Molar Degree Of Substitution Research Articles

Determination of the degree of molar substitution of hydroxypropyl cellulose by gas chromatography

Abstract We have improved the gas chromatography (GC) method with the aid of 1H NMR to determine the degree of molar substitution (MS) of hydroxypropyl cellulose (HPC). This improvement relied on our established dissolution approach for low-substituted HPC, facilitating NMR determination and subsequently expanding the working range of the MS determination from the lower limit of USP specified as 53.4% to 9.3% (MS 0.2). In this method, 2-iodopropane was produced by the reaction of hydroiodic acid with HPC at high-temperature and then measured by GC. 1H NMR was used for the correction of GC method. The MS results via the GC method (MSGC) exhibited a linear correlation with those obtained by the 1H NMR method (MSNMR), with correction equation of MSNMR=1.8026MSGC - 0.2046 (R2 = 0.9979). Method validation results showed that the average recovery and relative standard deviation (RSD) of MS are 103.5% and 0.83%, respectively. Detection limit and quantitation limit were 0.08 and 0.26, respectively. This method is accurate, sensitive with good precision, which is of great value for the production, research and development, and application of HPC, particularly the low-substituted HPC.

FTIR determination of the degree of molar substitution for hydroxypropyl chitosan

We developed and validated a novel Fourier transform infrared (FTIR) method to determine the degree of molar substitution (MS) for hydroxypropyl chitosan (HPCS) using nuclear magnetic resonance (1H NMR) as a reference, and investigated the factors influencing the MS assay. Through extensive screening of integration methods for candidate bands in the FTIR spectrum of HPCS using 20 HPCS samples with degrees of acetylation (DA) ranging from 0.003 to 0.139, we found that when using band area at 2970 cm−1 as a probe integral, the MS values obtained via the 1H NMR method exhibited linear correlations (R2 > 0.98) with at least 16 integral ratios derived from their FTIR spectra. The optimal reference bands with high reliability are located at 3440 cm−1 and 1415 cm−1, with R2 exceeding 0.99 and a MS range of 0.17–1.92. The band at 2875 cm−1 is less affected by the trace moisture present in HPCS samples than the others. The results of the method validation demonstrated a mean recovery of 98.9 ± 2.8 % and an RSD below 10 %, suggesting a simple, robust, and highly accurate and precise method. This method could be extendable for the determination of the MS of insoluble HPCS derivatives and other hydroxypropylated polysaccharides.

High-substituted hydroxypropyl cellulose prepared by homogeneous method and its clouding and self-assembly behaviors

Hydroxypropyl cellulose (HPC) is a sustainable cellulose derivative valued for its excellent biocompatibility and solubility and is widely used in various fields. Recent scientific research on high-substituted HPC mainly focused on its efficient preparation and phase transition behavior. Herein, a novel strategy of high-substituted HPC synthesis was demonstrated by employing DMSO/TBAF·3H2O as a cellulose solvent, exhibiting more efficiency than traditional approaches. High-substituted HPC prepared has remarkable thermal stability, exceptional hydrophilicity, and satisfactory solubility. Phase transition behavior of HPC with varying molar degrees of substitution (MS) was delved and a notable negative correlation between MS and cloud point temperature (TCP), was revealed, particularly evident at an MS of 12.3, where the TCP drops to 33 °C. Moreover, a unique self-assembly behavior featuring structural color and responsiveness to force in a solvent-free environment emerged when the MS exceeded 10.4. These insights comprehensively strengthen the understanding and knowledge of high-substituted HPC, simultaneously paving the way for further HPC investigation and exploitation.

Characterizations and film-forming properties of different fractionated high-amylose maize starches subjected to hydroxypropylation

Dual-modifications of jet milling and hydroxypropylation were used to improve the functional properties of maize starch (HM, containing 67 % amylose). The fractions obtained in three sizes (HM-S, HM-M, HM-L) were further treated with 10 % and 30 % propylene oxide (PO10 and PO30). The infrared peak of starch at 2794 cm−1 indicated the successful introduction of hydroxypropyl groups. The molar degree of substitution (MS) increased with the degree of jet milling. The MS of HM-L-PO10 is 0.4, that of HM-M-PO10 is 0.7, and that of HM-S-PO10 is 0.9. The crystallinity of dual-modified HM increased, but the crystal type remained unchanged, still being B-type. Dual-modification significantly improved the performance of starch, and the higher the degree of modification, the better the optimization effect. The lowest enthalpy changes of gelatinization (ΔH = 3.49 J/g), the best freeze–thaw stability, the highest elongation at break (110.42 %) and transmittance (81.22 %) were shown in HM-S-PO30. The present study confirms that HM-S-PO30 films have the best physicochemical and mechanical properties, which provide new insights into optimizing starch-based packaging materials.

NMR spectroscopy study of the structure of hypromellose phthalate, a component of enteric coatings of medicinal products

Scientific relevance. Hypromellose phthalate is a component of enteric coatings used to modify active substance release from oral medicinal products in the small intestine. The release rate directly depends on the non-stoichiometric composition of the polymer, first of all, on the proportion of phthalate groups in the macromolecule. It is therefore necessary to develop reliable analytical procedures for determining the structure of hypromellose phthalate to evaluate the dissolution rate of medicinal products containing the polymer.Aim. The study aimed to develop an analytical procedure for quantifying the proportion of phthalate groups in hypromellose phthalate samples using NMR spectroscopy and to determine the relationship between the polymer dissolution rate in aqueous buffer solutions and its structural features (degree of molar substitution and molecular mass).Materials and methods. The study examined hypromellose phthalate samples isolated from enteric coatings of proton-pump inhibitors and used the reference standard for hypromellose phthalate. The non-stoichiometric composition of the polymer was determined by 13C NMR spectroscopy.Results. The authors established the conditions required to separate hypromellose phthalate from the other coating components and identified the characteristic 13C NMR signals that may be used to differentiate between the structural fragments of hypromellose phthalate. The study demonstrated the relationship between the dissolution rate and the structure of the polymer. Commercial grades of hypromellose phthalate were shown to differ in composition and, as a result, in their dissolution kinetics (in particular, the threshold pH for the onset of dissolution (5.0–5.5), as well as the dissolution rates at the same pH).Conclusions. The authors developed NMR-based procedures to determine the proportion of phthalate groups on the basis of their mass fraction in a weighted hypromellose phthalate sample and the degree of molar substitution of the polymer. The results support the applicability of these analytical procedures to the characterisation of sample composition in polymer dissolution rate studies. In principle, it is possible to derive a multiple linear regression equation that describes the dissolution rate of hypromellose phthalate as a function of the molecular mass and the molar substitution with phthalate groups. Further investigation of a larger number of polymer samples with different compositions is needed to improve the regression model and demonstrate its statistical significance. In addition to the proportion of phthalate groups, the pharmacopoeial analysis of hypromellose phthalate should also control the molecular mass of the polymer.

A Photopolymerizable Biocompatible Hyaluronic Acid Hydrogel Promotes Early Articular Cartilage Repair in a Minipig Model In Vivo.

Articular cartilage defects represent an unsolved clinical challenge. Photopolymerizable hydrogels are attractive candidates supporting repair. This study investigates the short-term safety and efficacy of two novel hyaluronic acid (HA)-triethylene glycol (TEG)-coumarin hydrogels photocrosslinked in situ in a clinically relevant large animal model. It is hypothesized that HA-hydrogel-augmented microfracture (MFX) is superior to MFX in enhancing early cartilage repair, and that the molar degree of substitution and concentration of HA affects repair. Chondral full-thickness defects in the knees of adult minipigs are treated with either 1) debridement (No MFX), 2) debridement and MFX, 3) debridement, MFX, and HA hydrogel (30% molar derivatization, 30mg mL-1 HA; F3) (MFX+F3), and 4) debridement, MFX, and HA hydrogel (40% molar derivatization, 20mg mL-1 HA; F4) (MFX+F4). After 8 weeks postoperatively, MFX+F3 significantly improves total macroscopic and histological scores compared with all other groups without negative effects, besides significantly enhancing the individual repair parameters "defect architecture," "repair tissue surface" (compared with No MFX, MFX), and "subchondral bone" (compared with MFX). These data indicate that photopolymerizable HA hydrogels enable a favorable metastable microenvironment promoting early chondrogenesis in vivo. This work also uncovers a mechanism for effective HA-augmented cartilage repair by combining lower molar derivatization with higher concentrations.

Dextran Methacrylate Reactions with Hydroxyl Radicals and Hydrated Electrons in Water: A Kinetic Study Using Pulse Radiolysis.

Dextran methacrylate (Dex-MA) is a biodegradable polysaccharide derivative that can be cross-linked by ionizing radiation. It is therefore considered a potential replacement for synthetic hydrophilic polymers in current radiation technologies used for synthesizing hydrophilic cross-linked polymer structures such as hydrogels, mainly for medical applications. This work is focused on the initial steps of radiation-induced cross-linking polymerization of Dex-MA in water. Rate constants of two major transient water radiolysis products-hydroxyl radicals (•OH) and hydrated electrons (eaq-)-with various samples of Dex-MA (based on 6-500 kDa dextrans of molar degree of substitution or DS with methacrylate groups up to 0.66) as well as non-substituted dextran were determined by pulse radiolysis with spectrophotometric detection. It has been demonstrated that these rate constants depend on both the molecular weight and DS; reasons for these effects are discussed and reaction mechanisms are proposed. Selected spectral data of the transient species formed by •OH- and eaq--induced reactions are used to support the discussion. The kinetic data obtained in this work and their interpretation are expected to be useful for controlled synthesis of polysaccharide-based hydrogels and nanogels of predefined structure and properties.

Bacterial Cellulose Nanofibers Modified with Quaternary Ammonium Salts for Antimicrobial Applications

Nanofibrillated bacterial cellulose (NFBC) is a recyclable, biodegradable, and nontoxic biopolymer whose fibers are much longer than other cellulose nanofibers prepared from wood pulp. NFBC is a promising material for use as an additive in food and pharmaceutical industries and as a nanofiller in fiber-reinforced nanocomposite resins; however, it is easily microbially degraded and, consequently, cannot be used in long-term applications. In this study, NFBC was endowed with antimicrobial properties through modification by an aqueous alkaline solution of 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). The structure of the modified NFBC was analyzed in detail using solid-state NMR and infrared spectroscopy, as well as X-ray diffractometry, which revealed that only the surface layer of each fiber had been conjugated with quaternary ammonium EPTMAC groups, with the amount of EPTMAC added during preparation determining the degree of molar substitution (MS) of the cationic groups. In addition, increasing the MS of the modified NFBC resulted in a positive surface charge that led to an increase in the transparency of the nanofiber dispersion owing to electrostatic repulsion between nanofibers. Despite these differences, the fiber morphologies and crystal structures of the modified fibers were almost identical to those of pristine NFBC, suggesting that EPTMAC selectively reacts with the surface hydroxyl groups of NFBC. In addition, bacterial cell culture experiments revealed that the modified nanofibers are antimicrobial against Klebsiella pneumoniae, a Gram-negative bacterium, most likely because the surface of the modified NFBC is positively charged. Therefore, the quaternary-ammonium-salt-modified NFBC is a functional nanofiber endowed with both nanofiber features and antimicrobial properties and can possibly be used in fiber-reinforced nanofillers and as a flocculant for water-based paints and polar resins.

Composition mapping of highly substituted cellulose-ether monomers by liquid chromatography–mass spectrometry and probability-based data deconvolution

Cellulose ethers (CEs) are semi-synthetic polymers produced by derivatization of natural cellulose, yielding highly substituted products such as ethyl hydroxyethyl cellulose (EHEC) or methyl ethyl hydroxyethyl cellulose (MEHEC). CEs are commonly applied as pharmaceutical excipients and thickening agents in paints and drymix mortars. CE properties, such as high viscosity in solution, solubility, and bio-stability are of high interest to achieve required product qualities, which may be strongly affected by the substitution pattern obtained after derivatization. The average and molar degree of substitution often cannot explain functional differences observed among CE batches, and more in-depth analysis is needed. In this work, a new method was developed for the comprehensive mapping of the substitution degree and composition of β-glucose monomers of CE samples. To this end, CEs were acid-hydrolyzed and then analyzed by gradient reversed-phase liquid chromatography-mass spectrometry (LC-MS) using an acid-stable LC column and time-of-flight (TOF) mass spectrometer. LC-MS provided monomer resolution based on ethylene oxide, hydroxyl, and terminating methyl/ethyl content, allowing the assignment of detailed compositional distributions. An essential further distinction of constitutional isomer distributions was achieved using an in-house developed probability-based deconvolution algorithm. Aided by differential heat maps for visualization and straightforward interpretation of the measured LC-MS data, compositional variation between bio-stable and non-bio-stable CEs could be identified using this new approach. Moreover, it disclosed unexpected methylations in EHEC samples. Overall, the obtained molecular information on relevant CE samples demonstrated the method's potential for the study of CE structure-property relationships.

The effects of dual modification on functional, microstructural, and thermal properties of tapioca starch.

The aim of this study was to investigate the effects of dual modification on the functional, microstructural, and thermal properties of tapioca starch. Tapioca starch was first hydrolyzed by 0.14 M HCl for 0, 6, 12, 18, and 24 hr and then hydroxypropylated by adding 0%, 10%, 20%, and 30% (v/w) propylene oxide. The degree of hydroxypropylation, solubility, water absorption, rheological, thermal, and microstructure characterization of dually modified tapioca starch was determined. Hydroxypropylation did not cause any considerable changes in the starch granular size and shape of tapioca starch. Acid hydrolysis disrupts the starch granules, and the starches with smaller sizes were produced. The degree of molar substitution (DS) of dual modified starches ranged from 0.118 to 0.270. The dual modified starches significantly had higher solubility than native starch (p < .05). Hydrolysis of starches with acid decreases swelling power while hydroxypropylation increases the swelling power. The results also showed lower gelatinization (To, Tp, Tc, and ΔH) and pasting parameters (the peak and final viscosity, peak time, and pasting temperature) for the dual modified starches than other treatments. In summary, this study showed that dually modified tapioca starch has potential application in dip molding and coating.

Simultaneous determination of molar degree of substitution and its distribution fraction, degree of acetylation in hydroxypropyl chitosan by 1H NMR spectroscopy

Under the assistance of 13C NMR and 1H-13C HSQC, we develop a novel 1H NMR assay for the substitution sites and degrees in hydroxypropyl chitosan (HPCS) by optimizing sample preparation and measurement method. We find that the chemical shift of HOD peak increases linearly with the increase of DCl concentration but declines with the rise of measurement temperature. According to the regression line, the HOD peak could be moved to a desired position of non-interference with other peaks by changing DCl concentration. Other DCl-responsive peaks are found and elucidated. Accordingly, the substitution fraction (NH2-substitution and OH-substitution) and the degree of acetylation are well discriminated and determined. The total molar degree of substitution (MS) obtained is basically consistent with those of elemental analysis and the existing NMR methods. This structural analysis is extendable to other amino-containing saccharides. The 1H NMR method could be used widely in acid-soluble polysaccharides and their derivatives.

Nanofibrillated Bacterial Cellulose Modified with (3-Aminopropyl)trimethoxysilane under Aqueous Conditions: Applications to Poly(methyl methacrylate) Fiber-Reinforced Nanocomposites.

The development of eco-friendly fiber-reinforced composite resins is an important objective from an environmental perspective, and nanofibrillated bacterial cellulose (NFBC), with extremely long high-aspect-ratio fibers, is a filler material with high potential for use in such composite resins. In this study, we investigated chemical modification of the surfaces of NFBC fibers by coupling with (3-aminopropyl)trimethoxysilane and fabricated nanocomposite materials using the prepared surface-modified NFBC. The product prepared by the one-pot reaction of (3-aminopropyl)trimethoxysilane with NFBC microfibrils dispersed in aqueous acid retained the same nanofibril structure as the intact NFBC. The degree of molar substitution and the silicon states on the surface of the product depended on the NFBC/(3-aminopropyl)trimethoxysilane ratio. The thermal analysis revealed that the thermal degradation temperature of the products increases with an increase of degree of molar substitution. Highly transparent (78–89% at 600 nm) poly(methyl methacrylate)-based nanocomposites were prepared by solvent casting; the nanocomposite containing 1.0 wt % (3-aminopropyl)trimethoxysilylated NFBC was only 8% less transparent than neat poly(methyl methacrylate) at 600 nm. In addition, the tensile strength of the nanocomposite was more than twice that of neat poly(methyl methacrylate) when 1 wt % of the surface-modified NFBC was added. The surface-modified NFBC is expected to be a reinforcing nanofiber material that imparts excellent physical properties to fiber-reinforced resins.

Synthesis and Characterization of Hydroxyethyl Starch from Chips Wastes Under Microwave Irradiation

This article focuses on the synthesis of hydroxyethyl potato starch (HEPS) for liquid hand soap by evaluating waste potato starch (WPS), a byproduct in potato chips production. It is a cheap, biodegradable, non-toxic and renewable natural polymer, available in great quantities on a global level. In a factory producing potato chips, WPS, which remained in the aqueous medium during peeling, slicing, and washing the potatoes, was purified at the desired temperature with H2O2 and NaOH. HEPSs with the molar substitution (MS) in the range from 0.298 to 0.670, were synthesized under microwave irradiation in isopropanol (IPA) and NaOH solution by adding ethylene oxide (EO) to WPS. The selected reaction parameters were the concentration of NaOH, the proportion of EO, and reaction time in an attempt to understand their effects on the reaction. Considering all the studied conditions, the highest viscosity was reached at 250 cP for the highest MS in the sample of HEPS-4 when 15 g EO was used in 20 mL solution of 40% NaOH at 40 °C for 40 min under microwave irradiation. The structure of synthesized HEPSs has been characterized by FT-IR, XRD, 1H(13C)-NMR spectroscopic methods, and the degree of molar substitution was calculated from 1H-NMR spectra. In addition, thermal stability and surface morphology of characterized HEPSs were studied by DTG-TG and SEM, respectively. The thickener effect of hydroxyethyl starch in liquid hand soap was investigated. In this way, it has been understood that in the production of liquid hand soaps, hydroxyethyl potato starch can be used instead of coco diethanolamide (CDEA).

Characteristics of wheat starch-pectin hydrolysate complexes by dry heat treatment.

The objective of this study was to characterize dry heat-induced wheat starch-pectin hydrolysate (WST/PH) complexes to develop the retrogradation-retarded starch. Native (N-) and protease-treated (P-) WST were used as starch sources. Pectin hydrolysates were mixed independently with N-WST and P-WST to a mixing ratio of 49:1 (based on total solid contents), followed by drying below 10% moisture and dry heat treatment at 130°C for 4h. The molar degrees of substitution (MS) was higher for WST/PH complexes than its mixtures, and apparent amylose contents decreased with their MS. Relative to WST/PH mixtures, solubilities were higher for WST/PH complexes, while swelling powers didn't differ. WST/PH complexes showed the lower degree of retrogradation, setback viscosities, slowly gelling tendency, and syneresis. These phenomena were more pronounced in WST/PH mixtures and complexes prepared with P-WST. Overall results suggest that dry heat-induced WST/PH complexes could be a potential retrogradation-retarded starch to replace chemically-modified starches.

Impact of static and dynamic modes of semi-dry heat reaction on the characteristics of starch citrates

The objective of this study was to demonstrate the validity of dynamic semi-dry heat reaction (SDHR) by investigating the effects of static and dynamic SDHR on the characteristics of starch citrates. The starch (normal and waxy corn)-citric acid (CA) mixture was heated in a convection oven (static mode) or a twin-screw extruder without a die (dynamic mode). The ester bonds of starch citrates were confirmed by FT-IR, and their molar degree of substitution did not differ between the reaction modes for the tested starch genotypes. Starch citrates by dynamic SDHR exhibited higher relative crystallinity, resistant starch content, solubility, swelling power, and gelatinization compared to those by static SDHR. Although static SDHR did not show a viscosity development during pasting, dynamic SDHR increased their pasting viscosities. Overall, these results suggest that dynamic SDHR could improve the defects (i.e., lack of solubility, swelling, and pasting attributes) of the traditional starch citrates.

Bacterial Nanocellulose and Its Surface Modification by Glycidyl Methacrylate and Ethylene Glycol Dimethacrylate. Incorporation of Vancomycin and Ciprofloxacin.

Among nanocelluloses, bacterial nanocellulose (BNC) has proven to be a promising candidate in a range of biomedical applications, from topical wound dressings to tissue-engineering scaffolds. Chemical modifications and incorporation of bioactive molecules have been obtained, further increasing the potential of BNC. This study describes the incorporation of vancomycin and ciprofloxacin in BNC and in modified BNC to afford bioactive BNCs suitable for topical wound dressings and tissue-engineering scaffolds. BNC was modified by grafting glycidylmethacrylate (GMA) and further cross-linking with ethylene glycol dimethacrylate (EGDMA) with the formation of stable C–C bonds through a radical Fenton-type process that involves generation of cellulose carbon centred radicals scavenged by methacrylate structures. The average molar substitution degree MS (MS = methacrylate residue per glucose unit, measured by Fourier transform infrared (FT–IR) analysis) can be modulated in a large range from 0.1 up to 3. BNC-GMA, BNC-EGDMA and BNC-GMA-EGDMA maintain the hydrogel status until MS reaches the value of 1. The mechanical stress resistance increase of BNC-GMA and BNC-GMA-EGDMA of MS around 0.8 with respect to BNC suggests that they can be preferred to BNC for tissue-engineering scaffolds in cases where the resistance plays a crucial role. BNC, BNC-GMA, BNC-EGDMA and BNC-GMA-EGDMA were loaded with vancomycin (VC) and ciprofloxacin (CP) and submitted to release experiments. BNC-GMA-EGDMA of high substitution degree (0.7–1) hold up to 50 percentage of the loaded vancomycin and ciprofloxacin amount, suggesting that they can be further investigated for long-term antimicrobial activity. Furthermore, they were not colonized by Staphylococcus aureus (S.A.) and Klebsiella pneumonia (K.P.). Grafting and cross-linking BNC modification emerges from our results as a good choice to improve the BNC potential in biomedical applications like topical wound dressings and tissue-engineering scaffolds.

Probing of the oxygen-related defects response in Nd:phosphate glass within self-action of the laser radiation technique

Mixed barium‑strontium Nd:phosphate glasses of composition: 58P2O5–13K2O–8Al2O3–4B2O3–2.5La2O3–2SiO2–0.5Nd2O3–12(Ba1–xO/SrxO) with a different degree of molar substitution x were prepared. Optical properties of these glasses were examined by UV–Vis-IR and photoluminescence (PL) spectroscopies. Considering IR spectra, it was suggested a certain contribution of oxygen defects in the optical properties of glasses. UV–Vis absorbance and PL emission spectra owing to the internal f–f electron transitions of Nd3+ ions were shown a complex character of electronic processes. The result of a comprehensive analysis of the optical scattering indicatrices has revealed non-monotonic variations of the scattering efficiency against the ratio of Sr to Ba that is correlated with the suggested content of the oxygen defects in the mixed glasses. A cubic nonlinear optical (NLO) response under the pulsed laser radiation self-action at 1064 nm shows that the self-defocusing effect increases with the molar fraction of Ba. For a continuous wave laser excitation at 1064 nm, the most efficient NLO refractive response with Re(χ(3)) = 2.9 × 10−3 esu was obtained in the pure strontium Nd:phosphate glass, being classified as a promising for NLO applications.

Alginate-Based Hydrogel Containing Minoxidil/Hydroxypropyl-β-Cyclodextrin Inclusion Complex for Topical Alopecia Treatment

Cutaneous minoxidil (MXD) formulations were developed with the intent to reduce the side effects of the cosolvents propylene glycol and ethanol, frequently used in commercial MXD solutions. Completely aqueous alginate-based hydrogels were investigated and MXD aqueous solubility was improved using inclusion complexes with hydroxypropyl-β-cyclodextrin (HP-β-CD) at 2 different molar substitution degree (MS), namely 0.65 and 0.85. HP-β-CD MS 0.65 was selected for its improved solubilizing ability toward MXD. At concentration of 39% w/v, this cyclodextrin increased the intrinsic aqueous solubility of MXD of about 22-fold. The calculated complexation constant was 2309 ± 20 M−1, and the inclusion process was spontaneous and enthalpically driven. Nuclear magnetic resonance studies (Job plot, 1H, 2D correlations spectroscopy, nuclear overhauser effect spectroscopy, and rotating-frame overhauser enhancement spectroscopy) confirmed the stoichiometry 1:1 between MXD and HP-β-CD providing information about the exact geometry of the inclusion complex. Rheological and in vitro release studies performed on the formulation loaded with MXD 3.5% w/w proved that the inclusion complex increased the viscosity of the hydrogel modulating the release of the free drug. Furthermore, the hydrogel formulation facilitate MXD to permeate into the skin and did not damage epidermis, suggesting that these completely aqueous MXD delivery systems can be proposed as alternative formulations to commercial solutions.

Octenylsuccinate hydroxypropyl phytoglycogen, a dendrimer-like biopolymer, solubilizes poorly water-soluble active pharmaceutical ingredients

Effective solubilizers for poorly water-soluble active pharmaceutical ingredients (APIs) are highly desirable. This study introduced an amphiphilic dendrimer-like biopolymer, octenylsuccinate hydroxypropyl phytoglycogen (OHPP) as a new solubilizer. The molar substitution degree of octenylsuccinate and hydroxypropyl groups of OHPP was 0.51 and 1.69, respectively. The weight-average molecular weight, Z-average root mean square radius, and Zeta-potential of OHPP were 1.507×107g/mol, 22.6nm, and −23.6mV, respectively. OHPP was highly soluble in polar organic solvents and aqueous buffers with pH≥5.0. To evaluate its solubilization capability, each of five APIs (celecoxib, docetaxel, fenofibrate, griseofulvin, and resveratrol) was incorporated with OHPP to form solid dispersions (API-OHPP SD). API-OHPP SD reduced API crystallinity and increased API solubility by up to 1755 times. Over the 3h dissolution, the cumulative dissolved API with API-OHPP SD was in the range of 6.8∼84.9%. Evidently, OHPP was a potent and non-specific polymeric solubilizer of poorly water-soluble APIs.

Effects of Molar Substitution on the Mobility of Hydroxyethylstarch Macromolecules in Solution

The effects of molar substitution of hydroxyethylstarch on the macromolecule mobility in solution were studied by diffusion-ordered NMR spectroscopy (1H-DOSY) to measure mean self-diffusion coefficients of hydroxyethylstarch with different levels of modification of amylopectin. Molar substitution of hydroxyethylstarch had the opposite effect on macromolecule mobility from that of branching of the polymer chain. Standard samples and medicinal hydroxyethylstarch substances were shown to be nonuniform in terms of the degree of molar substitution. Inclusion of an additional parameter – molar substitution – into regression equations was found to increase the accuracy of measurement of the molecular weight of hydroxyethylstarches using analytical chemistry transport methods.