A new light-sensitive polymer containing multiple light-sensitive triggering groups along the backbone and incorporating a quinone-methide self-immolative moiety was developed and formulated into nanoparticles encapsulating a model dye Nile Red. Triggered burst-release of the payload upon irradiation and subsequent degradation of the nanoparticles was observed. This system is designed to be versatile where the triggering group can be sensitive to a number of wavelengths.
We report two polymers with UV- and NIR-removable end caps that respond to a single light activated event by complete cleavage of the polymer backbone via a self-immolative mechanism. Two photocleavable protecting groups were used to cap the polymers; o-nitrobenzyl alcohol (ONB) and bromo-coumarin (Bhc). GPC and 1H NMR confirmed complete degradation of the ONB-containing polymer in response to UV. The polymers were formulated into nanoparticles; fluorescence measurements of encapsulated Nile red confirmed release upon photolysis of the endcaps. Contrary to previous work using a similar backbone structure that degrades upon hydrolysis, here, the disassembly process and burst release of the payload are only activated on demand, illustrating the powerful capacity of light to trigger release from polymeric nanoparticles. Our design allows the signal to be amplified in a domino effect to fully degrade the polymer into small molecules. Thus, polymers and nanoparticles can reach maximal degradation without having to use intense and/or long periods of irradiation.
Near infrared (NIR) irradiation can penetrate up to 10 cm deep into tissues and be remotely applied with high spatial and temporal precision. Despite its potential for various medical and biological applications, there is a dearth of biomaterials that are responsive at this wavelength region. Herein we report a polymeric material that is able to disassemble in response to biologically benign levels of NIR irradiation upon two-photon absorption. The design relies on the photolysis of the multiple pendant 4-bromo7-hydroxycoumarin protecting groups to trigger a cascade of cyclization and rearrangement reactions leading to the degradation of the polymer backbone. The new material undergoes a 50% Mw loss after 25 sec of ultraviolet (UV) irradiation by single photon absorption and 21 min of NIR irradiation via two-photon absorption. Most importantly, even NIR irradiation at biologically benign laser power is sufficient to cause significant polymer disassembly. Furthermore, this material is well tolerated by cells both before and after degradation. These results demonstrate for the first time a NIR sensitive material with potential to be used for in vivo applications.
One of the most common and important interfaces is the boundary layer between an aqueous phase solution of ions and a hydrophobic medium. Whether the hydrophobic medium is a membrane, a macromolecular assembly, or a simple organic liquid, our molecular-level understanding of how ions in an adjacent aqueous phase approach, alter, and transport across the boundary is still quite deficient, largely due to experimental challenges in making the appropriate measurements. This paper reports some of the first measurements of the behavior of common inorganic ions at the interface between different aqueous phase salt solutions (NaCl, NaBr, NaNO 3 , and Na 2 SO 4 ) and a hydrophobic organic liquid (CCl 4 ). The results show that the ions reside within the interfacial region where they affect the water hydrogen bonding in a manner specific to the ion under study. Distinct differences in the behavior of ions at this interface relative to the air-water interface are found and discussed.
Understanding the behavior of water at hydrophobic surfaces has been a topic of much interest for many decades. In most areas of biological, environmental, or technological relevance, the aqueous phase is not pure water, but comprises a host of ions including those associated with the acidity or basicity of the solution. The notion that ions, including hydroxide and/or hydronium, accrue at hydrophobic interfaces is increasingly invoked as a possible explanation for the behavior of water adjacent to soft hydrophobic interfaces such as liquids and monolayers. The focus of this study is on exploring the behavior of aqueous solutions of salts, acids and bases in contact with hydrocarbon and fluorocarbon self-assembled monolayers (SAMs) using vibrational sum frequency spectroscopy (VSFS). The studies take a systematic approach to understanding how each component of the SAMs' interfaces contribute to the overall observed behavior of ions and water in the overall boundary region. To achieve this, the spectroscopy of the SAM/water interface in the presence and absence of aqueous phase ions, acids and bases is compared with similar measurements taken at the substrate (SiO 2 )/water interface and the hydrophobic liquid/ water interface. The results show that the behavior of water and ions at the SAM/aqueous interface is significantly influenced by the substrate surface for both hydrocarbon and fluorocarbon SAM systems. Conditions where water and ions near a SAM interface mimic that of a liquid hydrophobic surface are identified.
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