Carboxymethyl-Dextran-Coated Superparamagnetic Iron Oxide Nanoparticles for Drug Delivery: Influence of the Coating Thickness on the Particle Properties

Abstract

Carboxymethyl-dextran (CMD)-coated iron oxide nanoparticles (IONs) are of great interest in nanomedicine, especially for applications in drug delivery. To develop a magnetically controlled drug delivery system, many factors must be considered, including the composition, surface properties, size and agglomeration, magnetization, cytocompatibility, and drug activity. This study reveals how the CMD coating thickness can influence these particle properties. ION@CMD are synthesized by co-precipitation. A higher quantity of CMD leads to a thicker coating and a reduced superparamagnetic core size with decreasing magnetization. Above 12.5–25.0 g L−1 of CMD, the particles are colloidally stable. All the particles show hydrodynamic diameters < 100 nm and a good cell viability in contact with smooth muscle cells, fulfilling two of the most critical characteristics of drug delivery systems. New insights into the significant impact of agglomeration on the magnetophoretic behavior are shown. Remarkable drug loadings (62%) with the antimicrobial peptide lasioglossin and an excellent efficiency (82.3%) were obtained by covalent coupling with the EDC/NHS (N-ethyl-N′-(3-(dimethylamino)propyl)carbodiimide/N-hydroxysuccinimide) method in comparison with the adsorption method (24% drug loading, 28% efficiency). The systems showed high antimicrobial activity with a minimal inhibitory concentration of 1.13 µM (adsorption) and 1.70 µM (covalent). This system successfully combines an antimicrobial peptide with a magnetically controllable drug carrier.

Screening of superparamagnetic iron oxide nanoparticles for their application in the human body: Influence of various coatings

“…SAXS profiles showed aggregation and primary particle sizes around 20 nm for all particles investigated (Figure 3). The highest aggregation is visible for BIONs at pH 7, which is in excellent agreement with DLS data and data from previous studies [52,75]. Even though this aggregation of nanomaterials is visible and makes it challenging to interpret the SAXS data, these results help to verify XRD data as well as TEM studies (Figure 1, Figure 2).…”

“…All plotted curves showed the typical sigmoidal shape of superparamagnetic particles with no magnetization at a magnetic field strength of 0.00 Oe [11,76]. The used BIONs have a saturation magnetization of ± 67.0 emu g -1 [52]. A slightly lower saturation magnetization of 62.0 emu g -1 can be seen for the dextran-coated particles.…”

“…Unterweger et al also observed that ≥100 g L -1 dextran could prevent the particles from forming agglomerates [62]. Nevertheless, compared to BIONs with an IEP at 7.10, the dextran-coating led to a shift of the IEP to a lower pH value and better stabilization around the IEP [52,69]. ION@PLGA had an IEP at pH 2.88 (Figure 2E, Table 1).…”

“…The sedimentation rates in a magnetic field increase with higher agglomeration and higher saturation magnetization of the particles [75]. In comparable conditions, BIONs sank with a sedimentation velocity of 1.15 mm s -1 [52]. As ION@Dex formed large agglomerates at physiological pH values, ION@Dex sank faster with a velocity of 2.20 mm s -1 .…”

“…Additionally, the morphology and particle diameter were determined with TEM. The diameters of BIONs coincide, dScherrer = 8.76 ± 0.87 nm and dTEM = 8.74 ± 1.61 nm [52]. Therefore, the coating thickness was calculated by subtracting dScherrer from dTEM.…”