Iron Oxide Nanoparticle-Based Magnetic Resonance Method to Monitor Release Kinetics from Polymeric Particles with High Resolution

A new method to precisely monitor rapid release kinetics from polymeric particles using super paramagnetic iron oxide nanoparticles, specifically by measuring spin–spin relaxation time (<i>T</i>₂), is reported. Previously, we have published the formulation of logic gate particles from an acid-sensitive poly-β-aminoester ketal-2 polymer. Here, a series of poly-β-aminoester ketal-2 polymers with varying hydrophobicities were synthesized and used to formulate particles. We attempted to measure fluorescence of released Nile red to determine whether the structural adjustments could finely tune the release kinetics in the range of minutes to hours; however, this standard technique did not differentiate each release rate of our series. Thus, a new method based on encapsulation of iron oxide nanoparticles was developed, which enabled us to resolve the release kinetics of our particles. Moreover, the kinetics matched the relative hydrophobicity order determined by octanol–water partition coefficients. To the best of our knowledge, this method provides the highest resolution of release kinetics to date

Highest Efficiency Two-Photon Degradable Copolymer for Remote Controlled Release

To address the scarcity of polymers that degrade upon absorption of near-infrared (NIR) light, we introduce a new polymer containing moieties in its backbone capable of highly efficient NIR-triggered photocleavage. The polymer rapidly undergoes backbone scission in response to both UV–vis and near-infrared light via two-photon absorption, as revealed by gel permeation chromatography. Cleavage of photosensitive groups from the backbone is confirmed by ¹H NMR. These polymers were successfully formulated into particles encapsulating a dye that was released upon irradiation with UV–vis and NIR light, as indicated by changes in fluorescence characteristic of increased solvent interaction with cargo. Thus, this new polymer is readily photocleaved by UV–vis and NIR light, giving it a variety of potential applications in photopatterning and on-demand release

Collective Activation of MRI Agents via Encapsulation and Disease-Triggered Release

An activation mechanism based on encapsulated ultrasmall gadolinium oxide nanoparticles (Gd oxide NPs) in bioresponsive polymer capsules capable of triggered release in response to chemical markers of disease (i.e., acidic pH, H₂O₂) is presented. Inside the hydrophobic polymeric matrices, the Gd oxide NPs are shielded from the aqueous environment, silencing their ability to enhance water proton relaxation. Upon disassembly of the polymeric particles, activation of multiple contrast agents generates a strong positive contrast enhancement of >1 order of magnitude

Single UV or Near IR Triggering Event Leads to Polymer Degradation into Small Molecules

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; <i>o</i>-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 end-caps. 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 or long periods of irradiation