Synthesis and Characterization of Thiolated Nanoparticles Based on Poly (Acrylic Acid) and Algal Cell Wall Biopolymers for the Delivery of the Receptor Binding Domain from SARS-CoV-2

The COVID-19 pandemic required great efforts to develop efficient vaccines in a short period of time. However, innovative vaccines against SARS-CoV-2 virus are needed to achieve broad immune protection against variants of concern. Polymeric-based particles can lead to innovative vaccines, serving as stable, safe and immunostimulatory antigen delivery systems. In this work, polymeric-based particles called thiolated PAA/Schizo were developed. Poly (acrylic acid) (PAA) was thiolated with cysteine ethyl ester and crosslinked with a Schizochytrium sp. cell wall fraction under an inverse emulsion approach. Particles showed a hydrodynamic diameter of 313 ± 38 nm and negative Zeta potential. FT-IR spectra indicated the presence of coconut oil in thiolated PAA/Schizo particles, which, along with the microalgae, could contribute to their biocompatibility and bioactive properties. TGA analysis suggested strong interactions between the thiolated PAA/Schizo components. In vitro assessment revealed that thiolated particles have a higher mucoadhesiveness when compared with non-thiolated particles. Cell-based assays revealed that thiolated particles are not cytotoxic and, importantly, increase TNF-α secretion in murine dendritic cells. Moreover, immunization assays revealed that thiolated PAA/Schizo particles induced a humoral response with a more balanced IgG2a/IgG1 ratio. Therefore, thiolated PAA/Schizo particles are deemed a promising delivery system whose evaluation in vaccine prototypes is guaranteed.

New Bio-Based Polymer Sorbents out of Terpene Compounds or Vegetable Oils: Synthesis, Properties, Analysis of Sorption Processes

This research presents a synthesis and characterization of new bio-based polymer sorbents. Natural origin substances such as terpenes (citral, limonene, and pinene) or vegetable oils (argan, linseed, and rapeseed oils) were used as monomers, and divinylbenzene was applied as the cross-linker. The newly prepared polymers were characterized by means of ATR-FTIR, TG/DTG and titration methods (acid and iodine values), and N₂ physisorption experiments. Tests of sorption ability were carried out by a dynamic solid phase extraction method using a mixture of four phenols or single-component pharmaceutical solutions (salicylic acid, aspirin, ibuprofen, paracetamol, and ampicillin). The performed studies revealed that the terpene-based polymers possessed better-developed porous structures (420-500 m²/g) with more uniform pores than oil-based ones. However, the surface of the oil-based sorbents was more acidic in nature. The sorption tests showed that both the porosity and acidity of the surface significantly influenced the sorption. Recoveries of up to 90% were obtained for 2,4 dichlorophenol from C-DVB, L-DVB, and Ro-DVB. The lowest affinity to the polymers exhibited phenol (5-45%), aspirin (1-7%), and ampicillin (1-7%). A 70% recovery was achieved for ibuprofen from C-DVB. In-depth data analysis allowed the influence of various factors on the sorption process of test compounds of the studied polymers to be elucidated.