Rapid photochromic switching in a rigid polymer matrix using living radical polymerization

Fast switching of a photochromic dye in a rigid host matrix has been achieved without any modification of electronic nature of the photochromic entity. The method utilizes living radical polymerization (atom transfer radical polymerization (ATRP)) to grow a low glass transition temperature (T-g) poly(n-butyl acrylate) polymer from a spirooxazine core, creating a low-T-g environment to Cushion the photochromic dye while keeping the bulk matrix rigid. In these systems, decoloration speed of the photochromic (t(1/2)) was reduced by 40-75% depending on the molecular weight of the poly(n-butylacrylate) attached. We have demonstrated with this methodology a controlled tuning of photochromic switching. Coarse and rule tuning call be achieved by adjusting first the choice of polymer and second the molecular weight of the polymer

Tailoring photochromic performance of polymer-dye conjugates using living radical polymerization (ATRP)

The photochromic performance of polymer-dye conjugates was successfully tailored using the living radical polymerization technique ATRP. ATRP allowed the synthesis of photochromic dye-polymer conjugates consisting of polymer of defined chain length and polydispersity with a single photochromic dye attached at one end. Control over the photochromic switching speed was achieved solely thorough choice of the chain length of the polymer conjugate

Design of Degradable Click Delivery Systems

Click chemistry has had a significant impact in the field of materials science over the last 10 years, as it has enabled the design of new hybrid building blocks, leading to multifunctional and responsive materials. One key application for such materials is in the biomedical field, such as gene or drug delivery. However, to meet the functional requirements of such applications, tailored degradability of these materials under biological conditions is critical. There has been an increasing interest in combining click chemistry techniques with a range of degradable or responsive building blocks as well as investigating new or milder chemistries to design click delivery systems that are capable of physiologically relevant degradation. This Feature Article will cover some of the different approaches to synthesize degradable click delivery systems and their investigation for therapeutic release

Engineering Particles for Therapeutic Delivery: Prospects and Challenges

Nanoengineered particles that can facilitate drug formulation and passively target tumors have reached the clinic in recent years. These early successes have driven a new wave of significant innovation in the generation of advanced particles. Recent developments in enabling technologies and chemistries have led to control over key particle properties, including surface functionality, size, shape, and rigidity. Combining these advances with the rapid developments in the discovery of many disease-related characteristics now offers new opportunities for improving particle specificity for targeted therapy. In this Perspective, we summarize recent progress in particle-based therapeutic delivery and discuss important concepts in particle design and biological barriers for developing the next generation of particles

Biodegradable Click Capsules with Engineered Drug-Loaded Multilayers

We report the modular assembly of a polymer-drug conjugate into covalently stabilized, responsive, biodegradable, and drug-loaded capsules with control over drug dose and position in the multilayer film. The cancer therapeutic, doxorubicin hydrochloride (DOX), was conjugated to alkyne-functionalized poly(l-glutamic acid) (PGA(Alk)) via amide bond formation. PGA(Alk) and PGA(Alk+DOX) were assembled via hydrogen bonding with poly(N-vinyl pyrrolidone) (PVPON) on planar and colloidal silica templates. The films were subsequently covalently stabilized using diazide cross-linkers, and PVPON was released from the multilayers by altering the solution pH to disrupt hydrogen bonding. After removal of the sacrificial template, single-component PGA(Alk) capsules were obtained and analyzed by optical microscopy, transmission electron microscopy, and atomic force microscopy. The PGA(Alk) capsules were stable in the pH range between 2 and 11 and exhibited reversible swelling/shrinking behavior. PGA(Alk+DOX) was assembled to form drug-loaded polymer capsules with control over drug dose and position in the multilayer system (e.g., DOX in every layer or exclusively in layer 3). The drug-loaded capsules could be degraded enzymatically, resulting in the sustained release of active DOX over approximately 2 h. Cellular uptake studies demonstrate that the viability of cells incubated with DOX-loaded PGA(Alk) capsules significantly decreased. The general applicability of this modular approach, in terms of incorporation of polymer-drug conjugates in other click multilayer systems, was also demonstrated. Biodegradable click capsules with drug-loaded multilayers are promising candidates as carrier systems for biomedical applications

Peptide-Tunable Drug Cytotoxicity via One-Step Assembled Polymer Nanoparticles

A novel class of nanoparticles is developed for the co-delivery of a short cell penetrating peptide and a chemotherapeutic drug to achieve enhanced cytotoxicity. Tunable cytotoxicity is achieved through non-toxic peptide-facilitated gating. The strategy relies on a one-step blending process from polymer building blocks to form monodisperse, PEGylated particles that are sensitive to cellular pH variations. By varying the amount of peptide loading, the chemotherapeutic effects can be enhanced by up to 30-fold

Endocytic Capsule Sensors for Probing Cellular Internalization

A new class of polymer capsules with an in-built endocytic pH-coupled fluorescence switch is reported. These capsules display reversible "on/off" fluorescence in response to cellular pH variations. Using this system, the high-throughput quantification between surface-bound and internalized capsules is demonstrated. This system allows a fundamental study of the interaction between nanoengineered materials and biological systems at a cellular level