Design of synthetic polymer nanoparticles that inhibit glucose absorption from the intestine.

Synthetic polymers prepared using several functional monomers have attracted attention as cost-effective protein affinity reagents and alternative to antibodies. We previously reported the synthesis of poly NIPAm-based nanoparticles (NPs) using several functional monomers that can capture target molecules. In this study, we designed NPs for capturing glucose and inhibiting intestinal absorption in living mice. For capturing glucose, we focused on the Maillard reaction between primary amines and aldehyde residues. We hypothesized that the primary amine-containing NPs can capture the open-chain structure of glucose via the Maillard reaction and inhibit intestinal absorption. NPs were prepared by the precipitation polymerization of NIPAm, N-tert-butylacrylamide (TBAm), trifluoroacetate-protected N-(3-aminopropyl)methacrylamide (T-APM), and N,N'-methylenebisacrylamide. Then, T-APM in NPs was deprotected by NH3 (aq). The amount of glucose captured by NPs depended on the percentage of TBAm and APM in vitro. After 24 h, only 2% of orally administered NPs remained in the body after administration, suggesting that many NPs were excreted without being absorbed. The prepared NPs significantly inhibited an increase in blood glucose concentration after the oral administration of glucose and NPs, indicating that NPs capture glucose and inhibit intestinal absorption. These results show the potential of using synthetic polymer nanoparticles for inhibiting postprandial hyperglycemia.

Influence of Purification Process on the Function of Synthetic Polymer Nanoparticles.

Multifunctional synthetic polymers can bind to target molecules and are therefore widely investigated in diagnostics, drug delivery carriers, and separation carriers. Because these polymers are synthesized from nonbiological components, purification processes (e.g., chromatography, dialysis, extraction, and centrifugation) must be conducted after the synthesis. Although several purification methods are used for polymer purification, few reports have revealed the influence of purification process on the functions of polymer. In this study, we demonstrated that the characteristics, function, and stability of synthetic polymer depend on the purification process. N-Isopropylacrylamide-based polymer nanoparticles (NPs) and melittin (i.e., honey bee venom) were used as a model of synthetic polymer and target toxic peptide, respectively. Synthesized NPs were purified by dialysis in methanol, acetone precipitation, or centrifugation. NPs purified by dialysis in ultrapure water were used as control NPs. Then, NP size, surface charge, toxin neutralization effect, and stability were determined. NP size did not considerably change by purification with centrifugation; however, it decreased by purification using dialysis in methanol and acetone precipitation compared with that of control NPs. The ζ-potential of NPs changed after each purification process compared with that of control NPs. The melittin neutralization efficiency of NPs depended on the purification process; i.e., it decreased by acetone precipitation and increased by dialysis in methanol and centrifugation compared with that of control NPs. Of note, the addition of methanol and acetone decreased NP stability. These studies implied the importance of considering the effect of the purification method on synthetic polymer function.

Design of abiotic polymer ligand-decorated lipid nanoparticles for effective neutralization of target toxins in the blood.

Macromolecular toxins often induce inflammatory cytokine production, multiple-organ dysfunction, and cell death. Synthetic polymer ligands (PLs) prepared with several functional monomers have the potential of neutralizing target toxins after binding to them; therefore, they are of significant interest as abiotic antidotes. Although PLs show little toxin neutralization effect in the bloodstream because of immediate elimination from there, the toxin neutralization effect is significantly improved by the direct decoration of PLs onto lipid nanoparticles (PL-LNPs). However, this direct decoration decreases PL mobility, induces LNP aggregation after capturing the target, and decreases LNP blood circulation time. We designed novel PL-LNPs to improve PL mobility, inhibit the aggregation tendency after capturing the target, and increase LNP blood circulation time in order to achieve highly effective toxin neutralization in vivo. Specifically, LNPs were modified with PLs-conjugated polyethylene glycol (PEG), and additional PEG was used to modify the PL-decorated LNPs (PL-PEG-LNPs). Histones were used as target toxins, and N-isopropylacrylamide-based PLs were used for histone capture. PEGylation increased the plasma LNP level 24 h after intravenous injection by ∼90 times and inhibited LNP aggregation after histone capture. The dissociation constant (Kd) of PL-PEG-LNPs against histone was two times smaller compared to that of PL-LNPs. Although PL-LNPs inhibited histone-platelet interaction in the bloodstream, a large amount of histone-PL-LNP complexes accumulated in the lungs because of aggregation. However, PL-PEG-LNPs inhibited both histone-platelet interaction and histone accumulation in the lungs. Importantly, PL-PEG-LNP treatment increased the survival rate of histone-treated mice compared to PL-LNPs. These results provide a platform for the development of abiotic antidote nanoparticles in vivo.