Improvement of Peptide Affinity and Stability by Complexing to Cyclodextrin-Grafted Ammonium Chitosan

Abstract

Cyclodextrin-grafted polymers are attractive biomaterials that could bring together the host–guest complexing capability of pristine cyclodextrin and the pharmaceutical features of the polymeric backbone. The present paper is aimed at characterizing the potential application of ammonium–chitosan grafted with 2-methyl-β-cyclodextrin (N+-rCh-MCD) as the functional macromolecular complexing agent for the oral administration of the neuropeptide dalargin (DAL). Specific NMR characterization procedures, along with UV and fluorescence techniques, as well as biological in vitro assessments have been performed. The results indicate that N+-rCh-MCD forms water-soluble complexes with DAL, with a prevalent involvement of Tyr or Phe over Leu and Ala residues. The association constant of DAL with the polymeric derivative is one order of magnitude higher than that with the pristine cyclodextrin (Ka: 2600 M−1 and 120 M−1, respectively). Additionally, N+-rCh-MCD shields DAL from enzymatic degradation in gastrointestinal in vitro models with a three-fold time delay, suggesting a future pharmaceutical exploitation of the polymeric derivative. Therefore, the greater affinity of N+-rCh-MCD for DAL and its protective effect against enzymatic hydrolysis can be attributed to the synergistic cooperation between cyclodextrin and the polymer, which is realized only when the former is covalently linked to the latter.

Nanoparticles Based on Quaternary Ammonium Chitosan-methyl-β-cyclodextrin Conjugate for the Neuropeptide Dalargin Delivery to the Central Nervous System: An In Vitro Study

“…The free DAL sample was readily degraded in the apical chamber by the enzyme activity of the monolayer cells, and thus only 8.67 ± 0.80% of the drug was still present at the end of the experiment (3 h) [15]. The peptide degradation was such that its presence in the basolateral chamber could never be evidenced, in agreement with previous studies [15].…”

“…In the present work in particular, an N + -rCh-CD was obtained, which contained 52% by weight of MCD and was much more soluble than the polymer conjugates obtained previously [13,14], therefore allowing a better handling. NMR studies with model solutions containing DAL and MCD [15] in physiological conditions showed that the DAL-cyclodextrin interaction consisted in DAL inclusion within the oligosaccharide cavity and mainly involved the aromatic moieties of the tyrosine units, although interactions with phenylalanine and the alkyl residues of the leucine and alanine units were also observed. A stronger interaction of the aromatic than the aliphatic components resulted from the NMR studies.…”

“…These have been exploited to promote the oral absorption of hydrophobic small molecules [ 13 , 14 ]. Moreover, the DAL stabilizing power by the conjugate quaternary ammonium chitosan–MCD (N + -rCh-CD) in the presence of digestive enzymes has been demonstrated [ 15 ]. In fact, in the case of peptide active ingredients, cyclodextrins are often studied because the inclusion of hydrophobic amino acid residues in the toroid determines a stabilization of the tertiary structure and the slowdown of enzymatic reactions toward the active ingredients [ 16 ].…”

Quaternary Ammonium Chitosans: The Importance of the Positive Fixed Charge of the Drug Delivery Systems

“…The data showed a greater ability of QA-Ch-MCD to protect DAL from degradation by α-chymotrypsin compared to the physical mixture of the precursors. This ability can be attributed to a synergistic cooperation of cyclodextrin and polymer, which occurs only when the former is covalently linked to the latter [57].…”

State-of-the-Art Polymer Science and Technology in Italy

“…The association constant of DAL with the polymeric derivative is one order of magnitude higher than that with the pristine cyclodextrin (K a : 2600 M −1 and 120 M −1 , respectively). Additionally, N + -rCh-MCD shields DAL from enzymatic degradation in gastrointestinal in vitro models with a three-fold time delay, suggesting a future pharmaceutical exploitation of the polymeric derivative [13].…”