UV-Accelerated Synthesis of Gold Nanoparticle-Pluronic Nanocomposites for X-ray Computed Tomography Contrast Enhancement

Eco-friendly chemical methods using FDA-approved Pluronic F127 (PLU) block copolymer have garnered much attention for simultaneously forming and stabilizing Au nanoparticles (AuNPs). Given the remarkable properties of AuNPs for usage in various fields, especially in biomedicine, we performed a systematic study to synthesize AuNP-PLU nanocomposites under optimized conditions using UV irradiation for accelerating the reaction. The use of UV irradiation at 254 nm resulted in several advantages over the control method conducted under ambient light (control). The AuNP-PLU-UV nanocomposite was produced six times faster, lasting 10 min, and exhibited lower size dispersion than the control. A set of experimental techniques was applied to determine the structure and morphology of the produced nanocomposites as affected by the UV irradiation. The MTT assay was conducted to estimate IC50 values of AuNP-PLU-UV in NIH 3T3 mouse embryonic fibroblasts, and the results suggest that the sample is more compatible with cells than control samples. Afterward, in vivo maternal and fetal toxicity assays were performed in rats to evaluate the effect of AuNP-PLU-UV formulation during pregnancy. Under the tested conditions, the treatment was found to be safe for the mother and fetus. As a proof of concept or application, the synthesized Au:PLU were tested as contrast agents with an X-ray computed tomography scan (X-ray CT).

Probing human proteins for short encrypted antimicrobial peptides reveals Hs10, a peptide with selective activity for gram-negative bacteria

BACKGROUND

Some cationic and amphiphilic α-helical segments of proteins adsorb to prokaryotic membranes when synthesized as individual polypeptide sequences, resulting in broad and potent antimicrobial activity. However, amphiphilicity, a determinant physicochemical property for peptide-membrane interactions, can also be observed in some β-sheets.

METHODS

The software Kamal was used to scan the human reference proteome for short (7-11 amino acid residues) cationic and amphiphilic protein segments with the characteristic periodicity of β-sheets. Some of the uncovered peptides were chemically synthesized, and antimicrobial assays were conducted. Biophysical techniques were used to probe the molecular interaction of one peptide with phospholipid vesicles, lipopolysaccharides (LPS) and the bacterium Escherichia coli.

RESULTS

Thousands of compatible segments were found in human proteins, five were synthesized, and three presented antimicrobial activity in the micromolar range. Hs10, a nonapeptide fragment of the Complement C3 protein, could inhibit only the growth of tested Gram-negative microorganisms, presenting also little cytotoxicity to human fibroblasts. Hs10 interacted with LPS while transitioning from an unstructured segment to a β-sheet and increased the hydrodynamic radius of LPS particles. This peptide also promoted morphological alterations in E. coli cells.

CONCLUSIONS

Data presented herein introduce yet another molecular template to probe proteins in search for encrypted membrane-active segments and demonstrates that, using this approach, short peptides with low cytotoxicity and high selectivity to prokaryotic cells might be obtained.

GENERAL SIGNIFICANCE

This work widens the biotechnological potential of the human proteome as a source of antimicrobial peptides with application in human health.