No abstract

Quorum sensing (QS) inhibitor-based therapy is an attractive strategy to inhibit bacterial biofilm formation without excessive induction of antibiotic resistance. Thus, we designed Ca 2+ -binding poly(lactide-co-glycolide) (PLGA) microparticles that can maintain a sufficient concentration of QS inhibitors around hydroxyapatite (HA) surfaces in order to prevent biofilm formation on HA-based dental or bone tissues or implants and, therefore, subsequent pathogenesis. Poly(butyl methacrylate-co-methacryloyloxyethyl phosphate) (PBMP) contains both Ca 2+ -binding phosphomonoester groups and PLGA-interacting butyl groups. The PBMPcoated PLGA (PLGA/PBMP) microparticles exhibited superior adhesion to HA surfaces without altering the sustained release properties of uncoated PLGA microparticles. PLGA/PBMP microparticle-encapsulating furanone C-30, a representative QS inhibitor, effectively inhibited the growth of Streptococcus mutans and its ability to form biofilms on HA surface for prolonged periods of up to 100 h, which was much longer than either furanone C-30 in its free form or when encapsulated in noncoated PLGA microparticles.

DNA has been employed to either store digital information or to perform parallel molecular computing. Relatively unexplored is the ability to combine DNA-based memory and logical operations in a single platform. Here, we show a DNA tri-level cell non-volatile memory system capable of parallel random-access writing of memory and bit shifting operations. A microchip with an array of individually addressable electrodes was employed to enable random access of the memory cells using electric fields. Three segments on a DNA template molecule were used to encode three data bits. Rapid writing of data bits was enabled by electric field-induced hybridization of fluorescently labeled complementary probes and the data bits were read by fluorescence imaging. We demonstrated the rapid parallel writing and reading of 8 (23) combinations of 3-bit memory data and bit shifting operations by electric field-induced strand displacement. Our system may find potential applications in DNA-based memory and computations.

As molecular computing materials, information-encoded deoxyribonucleic acid (DNA) strands provide a logical computing process by cascaded and parallel chain reactions. However, the reactions in DNA-based combinational logic computing are mostly achieved through a manual process by adding desired DNA molecules in a single microtube or a substrate. For DNA-based Boolean logic, using microfluidic chips can afford automated operation, programmable control, and seamless combinational logic operation, similar to electronic microprocessors. In this paper, we present a programmable DNA-based microfluidic processing unit (MPU) chip that can be controlled via a personal computer for performing DNA calculations. To fabricate this DNA-based MPU, polydimethylsiloxane was cast using double-sided molding techniques for alignment between the microfluidics and valve switch. For a uniform surface, molds fabricated using a three-dimensional printer were spin-coated by a polymer. For programming control, the valve switch arms were operated by servo motors. In the MPU controlled via a personal computer or smartphone application, the molecules with two input DNAs and a logic template DNA were reacted for the basic AND and OR operations. Furthermore, the DNA molecules reacted in a cascading manner for combinational AND and OR operations. Finally, we demonstrated a 2-to-1 multiplexer and the XOR operation with a three-step cascade reaction using the simple DNA-based MPU, which can perform Boolean logic operations (AND, OR, and NOT). Through logic combination, this DNA-based Boolean logic MPU, which can be operated using programming language, is expected to facilitate the development of complex functional circuits such as arithmetic logical units and neuromorphic circuits.