Light-induced color changes of microgel-based etalons

Poly(N-isopropylacrylamide) (pNIPAm) microgel-based etalons were used to fabricate systems that change visual color in response to light exposure. These systems were fabricated by adding pH responsive microgel-based etalons to a solution composed of the photoacid o-nitrobenzaldehyde (o-NBA). Upon exposure of this system to ultraviolet (UV) irradiation, the photoacid released a proton, lowering the pH of the solution. Since the pNIPAm microgel-based etalon was responsive to pH, the etalon changed its optical properties and, hence, visual color. We went on to show that patterned etalons could be fabricated, which only contained pH-responsive microgels in specific regions. These etalons only changed color in the pH-responsive regions, to yield patterns that change color upon UV light exposure. Finally, the color of the etalon was shown to be fully reversible and could be switched multiple times. These unique systems could potentially be used for display technologies, and as a controlled/triggered drug delivery system.

UV light stimulated encapsulation and release by polyelectrolyte microcapsules

Layer-by-layer assembled polyelectrolyte capsules with well-controlled architectures and great versatility have been the subject of great interest, due to their unique advantages and tremendous potentials of being excellent candidates in multidisciplinary fields. UV light responsive microcapsules, as one class of the stimuli responsive capsules, possess the abilities to active their functionalities by responding to the UV stimulus remotely without requirement of direct contact or interaction. Therefore, any advances in this field will be of great value for the establishment of approaches to fabricate UV responsive polyelectrolyte capsules for desired uses. This review presents current development of UV responsive capsules, with emphasis on the underlying design strategies and their potential applications as delivery vesicles. In particular, UV-stimulated capsule functionalities, such as cargo encapsulation, release and combined multifunctionalities by the multilayers, have been addressed.

Light-Induced Remodeling of Physically Crosslinked Hydrogels Using Near-IR Wavelengths

Poly([6-bromo-7-hydroxycoumarin-4-yl]methyl methacrylate)-based triblock copolymers were synthesized by first preparing PMAA-PEG-PMAA triblocks using ATRP. 6-Bromo-4-chloromethyl-7-hydroxycoumarin was conjugated to PMAA-PEG-PMAA using 1,8-diazabicycloundec-7-ene (DBU). Rheological measurements were conducted using a HR-2 rheometer with a UV illumination accessory (TA Instruments). Single-photon uncaging was performed as previously described.20 Two-photon uncaging was performed using a LSM (Zeiss) equipped with a Ti: Sapphire laser (Coherent). All values reported as mean ± std. dev. unless otherwise stated. See Supporting Information for experimental details.

Dendrimersomes with photodegradable membranes for triggered release of hydrophilic and hydrophobic cargo

Amphiphilic Janus dendrimers with fully photodegradable hydrophobic blocks were synthesized and assembled into dendrimersomes in water. Irradiation with UV light triggered the release of hydrophobic and hydrophilic cargo.

A chaperonin as protein nanoreactor for atom-transfer radical polymerization

The group II chaperonin thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom-transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N-isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein-catalyst conjugate only yielded polymers with PDIs above 1.84.

Self-assembly and chemical processing of block copolymers: a roadmap towards a diverse array of block copolymer nanostructures

Block copolymers can yield a diverse array of nanostructures. Their assembly structures are influenced by their inherent structures, and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies. Some examples include self-assembly, directed assembly, coupling, as well as hierarchical assembly, which can yield assemblies having even higher structural order. These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching, the former technique leading to permanent structures, the latter towards sculpted and the combination of the two towards permanent sculpted structures. The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures. This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.

Photo-responsive block copolymer micelles: design and behavior

Stimuli-responsive block copolymer micelles are the topic of intense research since they are able to show sharp and eventually reversible responses to various environmental changes and find applications in various fields including controlled drug delivery. Among all the available stimuli, light has recently attracted much attention since it can be localized in time and space, and it can also be triggered from outside of the system. In this tutorial review, we highlight the progress realized in recent years. More precisely, we provide some guidelines towards the rational design of photo-responsive block copolymers and we present the different photo-responsive moieties that have been used so far. We also discuss the different types of irreversible and reversible responses encountered by photo-responsive block copolymer micelles. Finally, we suggest possible future developments including the design of biocompatible systems operating at excitation wavelengths compatible for biomedical applications.

Polymeric vesicles: from drug carriers to nanoreactors and artificial organelles

One strategy in modern medicine is the development of new platforms that combine multifunctional compounds with stable, safe carriers in patient-oriented therapeutic strategies. The simultaneous detection and treatment of pathological events through interactions manipulated at the molecular level offer treatment strategies that can decrease side effects resulting from conventional therapeutic approaches. Several types of nanocarriers have been proposed for biomedical purposes, including inorganic nanoparticles, lipid aggregates, including liposomes, and synthetic polymeric systems, such as vesicles, micelles, or nanotubes. Polymeric vesicles--structures similar to lipid vesicles but created using synthetic block copolymers--represent an excellent candidate for new nanocarriers for medical applications. These structures are more stable than liposomes but retain their low immunogenicity. Significant efforts have been made to improve the size, membrane flexibility, and permeability of polymeric vesicles and to enhance their target specificity. The optimization of these properties will allow researchers to design smart compartments that can co-encapsulate sensitive molecules, such as RNA, enzymes, and proteins, and their membranes allow insertion of membrane proteins rather than simply serving as passive carriers. In this Account, we illustrate the advances that are shifting these molecular systems from simple polymeric carriers to smart-complex protein-polymer assemblies, such as nanoreactors or synthetic organelles. Polymeric vesicles generated by the self-assembly of amphiphilic copolymers (polymersomes) offer the advantage of simultaneous encapsulation of hydrophilic compounds in their aqueous cavities and the insertion of fragile, hydrophobic compounds in their membranes. This strategy has permitted us and others to design and develop new systems such as nanoreactors and artificial organelles in which active compounds are simultaneously protected and allowed to act in situ. In recent years, we have created a variety of multifunctional, proteinpolymersomes combinations for biomedical applications. The insertion of membrane proteins or biopores into the polymer membrane supported the activity of co-encapsulated enzymes that act in tandem inside the cavity or of combinations of drugs and imaging agents. Surface functionalization of these nanocarriers permitted specific targeting of the desired biological compartments. Polymeric vesicles alone are relatively easy to prepare and functionalize. Those features, along with their stability and multifunctionality, promote their use in the development of new theranostic strategies. The combination of polymer vesicles and biological entities will serve as tools to improve the observation and treatment of pathological events and the overall condition of the patient.

Engineering Polymersome Protocells

The field of biomimicry is embracing the construction of complex assemblies that imitate both biological structure and function. Advancements in the design of these mimetics have generated a growing vision for creating an artificial or proto- cell. Polymersomes are vesicles that can be made from synthetic, biological or hybrid polymers and can be used as a model template to build cell-like structures. In this perspective, we discuss various areas where polymersomes have been used to mimic cell functions as well as areas in which the synthetic flexibility of polymersomes would make them ideal candidates for a biomembrane mimetic. Designing a polymersome that comprehensively displays the behaviors discussed herein has the potential to lead to the development of an autonomous, responsive particle that resembles the intelligence of a biological cell.