Nanoclusters of iron oxide: effect of core composition on structure, biocompatibility, and cell labeling efficacy

Histochemistry for nanomedicine: Novelty in tradition

During the last two centuries, histochemistry has provided significant advancements in many fields of life sciences. After a period of neglect due to the great development of biomolecular techniques, the histochemical approach has been reappraised and is now widely applied in the field of nanomedicine. In fact, the novel nanoconstructs intended for biomedical purposes must be visualized to test their interaction with tissue and cell components. To this aim, several long-established staining methods have been re-discovered and re-interpreted in an unconventional way for unequivocal identification of nanoparticulates at both light and transmission electron microscopy.

From Single-Core Nanoparticles in Ferrofluids to Multi-Core Magnetic Nanocomposites: Assembly Strategies, Structure, and Magnetic Behavior

Iron oxide nanoparticles are the basic components of the most promising magnetoresponsive nanoparticle systems for medical (diagnosis and therapy) and bio-related applications. Multi-core iron oxide nanoparticles with a high magnetic moment and well-defined size, shape, and functional coating are designed to fulfill the specific requirements of various biomedical applications, such as contrast agents, heating mediators, drug targeting, or magnetic bioseparation. This review article summarizes recent results in manufacturing multi-core magnetic nanoparticle (MNP) systems emphasizing the synthesis procedures, starting from ferrofluids (with single-core MNPs) as primary materials in various assembly methods to obtain multi-core magnetic particles. The synthesis and functionalization will be followed by the results of advanced physicochemical, structural, and magnetic characterization of multi-core particles, as well as single- and multi-core particle size distribution, morphology, internal structure, agglomerate formation processes, and constant and variable field magnetic properties. The review provides a comprehensive insight into the controlled synthesis and advanced structural and magnetic characterization of multi-core magnetic composites envisaged for nanomedicine and biotechnology.

Dextran-Coated Iron Oxide Nanoparticles as Biomimetic Catalysts for Localized and pH-Activated Biofilm Disruption

Biofilms are surface-attached bacterial communities embedded within an extracellular matrix that create localized and protected microenvironments. Acidogenic oral biofilms can demineralize the enamel-apatite on teeth, causing dental caries (tooth decay). Current antimicrobials have low efficacy and do not target the protective matrix and acidic pH within the biofilm. Recently, catalytic nanoparticles were shown to disrupt biofilms but lacked a stabilizing coating required for clinical applications. Here, we report dextran-coated iron oxide nanoparticles termed nanozymes (Dex-NZM) that display strong catalytic (peroxidase-like) activity at acidic pH values, target biofilms with high specificity, and prevent severe caries without impacting surrounding oral tissues in vivo. Nanoparticle formulations were synthesized with dextran coatings (molecular weights from 1.5 to 40 kDa were used), and their catalytic performance and bioactivity were assessed. We found that 10 kDa dextran coating provided maximal catalytic activity, biofilm uptake, and antibiofilm properties. Mechanistic studies indicated that iron oxide cores are the source of catalytic activity, whereas dextran on the nanoparticle surface provided stability without blocking catalysis. Dextran-coating facilitated NZM incorporation into exopolysaccharides (EPS) structure and binding within biofilms, which activated hydrogen peroxide (H₂O₂) for localized bacterial killing and EPS-matrix breakdown. Surprisingly, dextran coating enhanced selectivity toward biofilms while avoiding binding to gingival cells. Furthermore, Dex-NZM/H₂O₂ treatment significantly reduced the onset and severity of caries lesions (vs control or either Dex-NZM or H₂O₂ alone) without adverse effects on gingival tissues or oral microbiota diversity in vivo. Therefore, dextran-coated nanozymes have potential as an alternative treatment to control tooth decay and possibly other biofilm-associated diseases.

Targeting of p32 in peritoneal carcinomatosis with intraperitoneal linTT1 peptide-guided pro-apoptotic nanoparticles

Gastrointestinal and gynecological malignancies disseminate in the peritoneal cavity - a condition known as peritoneal carcinomatosis (PC). Intraperitoneal (IP) administration can be used to improve therapeutic index of anticancer drugs used for PC treatment. Activity of IP anticancer drugs can be further potentiated by encapsulation in nanocarriers and/or affinity targeting with tumor-specific affinity ligands, such as tumor homing peptides. Here we evaluated a novel tumor penetrating peptide, linTT1 (AKRGARSTA), as a PC targeting ligand for nanoparticles. We first demonstrated that the primary homing receptor for linTT1, p32 (or gC1qR), is expressed on the cell surface of peritoneal carcinoma cell lines of gastric (MKN-45P), ovarian (SKOV-3), and colon (CT-26) origin, and that peritoneal tumors in mice and clinical peritoneal carcinoma explants express p32 protein accessible from the IP space. Iron oxide nanoworms (NWs) functionalized with the linTT1 peptide were taken up and routed to mitochondria in cultured PC cells. NWs functionalized with linTT1 peptide in tandem with a pro-apoptotic [D(KLAKLAK)2] peptide showed p32-dependent cytotoxicity in MKN-45P, SKOV-3, and CT-26 cells. Upon IP administration in mice bearing MKN-45P, SKOV-3, and CT-26 tumors, linTT1-functionalized NWs showed robust homing and penetration into malignant lesions, whereas only a background accumulation was seen in control tissues. In tumors, the linTT1-NW accumulation was seen predominantly in CD31-positive blood vessels, in LYVE-1-positive lymphatic structures, and in CD11b-positive tumor macrophages. Experimental therapy of mice bearing peritoneal MKN-45P xenografts and CT-26 syngeneic tumors with IP linTT1-D(KLAKLAK)2-NWs resulted in significant reduction of weight of peritoneal tumors and significant decrease in the number of metastatic tumor nodules, whereas treatment with untargeted D(KLAKLAK)2-NWs had no effect. Our data show that targeting of p32 with linTT1 tumor-penetrating peptide improves tumor selectivity and antitumor efficacy of IP pro-apoptotic NWs. P32-directed intraperitoneal targeting of other anticancer agents and nanoparticles using peptides and other affinity ligands may represent a general strategy to increase their therapeutic index.

Magnetically Guided Viral Transduction of Gene-Based Sensitization for Localized Photodynamic Therapy To Overcome Multidrug Resistance in Breast Cancer Cells

Chemotherapy represents a conventional treatment for many cancers at different stages and is either solely prescribed or concomitant to surgery, radiotherapy, or both. However, treatment is tempered in instances of acquired drug resistance in response to either chemotherapy or targeted therapy, leading to therapeutic failure. To overcome this challenge, many studies focus on how cancer cells manipulate their genomes and metabolism to prevent drug influx and facilitate the efflux of accumulated chemotherapy drugs. Herein, we demonstrate magnetic adeno-associated virus serotype 2 (ironized AAV2) has an ability to be magnetically guided and transduce the photosensitive KillerRed protein to enable photodynamic therapy irrespective of drug resistance.

Nanoparticles and clinically applicable cell tracking

In vivo cell tracking has emerged as a much sought after tool for design and monitoring of cell-based treatment strategies. Various techniques are available for pre-clinical animal studies, from which much has been learned and still can be learned. However, there is also a need for clinically translatable techniques. Central to in vivo cell imaging is labelling of cells with agents that can give rise to signals in vivo, that can be detected and measured non-invasively. The current imaging technology of choice for clinical translation is MRI in combination with labelling of cells with magnetic agents. The main challenge encountered during the cell labelling procedure is to efficiently incorporate the label into the cell, such that the labelled cells can be imaged at high sensitivity for prolonged periods of time, without the labelling process affecting the functionality of the cells. In this respect, nanoparticles offer attractive features since their structure and chemical properties can be modified to facilitate cellular incorporation and because they can carry a high payload of the relevant label into cells. While these technologies have already been applied in clinical trials and have increased the understanding of cell-based therapy mechanism, many challenges are still faced.

Membrane mimetic surface functionalization of nanoparticles: methods and applications

Nanoparticles (NPs), due to their size-dependent physical and chemical properties, have shown remarkable potential for a wide range of applications over the past decades. Particularly, the biological compatibilities and functions of NPs have been extensively studied for expanding their potential in areas of biomedical application such as bioimaging, biosensing, and drug delivery. In doing so, surface functionalization of NPs by introducing synthetic ligands and/or natural biomolecules has become a critical component in regard to the overall performance of the NP system for its intended use. Among known examples of surface functionalization, the construction of an artificial cell membrane structure, based on phospholipids, has proven effective in enhancing biocompatibility and has become a viable alternative to more traditional modifications, such as direct polymer conjugation. Furthermore, certain bioactive molecules can be immobilized onto the surface of phospholipid platforms to generate displays more reminiscent of cellular surface components. Thus, NPs with membrane-mimetic displays have found use in a range of bioimaging, biosensing, and drug delivery applications. This review herein describes recent advances in the preparations and characterization of integrated functional NPs covered by artificial cell membrane structures and their use in various biomedical applications.

Inorganic nanocrystals as contrast agents in MRI: synthesis, coating and introduction of multifunctionality

Inorganic nanocrystals have myriad applications in medicine, including their use as drug or gene delivery complexes, therapeutic hyperthermia agents, in diagnostic systems and as contrast agents in a wide range of medical imaging techniques. In MRI, nanocrystals can produce contrast themselves, with iron oxides having been the most extensively explored, or can be given a coating that generates MR contrast, for example gold nanoparticles coated with gadolinium chelates. These MR-active nanocrystals can be used for imaging of the vasculature, liver and other organs, as well as molecular imaging, cell tracking and theranostics. As a result of these exciting applications, the synthesis and rendering of these nanocrystals as water soluble and biocompatible are therefore highly desirable. We discuss aqueous phase and organic phase methods for the synthesis of inorganic nanocrystals, such as gold, iron oxides and quantum dots. The pros and cons of the various methods are highlighted. We explore various methods for making nanocrystals biocompatible, i.e. direct synthesis of nanocrystals coated with biocompatible coatings, ligand substitution, amphiphile coating and embedding in carrier matrices that can be made biocompatible. Various examples are highlighted and their applications explained. These examples signify that the synthesis of biocompatible nanocrystals with controlled properties has been achieved by numerous research groups and can be applied to a wide range of applications. Therefore, we expect to see reports of preclinical applications of ever more complex MRI-active nanoparticles and their wider exploitation, as well as in novel clinical settings.

Chains, sheets, and droplets: assemblies of hydrophobic gold nanocrystals with saturated phosphatidylcholine lipid and squalene

Assemblies of saturated 1,2-diacylphosphatidylcholine lipid and hydrophobic dodecanethiol-capped 1.8 nm diameter gold nanocrystals were studied as a function of lipid chain length and the addition of the naturally occurring oil, squalene. The gold nanocrystals formed various lipid-stabilized agglomerates, sometimes fusing with lipid vesicle bilayers. The nanocrystal assembly structure depended on the hydrocarbon chain length of the lipid fatty acids. The lipid with the shortest fatty acid length studied, dilauroylphosphatidylcholine, created extended chains of gold nanocrystals. The lipid with slightly longer fatty acid chains created planar sheets of nanocrystals. Further increases of the fatty acid chain length led to spherical agglomerates. The inclusion of squalene led to lipid- and nanocrystal-coated oil droplets.