Microspheres for a Macroproblem: biomaterials grafted with antimicrobial peptides (MSI-78A) are highly efficient in Helicobacter pylori eradication

Helicobacter pylori is one of the most successful human pathogens worldwide. This bacterium infects the stomach of nearly half of the world’s population and is directly responsible for 90% of all diagnosed gastric cancers, the fifth most common and the fourth deadliest. One would think that in the 21^st century, this infection would be cleared using a course of antibiotics. Reality, powered by the antibiotic resistance crisis, is quite different, as 2 out of 5 people remain infected, even after several rounds using different antibiotics. In fact, the World Health Organization ranked H. pylori as one of the bacteria that poses the greatest threat in terms of public health.

To solve this problem, we bioengineered antibiotic-free microspheres grafted with an antimicrobial peptide (MSI-78A). This is a promising strategy for the treatment of H. pylori gastric infection, demonstrating excellent antimicrobial performance against H. pylori, killing more than 99% of the bacterial cells after 2h of exposure. 

Photo: Cristina Martins, Diana Fonseca and Paula Parreira.

Authors and Affiliations:

Diana R. Fonseca ^a,b,c, Ana Moura ^a,b,c, Victoria Leiro ^a,b, Ricardo Silva-Carvalho ^b, Berta N. Estevinho ^d, Catarina L. Seabra ^a,b,1 , Patrícia C. Henriques ^a,b,c,d, Mónica Lucena ^a,b,e, Cátia Teixeira ^f, Paula Gomes ^f, Paula Parreira ^a,b,2 , M. Cristina L. Martins ^a,b,e,2

^ai3S, Instituto de Investigação e Inovação em Saúde, Portugal;

^b INEB, Instituto de Engenharia Biomédica, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal;

^c Faculdade de Engenharia, Departamento de Engenharia Metalúrgica e de Materiais, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

^d LEPABE, Laboratório de Engenharia de Processos, Ambiente, Biotecnologia e Energia, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal;

^e ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal

^f LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Portugal;

¹ Current address: LAQV/REQUIMTE, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto;

² These authors contributed equally to this paper

Abstract:

MSI-78A (Pexiganan A) is one of the few antimicrobial peptides (AMPs) able to kill Helicobacter pylori, a pathogenic bacterium that colonizes the gastric mucosa of half of the world's population. Antibiotics fail in 20-40% of H. pylori-infected patients, reinforcing the need for alternative treatments. Herein, a bioengineered approach was developed. MSI-78A with a C-terminal cysteine was grafted onto chitosan microspheres (AMP-ChMic) by thiol-maleimide (Michael-addition) chemistry using a long heterobifunctional spacer (NHS-PEG₁₁₃-MAL).

Microspheres with ~4 µm diameter (near H. pylori length) and stable at low pH were produced by spray drying using a chitosan solution with an incomplete genipin crosslinking. A 3×10^-5 μg AMP/microsphere grafting was estimated/confirmed by UV/Vis and FTIR spectroscopies. AMP-ChMic were bactericidal against H. pylori J99 (highly pathogenic human strain) at lower concentrations than the free peptide (~277 µg grafted MSI-78A-SH/mL vs 512 μg free MSI-78A-SH/mL), even after pre-incubation in simulated gastric conditions with pepsin. AMP-ChMic killed H. pylori by membrane destabilization and cytoplasm release in a ratio of ~10 bacteria/microsphere. This can be attributed to H. pylori attraction to chitosan, facilitating the interaction of grafted AMP with bacterium membrane. Overall, it was demonstrated that the peptide-microsphere conjugation chemistry did not compromise the MSI-78A antimicrobial activity, instead it boosted its bactericidal performance against H. pylori.

Journal: Acta Biomaterialia

Link: https://doi.org/10.1016/j.actbio.2021.09.063