Development, validation, and uncertainty measurement of HPLC-DAD method for determination of some free amino acids in infant formula and medical food products for inborn errors of metabolism

This research aims at determining some free amino acids in amino acid-based infant formulas and amino acid-modified medical foods for inborn errors of metabolism to prove their quality. A method based on high-performance liquid chromatography and diode array detection was developed and validated. Then, overall uncertainty was estimated by the bottom-up approach. Applying the weighted least squares regression method suggested good linearity with coefficient of determinations ≥ 0.9960. The limits of detection were calculated between 0.01 and 0.28 μg/mL. The most repetitive recovery values were obtained in the range of 91-108%, with RSDs ≤ 15%. The expanded uncertainties were below 20% for most amino acids. The contributions of linear regression and repeatability are two main factors in estimating overall uncertainty. The results offer this method as a simple and easy procedure for analyzing free amino acids in seven powdered medical foods designed for phenylketonuria, maple syrup urine disease, methylmalonic, and propionic acidemia.

Catalytic and ionic cross-linking actions of l-glutamate salt for the modification of cellulose by 1,2,3,4-butanetetracarboxylic acid

The sodium l-glutamate is reported as an efficient catalyst for the cross-linking between 1,2,3,4-butanetetracarboxylic acid (BTCA) and cellulose. Results presented ester absorbance of the treated fabrics strongly increased in the presence of the homemade l-glutamate salt, a mixture of l-glutamic acid (LGA) and NaOH at a specific ratio. Importantly, anti-wrinkle properties of the treated fabrics were significantly improved. Based on the relative concentration calculation, l-glutamate promoted the reaction of BTCA with cellulose by accelerating the formation of BTCA anhydrides and the esterification of anhydrides with cellulose. Besides, the improved anti-wrinkle property was partially attributed to the fact that the generated LGA reacted with cellulose and formed ionic cross-linking networks through amino groups with carboxyl groups in BTCA, which was confirmed by the Fourier transform infrared spectra and the computational calculations. Through detailed comparisons, l-glutamate catalyzed fabrics showed as good durability as sodium hypophosphite, indicating a possible alternative for phosphorus-containing catalysts.

Multi-armed poly(L-glutamic acid)-graft-polypropyleneinime as effective and serum resistant gene delivery vectors

A new series of multi-armed MP-g-PPI dendrimers were synthesized by polymerization of BLG-NCA using G2.0PPI as macromolecular initiator and subsequent aminolysis with G1.0PPI or G2.0PPI. The chemical structure and composition of the MP-g-PPI dendrimers were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy ((1)H NMR). The MP-g-PPI showed a great ability to combine with pDNA to form complexes, which protect the pDNA from nuclease degradation. Dynamic light scattering (DLS) measurement illustrated that the sizes of complexes were in range of 111-219 nm. The transmission electron microscope (TEM) and atomic force microscope (AFM) observation showed that the morphology of these complexes was spherical. The MTT assay demonstrated that cytotoxicity of the MP-g-PPI was lower than that of PEI 25K. The in vitro transfection test indicated that MP-g-PPI gene vectors displayed relative high transfection efficiency than that of PEI 25K and Lipofectamine 2000 in serum-containing medium. Furthermore, MP-g-PPI at the weight ratio of 7.5 displayed better serum-resistant capability than that of PEI 25K and Lipofectamine 2000. The above facts revealed that multi-armed MP-g-PPI dendrimers may be promising gene vectors with low cytotoxicity, high transfection efficiency and serum-resistant ability.