molecular-entanglement-and-electrospinnability-of-biopolymers

Molecular Entanglement and Electrospinnability of Biopolymers

Electrospinning is a fascinating technique to fabricate micro- to nano-scale fibers from a wide variety of materials. For biopolymers, molecular ...

Pennsylvania State University

To evaluate the performance of dual-source computed tomography (DSCT) for the visualization of the coronary arteries in a population with atrial fibrillation (AF) compared to single-source CT (SSCT) and to explore the impact of patients' heart rate (HR) on image quality (IQ) and reconstruction timing.

Dual-source CT coronary angiography in patients with atrial fibrillation: comparison with single-source CT.

We have demonstrated a method of fabricating pure starch fibers with an average diameter in the order of micrometers. In the present study, correlation between the rheological properties of starch dispersions and the electrospinnability was attempted via the extrapolation of the critical entanglement concentration, which is the boundary between the semidilute unentangled regime and the semidilute entangled regime. Dispersions of high amylose starch containing nominally 80% amylose (Gelose 80) required 1.2-2.7 times the entanglement concentration for effective electrospinning. Besides starch concentration, molecular conformation, and shear viscosity were also of importance in determining the electrospinnability. The rheological properties and electrospinnability of different starches were studied. Hylon VII and Hylon V starches, containing nominally 70 and 50% amylose, respectively, required concentrations of 1.9 and 3.7 times their entanglement concentrations for electrospinning. Only poor fibers were obtained from mung bean starch, which contains about 35% amylose, while starches with even lower amylose contents could not be electrospun.

Role of molecular entanglements in starch fiber formation by electrospinning.

Starch is a promising bio-based material to replace synthetics in a number of applications. The production of starch-based fibers has been actively pursued in the patent literature. This article reviews patents on starch fiber technology, including fiber spinning from amylose, thermoplastic starch compositions, and non-thermoplastic starch compositions. Some new fiber spinning techniques, e.g. electrospinning and rotary jet spinning, employed for spinning starch fibers are also presented.

Patents on fiber spinning from starches.

The diameter of the starch fibers produced by electrospinning is a key parameter for most potential applications. In this study, a quantitative relationship between fiber diameter and certain electrospinning parameters, i.e. starch concentration, applied voltage, spinning distance and feed rate, was established by empirical modeling using a fractional factorial experimental design in a constrained region. Response surface methodology was employed to analyze the interactions of the electrospinning parameters and predict the direction to minimize and maximize the fiber diameters.

Quantitative relationship between electrospinning parameters and starch fiber diameter.

Bone can adjust its morphological structure to adapt to the changes of mechanical environment, i.e. the bone structure change is related to mechanical loading. This implies that osteoarthritis may be closely associated with knee joint deformity. The purposes of this paper were to simulate the internal bone mineral density (BMD) change in three-dimensional (3D) proximal tibia under different mechanical environments, as well as to explore the relationship between mechanical environment and bone morphological abnormity.

Simulation on the internal structure of three-dimensional proximal tibia under different mechanical environments.

The polymorphic structures of starch were characterized with vibrational sum frequency generation (SFG) spectroscopy. The noncentrosymmetry requirement of SFG spectroscopy allows for the detection of the ordered domains without spectral interferences from the amorphous phase and also the distinction of the symmetric elements among crystalline polymorphs. The V-type amylose was SFG-inactive due to the antiparallel packing of single helices in crystal unit cells, whereas the A- and B-type starches showed strong SFG peaks at 2904 cm(-1) and 2952-2968 cm(-1), which were assigned to CH stretching of the axial methine group in the ring and CH2 stretching of the exocyclic CH2OH side group, respectively. The CH2/CH intensity ratios of the A- and B-type starches are significantly different, indicating that the conformation of hydroxymethyl groups in these two polymorphs may be different. Cyclodextrin inclusion complexes were also analyzed as a comparison to the V-type amylose and showed that the head-to-tail and head-to-head stacking patterns of cyclodextrin molecules govern their SFG signals and peak positions. Although the molecular packing is different between V-type amylose and cyclodextrin inclusion complexes, both crystals show the annihilation of SFG signals when the functional group dipoles are arranged pointing in opposite directions.

Characterization of starch polymorphic structures using vibrational sum frequency generation spectroscopy.

To evaluate the image quality and radiation dose of combined heart, head, and neck CT angiography (CTA) using prospectively electrocardiography (ECG)-triggered high-pitch spiral scan protocol, compared with single coronary CTA.

Feasibility of low-dose contrast medium high pitch CT angiography for the combined evaluation of coronary, head and neck arteries.

In the present study, we introduce a simple method to prepare inclusion complexes by "inserting" guest molecules into preformed "empty" V-type amylose helices. Ascorbyl palmitate (AscP) was used as a model guest material to investigate the effect of solvent environment, complexation temperature, annealing and guest concentration on inclusion complex formation. High complexation temperature was not necessary for encapsulating guest molecules in amylose helices, avoiding thermal degradation of guest compounds. This method would also avoid the wasting of guest materials because uncomplexed guest can be reused. It was found in the study that intermediate ethanol and acetone concentrations (generally 40-60%, v/v) at room temperature were appropriate for the complexation between V-amylose and AscP. Annealing, i.e. heat treatment in ethanol solutions at elevated temperatures (45-70°C), was able to significantly increase the crystallinity of V-amylose and V-starch to as high as 65% and facilitate greater complexation evidenced from higher enthalpies, probably due to more regularly arranged helical cavities in larger crystalline phase. The complexation between V-amylose and AscP was also found to be enhanced with AscP concentration, while the dissociation temperature experienced a slight decrease.

Lingyan Kong

Department of Food Science

Pennsylvania State University

Molecular Entanglement and Electrospinnability of Biopolymers