Flexible organic frameworks sequester neuromuscular blocking agents in vitro and reverse neuromuscular block in vivo

Abstract

Supramolecular sequestration and reversal of neuromuscular block (NMB) have great clinical applications. Water-soluble flexible organic frameworks (FOFs) cross-linked by disulfide bonds are designed and prepared. Different linker lengths are introduced to FOFs to give them varied pore sizes. FOFs are anionic nanoscale polymers and capable of encapsulating cationic neuromuscular blocking agents (NMBAs), including rocuronium (Roc), vecuronium (Vec), pancuronium (Panc) and cisatracurium (Cis). A host-guest study confirms that FOFs bind NMBAs in water. The multivalency interaction between FOFs and NMBAs is able to sequester NMBAs, and prevent them from escaping. These FOFs are non-toxic and biocompatible. Animal studies show that FOFs are effective for the reversal of NMB induced by Roc, Vec and Cis, which shorten the time to a train-of-four ratio of 0.9 by 2.6, 3.8 and 5.7-fold compared to a placebo, respectively.

Scheme 1. Synthetic scheme for FOF-SS1-3 and chemical structures of NMBAs and acetylcholine.

Fig. 1. (a) ¹H NMR spectra (400 MHz, D₂O, 298 K) recorded for the formation of FOF-SS1 after the oxidant was added. ¹H NMR spectra (400 MHz, DMSO-d₆, 298 K) recorded for (b) T1 and acidulated FOF-SS1, (c) T2 and acidulated FOF-SS2, and (d) T3 and acidulated FOF-SS3. (e) Size distribution of Cis, T1-3, FOF-SS1-3 and FOF-SS1-3 + Cis in water. (f) Size distribution of FOF-SS1 at different concentrations in water (calculated based on [T1]).

Fig. 2. ¹H NMR spectra (400 MHz, D₂O, 298 K) recorded for (a) FOF-SS3 (2 mM, calculated based on [T3]), (b) a mixture of FOF-SS3 (2 mM) and Cis (2 mM), and (c) Cis (2 mM).

Fig. 3. (a) Fluorescence titration of FOF-SS3 (50 μM in PBS) by adding Cis (0–60 μM), λ_ex = 325 nm and λ_em = 752 nm. (b) Plot of differential power (μcal s⁻¹) vs. time from the titration of FOF-SS3 (0.1 mM) and with Cis (0.8 mM) in PBS (pH 7.4) and plot of the ΔH vs. molar ratio. The red line represents the best non-linear fit of the data K_a = (1.04 ± 0.11) × 10⁵ M⁻¹. (c) The time-dependent change of residual Cis with FOFs in a dialysis bag. [FOF-SS1] = [FOF-SS2] = [FOF-SS3] = 10 mg mL⁻¹and [Cis] = 1 mg mL⁻¹.

Fig. 4. Cell viability values (%) of H9C2 and L02 cells estimated by CCK-8 versus incubation concentrations of (a) FOF-SS1, (b) FOF-SS2, and (c) FOF-SS3. The hemolytic ratio (%) of human and rat erythrocytes versus incubation concentrations of (d) FOF-SS1, (e) FOF-SS2, and (f) FOF-SS3.

Fig. 5. Time to train-of-four (TOF) ratio of 0.9 recovery from: (a) Cis, (b) Roc (solid line) and Vec (dotted line) induced NMB after administration of FOFS, neostigmine or placebo. FOF-SS3 accelerated recovery significantly compared with a placebo (*P < 0.0001).