Temperature-Induced Emission Enhancement of Star Conjugated Copolymers with Poly(2-(dimethylamino)ethyl methacrylate) Coronas for Detection of Bacteria

Construction of a Drug Delivery System via pH-Responsive Polymeric Nanomicelles Containing Ferrocene for DOX Release and Enhancement of Therapeutic Effects

We report an amphiphilic block copolymer via poly(ethylene glycol) methyl ether-D_labile-poly(caprolactone)-ferrocene (mPEG-D_labile-PCL-Fc) to deliver anticancer drug doxorubicin (DOX). Lipase Novozyme-435 was used as a catalyst for ring-opening polymerization with ε-caprolactone, and an acid-sensitive Schiff base was used to connect the hydrophilic and hydrophobic parts; the ferrocene provided ferrous ions and was introduced at the end of the amphiphilic copolymer. The resulting copolymers were characterized by ¹H NMR/¹³C NMR and could be self-assembled in an aqueous solution to form nanomicelles with PCL-Fc as a hydrophobic core and mPEG as a hydrophilic shell. Transmission electron microscopy showed that the micelles were spherical and nanosized before and after DOX loading. The blank micelles also showed good biocompatibility. The drug-loaded polymeric nanomicelles exhibited a positive anticancer effect relative to the copolymers without ferrocene; the therapeutic effect of drug-loaded micelles containing ferrocene was more obvious. In vitro drug release results also showed that the polymer had a good pH response. Confocal microscopy also showed that polymeric micelles can effectively deliver and release the drug; the polymer containing ferrocene also leads to significantly improved ROS levels in tumor cells. Ferrocene can effectively and synergistically inhibit tumor cells with DOX.

Self-Organization in Dilute Aqueous Solutions of Thermoresponsive Star-Shaped Six-Arm Poly-2-Alkyl-2-Oxazines and Poly-2-Alkyl-2-Oxazolines

The behavior of star-shaped six-arm poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines in aqueous solutions on heating was studied by light scattering, turbidimetry and microcalorimetry. The core of stars was hexaaza [2₆] orthoparacyclophane and the arms were poly-2-ethyl-2-oxazine, poly-2-isopropyl-2-oxazine, poly-2-ethyl-2-oxazoline, and poly-2-isopropyl-2-oxazoline. The arm structure affects the properties of polymers already at low temperatures. Molecules and aggregates were present in solutions of poly-2-alkyl-2-oxazines, while aggregates of two types were observed in the case of poly-2-alkyl-2-oxazolines. On heating below the phase separation temperature, the characteristics of the investigated solutions did not depend practically on temperature. An increase in the dehydration degree of poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines led to the formation of intermolecular hydrogen bonds, and aggregation was the dominant process near the phase separation temperature. It was shown that the characteristics of the phase transition in solutions of the studied polymer stars are determined primarily by the arm structure, while the influence of the molar mass is not so significant. In comparison with literature data, the role of the hydrophobic core structure in the formation of the properties of star-shaped polymers was analyzed.

Nanotheranostics: A Possible Solution for Drug-Resistant Staphylococcus aureus and their Biofilms?

Staphylococcus aureus is a notorious pathogen that colonizes implants (orthopedic and breast implants) and wounds with a vicious resistance to antibiotic therapy. Methicillin-resistant S. aureus (MRSA) is a catastrophe mainly restricted to hospitals and emerged to community reservoirs, acquiring resistance and forming biofilms. Treating biofilms is problematic except via implant removal or wound debridement. Nanoparticles (NPs) and nanofibers could combat superbugs and biofilms and rapidly diagnose MRSA. Nanotheranostics combine diagnostics and therapeutics into a single agent. This comprehensive review is interpretative, utilizing mainly recent literature (since 2016) besides the older remarkable studies sourced via Google Scholar and PubMed. We unravel the molecular S. aureus resistance and complex biofilm. The diagnostic properties and detailed antibacterial and antibiofilm NP mechanisms are elucidated in exciting stories. We highlight the challenges of bacterial infections nanotheranostics. Finally, we discuss the literature and provide "three action appraisals". (i) The first appraisal consists of preventive actions (two wings), avoiding unnecessary hospital visits, hand hygiene, and legislations against over-the-counter antibiotics as the general preventive wing. Our second recommended preventive wing includes preventing the adverse side effects of the NPs from resistance and toxicity by establishing standard testing procedures. These standard procedures should provide breakpoints of bacteria's susceptibility to NPs and a thorough toxicological examination of every single batch of synthesized NPs. (ii) The second appraisal includes theranostic actions, using nanotheranostics to diagnose and treat MRSA, such as what we call "multifunctional theranostic nanofibers. (iii) The third action appraisal consists of collaborative actions.

Surface Functional Nanofiber Membrane for Ultrasensitive and Naked-Eye Visualization of Bacterial Concentration

Bacterial contamination in water is a serious health risk to human beings, so it is very important to realize the point-of-care (POC) bacterial detection in water. However, the traditional bacterial detection methods are time-consuming, professional- and equipment-dependent, and do not meet the needs of POC detection. There is a pressing need to develop a platform for POC bacterial detection to defeat the increasing risk of bacterial infections. Herein, a surface functional nanofiber membrane (NFM) is prepared by layer-by-layer (LBL) self-assembly as a platform for POC detection of bacterial concentration; it is naked-eye visualization and ultrasensitive. The platform shows obvious bacterial responsiveness, which allows naked-eye visualization of bacterial concentration (10²-10⁶ CFU/mL) within 30 min and can quantitatively detect the bacterial concentration (10¹-10⁶ CFU/mL) by fluorescence within 5 min. The platform not only exhibits high efficiency but also has a low threshold for bacterial concentration detection. Furthermore, the platform shows good consistency with traditional methods in the detection of bacteria in practical water samples, and has the potential for use in detecting bacterial concentrations in water supplies to protect human beings from health hazards. This work also provides useful reference for research on bacterial detection, taking advantage of the surface characteristics of bacteria and the high sensitivity of NFM.

Synthesis, Characterization, and Flocculation Studies of β-Cyclodextrin-Based Stimuli-Responsive Star Copolymer: An Environmental Remediation

Thermoresponsive star polymers are synthesized by using poly(NIPAM-b-DMA) diblock copolymer and β-cyclodextrin (β-CD). The synthesis of thermoresponsive diblock copolymer (TRP) is carried out by reversible addition-fragmentation chain transfer mediated aqueous polymerization using N-isopropylacrylamide (PNIPAM) and di-methylacrylamide as monomers. Mercaptopropionic acid is used as in situ chain transfer agent (CTA) to synthesize PNIPAM, i.e., macro-CTA. The polymeric materials are characterized by Fourier-transform infrared spectroscopy, gel permeation chromatography, 1H-NMR, particle size measurement, scanning electron microscopy, thermogravimetric analysis, UV-vis spectroscopy, and X-ray diffraction analysis. PNIPAM, TRP, and b-CD grafted thermoresponsive diblock copolymer (β-CD-TRP) show lower critical solution temperature at 32.8, 34.3, and 36.8 °C, respectively. TRP and β-CD-TRP are also studied for the removal of model contaminant (kaolin). Among all grades, β-CD-TRP 4 shows the best performance in the removal of kaolin from aqueous solution at 25 and 50 °C.

Detection of Bacterial Alkaline Phosphatase Activity by Enzymatic In Situ Self-Assembly of the AIEgen-Peptide Conjugate

Abnormal levels of alkaline phosphatase (ALP) activity are associated with various diseases, and many ALP probes have been developed to date. However, the development of ALP-sensitive probes for living cells, especially for the detection of bacterial ALP, remains challenging because of the complex and dynamic context. In this study, we constructed the first fluorescent probe (TPEPy-pY) for sensing bacterial ALP activity. TPEPy-pY is an AIEgen-peptide conjugate with property of aggregation-induced emission (AIE) and could turn on its fluorescence by ALP-catalyzed in situ self-assembly of the probe. The probe shows excellent selectivity and sensitivity for ALP activity, with a detection limit of 6.6 × 10^-3 U mL^-1. TPEPy-pY performs well in detection and in situ imaging of bacterial ALP activity against E. coli. Also, the detection does not require tedious washing steps and takes approximately 1 h, which is advantageous over commercial ALP kits. Therefore, the proposed strategy paved a new avenue for bacterial ALP detection, and we envision that more self-assembling fluorescent probes will be designed with higher sensitivity in the near future.

Star polymer-based unimolecular micelles and their application in bio-imaging and diagnosis

As a novel kind of polymer with covalently linked core-shell structure, star polymers behave in nanostructure in aqueous medium at all concentration range, as unimolecular micelles at high dilution condition and multi-micelle aggregates in other situations. The unique morphologies endow star polymers with excellent stability and functions, making them a promising platform for bio-application. A variety of functions including imaging and therapeutics can be achieved through rational structure design of star polymers, and the existence of plentiful end-groups on shell offers the opportunity for further modification. In the last decades, star polymers have become an attracting platform on fabrication of novel nano-systems for bio-imaging and diagnosis. Focusing on the specific topology and physicochemical properties of star polymers, we have reviewed recent development of star polymer-based unimolecular micelles and their bio-application in imaging and diagnosis. The main content of this review summarizes the synthesis of integrated architecture of star polymers and their self-assembly behavior in aqueous medium, focusing especially on the recent advances on their bio-imaging application and diagnosis use. Finally, we conclude with remarks and give some outlooks for further exploration in this field.

Flocculation and Dewatering of Mature Fine Tailings Using Temperature-Responsive Cationic Polymers

Temperature-responsive copolymer with cationic charge was prepared with N-isopropylacrylamide (NIPAm) and 2-aminoethyl methacrylamide hydrochloride (AEMA) by conventional free-radical polymerization. The flocculation performance of the copolymer, poly(AEMA-st-NIPAm), was compared to five different mixture ratios of polyNIPAm and cationic poly(acrylamide-st-diallyldimethylammonium chloride) (poly(AAm-st-DADMAC)). The effects of polymer mixture ratios, polymer dosages, and temperature on solid-liquid separation as a function of initial settling rates (ISR), supernatant turbidity, sediment solid content, and water recovery were investigated. Poly(NIPAm) can facilitate particles aggregation by bridging and hydrogen bonding under lower critical solution temperature (LCST); whereas, at temperature above LCST, the adsorption of poly(NIPAm) chains on particles can be enhanced by hydrophobic interaction. A two-step (25 °C → 50 °C → 25 °C) consolidation can further enhance the sediment solid content by polyNIPAm. While the neutral property of polyNIPAm resulted in high turbidity of supernatant, mixing with poly(AAm-st-DADMAC) increases the clarity of supernatant by neutralization of fine particles. The copolymer poly(AEMA-st-NIPAm) functions as a polyelectrolyte to enhance the polymer adsorption onto particles via electrostatic interactions, thus further improving ISR and supernatant clarity.

A facile route towards PDMAEMA homopolymer amphiphiles

Well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) has been modified at low degrees of quaternization of the tertiary amine groups using alkyl halides with long alkyl chains as the quaternization agents. The resulting PDMAEMA-co-PQDMAEMA copolymers were studied in aqueous solution using potentiometric titrations, turbidimetry, surface tensiometry, dynamic light scattering and zeta potential measurements. An increase of the hydrophilicity of the precursor polymer, leading to an increase or even elimination of the lower critical solution temperature (LCST) for the quaternized copolymers was found; this extended the temperature range of the stable polymer solution. At the same time, it was shown that the hydrophobic character of the polymer increases upon quaternization, leading to higher surface activity compared to the precursor PDMAEMA homopolymer, and, thus, to more effective polymeric surfactants. This contradiction in the copolymer behavior was attributed to the interplay between the polymer self-assembly in the aqueous medium and the polymer adsorption at the air/water interface, which dominate the cloud point and the surface properties, respectively.

Dipicolylamine Functionalized Polyfluorene Based Gel with Lower Critical Solution Temperature: Preparation, Characterization, and Application

A thermoresponsive fluorescent polymer gel with lower critical solution temperature (LCST) phase transition has been prepared by cooperating conjugated fluorene homopolymer poly(2,7-(9,9-di(8-di(2-picolyl)aminooctyl))fluorene) (PPAOF) and small organic dye sulforhodamine B (SRB) or its sodium salt (SRB-Na). The sol-gel phase transition originates from the electrostatic interactions between the protonated pyridyl/amino groups in PPAOF and the sulfonic groups in the organic dye molecules, as revealed by FTIR, variable-temperature ¹H NMR spectroscopies, and cyclic voltammetry measurements. Consequently, the LCST value can be finely controlled by simply tuning the component concentrations. Moreover, due to the inefficient energy transfer, the resulting fluorescent polymer gel exhibits two independent emission bands at 440 and 577 nm, assigned to the characteristic emissions from fluorene homopolymer and organic dye, respectively. Furthermore, this fluorescent polymer gel exhibits a reversible electrofluorochromic (EFC) property with high fluorescence contrast when it is assembled in a single-layer supporting electrolyte-free EFC device. Most interestingly, different fluorescence colors can be achieved from the two electrodes of the device. Our findings may present a new way to design conjugated polymer based LCST gels and EFC materials.

Synthesis and properties of well-defined carbazole-containing fluorescent star polymers of different arms

A series of fluorescent carbazole-containing star polymers with different arms were successfully synthesized using 9-(4-vinylbenzyl)9H-carbazole (VBCz) as monomer and multifunctional bromide as initiators via atom transfer radical polymerization (ATRP). The effect of the poly(9-(4-vinylbenzyl)-9H-carbazole) (PVBCz) star polymer architecture on their optical and electrochemical properties was investigated. All of the PVBCz star polymers absorbed light in the range of 280–360 nm both in solution and as polymer films. Meanwhile, the star polymers exhibited maximum fluorescent emission at 350 nm in solution, while at 406 nm as films. Moreover, the star polymers with different arm numbers showed different photoluminescence quantum efficiency and highest and lowest occupied molecular orbital (HOMO, LOMO, respectively) energy levels. It is proved that the PVBCz star polymers exhibited different photoelectronic properties by varying the molecular architectures.

Synthesis of platinum(ii) complex end functionalized star polymers: luminescence enhancements and unimolecular micelles in solvents of weakened quality

Platinum(ii) complex end functionalized star polymers have been synthesized by reacting K₂PtCl₄ with star ligands ended with 2,6-bis(benzimidazol-2′-yl)pyridine. They show luminescence enhancements and form unimolecular micelles in solvents of weakened quality.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

Dendritic Polymers for Theranostics

Dendritic polymers are highly branched polymers with controllable structures, which possess a large population of terminal functional groups, low solution or melt viscosity, and good solubility. Their size, degree of branching and functionality can be adjusted and controlled through the synthetic procedures. These tunable structures correspond to application-related properties, such as biodegradability, biocompatibility, stimuli-responsiveness and self-assembly ability, which are the key points for theranostic applications, including chemotherapeutic theranostics, biotherapeutic theranostics, phototherapeutic theranostics, radiotherapeutic theranostics and combined therapeutic theranostics. Up to now, significant progress has been made for the dendritic polymers in solving some of the fundamental and technical questions toward their theranostic applications. In this review, we briefly summarize how to control the structures of dendritic polymers, the theranostics-related properties derived from their structures and their theranostics-related applications.

Investigation on the fluorescence–(stimulus-response) properties of linear and star PVBCz-b-PDMAEMA block copolymers synthesized via ATRP

Linear and star PVBCz-b-PDMAEMA block copolymers were synthesized via ATRP, the properties of which were investigated including ultraviolet-visible absorption, fluorescence emission, stimulus-response and fluorescence-stimulus-response.

Recent development of unimolecular micelles as functional materials and applications

Unimolecular micelles have high functionalities, encapsulation capabilities and site specific confinement abilities in various applications.

Bioapplications of hyperbranched polymers

The recent research progress in biological and biomedical applications of hyperbranched polymers has been summarized in this review.

Amphiphilic star copolymer-based bimodal fluorogenic/magnetic resonance probes for concomitant bacteria detection and inhibition

Four-arm star-shaped copolymers, TPE-star-P(DMA-co-BMA-co-Gd), containing TPE cores with an aggregation-induced emission (AIE) feature, a T 1 -type magnetic resonance (MR) contrast agent, and amphiphilic cationic arms, are synthesized. By taking advantage of non-covalent interactions between star copolymers and bacteria surfaces, bimodal fluorometric/MR detection and concomitant inhibition of both Gram-positive and Gram-negative bacteria strains in aqueous media are explored.

Photo-responsive polymeric micelles

Photo-responsive polymeric micelles have received increasing attention in both academic and industrial fields due to their efficient photo-sensitive nature and unique nanostructure. In view of the photo-reaction mechanism, photo-responsive polymeric micelles can be divided into five major types: (1) photoisomerization polymeric micelles, (2) photo-induced rearrangement polymeric micelles, (3) photocleavage polymeric micelles, (4) photo-induced crosslinkable polymeric micelles, and (5) photo-induced energy conversion polymeric micelles. This review highlights the recent advances of photo-responsive polymeric micelles, including the design, synthesis and applications in various biomedical fields. Especially, the influence of different photo-reaction mechanisms on the morphology, structure and properties of the polymeric micelles is emphasized. Finally, the possible future directions and perspectives in this emerging area are briefly discussed.

Real-time monitoring of anticancer drug release with highly fluorescent star-conjugated copolymer as a drug carrier

Chemotherapy is one of the major systemic treatments for cancer, in which the drug release kinetics is a key factor for drug delivery. In the present work, a versatile fluorescence-based real-time monitoring system for intracellular drug release has been developed. First, two kinds of star-conjugated copolymers with different connections (e.g., pH-responsive acylhydrazone and stable ether) between a hyperbranched conjugated polymer (HCP) core and many linear poly(ethylene glycol) (PEG) arms were synthesized. Owing to the amphiphilic three-dimensional architecture, the star-conjugated copolymers could self-assemble into multimicelle aggregates from unimolecular micelles with excellent emission performance in the aqueous medium. When doxorubicin (DOX) as a model drug was encapsulated into copolymer micelles, the emission of star-conjugated copolymer and DOX was quenched. In vitro biological studies revealed that fluorescent intensities of both star-conjugated copolymer and DOX were activated when the drug was released from copolymeric micelles, resulting in the enhanced cellular proliferation inhibition against cancer cells. Importantly, pH-responsive feature of the star-conjugated copolymer with acylhydrazone linkage exhibited accelerated DOX release at a mildly acidic environment, because of the fast breakage of acylhydrazone in endosome or lysosome of tumor cells. Such fluorescent star-conjugated copolymers may open up new perspectives to real-time study of drug release kinetics of polymeric drug delivery systems for cancer therapy.