Abstract
Anionic poly(vinylcaprolactam-co-itaconicacid-co-dimethylitaconate) microgels were synthesized via dispersion polymerization and their responsiveness towards cations, namely Mg2+, Sr2+, Cu2+ and Fe3+, was investigated. The itaconic moieties chelate the metal ions which act as a crosslinker and decrease the electrostatic repulsion within the network, leading to a decrease in the gel size. The responsiveness towards the metal ion concentration has been studied via dynamic light scattering (DLS) and the number of ions bonded within the network has been quantified with ion chromatography. Through the protonation of the carboxylate groups in the gel network, their interaction with the cations is significantly lowered, and the metals are consequently released back in solution. The number of ions released was assessed also via ion chromatography for all four ions, whilst Mg2+ was also used as a model ion to display the reversibility of the system. The microgels can bond and release divalent cations over multiple cycles without undergoing any loss of functionality. Moreover, these gels also selectively entrap Fe3+ with respect to the remaining divalent cations, opening the possibility of using the proposed gels in the digestive tract as biocompatible chelating agents to fight iron overaccumulation.
Highlights
IntroductionDivalent and trivalent metal cations are of crucial importance in the elapse of biochemical reactions within the body, yet can act as toxic agents when they exceed physiological concentrations in the system.[1,2] For instance, some metals such as Cu2+ and Pb2+ are commonly known as pollutants due to their elevated toxicity in the body even at minimal concentrations, whilst other metals like Fe3+, generally not harmful, can lead to long-term damage when pre-existing conditions are present, such as b-thalassemia or diabetes.[3,4,5] The uncontrolled accumulation of metal ions or toxins in the body can lead to oxidative stress and cell damage, and their removal requires invasive and long therapies, such as injections of chelating agents and dialyses, multiple times a day.[5,6] The most common and effective chelating agent used in these therapies is ethylenediaminetetraacetic acid (EDTA), which has the major drawback to bond Ca2+
The gels were subsequently treated with 0.1 M NaOH to ensure the hydrolysis of the COOMe groups of the IADME monomer into its corresponding carboxyl group, which will act as a metal ion scavenger
As already shown in previous publication, due to the higher reactivity of IADME compared to VCL, the core of the microgel is richer in COOH groups
Summary
Divalent and trivalent metal cations are of crucial importance in the elapse of biochemical reactions within the body, yet can act as toxic agents when they exceed physiological concentrations in the system.[1,2] For instance, some metals such as Cu2+ and Pb2+ are commonly known as pollutants due to their elevated toxicity in the body even at minimal concentrations, whilst other metals like Fe3+, generally not harmful, can lead to long-term damage when pre-existing conditions are present, such as b-thalassemia or diabetes.[3,4,5] The uncontrolled accumulation of metal ions or toxins in the body can lead to oxidative stress and cell damage, and their removal requires invasive and long therapies, such as injections of chelating agents and dialyses, multiple times a day.[5,6] The most common and effective chelating agent used in these therapies is ethylenediaminetetraacetic acid (EDTA), which has the major drawback to bond Ca2+. This drawback has been positively exploited by Karamched et al, where they presented anti-elastin decorated albumin nanoparticles
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