The optimization of poly(vinyl)-alcohol-alginate beads with a slow-release compound for the aerobic cometabolism of chlorinated aliphatic hydrocarbons.

Chlorinated aliphatic hydrocarbons (CAHs), such as cis-1,2-dichloroethylene (cDCE), are prevalent in groundwater at many locations throughout the United States. When immobilized in hydrogel beads with slow-release compounds, the bacteria strain Rhodococcus rhodochrous ATCC 21198 can be used for the in situ bioremediation of cDCE. These hydrogel beads must exhibit high mechanical strength and resist degradation to extend the lifetime of slow-release compounds and bioremediation. We engineered poly(vinyl)-alcohol - alginate (PVA-AG) beads to immobilize ATCC 21198 with the slow-release compound, tetrabutoxysilane (TBOS) that produces 1-butanol as a growth substrate, for high mechanical strength. We optimized three inputs (concentration of PVA, concentration of AG, and the crosslinking time) on two responses (compressive modulus and rate of oxygen utilization) for batch incubation experiments between 1 and 30 days using a design of experiments approach. The predictive models generated from design of experiments were then tested by measuring the compressive strength, oxygen utilization, and abiotic rates of hydrolysis for a predicted optimal bead formulation. The result of this study generated a hydrogel bead with immobilized R. rhodochrous ATCC 21198 and TBOS that exhibited a high compressive modulus on day 1 and day 30, which was accurately predicted by models. These hydrogel beads exhibited low metabolic activity based on oxygen rates on day 1 and day 30 but were not accurately predicted by the models. In addition, the ratio between oxygen utilization and abiotic rates of hydrolysis were observed to be roughly half of what was expected stoichiometrically. Lastly, we demonstrated the capability to use these beads as a bioremediation technology for cDCE as we found that, for all bead formulations, cDCE was significantly reduced after 30 days. Altogether, this work demonstrates the capability to capture and enhance the material properties of the complex hydrogel beads with predictive models yet signals the need for more robust methods to understand the metabolic activity that occurs in the hydrogel beads.

Engineering high throughput screening platforms of cervical cancer.

Cervical cancer is the second leading cause of cancer-related death in women under 40 and is one of the few cancers to have an increased incidence rate and decreased survival rate over the last 10 years. One in five patients will have recurrent and/or distant metastatic disease and these patients face a 5-year survival rate of less than 17%. Thus, there is a pressing need to develop new anticancer therapeutics for this underserved patient population. However, the development of new anticancer drugs remains a challenge, as only 7% of novel anticancer drugs are approved for clinical use. To facilitate identification of novel and effective anticancer drugs for cervical cancer, we developed a multilayer multicellular platform of human cervical cancer cell lines and primary human microvascular endothelial cells that interfaces with high throughput drug screening methods to evaluate the anti-metastatic and anti-angiogenic drug efficacy simultaneously. Through the use of design of experiments statistical optimization, we identified the specific concentrations of collagen I, fibrinogen, fibronectin, GelMA, and PEGDA in each hydrogel layer that maximized both cervical cancer invasion and endothelial microvessel length. We then validated the optimized platform and assessed its viscoelastic properties. Finally, using this optimized platform, we conducted a targeted drug screen of four clinically relevant drugs on two cervical cancer cell lines. Overall, this work provides a valuable platform that can be used to screen large compound libraries for mechanistic studies, drug discovery, and precision oncology for cervical cancer patients.

Frugal Imaging Technique of Capillary Flow through Three-Dimensional Polymeric Printing Powders.

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in microfluidic and millifluidic studies. With the advent of three-dimensional (3D) printing, a new domain of materials has emerged, thereby increasing the demand for novel polymers. Specifically, polymeric powders, with average particle sizes on the order of a micron, are experiencing a growing interest from academic and industrial communities. Controlling material tunability at the mesoscopic to microscopic length scales creates opportunities to develop innovative materials, such as gradient materials. Recently, a need for micron-sized polymeric powders has been growing, as clear applications for the material are developing. Three-dimensional printing provides a high-throughput process with a direct link to new applications, driving investigations into the physio-chemical and transport interactions on a mesoscale. The protocol that is discussed in this article provides a non-invasive technique to image fluid flow in packed powder beds, providing high temporal and spatial resolution while leveraging mobile technology that is readily available from mobile devices, such as smartphones. By utilizing a common mobile device, the imaging costs that would normally be associated with an optical microscope are eliminated, resulting in a frugal-science approach. The proposed protocol has successfully characterized a variety of combinations of fluids and powders, creating a diagnostic platform for quickly imaging and identifying an optimal combination of fluid and powder.

Compressive properties of fibrous repair tissue compared to nucleus and annulus.

The wound healing process includes filling the void between implant and tissue edges by collagenous connective repair tissue. This fibrous repair tissue may load share or stabilize implants such as spinal disc replacements. The objective of this study was the biomechanical characterization of human fibrous tissue compared to annulus fibrosus and nucleus pulposus. Human lumbar discs (10 nucleus and annulus) and 10 lumbar deep wound fibrous tissue specimens were sectioned into 12mm diameter×6mm high cylindrical samples. Confined compression testing, after 2h swelling at 0.11MPa, was performed at 5%, 10% and 15% strain over 3.5h. Unconfined dynamic testing (2-0.001Hz) was performed at 5-15% strain. Semi-quantitative histology estimated the proportion of proteoglycan to collagen. Fibrous tissue exhibited a decrease in height during the swelling period whereas annulus and nucleus tissues did not. The aggregate modulus was significantly less for fibrous tissue (p<0.002). Percent stress relaxation was greatest for the fibrous tissue and similar for annulus and nucleus. Dynamic testing found the storage modulus (E') was greater than the loss modulus (E″) for all tissues. Annulus were found to have greater E' and E″ than nucleus, whereas E' and E″ were similar between annulus and fibrous tissue. Fibrous tissue had the greatest increase in both moduli at greater frequencies, but had the lowest hydration and proteoglycan content. Fibrous tissue would not be a substitute for native tissue within the disc space but if adjacent to a disc prosthesis may impart some degree of intersegmental stability during acute loading activities.

Rheological characterization of photopolymerized poly(vinyl alcohol) hydrogels for potential use in nucleus pulposus replacement.

Hydrogels have been proposed as candidates for nucleus pulposus replacement because of their similarity in mechanical behavior to the native tissue when subjected to transient or static loading; however, given the viscoelastic nature of soft biological tissues, the lack of dynamic testing is a significant inadequacy in the studies performed to date. In the present work, the viscoelastic behavior of a hydrogel system obtained via photopolymerization of glycidyl methacrylate modified poly(vinyl alcohol) (PVA) was evaluated in comparison to that of the nucleus pulposus when subjected to dynamic torsional shear. The complex shear moduli and phase shift angles were modulated through the variation of PVA molecular weight and concentration of polymer prior to photopolymerization. Hydrolysis resistance was assessed by evaluation of the viscoelastic behavior of hydrogels submerged in Hank's solution for progressively longer periods of time. The phase shift angles of all hydrogels were lower than those of the nucleus pulposi; however, the complex shear moduli of the synthetic system spanned the values observed for the natural system. Over the time frame of the experiment, no changes in moduli were observed following submersion in Hank's solution. This study represents the first attempt to successfully mimic the viscoelastic nature of the nucleus pulposus exhibited under dynamic torsional loading with that of materials intended for use in tissue replacement.