How to calculate starch lamellar features with improved accuracy by small angle X-ray scattering

In-situ sequential crystallization of fenofibrate and tristearin - Understanding the distribution of API in particles and stability of solid lipid microparticles from the perspective of crystallization

In-situ API crystallization in carrier matrices has attracted extensive attention in recent years for its advantages over traditional preparation processes. However, due to the lack of systemic research on molecular self-assembly behaviors, the products obtained by in-situ crystallization suffer from the problems of polymorphic transformation and drug expulsion during storage, limiting its industrial application. This paper investigates the in-situ sequential crystallization behavior of tristearin (SSS) and fenofibrate (FEN), utilizing SSS as the carrier and FEN as the API. It was found that the behavior of mixed crystallization significantly differs from single-component crystallization, including direct formation of stable form of SSS and the rapid crystallization of FEN. During the crystallization process, the melting FEN promotes the movement of SSS molecules, while the sliding of SSS lamellae, in turn, provides a mechanical stimulus to enhance the nucleation of FEN. Based on the observed synergistic crystallization behavior, the distribution and stability of the API within FEN solid lipid microparticles (SLMs) during storage were evaluated, while also examining the stability variations in SLMs formulated at different cooling rates and drug loading concentrations. The findings indicate that the initial nucleated FEN results in a decrease in the surrounding molten FEN and the irregularity of the SSS lamellas, thereby preventing the remaining molten FEN from achieving complete crystallization within a brief period. Due to the compatibility between FEN and SSS, some SSS may blend with the molten FEN, potentially resulting in further crystallization during storage and consequently increasing the risk of drug expulsion.

The multi-scale structures and in vitro digestibility of starches with different crystalline types induced by dielectric barrier discharge plasma

The effects of plasma treatment on multi-scale structures and in vitro digestibility of starches isolated from Tartary buckwheat (TBS), potato (PTS), and pea (PS), were investigated. The results from SEM and CLSM showed that plasma treatment resulted in the extension of pores from the starch hilum to the surface. The XRD and 13C CP/MAS NMR spectra demonstrated that the crystalline type of three starches was not changed by plasma treatment, while the RC and double helix content of TBS increased. Besides, the single helix content and the proportion of amorphous phase decreased following the treatment, which was consistent with the result of SAXS. However, the PTS and PS showed the opposite results by plasma treatment. In addition, the modification significantly changed the molecular weight (Mw) and chain length distribution of all the starches, among which the Mw of PTS fell drastically from 2.45 × 107 g/mol to 1.74 × 107 g/mol. The in vitro digestibility of starches increased significantly when treated with plasma, in which TBS exhibited the biggest increase for its inside-out and side-by-side digestion manners. Therefore, plasma treatment led to different alteration trends for multi-scale structures with quite various change extent for in vitro digestibility about different crystalline starches.

Comb Polybutadiene with Long Polystyrene Side Chains: A Solution for Tunable Flowability and Enhancing Dielectric Properties in High-Frequency Printed Board Adhesive Films

Liquid high-vinyl polybutadiene (PB) possessed excellent dielectric properties, rendering them suitable candidates for adhesive films of high-frequency printed boards. However, their inherent low molecular weights resulted in chain slippage and overflow during processing, thereby diminishing the performance of the adhesive films. To address this challenge, we synthesized comb PB with long polystyrene side chains via reversible addition-fragmentation chain transfer (RAFT) polymerization, effectively immobilizing the PB backbone and restricting relative chain slippage. Controlling the length and number of "comb teeth" (styrene side chains) efficiently regulated the flowability of comb PB, achieving distinct flow states. Simultaneously, molecular dynamics simulations revealed that the elongated and inflexible polystyrene side chains of comb PB could create minuscule cavities, which impeded close packing of molecules and led to low dielectric constants (2.39/2.01, 1 MHz/10 GHz) and ultralow dielectric losses (0.0071/0.0016, 1 MHz/10 GHz). Furthermore, a series of printed circuit boards were fabricated using a comb PB adhesive film, and the signal loss was significantly reduced to 48.8% (19 GHz) in comparison with a commercial epoxy adhesive. This study demonstrated the potential of comb PB with polystyrene side chains to achieve desirable flow and dielectric properties by introducing tangles, large volume potential resistance, and microporosity compared with block structures.

The alterations in granule, shell, blocklets, and molecular structure of pea starch induced by ultrasound

Understanding the alterations to starch multi-scale structure induced by ultrasound treatment can help in determining the effective application of ultrasound in functional-starch preparation. This study aimed to comprehensively characterize and understand the morphological, shell, lamellae, and molecular structures of pea starch granules treated by ultrasound under different temperatures. Scanning electron microscopy and X-ray diffraction analyses showed that UT (ultrasound treatment) did not change C-type of crystalline, but caused a pitted surface and endowed a looser structure and higher enzyme susceptibility as the temperature increased above 35 °C for pea starch granules. Fourier transform infrared spectroscopy and small-angle X-ray scattering analyses revealed that UT reduced the short-range ordering and increased the thickness of semi-crystalline and amorphous lamellae by inducing starch chain depolymerization, which was manifested by molecule weight and chain length distribution analysis. The sample ultrasound-treated at 45 °C had the higher proportion of B2 chains compared with the other ultrasound-treated samples because the higher ultrasonic temperature altered the disruption sites of starch chains.

Microstructures of Starch Granules with Different Amylose Contents and Allomorphs as Revealed by Scattering Techniques

In this study, as-is (ca. 12% moisture by mass) and hydrated (50% water by mass) granules of waxy potato (WP), waxy wheat (WW), waxy maize, normal maize, and high-amylose maize (HAM) starches were investigated by using small-angle neutron and X-ray scattering (SANS and SAXS), wide-angle X-ray scattering, and ultra-small-angle neutron scattering. The SANS and SAXS data were fitted using the two-phase stacking model of alternating crystalline and amorphous layers. The partial crystalline lamellar structures inside the growth rings of granules were analyzed based on the inter-lamellar distances, thicknesses of the crystalline lamellae and amorphous layers, thickness polydispersities, and water content in each type of layer. Despite having a longer average chain length of amylopectin, the WP and HAM starches, which had B-type allomorph, had a shorter inter-lamellar distance than the other three starches with A-type allomorph. The WP starch had the most uniform crystalline lamellar thickness. After hydration, the amorphous layers were expanded, resulting in an increase of inter-layer distance. The low-angle intensity upturn in SANS and SAXS was attributed to scattering from interfaces/surfaces of larger structures, such as growth rings and macroscopic granule surfaces. Data analysis methods based on model fitting and 1D correlation function were compared. The study emphasized─owing to inherent packing disorder inside granules─that a comprehensive analysis of different parameters was essential in correlating the microstructures with starch properties.

The Effects of Starch Molecular Fine Structure on Thermal and Digestion Properties of Rice Starch

Whole white rice is a major staple food for human consumption, with its starch digestion rate and location in the gastrointestinal tract having a critical role for human health. Starch has a multi-scale structure, which undergoes order-disorder transitions during rice cooking, and this structure is a major determinant of its digestibility. The length distributions of amylose and amylopectin chains are important determinants of rice starch gelatinization properties. Starch chain-length and molecular-size distributions are important determinants of nucleation and crystal growth rates, as well as of intra- and intermolecular interactions during retrogradation. A number of first-order kinetics models have been developed to fit starch digestograms, producing new information on the structural basis for starch digestive characteristics of cooked whole rice. Different starch digestible fractions with distinct digestion patterns have been found for the digestion of rice starch in fully gelatinized and retrograded states, the digestion kinetics of which are largely determined by starch fine molecular structures. Current insights and future directions to better understand digestibility of starch in whole cooked rice are summarized, pointing to ways of developing whole rice into a healthier food by way of having slower starch digestibility.

Relations between rice starch fine molecular and lamellar/crystalline structures

Starch lamellar and crystalline structures are important controller of its physicochemical and digestion properties. Here, starch lamellar/crystalline structures of 16 different rice starches were investigated and correlated with their chain-length distributions (CLDs) and molecular size distributions. Results showed that the thickness of amorphous lamellae was mainly correlated with the amount of amylose short and medium chains. Thickness of both amorphous and crystalline lamellae was negatively correlated with the amount of amylopectin medium chains and relative length of amylopectin short chains. The degree of crystallinity was negatively correlated with the amount of amylose short and long chains. The lamellar ordering, fractal nature and thickness polydispersity were also related to the starch CLDs. Whereas, starch molecular size distributions were shown to be lack of correlations with the starch lamellar/crystalline structures. This study helps a better understanding of the molecular nature of starch semi-crystalline lamellae.