Anion-Responsive Metallopolymer Hydrogels for Healthcare Applications

Abstract

Metallopolymers combine a processable, versatile organic polymeric skeleton with functional metals, providing multiple functions and methodologies in materials science. Taking advantage of cationic cobaltocenium as the key building block, organogels could be simply switched to hydrogels via a highly efficient ion exchange. With the unique ionic complexion ability, cobaltocenium moieties provide a robust soft substrate for recycling antibiotics from water. The essential polyelectrolyte nature offers the metallopolymer hydrogels to kill multidrug resistant bacteria. The multifunctional characteristics of these hydrogels highlight the potential for metallopolymers in the field of healthcare and environmental treatment.

Figure 1. Illustration of anion-paired (Cl⁻ (purple circles), PF₆− (green circles) and antibiotics) cobaltocenium-containing organogels and hydrogels.

Inserted: optical images of two representative gels (Scale Bar: 1 cm).

Figure 2

(a) Preparation of cationic cobaltocenium-containing organogels (PCoPF₆-Gel) via copolymerization of CoAEMAPF₆ and PEGDMA. (b) Preparation of chloride-paired hydrogel (PCoCl-Gel) from the organogel PCoPF₆-Gel via ion-exchange with tetrabutylammonium chloride (TBACl). (c) Solid state ³¹P NMR spectra of organogel PCoPF₆-Gel, hydrogel PCoCl-Gel and sodium hexafluorophosphate (NaPF₆, as a reference).

Figure 3. Mechanical properties of PCoCl-Gel; and PCoPF₆-Gel:

(a) The curves of shear storage modulus and shear loss modulus vs. strain for PCoCl-Gel and PCoPF₆-Gel performed by amplitude sweep under the frequency of 10 rad/s. (b) The shear storage modulus and shear loss modulus with different frequency performed by a frequency sweep under the strain at 0.2%.

Figure 4. Treatment of antibiotics in water by cobaltocenium-containing hydrogels:

PCoCl-Gel (dry weight: 4.5 mg) as an absorbent for β-lactam antibiotics: amoxicillin, cefazolin and cefoxitin; (a) UV-vis absorption curves of 2 mL, 2 g/L amoxicillin under different time intervals; (b) UV-vis absorption data for time-dependent antibiotics-uptake (2 mL, 2 g/L) of PCoCl-Gel; (c) UV-vis absorption curves of 10 mg/L amoxicillin under different time intervals; (d) UV-vis absorption data for time-dependent antibiotics-uptake under a low concentration (3 mL, 10 mg/L) of PCoCl-Gel. Inhibition of cobaltocenium-containing hydrogels (PCoCl-Gel) was observed against (e) Gram-negative E-coli; (f) Gram-positive S. aureus; and (g) HA-MRSA under different concentrations by standard solution micro-broth measurement.