In-Situ Quantitative and Multiscale Structural Study of Starch-Based Biomaterials Immersed in Water

A novel method for quantifying the short-range order in non-crystalline starch by Raman spectroscopy

A quantitative method was developed to characterize the short-range order in non-crystalline starch by Raman spectroscopy. The Raman spectra of three forms of non-crystalline starches (just-gelatinized starch, which was heated to the point of having just lost its long-range order but still retaining essentially all of its short-range order, gelatinized starch and amorphous starch) were resolved into subspectra to calculate the short-range ordered phases. By deducting the spectra of amorphous starch using a subtraction technique, the areas of subspectra for short-range ordered phases in just-gelatinized and gelatinized starches were obtained. The ratio of the area for short-range ordered phases in gelatinized starch relative to that in just-gelatinized starch was negatively correlated with water content for gelatinization. Based on this, we propose that this ratio of areas provides a quantitative measure for assessing the short-range order in non-crystalline starch. This study provides an alternative and simpler method to an X-ray diffraction protocol proposed previously.

Monitoring of water sorption and swelling of potato starch-glycerol extruded blend by magnetic resonance imaging and multivariate curve resolution

Magnetic resonance microimaging (MRμI) is an outstanding technique for studying water transfers in millimetric bio-based materials in a non-destructive and non-invasive manner. However, depending on the composition of the material, monitoring and quantification of these transfers can be very complex, and hence reliable image processing and analysis tools are necessary. In this study, a combination of MRμI and multivariate curve resolution-alternating least squares (MCR-ALS) is proposed to monitor the water ingress into a potato starch extruded blend containing 20% glycerol that was shown to have interesting properties for biomedical, textile, and food applications. In this work, the main purpose of MCR is to provide spectral signatures and distribution maps of the components involved in the water uptake process that occurs over time with various kinetics. This approach allowed the description of the system evolution at a global (image) and a local (pixel) level, hence, permitted the resolution of two waterfronts, at two different times into the blend that could not be resolved by any other mathematical processing method usually used in magnetic resonance imaging (MRI). The results were supplemented by scanning electron microscopy (SEM) observations in order to interpret these two waterfronts in a biological and physico-chemical point of view.

Reverse Engineering of Perseris and Development of Compositionally Equivalent Formulations

Six injectable, long-acting in situ forming implant drug products based on poly(lactide-co-glycolide) (PLGA) and N-Methyl-2-Pyrrolidone (NMP) are available on the market. However, generic products, which would likely be more affordable for patients, are not yet available. This is partially due to the unique complexity of these formulations as well as the inherent heterogeneity of PLGA and the challenges in the manufacture and characterization of this polymer. This article focuses on a comprehensive characterization of Perseris (risperidone) in situ forming implant drug product, and the development of compositionally equivalent formulations. The molecular weight (MW), lactide/glycolide (L/G) ratio, end group, blockiness and glass transition temperature (T_g) of PLGA, as well as the crystal form and particle size of risperidone powder used in Perseris were identified through reverse engineering. The dissolved/suspended drug ratio in the final implant suspension for administration, as well as the real-time drug solid state in the solidified Perseris drug depot were investigated. Two compositionally equivalent formulations prepared using customized PLGA polymers with similar properties to the Perseris PLGA showed similar in vitro release and swelling behavior to Perseris as demonstrated using a novel adapter-based dissolution method. The novelty of this dissolution method lies in its ability to control implant shape, generate reproducible data, distinguish different release phases, as well as identify formulation changes. The knowledge gained in this work and the methodology established for characterization of the implant formulations are important for implant formulation development.

Novel Approach for Quantitative Characterization of Short-Range Molecular Order in Gelatinized Starch by X-ray Diffraction

A novel quantitative method was developed to characterize short-range molecular order in gelatinized wheat and potato starches using X-ray diffraction (XRD). Gelatinized starches with different amounts of short-range molecular order and amorphous starches with no short-range molecular order were prepared and characterized by the intensity and area of Raman spectral bands. The degree of short-range molecular order in the gelatinized wheat and potato starches decreased with increasing water content used for gelatinization. By comparing XRD patterns of gelatinized and amorphous starch, the XRD peak at 33° (2θ) was shown to be typical of gelatinized starch. The relative peak area (RPA), intensity, and full width at half-maximum (FWHM) of the XRD peak at 33° (2θ) decreased with the increase in water content for gelatinization. We propose that the RPA of the XRD peak at 33° (2θ) can be used to quantify the amount of short-range molecular order in gelatinized starch. The method developed in this study will help to explore and understand the relationship between the structure and functionality of gelatinized starch in food and nonfood applications.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Dual-process of starch modification: Combining ozone and dry heating treatments to modify cassava starch structure and functionality

This work evaluated for the first time the effect of dual modification of cassava starch by using ozone (O₃) and dry heating treatment (DHT). The dual modification was capable to promote fissures on the surface of the starch granule (DHT + O₃), affected the starch amorphous domains, presented greater degree of starch oxidation (DHT + O₃) and different profiles of starch molecular size distribution. These modifications resulted in starches with different properties. Moreover, the sequence of treatments was decisive for the hydrogel properties: while DHT + O₃ resulted in formation of stronger gels, O₃ + DHT resulted in weaker gels. In conclusion, this proposed dual modification was capable to produce specific modified starch when compared with the isolated treatments, also expanding the potential of cassava starch applications.

Multi-scale characterization of thermoplastic starch structure using Second Harmonic Generation imaging and NMR

Starch granules can be extruded to obtain a thermoplastic material. Thermoplastic starch (TPS) usually requires a significant break down of the starch granular organization to form a continuous polysaccharide matrix. In this work, we extrude potato starch with and without a plasticizer and store samples at high humidity to generate recrystallization. A multi-scale investigation of the microstructure is performed by combining different techniques: WAXS and solid-state NMR to describe macromolecule organization and Second Harmonic Generation (SHG) imaging to provide spatial information. Finally, the ability of the material to swell and remain sound in water is assessed. Glycerol-plasticized samples swell the least despite many granules with native-like structure embedded in the starch matrix. Glycerol limits the fragmentation and melting of the granules and crystallites during extrusion but also reduces the proportion of starch molecules in constrained conformations, enabling the formation of a polymer network that can sustain the penetration of water.