Optimizing radiolabeling amine-functionalized silica nanoparticles using SarAr-NCS for applications in imaging and radiotherapy

An overview of nanoscale radionuclides and radiolabeled nanomaterials commonly used for nuclear molecular imaging and therapeutic functions

Recent advances in the field of nanotechnology applications in nuclear medicine offer the promise of better diagnostic and therapeutic options. In recent years, increasing efforts have been focused on developing nanoconstructs that can be used as core platforms for attaching medical radionuclides with different strategies for the purposes of molecular imaging and targeted drug delivery. This review article presents an introduction to some commonly used nanomaterials with zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structures, describes the various methods applied to radiolabeling of nanomaterials, and provides illustrative examples of application of the nanoscale radionuclides or radiolabeled nanocarriers in nuclear nanomedicine. Especially, the passive and active nanotargeting delivery of radionuclides with illustrating examples for tumor imaging and therapy was reviewed and summarized. The accurate and early diagnosis of cancer can lead to increased survival rates for different types of this disease. Although, the conventional single-modality diagnostic methods such as positron emission tomography/single photon emission computed tomography or MRI used for such purposes are powerful means; most of these are limited by sensitivity or resolution. By integrating complementary signal reporters into a single nanoparticulate contrast agent, multimodal molecular imaging can be performed as scalable images with high sensitivity, resolution, and specificity. The advent of radiolabeled nanocarriers or radioisotope-loaded nanomaterials with magnetic, plasmonic, or fluorescent properties has stimulated growing interest in the developing multimodality imaging probes. These new developments in nuclear nanomedicine are expected to introduce a paradigm shift in multimodal molecular imaging and thereby opening up an era of new diagnostic medical imaging agents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 251-285, 2019.

The Influence of Amino Group Position on Aryl Moiety of SarAr on Metal Complexation and Protein Labelling

New hexaazamacrobicyclic cage bi-functional chelators (BFCs), 1-N-(3-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (m-SarAr) and 1-N-(2-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (o-SarAr), were synthesised. Their complexation with selected transitions metal ions i.e. CuII, CoII, and CdII was investigated over a range of pH at micromolar concentrations. CuII was complexed by m-SarAr and o-SarAr rapidly within 5 min in pH range of 5–9 at ambient temperature. In contrast, the complexation of CoII and CdII by these ligands was slower. The conjugation efficiencies of p-SarAr, m-SarAr, and o-SarAr to bovine serum albumin (BSA) were compared under various reactions. Conditions were optimised to a molar ratio of BSA/N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC)/BFC of 1 : 250 : 50 in pH 5 buffer for 30 min at ambient temperature. Under these conditions, the average number of p-SarAr, m-SarAr, or o-SarAr attached to BSA were determined to be 2.21 ± 0.16, 4.90 × 10–1 ± 2.48 × 10–2, and 2.67 × 10–2 ± 2.67 × 10–3, respectively. This fundamental study clearly demonstrates that the position of the amine on the phenyl ring has a significant effect on the metal complexation and conjugation reactions with BSA.

Synthesis and surface functionalization of silica nanoparticles for nanomedicine

There are a wide variety of silica nanoformulations being investigated for biomedical applications. Silica nanoparticles can be produced using a wide variety of synthetic techniques with precise control over their physical and chemical characteristics. Inorganic nanoformulations are often criticized or neglected for their poor tolerance; however, extensive studies into silica nanoparticle biodistributions and toxicology have shown that silica nanoparticles may be well tolerated, and in some case are excreted or are biodegradable. Robust synthetic techniques have allowed silica nanoparticles to be developed for applications such as biomedical imaging contrast agents, ablative therapy sensitizers, and drug delivery vehicles. This review explores the synthetic techniques used to create and modify an assortment of silica nanoformulations, as well as several of the diagnostic and therapeutic applications.

Silica nanoparticles and polyethyleneimine (PEI)-mediated functionalization: a new method of PEI covalent attachment for siRNA delivery applications

Small-interfering RNA (siRNA) is a synthetic double-stranded RNA that consists of approximately 21 nucleotides (nts). It induces degradation of target mRNAs in a sequence-specific manner by the RNA interference (RNAi) mechanism. Thus, siRNAs offer a potential strategy for silencing mutated or defective genes that cause a variety of human diseases. The main obstacles of harnessing siRNAs as drugs are their inefficient delivery to cells and off-target effect making clinical applications very challenging. To address these issues, researchers have studied a variety of nanocarrier systems for siRNA delivery. This study presents the design, fabrication, and full characterization of innovative polyethyleneimine (PEI)-decorated polycationic 34.2 ± 4.2 nm silica (SiO2) NPs for siRNA-mediated gene silencing. More specifically, a new means of introduction (covalent mode of attachment) of the polycationic 25 kDa PEI polymer onto the SiO2 NP surface has been developed that makes use of an effective electrophilic double Michäel acceptor, divinyl sulfone (DVS). The resulting novel SiO2-PEI nanoparticles (SPEI NPs) have been fully characterized using a wide range of analytical, spectroscopic, and microscopic methods (TEM, DLS, ζ potential, elemental analysis (EA), XPS, TGA, and FTIR). Disclosing quite low cytotoxicity due to this unique mode of PEI covalent grafting, SPEI NPs/siRNA polyplexes have been successfully tested for the induction of gene silencing using dual-reporter luciferase transfected human osteosarcoma U2OS cells. The corresponding gene silencing data showed a clear correlation between PEI/siRNA ratios, siRNA concentration(s), and the level of gene silencing. Moreover, these SPEI NPs have been demonstrated to be thermodynamically stable with an ability to efficiently bind siRNAs and induce silencing for at least a one-year-long storage.