Peptide synthesis is an area with a wide field of application, from biomedicine to nanotechnology, that offers the option of simultaneously synthesizing a large number of sequences for the purpose of preliminary screening, which is a powerful tool. Nevertheless, standard protocols generate large volumes of solvent waste. Here, we present a protocol for the multiple Fmoc solid-phase peptide synthesis in tea bags, where reagent recycling steps are included. Fifty-two peptides with wide amino acid composition and seven to twenty amino acid residues in length were synthesized in less than three weeks. A clustering analysis was performed, grouping the peptides by physicochemical features. Although a relationship between the overall yield and the physicochemical features of the sequences was not established, the process showed good performance despite sequence diversity. The recycling system allowed to reduce N, N-dimethylformamide usage by 25–30% and reduce the deprotection reagent usage by 50%. This protocol has been optimized for the simultaneous synthesis of a large number of peptide sequences. Additionally, a reagent recycling system was included in the procedure, which turns the process into a framework of circular economy, without affecting the quality of the products obtained.

Cyclotides are circular peptides found in various plant families. A cyclized backbone, together with multiple disulfide bonds, confers the peptides’ exceptional stability against protease digestion and thermal denaturation. In addition, the features of these antimicrobial molecules make them suitable for use in animal farming, such as aquaculture. Fmoc solid phase peptide synthesis on 2-chlorotrityl chlorine (CTC) resin using the “tea-bag” approach was conducted to generate the VarvA cyclotide identified previously from Viola arvensis. MALDI-TOF mass spectrometry determined the correct peptide amino acid sequence and the cyclization sites-critical in this multicyclic compound. The cyclotide showed antimicrobial activity against various Gram-negative bacteria, including recurrent pathogens present in Chilean aquaculture. The highest antimicrobial activity was found to be against Flavobacterium psychrophilum. In addition, membrane blebbing on the bacterial surface after exposure to the cyclotide was visualized by SEM microscopy and the Sytox Green permeabilization assay showed the ability to disrupt the bacterial membrane. We postulate that this compound can be proposed for the control of fish farming infections.

Background/Objectives: Immunotherapy has shown promising results in some cancers, but its efficacy remains limited in pancreatic ductal adenocarcinoma (PDAC). Vaccines in nanoparticle form (nanovaccines) can incorporate immunostimulating components to induce a potent immune response. As mesothelin (MSLN) is a tumor-associated antigen overexpressed in PDAC, we evaluated the effect of MSLN nanovaccine in a syngeneic orthotopic KPC-PDAC mouse model. Methods: An MSLN peptide combining three MSLN epitopes and two adjuvants, poly I:C and R848, was encapsulated in PLGA–chitosan nanoparticles to generate the nanovaccine. Results: The MSLN nanovaccine was successfully taken up by dendritic cells in vitro and was found in inguinal lymph nodes 24 h after subcutaneous injection into C57BL/6 mice. Nanovaccine re-stimulation of splenocytes from vaccinated mice led to increased levels of interferon-γ in vitro compared to unstimulated splenocytes. Higher levels of MSLN-specific IgM and IgG antibodies were detected in the serum of vaccinated mice compared to that of control mice. Three vaccination regimens were tested: a prophylactic scheme that included vaccination before tumor induction and two therapeutic schemes involving early and late vaccination after tumor cell inoculation. MSLN nanovaccination inhibited KPC tumor progression and metastasis and induced higher CD8⁺ T cell infiltration in the tumor that developed in response to prophylactic and early therapeutic schedules but not in response to a later vaccination approach. Although the nanovaccine treatment elicited higher humoral and cellular antigen-specific responses in tumor-bearing mice for both vaccination strategies, the therapeutic vaccination also increased the expression of exhaustion markers in CD8⁺ T cells. Conclusions: Our results support the relevance of an MSLN-based nanovaccine as a new immunotherapy treatment for PDAC and propose an innovative method of vaccine delivery using NPs.