 My name is Anand Ramasubramanian and this is Anand Srinivasan. We are both in biomedical engineering department at the University of Texas at San Antonio. In this video abstract, we will describe to you a microarray platform for the culture of microorganisms that are encapsulated in a hydrogel matrix. And also we will describe to you some of our observations in screening antimicrobial drugs in these systems. As you will see, the conclusions that are drawn from this work are in general applicable for three-dimensional tissue engineered systems. Conventionally, microbial cultures are performed in large, earthenware flasks or petri dishes or test tubes or well plates. In such cases, the volumes range from a few hundreds of microliters to a few hundreds of milliliters or even liters. This has been in practice for a long, long time now. However, recently we have developed a microarray platform on a microscope glass lid at a chip that we call for the culture of microorganisms in volume as small as few tens of nanoliders. Such a system is very efficient in cutting down the cost, reagent volume, assay time and also allows for a truly high throughput screening in drug discovery and diagnostics. The microbial cellular microarray or the microbial chip consists of a modified glass surface and we spotted 30 nanoliders of cells mixed with hydrogel solutions such as collagen or alternate. The cells grow inside this gel and the effect of drugs can be tested by exposing each of these parts to different concentrations of various drugs and by quantifying cell viability using a live dead stain and a standard DNA microarray scanner. Some of the advantages of this chip are small volume, rapid, easy handling, simple Duncan Rins procedures and high sensitivity readouts. In this work, we cultured biofilms of fungal pathogen Canada albicans encapsulated in collagen or alternate matrices on the chip and it forms these beautiful biofilms in three dimension. We then tested the effect of common antifungal compound called Casper fungion on the biofilms and interestingly we found that only the biofilms grown in alternate is susceptible to Casper fungion but not when grown in collagen. We wanted to know why is that the biofilms grown in collagen is less susceptible to Casper fungion than when grown in alternate. We thought that the difference in susceptibility of the fungi to Casper fungion in different matrices may be because of the distribution of drug in the two matrices. Since we can't really visualize the drugs, we use cell viability as a surrogate to visualize drug distribution in the gels. So we tested the biofilm spots on the microarray with drugs stained with fluorescent dye and visualized the spots by confocal microscopy. We used two dyes, one is green fluorescent live stain while the other is a blue fluorescent cell wall stain. First, let's look at the biofilms that are not treated with any drugs. As you can see, the biofilms can be seen as strands and it looks whitish because of the overlay of green and blue colors. The cells look alike in both collagen and alginate gels. But when we look at the biofilms treated with Casper fungion, we see that the cells in the collagen and alginate look very different. The cell density has gone down significantly throughout the depth of the alginate gels but not so much in collagen gels. This shows that Casper fungion is concentrated only on the top and does not reach the bottom in collagen gels but not in alginate. We have also quantified these visual observations and have further confirmed using HPLC. In essence, whatever the data shows is that the apparent susceptibility of Candida albicans to an antifungal drug may depend upon the environment that the cells are in. So one can imagine similar effects that may influence the results you obtain in three-dimensional tissue engineered systems where the responses may depend upon the scaffolding material. Hence, by choosing either an inert matrix or a protein-rich matrix such as alginate or collagen, one can understand the effect of drug action on cells per se or the cumulative effect due to an extracellular matrix environment you find in vivo. For a more detailed study, we welcome you to read our article in the biotechnology and bioengineering journal. Thank you very much.