8 research outputs found
Electrospun Nanofibrous Conduit Filled with a Collagen-Based Matrix (ColM) for Nerve Regeneration
Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration and function recovery. Herein, a three-dimensional (3D) sponge-filled nanofibrous NGC (sf@NGC) resembling the structure of native peripheral nerves was developed. The conduit was fabricated by electrospinning a poly(L-lactide-co-glycolide) (PLGA) membrane, whereas the intraluminal filler was obtained by freeze-drying a collagen-based matrix (ColM) resembling the extracellular matrix. The effects of the electrospinning process and of the composition of ColM on the physicochemical performance of sf@NGC were investigated in detail. Furthermore, the biocompatibility of the PLGA sheath and ColM were evaluated. The continuous and homogeneous PLGA nanofiber membrane had high porosity and tensile strength. ColM was shown to exhibit an ECM-like architecture characterized by a multistage pore structure and a high porosity level of over 70%. The PLGA sheath and ColM were shown to possess stagewise degradability and good biocompatibility. In conclusion, sf@NGC may have a favorable potential for the treatment of nerve reconstruction
Engineering Biosensors with Dual Programmable Dynamic Ranges
Although extensively used in all
fields of chemistry, molecular recognition still suffers from a significant
limitation: hostâguest binding displays a fixed, hyperbolic
doseâresponse curve, which limits its usefulness in many applications.
Here we take advantage of the high programmability of DNA chemistry
and propose a universal strategy to engineer biorecognition-based
sensors with dual programmable dynamic ranges. Using DNA aptamers
as our model recognition element and electrochemistry as our readout
signal, we first designed a dual signaling âsignal-onâ
and âsignal-offâ adenosine triphosphate (ATP) sensor
composed of a ferrocene-labeled ATP aptamer in complex to a complementary,
electrode-bound, methylene-blue labeled DNA. Using this simple âdimericâ
sensor, we show that we can easily (1) tune the dynamic range of this
dual-signaling sensor through base mutations on the electrode-bound
DNA, (2) extend the dynamic range of this sensor by 2 orders of magnitude
by using a combination of electrode-bound strands with varying affinity
for the aptamers, (3) create an ultrasensitive dual signaling sensor
by employing a sequestration strategy in which a nonsignaling, high
affinity âdepletantâ DNA aptamer is added to the sensor
surface, and (4) engineer a sensor that simultaneously provides extended
and ultrasensitive readouts. These strategies, applicable to a wide
range of biosensors and chemical systems, should broaden the application
of molecular recognition in various fields of chemistry
Regulation of DNA Self-Assembly and DNA Hybridization by Chiral Molecules with Corresponding Biosensor Applications
Chirality is one of the fundamental
biochemical properties in a
living system, and a lot of biological and physiological processes
are greatly influenced by the chirality of molecules. Inspired by
this phenomenon, we study the covalent assembly of DNA on chiral molecule
modified surfaces and further discuss the hybridization of DNA on
chiral surfaces with nucleic acids. Take methylene blue (MB) modified
DNA as a model molecule, we show that the peak current of the L-NIBC
(NIBC, <i>N</i>-isobutyryl-lÂ(d)-cysteine)
modified gold surface (L-surface) is larger than the D-surface because
of a stronger interaction between short-chain DNA and the L-surface;
however, the D-surface has a higher hybridization efficiency than
the L-surface. Moreover, we apply this result to actual application
by choosing an electrochemical DNA (E-DNA) sensor as a potential platform.
Furthermore, we further amplify the difference of hybridization efficiency
using the supersandwich assay. More importantly, our findings are
successfully employed to program the sensitivity and limit of detection
Nanopore-Based DNA-Probe Sequence-Evolution Method Unveiling Characteristics of ProteinâDNA Binding Phenomena in a Nanoscale Confined Space
Almost
all of the important functions of DNA are realized by proteins
which interact with specific DNA, which actually happens in a limited
space. However, most of the studies about the proteinâDNA binding
are in an unconfined space. Here, we propose a new method, nanopore-based
DNA-probe sequence-evolution (NDPSE), which includes up to 6 different
DNA-probe systems successively designed in a nanoscale confined space
which unveil the more realistic characteristics of proteinâDNA
binding phenomena. There are several features; for example, first,
the edge-hindrance and core-hindrance contribute differently for the
binding events, and second, there is an equilibrium between proteinâDNA
binding and DNAâDNA hybridization