Functionalized Nanoporous Silica for the Removal of Heavy Metals from Biological Systems: Adsorption and Application

Abstract

Surface-functionalized nanoporous silica, often referred to as self-assembled monolayers on mesoporous supports (SAMMS), has previously demonstrated the ability to serve as very effective heavy metal sorbents in a range of aquatic and environmental systems, suggesting that they may be advantageously utilized for biomedical applications such as chelation therapy. Herein we evaluate surface chemistries for heavy metal capture from biological fluids, various facets of the materials’ biocompatibility, and the suitability of these materials as potential therapeutics. Of the materials tested, thiol-functionalized SAMMS proved most capable of removing selected heavy metals from biological solutions (i.e., blood, urine, etc.) Consequentially, thiol-functionalized SAMMS was further analyzed to assess the material’s performance under a number of different biologically relevant conditions (i.e., variable pH and ionic strength) to gauge any potentially negative effects resulting from interaction with the sorbent, such as cellular toxicity or the removal of essential minerals. Additionally, cellular uptake studies demonstrated no cell membrane permeation by the silica-based materials generally highlighting their ability to remain cellularly inert and thus nontoxic. The results show that organic ligand functionalized nanoporous silica could be a valuable material for a range of detoxification therapies and potentially other biomedical applications.

In vitro removal of toxic heavy metals by poly(γ-glutamic acid)-coated superparamagnetic nanoparticles

“…Based on a method used by Yantasee et al, 9 the effect of ionic strength in the biological matrix of metal removal by PGASPIONs was studied by spiking 50 mg/L of lead or cadmium solution in four different concentrations of sodium acetate (0.001, 0.01, 0.1, and 1 M) and mixing each with 0.5 mL of 0.2 g/L PGA-SPIONs. The mixtures were then shaken for 2 hours at 37°C, followed by magnetically decanting the metal-bound PGA-SPIONs for the analysis of free lead and cadmium in the solution.…”

“…Simulated gastrointestinal fluid (SGIF) was prepared daily by adopting the procedure outlined by US Pharmacopeia for drug dissolution studies, 27 and modifying the procedure based on a method described by Yantasee et al 9 The SGIF solution consisted of 0.03 M NaCl, 0.085 M HCl, and 0.32% (w/v) pepsin. For evaluating the effectiveness of PGASPIONs towards the removal of lead or cadmium at different gastrointestinal pH, 50 mg/L lead or cadmium solution was spiked into SGIF solutions and adjusted to different pH values (1, 2, 2.5, 3, 3.5, 4, 5, 6, 7, and 8) using 0.2 M sodium bicarbonate.…”

“…[6][7][8] Upon administration into the body, the organic chelators bind with heavy metals for eventual removal through the kidneys; however, these methods require multiple administrations, which may burden and damage the renal system during clearance of metal chelates from the body. 9 In addition, these chelating agents are capable of binding to essential metals, resulting in severe mineral deficiency and anemia. 10 For example, the occurrence of cardiac arrest due to hypocalcemia was reported in patients undergoing EDTA chelation therapy.…”

“…Moreover, such solid-phase adsorbents administered orally would facilitate the removal of toxic metals from the gastrointestinal tract, resulting in their subsequent elimination through feces. 9 Consequently, over a decade, dietary fibers from various food products such as rice bran, wheat bran, oat bran, and fruit fibers have been evaluated as alternatives to conventional organic chelators. 12,13 Nevertheless, recent advancements in the field of nanoscience and nanotechnology have paved the way for the tailored synthesis of nanoparticles by coating or encapsulating them with functional materials.…”

Facile Modification of Surface of Silica Particles with Organosilanepolyol and Their Characterization

“…[7][8][9] Originally SPs have lots of hydroxyl functionalities which are hydrophilic and reactive sites, and can be modified to alter functionalities on their surfaces. 10,11 Functional groups on the surface of modified SPs usually plays a critical role in the specific properties such as hydrophobicity, binding sites, and are chemically reactive.…”