The pH-Dependent Controlled Release of Encapsulated Vitamin B1 from Liposomal Nanocarrier

Chemical modification of α-chymotrypsin enabling its release from alginate hydrogel by electrochemically generated local pH change

This study investigates the controlled release of α-chymotrypsin from an alginate hydrogel matrix. When protein molecules entrapped in the hydrogel matrix have a size smaller than the hydrogel pores, their hold/release from the polymer matrix are controlled by the electrostatic interaction between the guest molecules and host polymer. α-Chymotrypsin, as a model protein, was chemically modified with negatively charged species to change its pI and to convert its attractive interaction with a negatively charged alginate hydrogel matrix to a repulsion interaction allowing its release by pH-triggered signal. Then, bulk pH changes and electrochemically controlled local pH changes resulting from oxygen reduction were used for the controlled release of the enzyme from the alginate hydrogel. Three batches of modified α-chymotrypsin with different linker/enzyme ratios were synthesized, and their release profiles were investigated. The activity of both unmodified and modified α-chymotrypsin was evaluated using a UV-visible spectrophotometer following the standard procedure for the enzymatic assay of α-chymotrypsin (EC 3.4.21.1) and compared across all batches. Direct infusion electrospray ionization mass spectrometry (DI ESI-MS) was used to analyze the protein modifications and their impact on the isoelectric point values.

Fabrication of k-Carrageenan/Alginate/Carboxymethyl Cellulose basedScaffolds via 3D Printing for Potential Biomedical Applications

Three-dimensional (3D) printing technology was able to generate great attention because of its unique methodology and for its major potential to manufacture detailed and customizable scaffolds in terms of size, shape and pore structure in fields like medicine, pharmaceutics and food. This study aims to fabricate an ink entirely composed of natural polymers, alginate, k-carrageenan and carboxymethyl cellulose (AkCMC). Extrusion-based 3D printing was used to obtain scaffolds based on a crosslinked interpenetrating polymer network from the alginate, k-carrageenan, carboxymethyl cellulose and glutaraldehide formulation using CaCl2, KCl and glutaraldehyde in various concentrations of acetic acid. The stabile bonding of the crosslinked scaffolds was assessed using infrared spectroscopy (FT-IR) as well as swelling, degradation and mechanical investigations. Moreover, morphology analysis (µCT and SEM) confirmed the 3D printed samples' porous structure. In the AkCMC-GA objects crosslinked with the biggest acetic acid concentration, the values of pores and walls are the highest, at 3.9 × 10-2 µm-1. Additionally, this research proves the encapsulation of vitamin B1 via FT-IR and UV-Vis spectroscopy. The highest encapsulation efficiency of vitamin B1 was registered for the AkCMC-GA samples crosslinked with the maximum acetic acid concentration. The kinetic release of the vitamin was evaluated by UV-Vis spectroscopy. Based on the results of these experiments, 3D printed constructs using AkCMC-GA ink could be used for soft tissue engineering applications and also for vitamin B1 encapsulation.

Stimulation-Inhibition of Protein Release from Alginate Hydrogels Using Electrochemically Generated Local pH Changes

The electrochemically controlled release of proteins was studied in a Ca²⁺-cross-linked alginate hydrogel deposited on an electrode surface. The electrochemical oxidation of ascorbate or reduction of O₂ was achieved upon applying electrical potentials +0.6 or -0.8 V (vs Ag/AgCl/KCl 3 M), respectively, resulting in decreasing or increasing pH locally near an electrode surface. The obtained local acidic solution resulted in the protonation of carboxylic groups in the alginate hydrogel and, as a result, the formation of a hydrophobic shrunken hydrogel film. Conversely, the produced alkaline local environment resulted in a hydrophilic swollen hydrogel film. The release of the proteins was effectively inhibited from the shrunk hydrogel and activated from the swollen hydrogel film. Overall, the electrochemically produced local pH changes allowed control over the biomolecule release process. While the release inhibition by applying +0.6 V was always effective and could be maintained as long as the positive potential was applied, the release activation was different depending on the protein molecular size, being more effective for smaller species, and molecule charge, being more effective for negatively charged species. The repetitive change from the inhibited to stimulated state of the biomolecule release process was obtained upon cyclic application of oxidative and reductive potentials (+0.6 V ↔ -0.8 V). The alginate hydrogel film shrinking-swelling as well as the protein release process were studied and visualized using a confocal fluorescent microscope. In order to be observed, an external surface of the alginate film and the loaded protein molecules were labeled with different fluorescent dyes, which then produced colored fluorescent images under a confocal microscope.

Antioxidants and Bioactive Compounds in Food: Critical Review of Issues and Prospects

This review paper gives an insight into the effective delivery mechanisms for health-promoting substances and highlights the challenges of using antioxidants and bioactives in foods. The selection criteria for choosing bioactives and their extraction in bioavailable form with their adequate incorporation techniques and delivery mechanisms are covered. Moreover, an overview of existing methods for determination of bioactivity is given. The importance of scientifically evaluating the effects of foods or food components on consumer health before making claims about the healthiness is aligned. Finally, a scientific perspective on how to respond to the booming demand for health-promoting products is given, and we acknowledge that despite the work done, there are still many challenges that need to be overcome.

Electrochemically produced local pH changes stimulating (bio)molecule release from pH-switchable electrode-immobilized avidin-biotin systems

Immobilized avidin-biotin complexes were used to release biotinylated (bio)molecules upon producing local pH changes near an electrode surface by electrochemical reactions. The nitro-avidin complex with biotin was dissociated by increasing local pH with electrochemical O₂ reduction. The avidin complex with iminobiotin was split by decreasing local pH with electrochemical oxidation of ascorbate. Both studied systems were releasing molecule cargo species in response to small electrical potentials (-0.4 V or 0.2 V for the O₂ reduction or ascorbate oxidation, respectively) applied on the modified electrodes.

Development of Lomustine and n-Propyl Gallate Co-Encapsulated Liposomes for Targeting Glioblastoma Multiforme via Intranasal Administration

This work aimed to develop lomustine (LOM) and n-propyl gallate (PG)-loaded liposomes suitable for targeting glioblastoma multiforme (GBM) via the auspicious nose-to-brain drug delivery pathway. The therapeutical effect of LOM, as a nitrosourea compound, can be potentiated by PG suitable for enhanced anti-cancer therapy. Nose-to-brain delivery of PG and LOM combined in liposomes can overcome the poor water solubility, absorption properties, and toxicity issues in the systemic circulation. Optimization and characterization of the liposomal carrier with binary drug contents were carried out in order to achieve adequate encapsulation efficiency, loading capacity, drug release, and ex vivo permeation. The optimized liposome co-encapsulated with both drugs showed suitable Z-average (127 ± 6.9 nm), size distribution (polydispersity index of 0.142 ± 0.009), zeta potential (−34 ± 1.7 mV), and high encapsulation efficacy (63.57 ± 1.3% of PG and 73.45 ± 2.2% of LOM, respectively) meeting the acceptance criteria of nose-to-brain transport for both drugs. MTT assays of PG-LOM formulations were also conducted on NIH/3T3 (murine embryonic fibroblast), U87 (glioblastoma), and A2780 (ovarian cancer) cell lines indicating reduced an antiproliferative effect on all types of cells. Our results supported the use of this novel combination of LOM and PG in a liposomal formulation as a promising carrier for glioblastoma targeting via the intranasal route.

Electrochemically Stimulated Protein Release from pH-Switchable Electrode-Immobilized Nitroavidin-Biotin and Avidin-Iminobiotin Systems

Bovine serum albumin (BSA), used as a model protein, was immobilized at a buckypaper electrode by formation of pH-sensitive affinity bonds produced between avidin/iminobiotin or nitroavidin/biotin. Local (interfacial) pH was...