protocells for biomedical applications.

Effects of Control Factors on Protein-Polyelectrolyte Complex Coacervation.

Protein-polyelectrolyte complex coacervation is of particular interest for mimicking intracellular phase separation and organization. Yet, the challenge arises from regulating the coacervation due to the globular structure and anisotropic distributed charges of protein. Herein, we fully investigate the different control factors and reveal their effects on protein-polyelectrolyte coacervation. We prepared mixtures of BSA (bovine serum albumin) with different cationic polymers, which include linear and branched polyelectrolytes covering different spacer and charge groups, chain lengths, and polymer structures. With BSA-PDMAEMA [poly(N,N-dimethylaminomethyl methacrylate)] as the main investigated pair, we find that the moderate pH and ionic strength are essential for the adequate electrostatic interaction and formation of coacervate droplets. For most BSA-polymer mixtures, excess polyelectrolytes are required to achieve the full complexation, as evidenced by the deviated optimal charge mixing ratios from the charge stoichiometry. Polymers with longer chains or primary amine groups and a branched structure endow a strong electrostatic interaction with BSA and cause a bigger charge ratio deviation associated with the formation of solid-like coacervate complexes. Nevertheless, both the liquid- and solid-like coacervates hardly interrupt the BSA structure and activity, indicating the safe encapsulation of proteins by the coacervation with polyelectrolytes. Our study validates the crucial control of the diverse factors in regulating protein-polyelectrolyte coacervation, and the revealed principles shall be instructive for establishing other protein-based coacervations and boosting their potential applications.

Development and validation of an artificial intelligence-powered acne grading system incorporating lesion identification.

Background: The management of acne requires the consideration of its severity; however, a universally adopted evaluation system for clinical practice is lacking. Artificial intelligence (AI) evaluation systems hold the promise of enhancing the efficiency and reproducibility of assessments. Artificial intelligence (AI) evaluation systems offer the potential to enhance the efficiency and reproducibility of assessments in this domain. While the identification of skin lesions represents a crucial component of acne evaluation, existing AI systems often overlook lesion identification or fail to integrate it with severity assessment. This study aimed to develop an AI-powered acne grading system and compare its performance with physician image-based scoring. Methods: A total of 1,501 acne patients were included in the study, and standardized pictures were obtained using the VISIA system. The initial evaluation involved 40 stratified sampled frontal photos assessed by seven dermatologists. Subsequently, the three doctors with the highest inter-rater agreement annotated the remaining 1,461 images, which served as the dataset for the development of the AI system. The dataset was randomly divided into two groups: 276 images were allocated for training the acne lesion identification platform, and 1,185 images were used to assess the severity of acne. Results: The average precision of our model for skin lesion identification was 0.507 and the average recall was 0.775. The AI severity grading system achieved good agreement with the true label (linear weighted kappa = 0.652). After integrating the lesion identification results into the severity assessment with fixed weights and learnable weights, the kappa rose to 0.737 and 0.696, respectively, and the entire evaluation on a Linux workstation with a Tesla K40m GPU took less than 0.1s per picture. Conclusion: This study developed a system that detects various types of acne lesions and correlates them well with acne severity grading, and the good accuracy and efficiency make this approach potentially an effective clinical decision support tool.

SA-RPN: A Spacial Aware Region Proposal Network for Acne Detection.

Automated detection of skin lesions offers excellent potential for interpretative diagnosis and precise treatment of acne vulgar. However, the blurry boundary and small size of lesions make it challenging to detect acne lesions with traditional object detection methods. To better understand the acne detection task, we construct a new benchmark dataset named AcneSCU, consisting of 276 facial images with 31777 instance-level annotations from clinical dermatology. To the best of our knowledge, AcneSCU is the first acne dataset with high-resolution imageries, precise annotations, and fine-grained lesion categories, which enables the comprehensive study of acne detection. More importantly, we propose a novel method called Spatial Aware Region Proposal Network (SA-RPN) to improve the proposal quality of two-stage detection methods. Specifically, the representation learning for the classification and localization task is disentangled with a double head component to promote the proposals for hard samples. Then, Normalized Wasserstein Distance of each proposal is predicted to improve the correlation between the classification scores and the proposals' intersection-over-unions (IoUs). SA-RPN can serve as a plug-and-play module to enhance standard two-stage detectors. Extensive experiments are conducted on both AcneSCU and the public dataset ACNE04, and the results show that the proposed method can consistently outperform state-of-the-art methods.

Aqueous coordination polymer complexes: From colloidal assemblies to bulk materials.

1-dimensional (1D) coordination polymers refer to the macromolecules that have metal ions incorporated in their pendent groups or main chain through metal-binding ligand groups. They have intrinsic advantages over traditional polymers to regulate the polymer structures and functions owing to the nature of the metal-ligand bond. Consequently, they have great potential for the development of smart and functional structures and materials and therapeutic agents. Water-soluble 1D coordination polymers and assemblies are an important subtype of coordination polymers with distinctive interests for demanding applications in aqueous systems, such as biological and medical applications. This review highlights the recent progress and research achievements in the design and use of water-soluble 1D coordination polymers and assemblies. The overview covers the design and structure control of 1D coordination polymers, their colloidal assemblies, including nanoparticles, nanofibers, micelles and vesicles, and fabricated bulk materials such as membraneless liquid condensates, security ink, hydrogel actuators, and smart fabrics. Finally, we discuss the potential applications of several of these coordination polymeric structures and materials and give an outlook on the field of aqueous coordination polymers.

Protein separation by sequential selective complex coacervation.

In food manufacturing and particular biomedical products selected proteins are often required. Obtaining the desired proteins in a pure form from natural resources is therefore important, but often very challenging. Herein, we design a sequential coacervation process that allows to efficiently isolate and purify proteins with different isoelectric points (pIs) from a mixed solution, namely Bovine Serum Albumin (BSA, pI = 4.9) and Peroxidase from Horseradish (HRP, pI = 7.2). The key to separation is introducing a suitable polyelectrolyte that causes selective complex coacervation at appropriate pH and ionic strength. Specifically, polyethyleneimine (PEI), when added into the mixture at pH 6.0, produces a coacervation which exclusively contains BSA, leading to a supernatant solution containing 100 % HRP with a purity of 91 %. After separating the dilute and dense phases, BSA is recovered by adding poly(acrylic acid) (PAA) to the concentrated phase, which displaces BSA from the complex because it interacts more strongly with PEI. The supernatant phase after this step contains approximately 75 % of the initial amount of BSA with a purity of 99 %. Our results confirm that coacervation under well-defined conditions can be selective, enabling separation of proteins with adequate purity. Therefore, the established approach demonstrates a facile and sustainable strategy with potential for protein separation at industrial scale.

Rational design of polymeric nanozymes with robust catalytic performance via copper-ligand coordination.

Incorporating copper (Cu) ions into polymeric particles can be a straightforward strategy for mimicking copper enzymes, but it is challenging to simultaneously control the structure of the nanozyme and of the active sites. In this report, we present a novel bis-ligand (L2) containing bipyridine groups connected by a tetra-ethylene oxide (4EO) spacer. In phosphate buffer the Cu-L2 mixture forms coordination complexes that (at proper composition) can bind polyacrylic acid (PAA) to produce catalytically active polymeric nanoparticles with well-defined structure and size, which we refer to as 'nanozymes'. Manipulating the L2/Cu mixing ratio and using phosphate as a co-binding motif, cooperative copper centres are realized that exhibit promoted oxidation activity. The structure and activity of the so-designed nanozymes remain stable upon increasing temperature and over multiple cycles of application. Increasing ionic strength causes enhanced activity, a response also seen for natural tyrosinase. By means of our rational design we obtain nanozymes with optimized structure and active sites that in several respects outperform natural enzymes. This approach therefore demonstrates a novel strategy for developing functional nanozymes, which may well stimulate the application of this class of catalysts.

Cationic Nanogels Enable Gold Nanoparticle Immobilization and Regulated Catalytic Activity.

Polyelectrolyte nanogel consisting of charged network is a prospective platform for developing nanoreactor due to their integrated features of both polyelectrolyte and hydrogel. In this work, cationic poly (methacrylatoethyl trimethyl ammonium chloride) (PMETAC) nanogels with regulated size (30-82 nm) and crosslinking degree (10-50%), has been synthesized by Electrostatic Assembly Directed Polymerization (EADP) method and applied to load gold nanoparticles (AuNPs). Based on the typical reduction reaction of 4-nitrophenol (4-NP), the catalytic performance of the constructed nanoreactor was examined by studying their kinetic process, where the loaded AuNPs exhibited dependent activity on crosslinking degree of nanogels, while independent catalytic activity on nanogel size. Our results validate that, polyelectrolyte nanogels are capable of loading metal NPs and regulating their catalytic performance, therefore demonstrates potential for developing functional nanoreactors.

Synthesis of zwitterionic polyelectrolyte nanogels via electrostatic-templated polymerization.

Zwitterionic polyelectrolyte nanogels are prospective nanocarriers due to their soft loading pocket and regulated charges. We here report a facile strategy, namely, electrostatic-templated polymerization (ETP) for synthesizing zwitterionic nanogels with controlled size and properties. Specifically, with anionic-neutral diblock polymers as the template, zwitterionic monomers such as carboxybetaine methacrylate (CBMA) or carboxybetaine acrylamide (CBAA) are polymerized together with a cross-linker at pH 2 where the monomers exhibit only positive charge due to the protonation of the carboxyl group. The obtained polyelectrolyte complex micelles dissociate upon introducing a concentrated salt. The subsequent separation yields the released template and zwitterionic nanogels with regulated size and swelling ability, achieved by tuning the salt concentration and cross-linker fraction during polymerization. The obtained PCBMA nanogels exhibit charges depending on the pH, which enables not only the selective loading of different dye molecules, but also encapsulation and intracellular delivery of cytochrome c protein. Our study develops a facile and robust way for fabricating zwitterionic nanogels and validates their potential applications as promising nanocarriers for load and delivery of functional charged cargos.

Rational polyelectrolyte nanoparticles endow preosteoclast-targeted siRNA transfection for anabolic therapy of osteoporosis.

Targeted transfection of siRNA to preosteoclasts features the potential of anti-osteoporosis, yet challenge arises from the development of satisfied delivery vehicles. Here, we design a rational core-shell nanoparticle (NP) composed of cationic and responsive core for controlled load and release of small interfering RNA (siRNA) and compatible polyethylene glycol shell modified with alendronate for enhanced circulation and bone-targeted delivery of siRNA. The designed NPs perform well on transfection of an active siRNA (siDcstamp) that interferes Dcstamp mRNA expression, leading to impeded preosteoclast fusion and bone resorption, as well as promoted osteogenesis. In vivo results corroborate the abundant siDcstamp accumulation on bone surfaces and the enhanced trabecular bone mass volume and microstructure in treating osteoporotic OVX mice by rebalancing bone resorption, formation, and vascularization. Our study validates the hypothesis that satisfied transfection of siRNA enables preserved preosteoclasts that regulate bone resorption and formation simultaneously as potential anabolic treatment for osteoporosis.