Bacterial cellulose (BC), a network of pure cellulose nanofibers with fine crystallinity, high mechanical strength and wet capability, and good biocompatibility, is a good material candidate for wound dressing. Hyaluronan (HA) has obvious curative properties, promoting the healing of wound skin tissue and reducing scar formation. This study explored an ''orifice plate'' culture method to obtain BC samples of different sizes but consistent thicknesses. Novel BC-HA nanocomposites with a 3-D network structure were obtained through a solution impregnation method. The total surface area and the pore volume of the BC-HA composite films gradually decreased with the increase of HA content. The elongation of BC-HA composite films at the break point gradually increased as the HA content increased while the tensile strength of the BC-HA composite films decreased during the same process. The BC-HA composite films had a better water uptake capability than pure BC, and water vapor transmission rate (WVTR) measurements showed that the BC-HA composite films can satisfy breathing requirements of injured skin. The BC-HA composite films facilitated the growth of primary human fibroblast cells, showing their low toxicity, and the BC-HA composite films with 0.1% HA lead to higher levels of cell viability than the pure BC. In vivo experiments indicated that the BC-HA with 0.1% HA had the shortest wound healing time while BC-HA with 0.05% HA yielded best tissue repair results. The BC-HA composite films are expected to be useful as novel wound dressing materials for clinical skin repair.
This paper presents a methodology for implementing digital signal processing (DSP) operations such as filtering with molecular reactions. Molecular reactions that produce time-varying output quantities of molecules as a function of time-varying input quantities are designed according to a DSP specification. Unlike all previous schemes for molecular computation, the methodology produces designs that are dependent only on coarse rate categories for the reactions ("fast" and "slow"). Given such categories, the computation is exact and independent of the specific reaction rates. The methodology is illustrated with the design of a simple moving-average filter as well as a more complex biquad filter. Both designs are translated into DNA strand displacement reactions. The designs are validated through transient stochastic simulations of the chemical kinetics at the DNA reactions level. Although conceptual for the time being, the proposed methodology has potential applications in domains of synthetic biology such as biochemical sensing and drug delivery.
Abstract-This paper presents a methodology for implementing digital logic with molecular reactions based on a bistable mechanism for representing bits. The value of a bit is not determined by the concentration of a single molecular type; rather, it is the comparison of the concentrations of two complementary types that determines if the bit is "0" or "1". This mechanism is robust: any small perturbation or leakage in the concentrations quickly gets cleared out and the signal value is not affected. Based on this representation for bits, a constituent set of logical components are implemented. These include combinational components -AND, OR, NOR, and XOR -as well as sequential components -D latches and D flip-flops. Using these components, three full-fledged design examples are given: a square-root unit, a binary adder and a linear feedback shift register. DNA-based computation via strand displacement is the target experimental chassis. The designs are validated through simulations of the chemical kinetics. The simulations show that the molecular systems compute digital functions accurately and robustly.
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