Nanoscale variation of bioadhesive substrates as a tool for engineering of cell matrix assembly

Plasma-micropatterning of albumin nanoparticles: Substrates for enhanced cell-interactive display of ligands

The authors demonstrate a novel, efficient, and widely applicable approach to direct the patterning of ligand-functionalized organic nanoparticles derived from albumin on nonconductive, biodegradable polymeric substrates. In contrast to traditional deposition methods for inorganic nanoparticles, the approach involves oxygen plasma treatment of spatially restricted regions on a nonbiopermissive polymer. Albumin nanoparticles conjugated with a truncated fragment of fibronectin containing the Arg-Gly-Asp domain were successfully patterned and used as templates to elicit adhesion and spreading of human mesenchymal stem cells and fibroblasts. Attachment and spreading of both cell types into the plasma-exposed polymer areas was considerably more pronounced than with the ligand alone. The authors hypothesize that the underlying mechanism is oxygen plasma treatment-induced selective enhancement of ligand exposure from the deposited functionalized nanoparticles, which facilitates ligand receptor clustering at the cell membrane. The results highlight a promising nanoscale approach to modulate ligand presentation and spatially direct cell attachment and phenotypic behaviors.

Detecting cell-adhesive sites in extracellular matrix using force spectroscopy mapping

The cell microenvironment is composed of extracellular matrix (ECM), which contains specific binding sites that allow the cell to adhere to its surroundings. Cells employ focal adhesion proteins, which must be able to resist a variety of forces to bind to ECM. Current techniques for detecting the spatial arrangement of these adhesions, however, have limited resolution and those that detect adhesive forces lack sufficient spatial characterization or resolution. Using a unique application of force spectroscopy, we demonstrate here the ability to determine local changes in the adhesive property of a fibronectin substrate down to the resolution of the fibronectin antibody-functionalized tip diameter, ~20 nm. To verify the detection capabilities of force spectroscopy mapping (FSM), changes in loading rate and temperature were used to alter the bond dynamics and change the adhesion force. Microcontact printing was also used to pattern fluorescein isothiocyanate-conjugated fibronectin in order to mimic the discontinuous adhesion domains of native ECM. Fluorescent detection was used to identify the pattern while FSM was used to map cell adhesion sites in registry with the initial fluorescent image. The results show that FSM can be used to detect the adhesion domains at high resolution and may subsequently be applied to native ECM with randomly distributed cell adhesion sites.

New directions in nanofibrous scaffolds for soft tissue engineering and regeneration

This review focuses on the role of nanostructure and nanoscale materials for tissue engineering applications. We detail a scaffold production method (electrospinning) for the production of nanofiber-based scaffolds that can approximate many critical features of the normal cellular microenvironment, and so foster and direct tissue formation. Further, we describe new and emerging methods to increase the applicability of these scaffolds for in vitro and in vivo application. This discussion includes a focus on methods to further functionalize scaffolds to promote cell infiltration, methods to tune scaffold mechanics to meet in vivo demands and methods to control the release of pharmaceuticals and other biologic agents to modulate the wound environment and foster tissue regeneration. This review provides a perspective on the state-of-the-art production, application and functionalization of these unique nanofibrous structures, and outlines future directions in this growing field.

Pollution dilemma in Asian population: CNG and wound healing

Automobile exhaust constituents contribute significantly to air pollution in urban areas and compressed natural gas (CNG) is considered one of the most promising fuel alternatives for the future. CNG-powered four-stroke engine auto-rickshaws are ubiquitous in South Asian cities as taxi and for commercial transportation. Automotive exhaust contains several toxins, which are overwhelmingly toxic to the processes of wound healing. By utilizing the in vivo mouse model of wound healing, this report analyzes the effects of CNG-powered four-stroke auto-rickshaws smoke solution (4SARSS) on different events of wound healing; dermal matrix regeneration, re-epithelialization and neovascularization. A total of 72 adult mice, divided in eight groups were exposed to 4SARSS for 12 days. A highly significant reduction (P<0.001) in wound closure was observed among all 4SARSS treated groups, at each time point of the experiment. An immature development in both the neoepidermis and the neodermis was observed among all 4SARSS treated wounds with defective re-epithelialization, dermal matrix regeneration and maturation of collagen bundles. Abbott curve, angular spectrum, 3D surface topographies, and histological investigations of wounds explicated highly significant activation (P<0.001) of delayed-neovascularization among 4SARSS treated wounds. All these annotations advocate excessive toxicity of emission from CNG-powered auto-rickshaws to the process of wound healing and people occupationally exposed to this toxic emissions may suffer varying degree of delayed wound healing.

Toxicological evaluation of the effects of 2-stroke auto-rickshaw smoke solutions on wound healing

Vehicle exhaust from traffic is a widespread air pollutant. The use of 3-wheel auto-rickshaws powered by a 2-stroke engine is widespread in south Asia; exhaust from these vehicles may cause different types of toxicities resulting in different pathologies. The aim of this study was to explore the association between exposure to 2-stroke auto-rickshaw smoke solution (2SARSS) and wound healing. The in vivo model of wound healing was customized to evaluate different stages of wound healing: dermal matrix regeneration, re-epithelialization, and neovascularization. A total of 72 adult mice were divided into 8 groups and exposed to 2SARSS for 12 days. A highly significant reduction (p<0.001) in wound closure was observed among all 2SARSS-treated groups at day 8 post-wounding. Histological examination revealed a significant delay in the outcome of re-epithelialization, dermal matrix regeneration, and maturation of collagen bundles among all 2SARSS-exposed wounds. Delayed activation of neovascularization was seen in the 2SARSS-treated groups at day 12 post-wounding. The Abbot curve, angular spectrum, and several other 3D surface parameters of reverse wound topographies revealed a highly significant reduction (p<0.001) in angiogenesis. These results demonstrate that application of 2SARSS causes a substantial delay in the progression of angiogenesis, resulting in delayed onset of wound healing. These observations validate the damaging effects of 2SARSS on wound healing. Thus, people who are directly or indirectly exposed to this toxic exhaust are expected to have delayed wound healing, which could result in chronic wounds.