Iron Oxide Nanoparticles with Grafted Polymeric Analogue of Dimethyl Sulfoxide as Potential Magnetic Resonance Imaging Contrast Agents

Magnetic Iron Oxide Nanoparticles for Brain Imaging and Drug Delivery

Central nervous system (CNS) disorders affect as many as 1.5 billion people globally. The limited delivery of most imaging and therapeutic agents into the brain is a major challenge for treatment of CNS disorders. With the advent of nanotechnologies, controlled delivery of drugs with nanoparticles holds great promise in CNS disorders for overcoming the blood-brain barrier (BBB) and improving delivery efficacy. In recent years, magnetic iron oxide nanoparticles (MIONPs) have stood out as a promising theranostic nanoplatform for brain imaging and drug delivery as they possess unique physical properties and biodegradable characteristics. In this review, we summarize the recent advances in MIONP-based platforms as imaging and drug delivery agents for brain diseases. We firstly introduce the methods of synthesis and surface functionalization of MIONPs with emphasis on the inclusion of biocompatible polymers that allow for the addition of tailored physicochemical properties. We then discuss the recent advances in in vivo imaging and drug delivery applications using MIONPs. Finally, we present a perspective on the remaining challenges and possible future directions for MIONP-based brain delivery systems.

Star Polymers with Designed Reactive Oxygen Species Scavenging and Agent Delivery Functionality Promote Plant Stress Tolerance

Plant abiotic stress induces reactive oxygen species (ROS) accumulation in leaves that can decrease photosynthetic performance and crop yield. Materials that scavenge ROS and simultaneously provide nutrients in vivo are needed to manage this stress. Here, we incorporated both ROS scavenging and ROS triggered agent release functionality into an ∼20 nm ROS responsive star polymer (RSP) poly(acrylic acid)-block-poly((2-(methylsulfinyl)ethyl acrylate)-co-(2-(methylthio)ethyl acrylate)) (PAA-b-P(MSEA-co-MTEA)) that alleviated plant stress by simultaneous ROS scavenging and nutrient agent release. Hyperspectral imaging indicates that all of the RSP penetrates through the tomato leaf epidermis, and 32.7% of the applied RSP associates with chloroplasts in mesophyll. RSP scavenged up to 10 μmol mg^-1 ROS in vitro and suppressed ROS in vivo in stressed tomato (Solanum lycopersicum) leaves. Reaction of the RSP with H₂O₂in vitro enhanced the release of nutrient agent (Mg²⁺) from star polymers. Foliar applied RSP increased photosynthesis in plants under heat and light stress compared to untreated controls, enhancing the carbon assimilation, quantum yield of CO₂ assimilation, Rubisco carboxylation rate, and photosystem II quantum yield. Mg loaded RSP improved photosynthesis in Mg deficient plants, mainly by promoting Rubisco activity. These results indicate the potential of ROS scavenging nanocarriers like RSP to alleviate abiotic stress in crop plants, allowing crop plants to be more resilient to heat stress, and potentially other climate change induced abiotic stressors.

Star Polymer Size, Charge Content, and Hydrophobicity Affect their Leaf Uptake and Translocation in Plants

Determination of how the properties of nanocarriers of agrochemicals affect their uptake and translocation in plants would enable more efficient agent delivery. Here, we synthesized star polymer nanocarriers poly(acrylic acid)-block-poly(2-(methylsulfinyl)ethyl acrylate) (PAA-b-PMSEA) and poly(acrylic acid)-block-poly((2-(methylsulfinyl)ethyl acrylate)-co-(2-(methylthio)ethyl acrylate)) (PAA-b-P(MSEA-co-MTEA)) with well-controlled sizes (from 6 to 35 nm), negative charge content (from 17% to 83% PAA), and hydrophobicity and quantified their leaf uptake, phloem loading, and distribution in tomato (Solanum lycopersicum) plants 3 days after foliar application of 20 μL of a 1g L^-1 star polymer solution. In spite of their property differences, ∼30% of the applied star polymers translocated to other plant organs, higher than uptake of conventional foliar applied agrochemicals (<5%). The property differences affected their distribution in the plant. The ∼6 nm star polymers exhibited 3 times higher transport to younger leaves than larger ones, while the ∼35 nm star polymer had over 2 times higher transport to roots than smaller ones, suggesting small star polymers favor symplastic unloading in young leaves, while larger polymers favor apoplastic unloading in roots. For the same sized star polymer, a smaller negative charge content (yielding ζ ∼ -12 mV) enhanced translocation to young leaves and roots, whereas a larger negative charge (ζ < -26 mV) had lower mobility. Hydrophobicity only affected leaf uptake pathways, but not translocation. This study can help design agrochemical nanocarriers for efficient foliar uptake and targeting to desired plant organs, which may decrease agrochemical use and environmental impacts of agriculture.

An ICP-MS-based assay for characterization of gold nanoparticles with potential biomedical use

Most of potential diagnostic and therapeutic nanoparticles fail to reach clinical trials because assessment of their 'drug-like' properties is often overlooked during the discovery stage. This compromises the results of cell culture and animal experiments, making them insufficient to evaluate the lead candidates for testing on patients. In this study, we demonstrate the potential of high-resolution inductively coupled plasma mass spectrometry (ICP-MS) as a nanoparticle qualification tool. Using novel gold nanoparticles stabilized by N-heterocyclic carbenes as test nanoparticles, it was shown that important prerequisites for biomedical applications, such as resistance to the action of human serum milieu or reactivity toward serum biomolecules, can be reliably assessed by recording the signals of gold or sulfur isotopes. Implemented during the screening stage, the method would provide benefits in shortening timelines and reducing cost for selection and initial testing of medicinal nanoparticle candidates.

Antifouling Surfaces Enabled by Surface Grafting of Highly Hydrophilic Sulfoxide Polymer Brushes

Antifouling surfaces are important in a broad range of applications. An effective approach to antifouling surfaces is to covalently attach antifouling polymer brushes. This work reports the synthesis of a new class of antifouling polymer brushes based on highly hydrophilic sulfoxide polymers by surface-initiated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The sulfoxide polymer brushes are able to effectively reduce nonspecific adsorption of proteins and cells, demonstrating remarkable antifouling properties. Given the outstanding antifouling behavior of the sulfoxide polymers and versatility of surface-initiated PET-RAFT technology, this work presents a useful and general approach to engineering various material surfaces with antifouling properties, for potential biomedical applications in areas such as tissue engineering, medical implants, and regenerative medicine.

Proteins Conjugated with Sulfoxide-Containing Polymers Show Reduced Macrophage Cellular Uptake and Improved Pharmacokinetics

The conjugation of hydrophilic polymers to proteins is an effective approach to prolonging their circulation time in the bloodstream and, hence, improving their delivery to the target region of interest. In this work, we report the synthesis of protein-polymer conjugates using a highly water-soluble sulfoxide-containing polymer, poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA), through a combination of "grafting-to" and "grafting-from" methods. Oligomeric MSEA was synthesized by conventional reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently conjugated to lysozyme to produce a macromolecular chain transfer agent. This was followed by a visible light-mediated chain extension polymerization of MSEA to obtain a lysozyme-PMSEA conjugate (Lyz-PMSEA). It was found that the Lyz-PMSEA conjugate exhibited much reduced macrophage cellular uptake compared with unmodified and PEGylated lysozyme. Moreover, the Lyz-PMSEA conjugate was able to circulate longer in the bloodstream, demonstrating significantly improved pharmacokinetics demanded for pharmaceutical applications.

Attachment of streptavidin-modified superparamagnetic iron oxide nanoparticles to the PC-12 cell membrane

Efficient attachment of magnetic nanoparticles to cell membranes plays an important role in the activation of cell membrane channels. Streptavidin (SA) was successfully modified to Poly (ethylene imine) (PEI)-superparamagnetic iron oxide nanoparticles (SPIONs) to form SA/PEI-SPIONs, which have high colloidal stability and low cytotoxicity. The SA/PEI-SPIONs were incubated with PC-12 cells which had first been cultured in a Roswell Park Memorial Institute medium 1640 containing 0.2 mg l^-1 biotin for 12 h. The cells were observed by transmission electron microscopy, and the nanoparticles were clearly attached on the cell membrane, which can be attributed to the specific binding between the SA and biotin sites on the cell surface. This work provides a simple way to attach SA-modified nanoparticles on the membranes of cells by only culturing cells in a biotin-containing medium. This work makes possible biomedical applications that require nanoparticles to target cell membranes.

Surface-Initiated Atom Transfer Radical Polymerization for the Preparation of Well-Defined Organic-Inorganic Hybrid Nanomaterials

Surface-initiated atom transfer radical polymerization (SI-ATRP) is a powerful tool that allows for the synthesis of organic-inorganic hybrid nanomaterials with high potential applications in many disciplines. This review presents synthetic achievements and modifications of nanoparticles via SI-ATRP described in literature last decade. The work mainly focuses on the research development of silica, gold and iron polymer-grafted nanoparticles as well as nature-based materials like nanocellulose. Moreover, typical single examples of nanoparticles modification, i.e., ZnO, are presented. The organic-inorganic hybrid systems received according to the reversible deactivation radical polymerization (RDRP) approach with drastically reduced catalyst complex concentration indicate a wide range of applications of materials including biomedicine and microelectronic devices.