Single-Particle Tracking in Poly(Ethylene Glycol) Diacrylate: Probe Size Effect on the Diffusion Behaviors of Nanoparticles in Unentangled Polymer Solutions.

A thorough understanding of the relevant factors governing the transport of nanoparticles in poly(ethylene glycol) diacrylate (PEGDA) is crucial for many applications utilizing this polymer. Here, single-particle tracking (SPT) was used to systematically investigate the role of the probe size (3-200 nm) on the diffusion behaviors of individual fluorescent nanoparticles in semidilute and unentangled PEGDA solutions. The quantitative assessment of the SPT data via the recorded single-particle trajectories and diffusion coefficients () not only showed that the observed probe dynamics in PEGDA were temporally and spatially heterogeneous, but more importantly that the measured were observed to be significantly reduced (vs in solvent) and strongly size-dependent.

Alkaline activation of endogenous latent TGFβ1 by an injectable hydrogel directs cell homing for in situ complex tissue regeneration.

Utilization of the body's regenerative potential for tissue repair is known as in situ tissue regeneration. However, the use of exogenous growth factors requires delicate control of the dose and delivery strategies and may be accompanied by safety, efficacy and cost concerns. In this study, we developed, for the first time, a biomaterial-based strategy to activate endogenous transforming growth factor beta 1 (TGFβ1) under alkaline conditions for effective in situ tissue regeneration.

Confocal Rheology Probes the Structure and Mechanics of Collagen through the Sol-Gel Transition.

Fibrillar type I collagen-based hydrogels are commonly used in tissue engineering and as matrices for biophysical studies. Mechanical and structural properties of these gels are known to be governed by the conditions under which fibrillogenesis occurs, exhibiting variation as a function of protein concentration, temperature, pH, and ionic strength. Deeper understanding of how macroscopic structure affects viscoelastic properties of collagen gels over the course of fibrillogenesis provides fundamental insight into biopolymer gel properties and promises enhanced control over the properties of such gels.

Longitudinally Controlled Modification of Cylindrical and Conical Track-Etched Poly(ethylene terephthalate) Pores Using an Electrochemically Assisted Click Reaction.

In this study, the longitudinally controlled modification of the inner surfaces of poly(ethylene terephthalate) (PET) track-etched pores was explored using an electrochemically assisted Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. Cylindrical or conical PET track-etched pores were first decorated with ethynyl groups via the amidation of surface -COOH groups, filled with a solution containing Cu(II) and azide-tagged fluorescent dye, and then sandwiched between comb-shaped and planar gold electrodes. Cu(I) was produced at the comb-shaped working electrode by the reduction of Cu(II); it diffused along the pores toward the other electrode and catalyzed CuAAC between an azide-tagged fluorescent dye and a pore-tethered ethynyl group.

A biomimetic gelatin-based platform elicits a pro-differentiation effect on podocytes through mechanotransduction.

Using a gelatin microbial transglutaminase (gelatin-mTG) cell culture platform tuned to exhibit stiffness spanning that of healthy and diseased glomeruli, we demonstrate that kidney podocytes show marked stiffness sensitivity. Podocyte-specific markers that are critical in the formation of the renal filtration barrier are found to be regulated in association with stiffness-mediated cellular behaviors. While podocytes typically de-differentiate in culture and show diminished physiological function in nephropathies characterized by altered tissue stiffness, we show that gelatin-mTG substrates with Young's modulus near that of healthy glomeruli elicit a pro-differentiation and maturation response in podocytes better than substrates either softer or stiffer.

Single-Molecule Tracking Study of the Permeability and Transverse Width of Individual Cylindrical Microdomains in Solvent-Swollen Polystyrene-block-poly(ethylene oxide) Films.

Understanding the properties of solvent-swollen block copolymer (BCP) microdomains is important for better solvent-based control of microdomain morphology, orientation, and permeability. In this study, single-molecule tracking (SMT) was explored to assess the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene-block-poly(ethylene oxide) (PS-b-PEO) films. PS-b-PEO films comprising shear-elongated cylindrical PEO microdomains were prepared by sandwiching its benzene or tetrahydrofuran (THF) solution between two glass substrates.

Single-Molecule Investigations of Morphology and Mass Transport Dynamics in Nanostructured Materials.

Nanostructured materials such as mesoporous metal oxides and phase-separated block copolymers form the basis for new monolith, membrane, and thin film technologies having applications in energy storage, chemical catalysis, and separations. Mass transport plays an integral role in governing the application-specific performance characteristics of many such materials. The majority of methods employed in their characterization provide only ensemble data, often masking the nanoscale, molecular-level details of materials morphology and mass transport.

Fluorescence Recovery after Photobleaching and Single-Molecule Tracking Measurements of Anisotropic Diffusion within Identical Regions of a Cylinder-Forming Diblock Copolymer Film.

This work demonstrates ensemble and single-molecule diffusion measurements within identical regions of a cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) film using fluorescence recovery after photobleaching (FRAP) and single-molecule tracking (SMT). A PS-b-PEO film (∼4 μm thick) with aligned cylindrical PEO microdomains containing 10 μM sulforhodamine B (SRB) was prepared by directional solvent-vapor penetration (SVP) of 1,4-dioxane. The ensemble diffusion behavior of SRB in the microdomains was assessed in FRAP studies of circular photobleached regions (∼7 μm in diameter).

Trajectory-profile-guided single molecule tracking for assignment of one-dimensional diffusion trajectories.

A variety of algorithms exist for optical single molecule tracking in two and three dimensions. One general class of algorithms employs cost-functionals to link the individual fluorescent spots, produced by a molecule in sequential video frames, into trajectories. This method has also been used to track one-dimensional (1D) molecular motions for relatively low diffusion rates (i.

Single-molecule tracking studies of flow-induced microdomain alignment in cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer films.

Flow-based approaches are promising routes to preparation of aligned block copolymer microdomains within confined spaces. An in-depth characterization of such nanoscale morphologies within macroscopically nonuniform materials under ambient conditions is, however, often challenging. In this study, single-molecule tracking (SMT) methods were employed to probe the flow-induced alignment of cylindrical microdomains (ca.

Trajectory angle determination in one dimensional single molecule tracking data by orthogonal regression analysis.

The quantitative assessment of single molecule diffusion trajectories by orthogonal regression analysis is reported. This analysis is broadly applicable to any single particle tracking experiments in which diffusion along one dimension (1D) is expected. It affords quantitative data on the (in plane) orientation of 1D trajectories, allowing for their absolute orientations to be determined.