Target-Specific Superparamagnetic Hydrogel with Excellent pH Sensitivity and Reversibility: A Promising Platform for Biomedical Applications

Abstract

Superparamagnetism has been widely used for many biomedical applications, such as early detection of inflammatory cancer and diabetes, magnetic resonance imaging (MRI), hyperthermia, etc., whereas incorporation of superparamagnetism in stimulus-responsive hydrogels has now gained substantial interest and attention for application in these fields. Recently, pH-responsive superparamagnetic hydrogels showing the potential use in disease diagnosis, biosensors, polymeric drug carriers, and implantable devices, have been developed based on the fact that pH is an important environmental factor in the body and some disease states manifest themselves by a change in the pH value. However, improvement in pH sensitivity of magnetic hydrogels is a dire need for their practical applications. In this study, we report the distinctly high pH sensitivity of new synthesized dual-responsive magnetic hydrogel nanocomposites, which was accomplished by copolymerization (free-radical polymerization) of two pH-sensitive monomers, acrylic acid (AA) and vinylsulfonic acid (VSA) with an optimum ratio, in the presence of presynthesized superparamagnetic iron oxide nanoparticles (Fe 3 O 4 (OH) x ). The monomers contain pH-sensitive functional groups (COO – and SO 3 – for AA and VSA, respectively), and they have also been widely used as biomaterials because of the good biocompatibility. The pH sensitivity of the superparamagnetic hydrogel, poly(acrylic acid- co -vinylsulfonic acid), PAAVSA/Fe 3 O 4 , was investigated by swelling studies at different pH values from pH 7 to 1.4. Distinct pH reversibility of the system was also demonstrated through swelling/deswelling analysis. Thermal stability, chemical configuration, magnetic response, and structural properties of the system have been explored by suitable characterization techniques. Furthermore, the study reveals a pH-responsive significant change in the overall morphology and packing fraction of iron oxide nanoparticles in PAAVSA/Fe 3 O 4 via energy-dispersive X-ray (EDX) elemental mapping with the field emission scanning electron microscopy (FESEM) study (for freeze-dried PAAVSA/Fe 3 O 4 , swelled at different pH values), implying a drastic change in susceptibility and induced saturation magnetization of the system. These important features could be easily utilized for the purpose of diagnosis using magnetic probe and/or impedance analysis techniques.

A Biocompatible, pH-Sensitive, and Magnetically Separable Superparamagnetic Hydrogel Nanocomposite as an Efficient Platform for the Removal of Cationic Dyes in Wastewater Treatment

“…The existence and crystallinity of SPIONs (i.e., Fe 3 O 4 nanoparticles) in synthesized AA-VSA-P/SPIONs-I, AA-VSA-P/SPIONs-II, and AA-VSA-P/SPIONs-III were investigated by the XRD analysis, as shown in Figure , along with XRD data of pristine SPIONs (i.e., Fe 3 O 4 nanoparticles) and AA-VSA-P hydrogel. The AA-VSA-P hydrogel shows amorphous nature, which is consistent with the characteristic structural properties of the polymer Figure demonstrates that the diffraction patterns of synthesized pristine iron oxide nanoparticles (i.e., SPIONs or Fe 3 O 4 nanoparticles) and superparamagnetic hydrogel nanocomposites (with different weight percentages of SPIONs) match with the standard diffraction pattern of cubic Fe 3 O 4 (magnetite) with a space group of Fd 3̅ m (227) (JCPDS PDF card no.…”

“…The emergence of additional peaks at 1431 and 1597 cm –1 in the Raman spectra of the composite hydrogel AA-VSA-P/SPIONs-III signifies the formation of the COO – and Fe complex. 28 The results indicate the adherence (binding) of SPIONs with the polymer (AA-VSA-P) chain in the hydrogel network. Such indication of the interaction of SPIONs with the polymer chain in the hydrogel network was also evident in our previous study.…”

“…Debye–Scherrer expression was utilized to evaluate the average particle size of SPIONs. 28 where D , K , and β denote respectively the average size of the crystallites, shape factor ( K = 0.94, considering the spherical shape of SPIONs), and full width at half-maximum of the highest intensity diffraction peak at angle θ. λ is the X-ray wavelength . The estimated average size of SPIONs was ∼8 nm as extracted from XRD patterns of pristine SPIONs and different sets of AA-VSA-P/SPIONs composite hydrogels (AA-VSA-P/SPIONs-I, AA-VSA-P/SPIONs-II, and AA-VSA-P/SPIONs-III).…”

“…Such indication of the interaction of SPIONs with the polymer chain in the hydrogel network was also evident in our previous study. 28 …”

Fabrication of Multiresponsive Magnetic Nanocomposite Double‐Network Hydrogels for Controlled Release Applications

“…NC hydrogels with magnetic nanomaterials (e.g., γ‐Fe 2 O 3 , [ 15 ] Fe 3 O 4 , [ 15,45,46 ] and CoFe 2 O 4 [ 47,48 ] ) are particularly of interest for biomedical applications. Magnetic NC hydrogels can be quickly guided to a specific location by a magnetic induction, [ 18,49,50 ] and also can generate heat energy under an alternating magnetic field (AMF). [ 51–55 ] Magnetic induced hyperthermia can also spatiotemporally trigger tumor cell apoptosis and reduce the damage to other normal cells by the remote control of local heating.…”