Alginates

We have developed a novel three-dimensional (3D) cellular microarray platform to enable the rapid and efficient tracking of stem cell fate and quantification of specific stem cell markers. This platform consists of a miniaturized 3D cell culture array on a functionalized glass slide for spatially addressable high-throughput screening. A microarray spotter was used to deposit cells onto a modified glass surface to yield an array consisting of cells encapsulated in alginate gel spots with volumes as low as 60 nL. A method based on an immunofluorescence technique scaled down to function on a cellular microarray was also used to quantify specific cell marker protein levels in situ. Our results revealed that this platform is suitable for studying the expansion of mouse embryonic stem (ES) cells as they retain their pluripotent and undifferentiated state. We also examined neural commitment of mouse ES cells on the microarray and observed the generation of neuroectodermal precursor cells characterized by expression of the neural marker Sox-1, whose levels were also measured in situ using a GFP reporter system. In addition, the high-throughput capacity of the platform was tested using a dual-slide system that allowed rapid screening of the effects of tretinoin and fibroblast growth factor-4 (FGF-4) on the pluripotency of mouse ES cells. This high-throughput platform is a powerful new tool for investigating cellular mechanisms involved in stem cell expansion and differentiation and provides the basis for rapid identification of signals and conditions that can be used to direct cellular responses. Biotechnol. Bioeng. 2010; 106: 106–118. © 2010 Wiley Periodicals, Inc.

This paper reports an efficient protoplast culture technique, the “extra thin alginate film” technique. The development of this improved method of protoplast culture was an outcome of an assessment of the efficiency and shortcomings of various protoplast culture techniques. The efficiency of this technique was evaluated with two model plant systems, viz., Nicotiana tabacum and Lotus corniculatus, and a comparison was made with the “thin alginate layer” technique, another efficient protoplast culture system. Results indicate that the culture technique with extra thin alginate film is as efficient as the technique with thin alginate layer, with many additional advantages. The present innovation overcomes most of the limitations of protoplast culture techniques described so far and can now be applied to a wide variety of crops to check its general applicability.

To accomplish continuous flow ohmic heating of a low-acid food product, sufficient heat treatment needs to be delivered to the slowest heating particle at the outlet of the holding section. This research was aimed at developing mathematical models for sterilization of a multicomponent food in a pilot-scale ohmic heater and verifying microbial inactivation by inoculated particle methods. Thermal verification of the mathematical model showed good agreement between calculated and experimental fluid temperatures (P>0.05) at heater and holding tube exits. In addition, a microbiological verification test was conducted using chicken-alginate particles inoculated with spores of Clostridium sporogenes. The test indicated the absence of viable microorganisms at the target treatment and its presence for a sub-target treatment, thereby verifying model predictions.

3D printed biomaterials with spatial and temporal functionality could enable interfacial manipulation of fluid flows and motile cells. However, such dynamic biomaterials are challenging to implement since they must be responsive to multiple, biocompatible stimuli. Here, we show stereolithographic printing of hydrogels using noncovalent (ionic) crosslinking, which enables reversible patterning with controlled degradation. We demonstrate this approach using sodium alginate, photoacid generators and various combinations of divalent cation salts, which can be used to tune the hydrogel degradation kinetics, pattern fidelity, and mechanical properties. This approach is first utilized to template perfusable microfluidic channels within a second encapsulating hydrogel for T-junction and gradient devices. The presence and degradation of printed alginate microstructures were further verified to have minimal toxicity on epithelial cells. Degradable alginate barriers were used to direct collect...

The surface charge of a biomaterial represents a promising tool to direct cellular behavior, which is crucial for therapeutic approaches in regenerative medicine. To expand the understanding of how the material surface charge affects protein adsorption and mesenchymal stem cell behavior, differently charged surfaces with zeta potentials spanning from -25 mV to +15 mV were fabricated by the conjugation of poly(amidoamine) to alginate-based hydrogels. We showed that the increase of the biomaterials surface charge resulted in enhanced quantities of biologically available, surface-attached proteins. Since different surface charges were equalized after protein adsorption, mesenchymal stem cells interacted rather with diverse protein compositions instead of different surface features. Besides an enhanced cell attachment to increasingly positively charged surfaces, the cell spreading area and the expression of adhesion-related genes integrin α5 and tensin 1 were found to be increased after...

Beads with enhanced-stability acid media, which were based on alginate and chitosan functionalized by succinylation (increasing the anionic charges able to retain protons) or by acylation (improving matrix hydrophobicity), were developed for immobilization of bacterial cells. Beads (3 mm diameter) formed by ionotropic gelation with CaCl(2) presented good mechanical characteristics. After 30 min incubation of viable free Lactobacillus rhamnosus cells in simulated gastric fluid (pH 1.5), we noticed that the level of viable bacteria was undetectable. Bacterial immobilization in native-alginate-based beads generated a viable-cell count of 22-26%, whereas, when entrapped in succinylated alginate and chitosan beads, the percentage of viable cells was of 60 and 66%, respectively. Best viability (87%) was found for bacteria immobilized in N -palmitoylaminoethyl alginate, which affords a high protective effect, probably due to long alkyl pendants that improve the beads' hydrophobicity, l...