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Light-responsive nanoparticles based on new polycarbonate polymers as innovative drug delivery systems for photosensitizers in PDT
摘要： Nanoparticles based on biodegradable polymers are well-known as approved carrier systems for a diversity of drugs. Despite their advantages, such as the option of an active drug targeting or the physicochemical protection of instable payloads, the controlled drug release often underlies intra- and interindividual influences and is therefore difficult to predict. To circumvent this limitation, the release behavior can be optimized using light-responsive materials for the nanoparticle preparation. The resulting light-responsive nanoparticles are able to release the embedded drug after an external light-stimulus, thereby increasing efficacy and safety of the therapy. In the present study light-responsive self-immolative polymers were used for the nanoparticle manufacturing. Light-responsive polycarbonates (LrPC) as well as PEGylated LrPC (LrPC-PEG) were synthesized via ring-opening polymerization of trimethylene carbonate-based monomers and fully physico-chemically characterized. Light-responsive nano formulations were obtained by blending LrPC or (LrPC-PEG) with the FDA-approved polymer poly(lactic-co-glycolic-acid) (PLGA). The nanoparticles were loaded with the photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (mTHPC). The light-induced nanoparticle degradation was analyzed as well as the drug release behavior with and without illumination. Furthermore, biological safety of the degradation products was investigated in an in vitro cell culture study.
关键词： light-responsive polymers,Nanoparticles,intestinal cancer,photodynamic therapy,poly(lactic-co-glycolic acid)
更新于2025-09-23 15:22:29
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Two-Stage Collapse of PNIPAM Brushes: Viscoelastic Changes Revealed by an Interferometric Laser Technique
摘要： Many temperature-responsive polymers exhibit a single-phase transition at the lower critical solution temperature (LCST). One exception is poly(N-isopropylacryamide) (PNIPAM). PNIPAM brush layers (51 ± 3 nm thick) that are end-grafted onto glass beads collapse in two stages. The viscoelastic changes of a PNIPAM brush layers were investigated with an interferometric laser method at different temperatures. This method is able to measure the two-stage collapse of beads coated with a polymer brush layer. When these beads are situated close to a hydrophilic glass surface, they exhibit Brownian motion. As this Brownian motion changes with temperature, it reveals the collapse of the polymer layer. The characteristic spectrum of the Brownian motion of beads are modelled by a damped harmonic oscillator, where the polymer layer acts as both spring and damping. The change of the Brownian motion spectrum with temperature indicates two transitions of the PNIPAM brush layer, one at 36 °C and one at 46 °C. We attribute the first transition to the LCST volume collapse of PNIPAM. Here, changes of the density and viscosity of the brush dominate. The second transition is dominated by a stiffening of the brush layer.
关键词： PNIPAM,viscoelastic changes,interferometric laser technique,brush layers,temperature-responsive polymers,two-stage collapse
更新于2025-09-19 17:13:59
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Color‐Based Optical Detection of Glass Transitions on Microsecond Timescales Enabled by Exciplex Dynamics
摘要： Every measurement technique operates on a given timescale and measurements using emissive small molecule sensors are no exception. A family of luminescent sensors providing first optical characterization of dynamic phenomena in polymers at a timescale of several microseconds is described. This performance originates from the dynamics manifested in the excited state of the sensor molecules where diffusioncontrolled events select the emission color while radiative phenomena define the global operation timescale. Since the mechanism responsible for signal generation is confined to the short lived excited state of emissive probe, it is possible observe an unprecedented link between the timescale of sensory action and that of photoluminescence. An application of this new methodology is demonstrated by performing general, short timescale detection of glass transitions in a temperature ranges precluding the informative range of conventional techniques by tens of degrees.
关键词： glass transition,copper,luminescent sensors,responsive polymers
更新于2025-09-11 14:15:04
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A Spectroscopic Study of a Cyclodextrin-Based Polymer and the “Molecular Accordion” Effect
摘要： The formation of host-guest complexes was studied for two hosts; β-cyclodextrin (β-CD) and a cross-linked polymer containing an equimolar ratio of β-CD and hexamethylene diisocyanate (HDI), denoted as HDI-1. The thermodynamics of host-guest binding was studied with 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) using steady-state fluorescence spectroscopy in aqueous solution at variable temperature and ambient pH. The association of 1,8-ANS with β-CD and HDI-1, showed a fluorescence enhancement of ~4 and 12 units, respectively. Greater fluorescence enhancement for the polymer/dye system indicates the presence of multiple binding sites (inclusion vs. interstitial). By contrast, the β-CD/dye system adopt trends that indicate the formation of well-defined inclusion complexes. HDI-1 has inclusion sites (β-CD) and interstitial domains (HDI) that afford dual binding with variable binding affinity. Simplified binding models employed herein address the role of inclusion binding without an explicit account for higher order or secondary binding equilibria. The approximate 1:1 binding constant (K1:1) for CD/1,8-ANS is about two-fold greater over the HDI-1/1,8-ANS system. HDI-1 displays cooperative effects among the polymer subunits, according to changes in relative fluorescence intensity due to structural transitions and binding site loci. The relative fluorescence intensities of the HDI-1/1,8-ANS system relate to a reversible temperature-driven structural transition (globular ? extended) between 5 oC and 60 °C of the polymer, in contrast to the β-CD/1,8-ANS complex. The temperature- and guest-driven structural transition, described as the “molecular accordion” effect is supported by new insight provided by complementary fluorescence and 1H NMR spectral results in aqueous solution.
关键词： Complex formation,Host-Guest,Fluorescence,Responsive polymers,Cyclodextrin
更新于2025-09-04 15:30:14
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Self‐Regulating Capabilities in Photonic Robotics
摘要： Traditional robots are machines programmed to accomplish tasks, thanks to a complex ensemble of sensors connected to a computer “brain” which elaborate signals to drive specific actions. This complex network suffers from limitations—the need for a central computer, for instance, poses a limit to device miniaturization and requires a large amount of energy. A promising development, made possible by recent advances in material science, endeavors a new generation of soft robots that are multifunctional, compliant, and autonomous in ways that are similar to biological organisms. In particular, photoresponsive polymers are demonstrated to be valid candidates to substitute the computer-based intelligence with an “intrinsic” material cleverness. First demonstrations of self-sustained motions as oscillations or autonomous walking are described. In these cases, light also provides a solution to a second, very important, issue in microrobotics, which is the availability of a source of energy. Light actuation together with smart polymers can be combined into self-controlled robots capable of simple decision-making processes, for example with robotic grippers that are able to distinguish particles with different colors. In addition, the most recent examples about the integration of a form of robotic “intelligence” into a single material with a minimal level of consciousness are reported.
关键词： smart soft robotics,self-sustained motions,light responsive polymers,autonomous decisions,photonic robotics
更新于2025-09-04 15:30:14