Controlled construction of gold nanoparticles in situ from β-cyclodextrin based unimolecular micelles for in vitro computed tomography imaging

Poly(Photosensitizer-Prodrug) Unimolecular Micelles for Chemo-Photodynamic Synergistic Therapy of Antitumor and Antibacteria

It is crucial to use simple methods to prepare stable polymeric micelles with multiple functions for cancer treatment. Herein, via a "bottom-up" strategy, we reported the fabrication of β-CD-(PEOSMA-PCPTMA-PPEGMA)21 (βPECP) unimolecular micelles that could simultaneously treat tumors and bacteria with chemotherapy and photodynamic therapy (PDT). The unimolecular micelles consisted of a 21-arm β-cyclodextrin (β-CD) core as a macromolecular initiator, photosensitizer eosin Y (EOS-Y) monomer EOSMA, anticancer drug camptothecin (CPT) monomer, and a hydrophilic shell PEGMA. Camptothecin monomer (CPTMA) could achieve controlled release of the CPT due to the presence of responsively broken disulfide bonds. PEGMA enhanced the biocompatibility of micelles as a hydrophilic shell. Two βPECP with different lengths were synthesized by modulating reaction conditions and the proportion of monomers, which both were self-assembled to unimolecular micelles in water. βPECP unimolecular micelles with higher EOS-Y/CPT content exhibited more excellent 1O2 production, in vitro drug release efficiency, higher cytotoxicity, and superior antibacterial activity. Also, we carried out simulations of the self-assembly and CPT release process of micelles, which agreed with the experiments. This nanosystem, which combines antimicrobial and antitumor functions, provides new ideas for bacteria-mediated tumor clinical chemoresistance.

Aggregation-induced emission nanoparticles with improved optical absorption for boosting fluorescence signal of tumors in vivo

Nanomaterial development has been extensively investigated for several decades to realize sensitive and accurate imaging of tumors in vivo. The manufacturing of nanoparticles with highly efficient tumor targeting and excellent optical properties is still an important research topic. The structure and composition ratio of materials that decisively contribute to the brightness and size of nanoparticles have a great influence on image sensitivity and tumor targeting efficiency. In this study, we developed aggregation-induced emission (AIE) nanoparticles with a widened light absorption window (nanoPMeOCN/BDP) to enable sensitive in vivo tumor imaging. The signal of nanoparticles is enhanced by integrating a high-density AIE polymer (PMeOCN) and light-absorbing fluorescent dye (BDP) in a nanoscopic space. BDP not only improves the light absorption of particles but also enhances the fluorescence signal of particles by effectively transferring absorbed energy to PMeOCN. The physically blended nanoPMeOCN/BDP show strong light absorption and improved sensitivity for the imaging of biological tissues because of their excellent optical performance compared to nanoPMeOCN of similar nanosizes (∼19 nm in size). In vivo imaging results further confirm that nanoPMeOCN/BDP can provide amplified signals with the successful accumulation of tumor tissue through the enhanced permeability and retention effect. We expect that the design strategy of nanoparticles with improved light absorption will provide a simple and general method for improving the accuracy of disease diagnosis.

Preparation and Release of pH-Sensitive β-Cyclodextrin Derivative Micelles Loaded with Paclitaxel

In this paper, a new amphiphilic mono-6-β-cyclodextrin octadecylimine (6-β-CD-N-ODMA) copolymer was synthesized based on β-cyclodextrin and octadecylamine, which can self-assemble to form polymeric micelles. Drug-loaded micelles (a new drug carrier) were obtained using 6-β-CD-N-ODMA and paclitaxel (PTX) by the dialysis method. Orthogonal experiments were used to optimize the preparation method of the drug-loaded micelles. The drug-loading content of the carrier prepared by the optimized method was 1.97%. The physicochemical properties of blank micelles and drug-loaded micelles were evaluated by the fluorescence probe method, infrared spectra, dynamic light scattering, and scanning electron microscopy. The release properties of the carrier were investigated. The carrier has good pH sensitivity and the cumulative release rate after 96 h was 88% in PBS (pH = 5.0). The Ritger–Peppas equation is the optimal model for PTX released at pH 5.0, implying that the hydrolysis effect of 6-β-CD-N-ODMA is the main reason for PTX release. The results indicate that the developed carrier can increase the solubility of PTX and possess potential for increased clinical efficacy of PTX.

Biologically Relevant Micellar Nanocarrier Systems for Drug Encapsulation and Functionalization of Metallic Nanoparticles

The preparation of new and functional nanostructures has received more attention in the scientific community in the past decade due to their wide application versatility. Among these nanostructures, micelles appear to be one of the most interesting supramolecular organizations for biomedical applications because of their ease of synthesis and reproducibility and their biocompatibility since they present an organization similar to the cell membrane. In this work, we developed micellar nanocarrier systems from surfactant molecules derived from oleic acid and tetraethylene glycol that were able to encapsulate and in vitro release the drug dexamethasone. In addition, the designed micelle precursors were able to functionalize metallic NPs, such as gold NPs and iron oxide NPs, resulting in monodispersed hybrid nanomaterials with high stability in aqueous media. Therefore, a new triazole-derived micelle precursor was developed as a versatile encapsulation system, opening the way for the preparation of new micellar nanocarrier platforms for drug delivery, magnetic resonance imaging, or computed tomography contrast agents for therapeutic and diagnostic applications.

Synthesis of enzyme-responsive theranostic amphiphilic conjugated bottlebrush copolymers for enhanced anticancer drug delivery

Synthesis of polyfluorene (PF) based theranostic amphiphilic copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for promoted intracellular drug release and enhanced cancer therapy has been rarely reported likely due to the lack of efficient synthetic approaches to integrate these desirable properties. In this work, we recorded the successful preparation of well-defined theranostic amphiliphilic bottlebrush copolymers composing of fluorescent backbone of PF and tunable enzyme-degradable side chains of polytyrosine (PTyr) and POEGMA by integrating Suzuki coupling, NCA ROP and ATRP techniques. Notably, the resulting copolymer, PF₂₅-g-(PTyr₂₆-b-(POEGMA₂₈)₂ (P₄) with two branched POEGMA brushes tethered to one PTyr termini for each unit could form steady unimolecular micelles with higher fluorescence quantum yield of 18.3% in aqueous and greater entrapment efficiency (EE) of 91.0% for DOX ascribed to the efficient π-π stacking interactions between PTyr blocks and drug molecules and the unique structure of branched hydrophilic brushes with a moderate chain length. DOX@P₄ micelles revealed visualization of intracellular trafficking and accelerated drug release due to the enzyme-triggered degradation of PTyr blocks with proteinase K and subsequent deshielding of POEGMA corona for micelle destruction. In vitro and In vivo animal study further verified the intensive therapeutic efficiency with attenuated systematic toxicity. Taken together, we provided a universal strategy toward multifunctional polymeric delivery vehicles based on conjugated PF and biocompatible and degradable polypeptide by integratied Suzuki coupling and NCA ROP, and identified the branched structure of hydrophilic brushes for better performance of bottlebrush copolymers-based micelles for drug delivery applications. STATEMENT OF SIGNIFICANCE: Synthesis of polyfluorene (PF)-based theranostic amphiphilic copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for promoted intracellular drug release and enhanced cancer therapy has been rarely reported likely due to the lack of efficient synthetic approaches to integrate these desirable properties. We reported herein successful preparation of enzyme-responsive theranostic amphiliphilic bottlebrush copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for enhanced chemotherapy in vivo. This study therefore not only developed a universal strategy for the construction of multifunction polymeric vehicles based on the conjugated polymer of PF and degradable polypeptide by integrated Suzuki coupling and NCA ROP, but also emphasized the better stability of micelles endowed by the branched hydrophilic brushes than linear ones.

Cyclodextrin-Based Contrast Agents for Medical Imaging

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides consisting of multiple glucose subunits. CDs are widely used in host–guest chemistry and biochemistry due to their structural advantages, biocompatibility, and ability to form inclusion complexes. Recently, CDs have become of high interest in the field of medical imaging as a potential scaffold for the development of a large variety of the contrast agents suitable for magnetic resonance imaging, ultrasound imaging, photoacoustic imaging, positron emission tomography, single photon emission computed tomography, and computed tomography. The aim of this review is to summarize and highlight the achievements in the field of cyclodextrin-based contrast agents for medical imaging.

Polymer-Ligated Nanocrystals Enabled by Nonlinear Block Copolymer Nanoreactors: Synthesis, Properties, and Applications

The past several decades have witnessed substantial advances in synthesis and self-assembly of inorganic nanocrystals (NCs) due largely to their size- and shape-dependent properties for use in optics, optoelectronics, catalysis, energy conversion and storage, nanotechnology, and biomedical applications. Among various routes to NCs, the nonlinear block copolymer (BCP) nanoreactor technique has recently emerged as a general yet robust strategy for crafting a rich diversity of NCs of interest with precisely controlled dimensions, compositions, architectures, and surface chemistry. It is notable that nonlinear BCPs are unimolecular micelles, where each block copolymer arm of nonlinear BCP is covalently connected to a central core or polymer backbone. As such, their structures are static and stable, representing a class of functional polymers with complex architecture for directing the synthesis of NCs. In this review, recent progress in synthesizing NCs by capitalizing on two sets of nonlinear BCPs as nanoreactors are discussed. They are star-shaped BCPs for producing 0D spherical nanoparticles, including plain, hollow, and core-shell nanoparticles, and bottlebrush-like BCPs for creating 1D plain and core/shell nanorods (and nanowires) as well as nanotubes. As the surface of these NCs is intimately tethered with the outer blocks of nonlinear BCPs used, they can thus be regarded as polymer-ligated NCs (i.e., hairy NCs). First, the rational design and synthesis of nonlinear BCPs via controlled/living radical polymerizations is introduced. Subsequently, their use as the NC-directing nanoreactors to yield monodisperse nanoparticles and nanorods with judiciously engineered dimensions, compositions, and surface chemistry is examined. Afterward, the intriguing properties of such polymer-ligated NCs, which are found to depend sensitively on their sizes, architectures, and functionalities of surface polymer hairs, are highlighted. Some practical applications of these polymer-ligated NCs for energy conversion and storage and drug delivery are then discussed. Finally, challenges and opportunities in this rapidly evolving field are presented.

New insights into the synthesis, toxicity and applications of gold nanoparticles in CT imaging and treatment of cancer

The past decades have witnessed enormous development of gold nanoparticles (AuNPs) and their applications in the biomedical field, an area in which they show infinite potential. Abundant investigations have been conducted in improving AuNP synthesis, aimed at obtaining water-dispersible ultrasmall AuNPs, which can exhibit biocompatibility, renal clearance and minimal toxicity. Due to their excellent x-ray attenuation ability, special optical properties and surface modification properties, AuNPs are reported to be promising as computed tomography contrast agents and can be applied in radiotherapy, photothermal and photodynamic therapies, and drug delivery. In this review, synthesis methods and toxicity of AuNPs have been summarized, emphasizing the preparation of ultra-small AuNPs. Applications of AuNPs in computed tomography imaging and cancer treatment are also considered, revealing their potential in the clinic.

pH-Sensitive Mixed Micelles Assembled from PDEAEMA-PPEGMA and PCL-PPEGMA for Doxorubicin Delivery: Experimental and DPD Simulations Study

To decrease critical micelle concentration (CMC), improve stability, and keep high drug-loading capacity, three pH-sensitive mixed micelles applied for anticancer drug controlled delivery were prepared by the mixture of polymers poly (N,N-diethylaminoethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PDEAEMA-PPEGMA) and polycaprolactone-b-poly (poly(ethylene glycol) methyl ether methacrylate) (PCL-PPEGMA), which were synthesized and confirmed by 1H NMR and gel permeation chromatographic (GPC). The critical micelle concentration (CMC) values of the prepared mixed micelles were low, and the micellar sizes and zeta potentials of the blank mixed micelles demonstrated good pH-responsive behavior. Combined experimental techniques with dissipative particle dynamics (DPD) simulation, the particle sizes, zeta potentials, drug loading content (LC), encapsulation efficiency (EE), aggregation morphologies, and doxorubicin (DOX) distribution of the mixed micelles were investigated, and the high DOX-loading capacity of the mixed micelles was found. Both in vitro DOX release profiles and DPD simulations of the DOX dynamics release process exhibited less leakage and good stability in neutral conditions and accelerated drug release behavior with a little initial burst in slightly acidic conditions. Cytotoxicity tests showed that the polymer PDEAEMA-PPEGMA and the blank mixed micelles had good biocompatibility, and DOX-loaded mixed micelles revealed certain cytotoxicity. These results suggest that the drug-loaded mixed micelles that consisted of the two polymers PDEAEMA-PPEGMA and PCL-PPEGMA can be new types of pH-responsive well-controlled release anticancer drug delivery mixed micelles.

Red fluorescent pyrazoline-BODIPY nanoparticles for ultrafast and long-term bioimaging

Fluorescence bioimaging is very significant in studying biological processes. Fluorescent nanoparticles (NPs) manufactured from aggregation-induced emission (AIE) materials, as promising candidates, have attracted more attention. However, it is still a challenge to explore suitable AIE NPs for bioimaging. Herein, we synthesized pyrazoline-BODIPY (PZL-BDP) with a donor and acceptor (D-A) structure by a condensation reaction, cultured its single crystal, and studied its twisted intramolecular charge transfer (TICT) and AIE effects. PZL-BDP could self-assemble to form red fluorescent nanoparticles (PZL-BDP NPs) which showed a good fluorescence quantum yield of 15.8% in water. PZL-BDP NPs with excellent stability and biocompatibility exhibited a large Stokes shift (Δλ = 111 nm) which resulted in the reduction of external interference and enhancement of the fluorescence contrast. Furthermore, these nanoparticles could be readily internalized by HeLa cells and they stain the cells in just five seconds, indicating an ultrafast bioimaging protocol. Moreover, long-term tracking fluorescence signals in vivo for about 12 days were obtained. The bright red fluorescence, ultrafast cell staining ability, and long-term in vivo tracking competence outline the great potential of rational design nanomaterials with AIE characteristics for monitoring biological processes.

pH/Reduction Dual-Stimuli-Responsive Cross-Linked Micelles Based on Multi-Functional Amphiphilic Star Copolymer: Synthesis and Controlled Anti-Cancer Drug Release

Novel approach has been constructed for preparing the amphiphilic star copolymer pH/reduction stimuli-responsive cross-linked micelles (SCMs) as a smart drug delivery system for the well-controlled anti-tumor drug doxorubicin (DOX) release. The SCMs had a low CMC value of 5.3 mg/L. The blank and DOX-loaded SCMs both had a spherical shape with sizes around 100-180 nm. In addition, the good stability and well pH/reduction-sensitivity of the SCMs were determined by dynamic light scattering (DLS) as well. The SCMs owned a low release of DOX in bloodstream and normal tissues while it had a fast release in tumor higher glutathione (GSH) concentration and/or lower pH value conditions, which demonstrates their pH/reduction dual-responsiveness. Furthermore, we conducted the thermodynamic analysis to study the interactions between the DOX and polymer micelles in the DOX release process. The values of the thermodynamic parameters at pH 7.4 and at pH 5.0 conditions indicated that the DOX release was endothermic and controlled mainly by the forces of an electrostatic interaction. At pH 5.0 with 10 mM GSH condition, electrostatic interaction, chemical bond, and hydrophobic interactions contributed together on DOX release. With the low cytotoxicity of blank SCMs and well cytotoxicity of DOX-loaded SCMs, the results indicated that the SCMs could form a smart cancer microenvironment-responsive drug delivery system. The release kinetic and thermodynamic analysis offer a theoretical foundation for the interaction between drug molecules and polymer matrices, which helps provide a roadmap for the oriented design and control of anti-cancer drug release for cancer therapy.

Mesoscale Simulations of pH-Responsive Amphiphilic Polymeric Micelles for Oral Drug Delivery

It is of great significance to study the structure property and self-assembly of amphiphilic block copolymer in order to effectively and efficiently design and prepare drug delivery systems. In this work, dissipative particle dynamics (DPD) simulation method was used to investigate the structure property and self-assembly ability of pH-responsive amphiphilic block copolymer poly(methyl methacrylate-co-methacrylic acid)-b-poly(aminoethyl methacrylate) (poly(MMA-co-MAA)-b-PAEMA). The effects of different block ratios (hydrophilic PAEMA segment and pH-sensitive PMAA segment) in copolymer on self-assembly and drug loading capacity including drug distribution were extensively investigated. The increase of hydrophilic PAEMA facilitated the formation of a typical core-shell structure as well as a hydrophobic PMAA segment. Furthermore, the optimal drug-carrier ratio was confirmed by an analysis of the drug distribution during the self-assembly process of block copolymer and model drug Ibuprofen (IBU). In addition, the drug distribution and nanostructure of IBU-loaded polymeric micelles (PMs) self-assembled from precise block copolymer (PMMA-b-PMAA-b-PAEMA) and block copolymer (poly(MMA-co-MAA)-b-PAEMA) with random pH-responsive/hydrophobic structure were evaluated, showing that almost all drug molecules were encapsulated into a core for a random copolymer compared to the analogue. The nanostructures of IBU-loaded PMs at different pH values were evaluated. The results displayed that the nanostructure was stable at pH < pK_a and anomalous at pH > pK_a which indicated drug release, suggesting that the PMs could be used in oral drug delivery. These findings proved that the amphiphilic block copolymer P(MMA₃₀-co-MAA₃₃)-b-PAEMA₃₈ with random structure and pH-sensitivity might be a potential drug carrier. Moreover, DPD simulation shows potential to study the structure property of PMs self-assembled from amphiphilic block copolymer.

Biodegradable Redox-Sensitive Star Polymer Nanomicelles for Enhancing Doxorubicin Delivery

A typical amphiphilic star polymer adamantane-[poly(lactic-co-glycolic acid)-bis(2-carboxyethyl) sulfide-poly(ethylene glycol) monomethyl ether)]₄ with a specific hydrophilic/redox-sensitive/hydrophobic structure was designed and synthesized through ring opening and esterification reactions. The self-assembled nanomicelles were used as doxorubicin (DOX) delivery vehicles with suitable critical micelle concentrations (5.0 mg/L). After the drug being loaded, drug-loaded micelles showed good drug-loading efficiency (10.39%), encapsulation efficiency (58.1%), and drug release (up to 60%) under simulated biological environment conditions. In addition, the backbone structure of the biodegradable polymer was easily hydrolyzed by the action of biological enzymes. As expected, cell-based studies showed that the designed polymer micelles possessed good biocompatibility (a survival rate of 85% for NH-3T3 cells). Moreover, the drug (DOX) still maintained good anti-cancer effects after being loaded, which caused 40% of MCF-7 cells to survive. These redox-sensitive micelles showed anti-tumor therapeutic potential.

Effect of capping methods on the morphology of silver nanoparticles: study on the media-induced release of silver from the nanocomposite β-cyclodextrin/alginate

Novel multi-functional nanocomposites were fabricated from polysaccharides, alginate (Alg) and β-cyclodextrin (β-CD) via the ionotropic gelation mechanism.

Biodegradable polyester unimolecular systems as emerging materials for therapeutic applications

Unimolecular micelles, as a class of single-molecular micelles, are structurally stable regardless of their concentrations or alterations of the outer environment such as pH, temperature, ion strength etc. in comparison with conventional polymeric micelles. Polyester unimolecular micelles are extensively applied in bio-medical fields because of their stability, biocompatibility, biodegradability, structural-controllabilty etc. In this review, the most recent developments in polyester unimolecular micelle designs in terms of Boltorn polymer H40 core, cyclodextrin, dendrimer or dendrimer-like polymer, or polyhedral oligomeric silsesquioxane (POSS) based polyester unimolecular micelles are presented. The significance and application in biomedical fields including drug delivery, bio-imaging and theranostics are also classified in this review. Finally, the remaining challenges and future perspectives for further development of unimolecular micelles as therapeutic materials are also discussed.