Browsing by Author "Ibrahim, Mohamed"
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Item Open Access Characterization of the Foreign Body Response to Common Surgical Biomaterials in a Murine Model.(European journal of plastic surgery, 2017-11) Ibrahim, Mohamed; Bond, Jennifer; Medina, Manuel A; Chen, Lei; Quiles, Carlos; Kokosis, George; Bashirov, Latif; Klitzman, Bruce; Levinson, HowardBACKGROUND:Implanted biomaterials are subject to a significant reaction from the host, known as the foreign body response (FBR). We quantified the FBR to five materials following subcutaneous implantation in mice. MATERIALS AND METHODS:Polyvinyl alcohol (PVA) and silicone sheets are considered highly biocompatible biomaterials and were cut into 8mm-diameter disks. Expanded PTFE (ePTFE)and polypropylene are also widely used biocompatible biomaterials and were cut into 2cm-long cylinders. Cotton was selected as a negative control material that would invoke an intense FBR, was cut into disks and implanted. The implants were inserted subcutaneously into female C57BL/6 mice. On post-implantation days 14, 30, 60, 90 and 180, implants were retrieved. Cellularity was assessed with DAPI stain, collagen with Masson's trichrome stain. mast cells with toluidine-blue, macrophages with F4/80 immunohistochemical-stain, and capsular thickness and foreign body giant cells with hematoxylin & eosin. RESULTS:DAPI revealed a significantly increased cellularity in both PVA andsilicone, and ePTFE had the lowest cell density. Silicone showed the lowest cellularity at d14 and d90 whereas ePTFE showed the lowest cellularity at days 30, 60, and 180. Masson's trichrome staining demonstrated no apparent difference in collagen. Toluidine blue showed no differences in mast cells. There were, however, fewer macrophages associated with ePTFE. On d14, PVA had highest number of macrophages, whereas polypropylene had the highest number at all time points after d14. Giant cells increased earlier and gradually decreased later. On d90, PVA exhibited a significantly increased number of giant cells compared to polypropylene and silicone. Silicone consistently formed the thinnest capsule throughout all time points. On d14, cotton had formed the thickest capsule. On d30 polypropylenehas formed thickest capsule and on days 60, 90 and 180, PVA had formed thickest capsule. CONCLUSION:These data reveal differences in capsule thickness and cellular response in an implant-related manor, indicating that fibrotic reactions to biomaterials are implant specific and should be carefully considered when performing studies on fibrosis when biomaterials are being used.Item Open Access Optimization of Trustworthy Biomolecular Quantitative Analysis Using Cyber-Physical Microfluidic Platforms(2018) Ibrahim, MohamedConsiderable effort has been devoted in recent years to the design and implementation of microfluidic platforms for biomolecular quantitative analysis. However, today's platforms suffer from two major limitations: (1) they were optimized for sample-limited analyses, thus they are inadequate for practical quantitative analysis and the processing of multiple samples through independent pathways; (2) the integrity of these platforms and their biochemical operations is still an open question, since no protection schemes were developed against adversarial contamination or result-manipulation risks.
Design optimization techniques for microfluidics have been studied in recent years, but they overlook the myriad complexities of biomolecular protocols and are yet to make an impact in microbiology research. The realization of microfluidic platforms for real-life quantitative analysis requires: (1) a new optimization flow that is based on the realistic modeling of biomolecular protocols, and (2) a microfluidic security flow that provides a high-level of confidence in the integrity of miniaturized quantitative analysis.
Motivated by the above needs, this dissertation is focused on optimized and trustworthy transfer of benchtop biomolecular analysis, particularly epigenetic studies, to programmable and cyber-physical microfluidic biochips. The dissertation first presents a set of optimization mechanisms that leverages cyber-physical integration to enable real-time execution of multi-sample biomolecular analysis. The proposed methods include a resource-allocation scheme that responds to decisions about the protocol flow, an interactive firmware that collects and analyzes sensor data, and a spatio-temporal reconfiguration technique that aims to enhance the reliability of the microfluidic system. An envisioned design for an Internet-of-Things (IoT)-based microfluidics-driven service is also presented to cope with the complexity of coordinated biomolecular research.
Next, this dissertation advances single-cell protocols by presenting optimized microfluidic methods for high-throughput cell differentiation. The proposed methods target pin-constrained design of reconfigurable microfluidic systems and real-time synthesis of a pool of heterogeneous cells through the complete flow of single-cell analysis. A performance model related to single-cell screening is also presented based on computational fluid-dynamics simulations.
With the increasing complexity of microbiology research, optimized protocol preparation and fault-tolerant execution have become critical requirements in today's biomolecular frameworks. This dissertation presents a design method for reagent preparation for parameter-space exploration. Trade-offs between reagent usage and protocol efficiency are investigated. Moreover, an integrated design for automated error recovery in cyber-physical biochips is demonstrated using a fabricated chip.
In order to ensure high confidence in the outcome of biomolecular experiments, appropriate security mechanisms must be applied to the microfluidic design flow. This dissertation provides an assessment of potential security threats that are unique to biomolecular analysis. Security countermeasures are also proposed at different stages of the biomolecular information flow to secure the execution of a quantitative-analysis framework. Related benchtop studies are also reported.
In summary, the dissertation tackles important problems related to key stages of the biomolecular workflow. The results emerging from this dissertation provide the first set of optimization and security methodologies for the realization of biomolecular protocols using microfluidic biochips.