Micromechanical Compatibility between Cells and Scaffolds Directs the Phenotypic Transition of Stem Cells.

This study experimentally substantiates that the micromechanical compatibility between cell and substrate is essential for cells to achieve energetically favorable mechanotransduction that directs phenotypic transitions. The argument for this compatibility is based on a thermodynamic model that suggests that the response of cells to their substrate mechanical environment is a consequence of the interchange between forms of energy governing the cell-substrate interaction. Experimental validation for the model has been carried out by investigating the osteogenic differentiation of dental follicle stem cells (DFSCs) seeded on electrospun fibrous scaffolds.

Toward absolute viability measurements for bacteria.

We aim to develop a quantitative viability method that distinguishes individual quiescent from dead cells and is measured in time (ns) as a referenceable, comparable quantity. We demonstrate that fluorescence lifetime imaging of an anionic, fluorescent membrane voltage probe fulfills these requirements for Streptococcus mutans. A random forest machine-learning model assesses whether individual S.

Early time-point cell morphology classifiers successfully predict human bone marrow stromal cell differentiation modulated by fiber density in nanofiber scaffolds.

Nanofiber scaffolds can induce osteogenic differentiation and cell morphology alterations of human bone marrow stromal cells (hBMSCs) without introduction of chemical cues. In this study, we investigate the predictive power of day 1 cell morphology, quantified by a machine learning based method, as an indicator of osteogenic differentiation modulated by nanofiber density. Nanofiber scaffolds are fabricated via electrospinning.

Structural insights into DNA-stabilized silver clusters.

Despite their great promise as fluorescent biological probes and sensors, the structure and dynamics of Ag complexes derived from single stranded DNA (ssDNA) are less understood than their double stranded counterparts. In this work, we seek new insights into the structure of single AgNssDNA clusters using analytical ultracentrifugation (AUC), nuclear magnetic resonance spectroscopy, infrared spectroscopy and molecular dynamics simulations (MD) of a fluorescent (AgNssDNA)8+ nanocluster. The results suggest that the purified (AgNssDNA)8+ nanocluster is a mixture of predominantly Ag15 and Ag16 species that prefer two distinct long-lived conformational states: one extended, the other approaching spherical.

Machine learning based methodology to identify cell shape phenotypes associated with microenvironmental cues.

Cell morphology has been identified as a potential indicator of stem cell response to biomaterials. However, determination of cell shape phenotype in biomaterials is complicated by heterogeneous cell populations, microenvironment heterogeneity, and multi-parametric definitions of cell morphology. To associate cell morphology with cell-material interactions, we developed a shape phenotyping framework based on support vector machines.

Single cell viability measurements in 3D scaffolds using in situ label free imaging by optical coherence microscopy.

The focus on creating tissue engineered constructs of clinically relevant sizes requires new approaches for monitoring construct health during tissue development. A few key requirements are that the technology be in situ, non-invasive, and provide temporal and spatial information. In this work, we demonstrate that optical coherence microscopy (OCM) can be used to assess cell viability without the addition of exogenous probes in three-dimensional (3D) tissue scaffolds maintained under standard culture conditions.

Analyses of a cantilever-beam based instrument for evaluating the development of polymerization stresses.

Objective: This investigation was to generate (1) guidelines for designing a tensometer that satisfies the necessary accuracy and sensitivity requirements for measuring polymerization stress (PS), and (2) a formula for calculating PS. Polymerization stress remains one of the most critical properties of polymeric dental materials, yet methods that can accurately quantify PS have been limited in part due to the complexity of polymerization, and in part due to the instrumentation itself.

Method: In this study, we performed analytical and finite element analyses on a cantilever-beam based tensometer that is used to evaluate shrinkage stresses during the polymerization of dental restorative composites.

Solutions for determining equibiaxial substrate strain for dynamic cell culture.

In this work, empirical and analytical solutions of equibiaxial strain on a flexible substrate are derived for a dynamic cell culture system. The empirical formula, which fulfills the mechanistic conditions of the culture system, is based on a regression analysis from finite element analyses for a substrate undergoing large strains (<15%). The analytical (closed-form) solution is derived from the superposition of two elastic responses induced in the equibiaxial strain culture system after applying pressure to a substrate undergoing small strains (microstrains).

Local thickness and anisotropy approaches to characterize pore size distribution of three-dimensional porous networks.

Two image-analysis approaches for pore size distribution (PSD) of porous media are proposed. The methods are based on the skeleton representation of a porous object. One approach gives the local thickness of the pore object to represent the pore size corresponding to a lower limit of PSD.

Measurement Tools for the Immersive Visualization Environment: Steps Toward the Virtual Laboratory.

This paper describes a set of tools for performing measurements of objects in a virtual reality based immersive visualization environment. These tools enable the use of the immersive environment as an instrument for extracting quantitative information from data representations that hitherto had be used solely for qualitative examination. We provide, within the virtual environment, ways for the user to analyze and interact with the quantitative data generated.

Quantifying the directional parameter of structural anisotropy in porous media.

A new method has been developed to define the directional parameter and characterize the structural anisotropy of a highly porous structure with extensive pore interconnectivity and surface area, such as scaffolds in tissue engineering. This new method called intercept segment deviation (ISD) was validated through the comparison of structural anisotropy from ISD measurements with mechanical anisotropy from finite-element stress analysis. This was carried out on a generated two-dimensional (2D) image of a two-phase material and a real three-dimensional (3D) image of a tissue scaffold.

Characterization of sizing layers and buried polymer/sizing/substrate interfacial regions using a localized fluorescent probe.

A novel technique is described to investigate buried polymer/sizing/substrate interfacial regions, in situ, by localizing a fluorescent probe molecule in the sizing layer. Epoxy functional silane coupling agent multilayers were deposited on glass microscope cover slips and doped with small levels of a fluorescently labeled silane coupling agent (FLSCA). The emission of the grafted FLSCA was dependent on the silane layer thickness, showing blue-shifted emission with decreasing thickness.