Synthetic Biology and Tissue Engineering: Toward Fabrication of Complex and Smart Cellular Constructs

Tissue engineering approaches, with the goals of replacing or recovering damaged or diseased tissues, or of reconstituting tissues in vitro for disease modeling and drug development, have the potential to make significant contributions to medicine. Advances in stem cell biology, biomaterial synthesis and characterization, and microscale technologies have made engineered tissues a reality. However, the classic tools used to build tissues in the lab do not allow for complete control of cell behaviors. More recently, synthetic biology principles have developed robust and versatile approaches to program cells with artificial genetic circuits, where cell behavior and function can be manipulated. At the interface between synthetic biology and tissue engineering, there is space for a new area of investigation where material engineering and cellular engineering complement and sustain each other. In this progress report, synthetic biology principles and how they have been used to engineer cells with potential to dictate cell behavior and function in tissue constructs of the future are briefly described. It is believed that this research area still needs further exploration to fully exploit synthetic biology to make smart and functional cellular constructs for therapeutic and in vitro applications.     

Measurement of decarburisation of steel rods with an electromagnetic sensor using an analytical model

This paper presents the measurement of decarburization of steel rods with an electromagnetic sensor using an analytical model both in online and offline scenarios. Loss of carbon (decarburization) at the steel surface can have a significantly detrimental effect on mechanical properties of products, since hardness, fatigue, strength and wear properties are strongly dependent on carbon content. Currently, measurement of decarburization is by destructive methods, such as metallographic observation or hardness tests on a sample cross-section after processing. A non-destructive EM method is proposed in this paper. An analytical solution for the inductance of a circular air-cored coil encircling a steel rod is deduced and further a simplified model is obtained which shows that for both online and offline cases, the thickness of the decarburisation layer is proportional to the inductance difference with and without decarburisation. Using this simplified model, decarburisation thickness can be obtained. The results have been verified by both finite element models and metallographic observations.     

A model predictive control package for undergraduate education

Model predictive control (MPC) techniques are extremely profitable control strategies and are well accepted in the chemical processing industry so it is important that chemical engineering graduates have a fundamental understanding of MPC. This understanding will help them make contributions in industry where these control strategies abound. Without such knowledge, graduates would not understand a major part of the control structure present in modern manufacturing systems and would have difficulty understanding how to modify and improve those chemical manufacturing systems to take advantage of new technology.In this paper we describe a new software package developed and tested by the authors for teaching undergraduates the fundamentals of MPC including its suggested application in the classroom. The package is similar to existing industrial model predictive control packages in that the same steps are required to implement a model predictive controller as follows: model identification, controller configuration, controller simulation and tuning. We describe our experience using the package to introduce MPC to an advanced undergraduate process control II class. The package has also been used to provide an MPC laboratory experience for a graduate class on industrial process control.     

Gelatin Methacryloyl Microneedle Patches for Minimally Invasive Extraction of Skin Interstitial Fluid

The extraction of interstitial fluid (ISF) from skin using microneedles (MNs) has attracted growing interest in recent years due to its potential for minimally invasive diagnostics and biosensors. ISF collection by absorption into a hydrogel MN patch is a promising way that requires the materials to have outstanding swelling ability. Here, a gelatin methacryloyl (GelMA) patch is developed with an 11 × 11 array of MNs for minimally invasive sampling of ISF. The properties of the patch can be tuned by altering the concentration of the GelMA prepolymer and the crosslinking time; patches are created with swelling ratios between 293% and 423% and compressive moduli between 3.34 MPa and 7.23 MPa. The optimized GelMA MN patch demonstrates efficient extraction of ISF. Furthermore, it efficiently and quantitatively detects glucose and vancomycin in ISF in an in vivo study. This minimally invasive approach of extracting ISF with a GelMA MN patch has the potential to complement blood sampling for the monitoring of target molecules from patients.     

Output frequency response characteristics of nonlinear systems. Part I: general multi-tone inputs

A systematic algorithm for determining the output frequencies generated by a nonlinear system subject to a general multi-tone input, including a bias input, is presented. The algorithm is very efficient, and circumvents many of the difficulties of ‘duplicate frequencies’ that are often generated using previous methods. The inclusion of the dc bias component in the analysis is also important because of the significant effect that non-zero mean inputs can have on nonlinear system response. The algorithm is straightforward to implement on a computer, and the results are illustrated by means of an example.     

Imaging the continuous conductivity profile within layered metal structures using inductance spectroscopy

This paper presents an inverse method for determining the conductivity distribution of a flat, layered conductor using a multifrequency electromagnetic sensor. Eddy-current sensors are used in a wide range of nondestructive testing applications. Single-frequency sensors are very common; however, the potential of an eddy-current sensor with spectroscopic techniques offers the ability to extract depth profiles and examine more fully the internal structure of the test piece. In this paper, the forward solution for a small right-cylindrical air-cored coil placed next to a layered conductor is based on the analytic solution provided by the transfer matrix approach. For an inverse solution, a modified Newton-Raphson method was used to adjust the conductivity profile to fit a set of multifrequency inductances in a least-squared sense. The approximate Jacobian matrix (sensitivity matrix) was obtained by the perturbation method. Numerical results of the forward solution are provided for cases of step, continuous conductivity profiles. Good estimates for the conductivity profile were obtained. Experimental eddy-current tests are performed by taking the difference in inductance of the coil when placed next to a reference conductor and next to a layered conductor over the range 100 kHz - 1 MHz. Inverse results based on experimental and simulated data verified this method.     

Combined Electromagnetic Tomography for Determining Two-phase Flow Characteristics in the Submerged Entry Nozzle and in the Mold of a Continuous Casting Model

This article describes experiments on the combined determination of the distribution of liquid metal and argon in the submerged entry nozzle (SEN) and of the flow in the mold of a small-scale physical model of a continuous slab caster. For visualizing the metal distribution in the SEN, mutual inductance tomography (MIT) is applied, while the flow in the mold is determined by contactless inductive flow tomography (CIFT). The results of the latter are validated in part by ultrasonic Doppler velocimetry (UDV). Accompanying measurements provide information about the levels in the tundish and in the mold, as well as on the pressure in the SEN. Depending on the gas flow rate, various flow regimes are identified, among them pressure and mold level oscillations, transitions between double and single vortex flows, and transient single port ejections.     

Reduction of Cr(VI) under acidic conditions by the facultative Fe(lll)-reducing bacterium Acidiphilium cryptum

The potential for biological reduction of Cr(VI) under acidic conditions was evaluated with the acidophilic, facultatively metal-reducing bacterium Acidiphilium cryptum strain JF-5 to explore the role of acidophilic microorganisms in the Cr cycle in low-pH environments. An anaerobic suspension of washed A. cryptum cells rapidly reduced 50 microM Cr(VI) at pH 3.2; biological reduction was detected from pH 1.7-4.7. The reduction product, confirmed by XANES analysis, was entirely Cr(III) that was associated predominantly with the cell biomass (70-80%) with the residual residing in the aqueous phase. Reduction of Cr(VI) showed a pH optimum similar to that for growth and was inhibited by 5 mM HgCl2, suggesting that the reaction was enzyme-mediated. Introduction of O2 into the reaction medium slowed the reduction rate only slightly, whereas soluble Fe(III) (as ferric sulfate) increased the rate dramatically, presumably by the shuttling of electrons from bioreduced Fe(II) to Cr(VI) in a coupled biotic-abiotic cycle. Starved cells could not reduce Cr(VI) when provided as sole electron acceptor, indicating that Cr(VI) reduction is not an energy-conserving process in A. cryptum. We speculate, rather, that Cr(VI) reduction is used here as a detoxification mechanism.