Functionalized Thermoresponsive Micelles Self-Assembled from Biotin-PEG-b-P(NIPAAm-co-HMAAm)-b-PMMA for Tumor Cell Target

A Bibliometric Analysis and Systematic Review of Research Advances in In Situ Gel Drug Delivery Systems from 2003 to 2023

Objective: We aimed analyze research trends in in situ gel drug delivery systems. Methods: Studies from 2003 to 2023 were systematically obtained from the Web of Science database and analyzed using VOSviewer software to evaluate publication trends, citation patterns, and collaborative networks. Results: A total of 990 articles were reviewed. There has been a significant increase in publications since 2019, with the highest number of publications occurring in 2023. China was the leading country in terms of publication output. Cairo University and King Abdulaziz University were identified as the top contributing institutions. Key researchers included Zhao, Xia, Hosny, and Kim. The research primarily focused on developing new formulations, optimizing materials (e.g., biocompatible and biodegradable materials), and exploring clinical applications such as nasal-brain delivery for Alzheimer's treatment. Conclusions: In situ gel systems have gained widespread use in clinical practice due to their ability to provide prolonged drug release and enhance patient compliance. This area remains crucial for future research, particularly in formulation design and administration methods.

Current Principles, Challenges, and New Metrics in pH-Responsive Drug Delivery Systems for Systemic Cancer Therapy

The paradigm of drug delivery via particulate formulations is one of the leading ideas that enable overcoming limitations of traditional chemotherapeutic agents. The trend toward more complex multifunctional drug carriers is well-traced in the literature. Nowadays, the prospectiveness of stimuli-responsive systems capable of controlled cargo release in the lesion nidus is widely accepted. Both endogenous and exogenous stimuli are employed for this purpose; however, endogenous pH is the most common trigger. Unfortunately, scientists encounter multiple challenges on the way to the implementation of this idea related to the vehicles' accumulation in off-target tissues, their immunogenicity, the complexity of drug delivery to intracellular targets, and finally, the difficulties in the fabrication of carriers matching all imposed requirements. Here, we discuss fundamental strategies for pH-responsive drug delivery, as well as limitations related to such carriers' application, and reveal the main problems, weaknesses, and reasons for poor clinical results. Moreover, we attempted to formulate the profiles of an "ideal" drug carrier in the frame of different strategies drawing on the example of metal-comprising materials and considered recently published studies through the lens of these profiles. We believe that this approach will facilitate the formulation of the main challenges facing researchers and the identification of the most promising trends in technology development.

Biotin-decorated all-HPMA polymeric micelles for paclitaxel delivery

To avoid poly(ethylene glycol)-related issues of nanomedicines such as accelerated blood clearance, fully N-2-hydroxypropyl methacrylamide (HPMAm)-based polymeric micelles decorated with biotin for drug delivery were designed. To this end, a biotin-functionalized chain transfer agent (CTA), 4-cyano-4-[(dodecylsulfanylthiocarbonyl)-sulfanyl]pentanoic acid (biotin-CDTPA), was synthesized for reversible addition-fragmentation chain-transfer (RAFT) polymerization. Amphiphilic poly(N-2-hydroxypropyl methacrylamide)-block-poly(N-2-benzoyloxypropyl methacrylamide) (p(HPMAm)-b-p(HPMAm-Bz)) with molecular weights ranging from 8 to 24 kDa were synthesized using CDTPA or biotin-CDTPA as CTA and 2,2'-azobis(2-methylpropionitrile) as initiator. The copolymers self-assembled in aqueous media into micelles with sizes of 40-90 nm which positively correlated to the chain length of the hydrophobic block in the polymers, whereas the critical micelle concentrations decreased with increasing hydrophobic block length. The polymer with a molecular weight of 22.1 kDa was used to prepare paclitaxel-loaded micelles which had sizes between 61 and 70 nm, and a maximum loading capacity of around 10 wt%. A549 lung cancer cells overexpressing the biotin receptor, internalized the biotin-decorated micelles more efficiently than non-targeted micelles, while very low internalization of both types of micelles by HEK293 human embryonic kidney cells lacking the biotin receptor was observed. As a consequence, the paclitaxel-loaded micelles with biotin decoration exhibited stronger cytotoxicity in A549 cells than non-targeted micelles. Overall, a synthetic pathway to obtain actively targeted poly(ethylene glycol)-free micelles fully based on a poly(HPMAm) backbone was established. These polymeric micelles are promising systems for the delivery of hydrophobic anticancer drugs.

100th Anniversary of Macromolecular Science Viewpoint: Poly(N-isopropylacrylamide)-Based Thermally Responsive Micelles

Poly(N-isopropylacrylamide) (PNIPAAm)-based thermally responsive micelles are of great importance as smart materials for a number of applications such as drug delivery and biosensing, owing to their tunable lower critical solution temperature (LCST). Their design and synthesis in the nanoscale size range have been widely studied, and research interest in their structural and physic-chemical properties is continually growing. In this Viewpoint, representative research on the construction of PNIPAAm-based thermally responsive micelles as well as their applications are highlighted and discussed, which would serve as a good start for newcomers in this field and a positive guide for future research.

Influence of Hydrophobic Chains in Nanocarriers on Antitumor Efficacy of Docetaxel Nanoparticles

The composition of amphiphilic nanocarriers can affect the antitumor efficacy of drug-loaded nanoparticles and should be researched systematically. In this paper, to study the influence of hydrophobic chains, an amphiphilic copolymer (PEG₄₅PCL₁₇) and hydrophilic PEG (PEG₄₅) were utilized as nanocarriers to prepare docetaxel-loaded nanoparticles (DTX/PEG₄₅PCL₁₇ nanoparticles and DTX/PEG₄₅ nanoparticles) through an antisolvent precipitation method. The two DTX nanoparticles presented a similar drug loading content of approximately 60% and a sheet-like morphology. During the preparation procedure, the drug loading content affected the morphology of DTX nanoparticles, and the nanocarrier composition influenced the particle size. Compared with DTX/PEG₄₅ nanoparticles, DTX/PEG₄₅PCL₁₇ nanoparticles showed a smaller mean diameter and better in vitro and in vivo antitumor activity. The cytotoxicity of DTX/PEG₄₅PCL₁₇ nanoparticles against 4T1 cells was 1.31 μg mL^-1, 3.4-fold lower than that of DTX/PEG₄₅ nanoparticles. More importantly, DTX/PEG₄₅PCL₁₇ nanoparticles showed significantly higher antitumor activity in vivo, with an inhibition rate over 80%, 1.5-fold higher than that of DTX/PEG₄₅ nanoparticles. Based on these results, antitumor activity appears to be significantly affected by the particle size, which was determined by the composition of the nanocarrier. In summary, to improve antitumor efficacy, the amphiphilic structure should be considered and optimized in the design of nanocarriers.

Influence of Grafted Block Copolymer Structure on Thermoresponsiveness of Superparamagnetic Core-Shell Nanoparticles

The morphology and topology of thermoresponsive polymers have a strong impact on their responsive properties. Grafting onto spherical particles has been shown to reduce responsiveness and transition temperatures; grafting of block copolymers has shown that switchable or retained wettability of a surface or particle during desolvation of one block can take place. Here, doubly thermoresponsive block copolymers were grafted onto spherical, monodisperse, and superparamagnetic iron oxide nanoparticles to investigate the effect of thermal desolvation on spherical brushes of block copolymers. By inverting the block order, the influence of core proximity on the responsive properties of the individual blocks could be studied as well as their relative influence on the nanoparticle colloidal stability. The inner block was shown to experience a stronger reduction in transition temperature and transition enthalpy compared to the outer block. Still, the outer block also experiences a significant reduction in responsiveness due to the restricted environment in the nanoparticle shell compared to that of the free polymer state. The demonstrated pronounced distance dependence importantly implies the possibility, but also the necessity, to radially tailor polymer hydration transitions for applications such as drug delivery, hyperthermia, and biotechnological separation for which thermally responsive nanoparticles are being developed.

Well-defined podophyllotoxin polyprodrug brushes: preparation via RAFT polymerization and evaluation as drug carriers

Novel poly(triethylene glycol methacrylate)-b-poly(podophyllotoxin methacrylate) copolymers (PTP) with a well-defined structure were designed and synthesized by direct RAFT polymerization with the hydrophobic monomer derivative from the anticancer drug podophyllotoxin.

pH-Activated Targeting Drug Delivery System Based on the Selective Binding of Phenylboronic Acid

Phenylboronic acid (PBA) is a tumor-targeting molecule, but its nonspecific interaction with normal cells or other components containing cis-diol residues undoubtedly limits its potential application in tumor-targeting drug delivery. Herein, we developed fructose-coated mixed micelles via PBA-terminated polyethylene glycol monostearate (PBA-PEG-C18) and Pluronic P123 (PEG20-PPG70-PEG20) to solve this problem, as the stability of borate formed by PBA and fructose was dramatically dependent on pH. The fluorescence spectroscopic results indicated that the borate formed by PBA and fructose decomposed at a decreased pH, and better binding between PBA and sialic acid (SA) was observed at a low pH. These results implied that the fructose groups decorated on the surface of the micelles could be out-competed by SA at a low pH. In vitro uptake and cytotoxicity studies demonstrated that the fructose coating on the mixed micelles improved the endocytosis and enhanced the cytotoxicity of drug-loaded mixed micelles in HepG2 cells but reduced the cytotoxicity in normal cells. These results demonstrate that a simple decorating strategy may facilitate PBA-targeted nanoparticles for tumor-specific drug delivery.

Stimuli-responsive and hemocompatible pseudozwitterionic interfaces

We report a novel biomacromolecular formula for the design of hemocompatible gel interfaces of N-isopropylacrylamide (NIPAAm) and mixed-charge pairs of [2-(methacryloyloxy)ethyl]trimethylammonium (TMA) and 3-sulfopropyl methacrylate (SA) with overall electrical neutrality. The study stresses on how well-defined compositions of nonionic NIPAAm and pseudozwitterionic TMA/SA in the poly(NIPAAm-co-TMA/SA) hydrogels along with environmental conditions (temperature, ionic strength, and solution pH) affect swelling and adhesion of biofoulants on their surfaces. When challenged with plasma proteins, bacteria, recalcified platelets, or whole blood, stimuli-responsive hydrogels better resisted their adhesion as the content of mixed charges in the copolymer increased, to reach nonbiofouling for the gels made of 100% TMA/SA. The low hemolytic activity (0.5%) associated with a long plasma clotting time (10 min) suggests excellent hemocompatibility excellent hemocompatibility. Finally, hydrogels containing both NIPAAm and TMA/SA tend to exhibit preferential adhesion of leukocytes.

Thermoresponsive block copolymer micelles with tunable pyrrolidone-based polymer cores: structure/property correlations and application as drug carriers

Residue structure affects the physicochemical properties, drug loading efficiency, and thermoresponsive drug release profiles of block copolymer micelles with pyrrolidone-based polymer cores.

Targeted delivery of Doxorubicin by folic acid-decorated dual functional nanocarrier

Doxorubicin (DOX) is one of the most commonly used antineoplastic agents, but its clinical application is oftentimes coupled with severe side effects. Selective delivery of DOX to tumors via nanosized drug carrier represents an attractive approach to this problem. Previously, we developed a dual functional nanomicellar carrier, PEG5K-embelin2 (PEG5K-EB2), which was able to deliver paclitaxel (PTX) selectively to tumors and to achieve an enhanced therapeutic effect. In the present study, we examined the utility of PEG5K-EB2 to deliver DOX to tumors. In addition, folic acid (FA) was coupled to the surface of the PEG5K-EB2 micelles (FA-PEG5K-EB2) to further improve the selective targetability of the system. DOX-loaded PEG5K-EB2 micelles were uniformly spherical particles with a diameter of approximately 20 nm. Incorporation of FA had minimal effect on the size of the particles. The DOX loading efficiency was as high as 91.7% and 93.5% for PEG5K-EB2 and FA-PEG5K-EB2, respectively. DOX formulated in PEG5K-EB2 micelles (with or without FA decoration) demonstrated sustained kinetics of DOX release compared to free DOX. FA-PEG5K-EB2 significantly facilitated the intracellular uptake of DOX over free DOX and PEGylated liposomal DOX (Doxil) in breast cancer cells, 4T1.2, and drug resistant cells, NCI/ADR-RES. P-gp ATPase assay showed that PEG5K-EB2 significantly inhibited the function of the P-gp efflux pump. The maximum tolerated dose of DOX-loaded PEG5K-EB2 micelles was 15 mg/kg in mice, which was 1.5-fold greater than that for free DOX. Pharmacokinetics (PK) and biodistribution studies showed that both types of DOX-loaded micelles, especially FA-PEG5K-EB2, were able to significantly prolong the blood circulation time of DOX and facilitate its preferential accumulation at the tumor tissue. Finally, DOX/PEG5K-EB2 mixed micelles demonstrated significantly enhanced tumor growth inhibitory effect with minimal toxicity in comparison to free DOX and Doxil and the antitumor activity was further enhanced after the decoration by folic acid. Our data suggest that FA-PEG5K-EB2 micelles represent a promising DOX delivery system that warrants more study in the future.

Thermo-triggered drug delivery from polymeric micelles of poly(N-isopropylacrylamide-co-acrylamide)-b-poly(n-butyl methacrylate) for tumor targeting

Novel temperature-sensitive micelles, possessing a core-shell structure, were successfully fabricated and evaluated as possible systems for targeting anticancer drugs to solid tumors. The amphiphilic block copolymer poly( N-isopropylacrylamide- co-acrylamide)-b-poly( n-butyl methacrylate) was used to achieve a stimuli-responsive on/off release and spatial specificity. The anticancer drug methotrexate, which is poorly water soluble, was used as the model. Fourier transform–infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel-permeation chromatography, and critical micelle concentration were used to evaluate the successful synthesis of block copolymers with a lower critical solution temperature ~40°C. Based on transmission electron microscope images, the micelles are spherical particles with narrow size distribution. The thermally triggered release of methotrexate was observed in vitro. Quartz crystal microbalance with dissipation was used to investigate the interactions of the polymeric micelles with bovine serum albumin, to illustrate protein adsorption and cell attachment. Cytotoxicity studies were conducted on Lewis lung carcinoma cells, and the anticancer activity of methotrexate-loaded micelles was significantly enhanced in combination with hyperthermia. The thermo-sensitive characteristics of the micelles make them applicable as smart drug delivery systems, when combined with localized hyperthermia.

Poly(ethylene oxide) (PEO)-based ABC triblock terpolymers – synthetic complexity vs. application benefits

This review presents a short summary of possible synthetic routes for the synthesis of poly(ethylene oxide) (PEO) containing triblock terpolymers, as well as different applications in the bulk or in solution – including the preparation of porous materials, hybrid systems, and carriers for controlled drug delivery.

Facile fabrication of multistimuli-responsive metallo-supramolecular core cross-linked block copolymer micelles

Metallo-supramolecular core cross-linked (CCL) micelles are fabricated from terpyridine-functionalized double hydrophilic block copolymers, poly(2-(2-methoxyethoxy)ethyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate-co-4'-(6-methacryloxyhexyloxy)-2,2':6',2″-terpyridine) [PMEO2 MA-b-P(DEA-co-TPHMA)] via the formation of bis(terpyridine)ruthenium(II) complexes. These metallo-supramolecular CCL micelles exhibit not only high structural integrity under different pH values and temperatures in aqueous solution, but multistimuli responsiveness including pH-responsive cores, thermo-responsive shells, and reversible dissociation of bis(terpyridine)ruthenium(II) complexes upon addition of competitive metal ion chelator, which allows for precisely controlled release of the encapsulated hydrophobic guest molecules via the combination of different stimuli.

Stimulus-sensitive polymeric nanoparticles and their applications as drug and gene carriers

Polymeric nanoparticles are promising candidates as drug and gene carriers. Among polymeric nanoparticles, those that are responsive to internal or external stimuli are of greater interest because they allow more efficient delivery of therapeutics to pathological regions. Stimulus-sensitive polymeric nanoparticles have been fabricated based on numerous nanostructures, including micelles, vesicles, crosslinked nanoparticles, and hybrid nanoparticles. The changes in chemical or physical properties of polymeric nanoparticles that occur in response to single, dual, or multiple stimuli endow these nanoparticles with the ability to retain cargoes during circulation, target the pathological region, and release their cargoes after cell internalization. This Review focuses on the most recent developments in the preparation of stimulus-sensitive polymeric nanoparticles and their applications in drug and gene delivery.

Protein-polymer hybrid nanoparticles for drug delivery

Amphiphilic bovine serum albumin-poly(methyl methacrylate) conjugate forms nanoparticles with the uniform size of ~100 nm by self-assembling. Loaded with the hydrophobic anti-tumor drug camptothecin, the nanoparticle efficiently delivers drugs into cancer cells, and thus inhibits ~79% of tumor growth in animals compared with free drug.

In vitro and in vivo antitumor activity of a novel pH-activated polymeric drug delivery system for doxorubicin

Background

Conventional chemotherapy agent such as doxorubicin (DOX) is of limited clinical use because of its inherently low selectivity, which can lead to systemic toxicity in normal healthy tissue.

Methods

A pH stimuli-sensitive conjugate based on polyethylene glycol (PEG) with covalently attachment doxorubicin via hydrazone bond (PEG-hyd-DOX) was prepared for tumor targeting delivery system. While PEG-DOX conjugates via amid bond (PEG-ami-DOX) was synthesized as control.

Results

The synthetic conjugates were confirmed by proton nuclear magnetic resonance (NMR) spectroscopy, the release profile of DOX from PEG-hyd-DOX was acid-liable for the hydrazone linkage between DOX and PEG, led to different intracellular uptake route; intracellular accumulation of PEG-hyd-DOX was higher than PEG-ami-DOX due to its pH-triggered profile, and thereby more cytotoxicity against MCF-7, MDA-MB-231 (breast cancer models) and HepG2 (hepatocellular carcinoma model) cell lines. Following the in vitro results, we xenografted MDA-MB-231 cell onto SCID mice, PEG-hyd-DOX showed stronger antitumor efficacy than free DOX and was tumor-targeting.

Conclusions

Results from these in vivo experiments were consistent with our in vitro results; suggested this pH-triggered PEG-hyd-DOX conjugate could target DOX to tumor tissues and release free drugs by acidic tumor environment, which would be potent in antitumor drug delivery.

Luminescent Iridium(III)-Containing Block Copolymers: Self-Assembly into Biotin-Labeled Micelles for Biodetection Assays

Luminescent polymers containing Ir(ppy)₂(bpy) PF₆ complexes, biocompatible poly(ethylene glycol) (PEG) chains, and biotin moieties were synthesized via ring-opening metathesis polymerization (ROMP). Their self-assembly in water into micelles resulted in an increased quantum yield compared to open polymer chains in acetonitrile, which is likely due to core rigidity and desolvation. Streptavidin coated magnetic beads were employed to analyze the binding ability of these micelles. The positioning of the molecular recognition moiety biotin within the polymer chain had a very significant effect on the availability of biotin on the micelle surface and the ability of the micelles to bind to streptavidin. Simply attaching biotin to the end of the ROMP polymer yielded micelles in which the biotin units were shielded by the PEG chains, whereas the synthesis of a new ROMP monomer containing biotin at the end of the PEG chains resulted in improved surface availability of the biotin group. Preliminary experiments in which streptavidin was microcontact-printed onto functionalized glass coverslips also indicated specific binding between the micelles and streptavidin and further demonstrated the potential of these micelle systems to function as luminescent probes in solid-phase biodetection assays.

Tumor accumulation, penetration, and antitumor response of cisplatin-loaded gelatin/poly(acrylic acid) nanoparticles

In this report, the cisplatin (CDDP)-loaded gelatin/poly(acrylic acid) (GEL-PAA) nanoparticles with a spherical shape and drug loading content of 24.6% were prepared. In vivo near-infrared fluorescence (NIRF) imaging and ex vivo gamma scintillation counting analyses reveal that CDDP-loaded GEL-PAA nanoparticles have prominent passive tumor-targeting ability and the nontarget nanoparticles can be readily excreted from the body. Further, it is demonstrated that the CDDP-loaded nanoparticles have the ability to penetrate the tumor after their extravasation through the leaky vessels and distribute in a distance of about 20 μm from the vessels at 24 h postinjection. The in vivo antitumor responses reveal that the nanoparticle formulation exhibits significantly superior in vivo antitumor effect than free CDDP by the comparison of tumor volume and the examinations of cell apoptosis and proliferation in tumor tissues through proliferating cell nuclear antigen (PCNA) and terminal deoxynucleotidyl-transferase-mediated nick end labeling (TUNEL) methods.

To exploit the tumor microenvironment: Passive and active tumor targeting of nanocarriers for anti-cancer drug delivery

Because of the particular characteristics of the tumor microenvironment and tumor angiogenesis, it is possible to design drug delivery systems that specifically target anti-cancer drugs to tumors. Most of the conventional chemotherapeutic agents have poor pharmacokinetics profiles and are distributed non-specifically in the body leading to systemic toxicity associated with serious side effects. Therefore, the development of drug delivery systems able to target the tumor site is becoming a real challenge that is currently addressed. Nanomedicine can reach tumor passively through the leaky vasculature surrounding the tumors by the Enhanced Permeability and Retention effect whereas ligands grafted at the surface of nanocarriers allow active targeting by binding to the receptors overexpressed by cancer cells or angiogenic endothelial cells. This review is divided into two parts: the first one describes the tumor microenvironment and the second one focuses on the exploitation and the understanding of these characteristics to design new drug delivery systems targeting the tumor. Delivery of conventional chemotherapeutic anti-cancer drugs is mainly discussed.

Hyperbranched amphiphilic polymer with folate mediated targeting property

Hyperbranched amphiphilic polymer PG6-PLA-PEG was synthesized through grafting hydrophobic poly(D,L-lactide) (PLA) segments and hydrophilic poly(ethylene glycol) (PEG) blocks to hydrophilic hyperbranched polyglycerol core (PG6), subsequently. To achieve cell targeting property, folic acid (FA) was further incorporated to the hyperbranched polymer to obtain PG6-PLA-PEG-FA. The polymers were characterized by (1)H NMR, UV-vis spectroscopy and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. Due to the amphiphilicity, PG6-PLA-PEG and PG6-PLA-PEG-FA could self-assemble to form nanoparticles in aqueous solutions. Antineoplastic drug, paclitaxel (PTX), was encapsulated into the nanoparticles. The nanoparticles were observed by transmission electron microscopy (TEM). The targeting property of PG6-PLA-PEG-FA was evaluated in vitro. The results showed that the PTX loaded PG6-PLA-PEG-FA nanoparticles exhibited enhanced inhibition on folate receptor positive tumor cells due to the folate mediated targeting.

Lactose mediated liver-targeting effect observed by ex vivo imaging technology

Two kinds of micelles containing Rhodamine B were prepared by a solvent evaporation method. One (Lac-f-micelles: lactose-free micelles) was from a Rhodamine-containing copolymer, poly(ethylene glycol)-b-poly(l-lactide-co-2,2-dihydroxylmethyl-propylene carbonate/Rhodamine) [PEG(5000)-b-P(LA(4000)-co-DHP(600)/Rhodamine)], and the other (Lac+micelles lactose-containing micelles) was from a mixture of the targeting copolymer lactose-poly(ethylene glycol)-poly (l-Lactide) [Lac-PEG(4600)-PLA(4500)] and the Rhodamine-containing copolymer PEG(5000)-b-P(LA(4000)-co-DHP(600)/Rhodamine). ESEM and DLS measurements showed that the two kinds of micelles have similar size (in the range of 60-100 nm) and size distribution. Cellular uptake studies in vitro revealed that the Lac+micelles showed stronger endocytosis ability than Lac-f-micelles in SMMC7221 human liver cancer cells, but the Lac+micelles were rarely internalized by Vero cells. The micelle solutions were administrated into mice via tail intravenous injection. Then, five visceral organs were isolated from the mice at specified time intervals and relative fluorescent intensities of the ex vivo organs and their homogenates were examined by CRI Maestro 500FL in vivo imaging system. The results showed that the Lac+micelles showed more remarkable liver-targeting effect than the Lac-f-micelles. And the liver-targeting effect could be established in ca. 12 h after tail i.v. injection.

Fast thermoresponsive BAB-type HEMA/NIPAAm triblock copolymer solutions for embolization of abnormal blood vessels

Thermoresponsive BAB-type HEMA/NIPAAm triblock copolymers (A = NIPAAm, B = HEMA) were prepared by atomic transfer radical polymerization (ATRP). BAB1-6 with shorter PNIPAAm blocks failed to form stable gel; while a relatively stable gel could be achieved by BAB1-8 with longer PNIPAAm blocks when copolymer aqueous solution was heated up. Introducing radiopaque agent (RA) was shown to slightly increase the transition temperature and gelation time, but the gelling ability was strengthened due to slightly weakening dehydration of copolymer in the mixture of water and RA. BAB1-8 aqueous solution about 5 wt% in the presence of RA was demonstrated to successfully occlude the cerebral rete mirabiles (RMs) and renal arteries of pigs. Within 3-month surgery, no recanalization was observed and the embolized kidney shrank considerably. Histological assay of embolized kidney demonstrated interstitial fibrosis and calcification as well as the thickening of renal small artery. This temperature sensitive copolymer with well-defined architecture holds a great potential as an embolic agent for treating arteriovenous malformations (AVMs) and renal disease due to the design flexibility of ATRP.

Bioconjugation of biotin to the interfaces of polymeric micelles via in situ click chemistry

Azido-containing amphiphilic triblock copolymer poly(ethylene glycol)-b-poly(azidoethyl methacrylate)-b-poly(methyl methacrylate) (PEG-b-PAzEMA-b-PMMA) was prepared by postpolymerization functionalization of poly(ethylene glycol)-b-poly(hydroxyethyl methacrylate)-b-poly(methyl methacrylate) (PEG-b-PHEMA-b-PMMA). In aqueous media, PEG-b-PAzEMA-b-PMMA self-assembled into spherical micelles with the azide groups at the hydrophobic/hydrophilic interface due to the molecular architecture. Biotin was conjugated to the micelles by in situ click chemistry between azide groups and alkynated biotin, resulting in the formation of a functional interface between the hydrophilic shell and the hydrophobic core. The bioavailability of biotin to avidin was demonstrated by an avidin/4'-hydroxyazobenzene-2-carboxylic acid (avidin/HABA) assay, transmission electron microscopy, and dynamic light scattering investigations.