Polysaccharide-modified iron oxide nanoparticles as an effective magnetic affinity adsorbent for bovine serum albumin

Tamarindus indica seed polysaccharide-copper nanocomposite: An innovative solution for green environment and antimicrobial studies

The purpose of this study was to synthesize ecofriendly nano-composite in which agricultural waste (seeds of Tamarindus indica) was used to synthesize tamarind seed polysaccharides (TSP) and its composite with copper nanoparticles (Cu-NPs) for the purpose of green and clean environment as well as reduction of green-house gases. Confirmation of extracted TSP, synthesized nanocomposite was carried out using FTIR, SEM, PXRD and EDX techniques. In FTIR analysis TSP gives a strong broad peak at 3331 cm-1 due to -OH group and in case of composite its intensity is reduced which might be due to the interactions between -OH and Cu+2 ions. SEM analysis gives that TSP have irregular and rough surface while Cu-NPs exhibited spherical morphology and composite showed clustering of spherical shape to rough surface. EDX analysis quantitatively represented copper having atomic ratio 0.57 % which confirms the synthesis of composite. Furthermore, synthesized composite demonstrated excellent antibacterial activity against gram-positive (S.aureus) and gram-negative bacteria (E.coli) even greater than standard medicine (ciprofloxacin). From this study it was revealed that agriculture waste can be utilized to make environment green as well as synthesized composite from agricultural waste seed also displayed excellent antimicrobial activities which directs that they can be utilized in medical field. This study aims to assess the antimicrobial properties of the nanocomposite, aiming to contribute to the development of effective antimicrobial agents. Through these objectives, the research seeks to bridge the gap between green technology and antimicrobial efficacy, offering a promising avenue for both environmental conservation and healthcare advancements.

Adsorption of proteins on oral Zn2+ doped iron oxide nanoparticles in mouse stomach and in vitro: triggering nanoparticle aggregation

Oral route is one of the most important portals of nanoparticle entry to the body. However, in vivo protein corona formed in the gastrointestinal tract has not been studied owing to the difficulty for the recovery of nanoparticles from the in vivo environment. In this study, by using the magnetic property of iron oxide nanoparticles (Fe3O4 NPs) and Zn2+ doped iron oxide nanoparticles (Zn0.4Fe2.6O4 NPs), the nanoparticles were separated from the gastric fluid after oral administration in mice. The effects of Zn2+ doping and static magnetic field (SMF) treatment on the protein adsorption on the nanoparticles were investigated in vitro and in vivo. Zn2+ doping decreases the adsorption of pepsin on the nanoparticles in vitro and affects the composition of the protein corona in vivo and enhances protein adsorption-induced aggregation of the nanoparticles in vitro and in vivo. SMF treatment affects the composition of the protein corona of Fe3O4 NPs and Zn0.4Fe2.6O4 NPs, and enhances the aggregation of Fe3O4 NPs and Zn0.4Fe2.6O4 NPs in vivo. Furthermore, the results demonstrate that electrostatic attraction is the crucial force to drive adsorption of proteins on Fe3O4 NPs and Zn0.4Fe2.6O4 NPs and protein adsorption-induced change in the surface charge of nanoparticles plays an important role in the pH-dependent aggregation of the nanoparticles. In addition, the work provides the evidence that the protein adsorption-induced aggregation of Fe3O4 NPs and Zn0.4Fe2.6O4 NPs has no effect on their magnetic susceptibility. The results highlight that Zn0.4Fe2.6O4 NPs may be used as a potential oral magnetic resonance imaging contrast agent in diagnosis of gastrointestinal disease.

Magnetic iron oxide nanoparticles for imaging, targeting and treatment of primary and metastatic tumors of the brain

Magnetic nanoparticles in general, and iron oxide nanoparticles in particular, have been studied extensively during the past 20 years for numerous biomedical applications. The main applications of these nanoparticles are in magnetic resonance imaging (MRI), magnetic targeting, gene and drug delivery, magnetic hyperthermia for tumor treatment, and manipulation of the immune system by macrophage polarization for cancer treatment. Recently, considerable attention has been paid to magnetic particle imaging (MPI) because of its better sensitivity compared to MRI. In recent years, MRI and MPI have been combined as a dual or multimodal imaging method to enhance the signal in the brain for the early detection and treatment of brain pathologies. Because magnetic and iron oxide nanoparticles are so diverse and can be used in multiple applications such as imaging or therapy, they have attractive features for brain delivery. However, the greatest limitations for the use of MRI/MPI for imaging and treatment are in brain delivery, with one of these limitations being the brain-blood barrier (BBB). This review addresses the current status, chemical compositions, advantages and disadvantages, toxicity and most importantly the future directions for the delivery of iron oxide based substances across the blood-brain barrier for targeting, imaging and therapy of primary and metastatic tumors of the brain.

Structure characterization of low molecular weight sulfate Ulva polysaccharide and the effect of its derivative on iron deficiency anemia

Sulfate Ulva polysaccharide with low molecular weight was prepared by enzymatic method and name SUE. The structural characterization of SUE and the effect of its derivative SUE-iron (III) on iron deficiency anemia were studied. Results showed SUE with molecular weight of 178 kDa were consisted of 57.9% rhamnose, 12.1% glucose, 16.3% glucuronic acid, and 13.7% xylose. The backbone contained (1 → 3, 4)-linked rhamnose, (1 → 4)-linked xylose, (1 → 6)-linked glucose and sulfate substitution was at C-3 of rhamnose. Due to high contents of sulfate group (23.7 ± 1.1%) and uronic acid, SUE-iron (III) with 20.3% iron content was synthesized. In order to evaluate the effects of SUE-iron (III) supplementation, an IDA animal model was created. After iron supplement administration, the SUE‑iron (III) showed effective effect on returning hemoglobin, red blood cells, serum iron, and erythropoietin to the normal levels. The hematological index of rats showed no difference from that in positive group. Besides, SUE-iron (III) is beneficial to alleviate inflammatory damage caused by IDA. These suggest that SUE-iron (III) might be exploited as safe and effective new iron supplement.

Magnetically Guided Self-Assembled Protein Micelles for Enhanced Delivery of Dasatinib to Human Triple-Negative Breast Cancer Cells

Magnetic nanocarriers are useful in targeted cancer therapy. Dasatinib (DAS)-loaded magnetic micelles were prepared for magnetically guided drug delivery. The magnetic nanoplatform is composed of hydrophobic oleic acid-coated magnetite (Fe₃O₄) core along with DAS encapsulated in amphiphilic zein-lactoferrin self-assembled polymeric micelles. Transmission electron microscope analysis manifested formation of these magnetic micelles with a mean diameter of about 100 nm. In addition, drug-loaded magnetic micelles displayed a saturation magnetization of about 10.01 emu.g^-1 with a superparamagnetic property. They also showed good in vitro serum stability and hemocompatibility accompanied with a sustained release of DAS in acidic pH. More importantly, they exhibited 1.35-fold increase in their in vitro cytotoxicity against triple-negative human breast cancer cell line (MDA-MB-231) using an external magnetic field compared to drug-loaded magnetic micelles in the absence of a magnetic field. Enhanced inhibition of p-c-Src protein expression level and in vitro cellular migration under the effect of magnetic field was noted owing to the dual-targeting strategy offered by the presence of a magnetic sensitive core, as well as the active targeting property of lactoferrin corona. Taken all together, these results suggest that DAS-loaded magnetic micelles possess a great potential for targeted therapy of breast cancer.

The role played by modified bioinspired surfaces in interfacial properties of biomaterials

The success of a biomaterial relies on an appropriate interaction between the surface of that biomaterial and the surrounding environment; more specifically, the success of a biomaterial depends on how fluids, proteins, and cells interact with the foreign material. For this reason, the surface properties of biomaterial, such as composition, charge, wettability, and roughness, must be optimized for a desired application to be achieved. In this review we highlight different bioinspired approaches that are used to manipulate and fine-tune the interfacial properties of biomaterials. Inspired by noteworthy natural processes, researchers have developed materials with a functional anatomy that range from hierarchical hybrid structures to self-cleaning interfaces. In this review we focus on (1) the creation of particles and modified surfaces inspired by the structure and composition of biogenic mineralized tissues, (2) the development of biofunctional coatings, (3) materials inspired by biomembranes and proteins, and (4) the design of superwettable materials. Our intention is to point out different bioinspired methodologies that have been used to design materials for biomedical applications and to discuss how interfacial properties modified by manipulation of these materials determine their final biological response. Our objective is to present future research directions and to highlight the potential of bioinspired materials. We hope this review will provide an understanding of the interplay between interfacial properties and biological response so that successful biomaterials can be achieved.

Synthesis and characterization of magnetite nanoparticles having different cover layer and investigation of cover layer effect on the adsorption of lysozyme and bovine serum albumin

In this study, differently coated superparamagnetic Fe₃O₄ (magnetite) nanoparticles were synthesized, characterized and used for lysozyme (Ly) and bovine serum albumin (BSA) adsorption. SiO₂, carbon nanotubes (CNTs) and graphene were used for covering the readily synthesized magnetite nanoparticles to elucidate the effect of cover layer on the protein adsorption kinetics and capacities of nanostructure. XRD, FTIR, AFM, SEM, VSM and fluorescence measurements were used for the characterization of the samples and investigating the adsorption kinetics of Ly and BSA by these nanoparticles. The average particle size of the Fe₃O₄ nanoparticles are approximately found as 10nm and VSM measurement shows that the Fe₃O₄ particles have superparamagnetic behavior with no hysteresis and remnant. The adsorption kinetic of proteins on nanosized material is followed via fluorescence method. All the nanostructures with different cover layers obey pseudo first order kinetics and SiO₂ coated nanoparticles show the fastest kinetics and capabilities for Ly and BSA adsorption.

Designed synthesis and surface engineering strategies of magnetic iron oxide nanoparticles for biomedical applications

Iron oxide nanoparticles (NPs) hold great promise for future biomedical applications because of their magnetic properties as well as other intrinsic properties such as low toxicity, colloidal stability, and surface engineering capability. Numerous related studies on iron oxide NPs have been conducted. Recent progress in nanochemistry has enabled fine control over the size, crystallinity, uniformity, and surface properties of iron oxide NPs. This review examines various synthetic approaches and surface engineering strategies for preparing naked and functional iron oxide NPs with different physicochemical properties. Growing interest in designed and surface-engineered iron oxide NPs with multifunctionalities was explored in in vitro/in vivo biomedical applications, focusing on their combined roles in bioseparation, as a biosensor, targeted-drug delivery, MR contrast agents, and magnetic fluid hyperthermia. This review outlines the limitations of extant surface engineering strategies and several developing strategies that may overcome these limitations. This study also details the promising future directions of this active research field.

Antimicrobial peptides: Possible anti-infective agents

Multidrug-resistant bacterial, fungal, viral, and parasitic infections are major health threats. The Infectious Diseases Society of America has expressed concern on the decrease of pharmaceutical companies working on antibiotic research and development. However, small companies, along with academic research institutes, are stepping forward to develop novel therapeutic methods to overcome the present healthcare situation. Among the leading alternatives to current drugs are antimicrobial peptides (AMPs), which are abundantly distributed in nature. AMPs exhibit broad-spectrum activity against a wide variety of bacteria, fungi, viruses, and parasites, and even cancerous cells. They also show potential immunomodulatory properties, and are highly responsive to infectious agents and innate immuno-stimulatory molecules. In recent years, many AMPs have undergone or are undergoing clinical development, and a few are commercially available for topical and other applications. In this review, we outline selected anion and cationic AMPs which are at various stages of development, from preliminary analysis to clinical drug development. Moreover, we also consider current production methods and delivery tools for AMPs, which must be improved for the effective use of these agents.

An extracellular polymer at the interface of magnetic bioseparations

FucoPol, a fucose-containing extracellular polysaccharide (EPS) produced by bacterium Enterobacter A47 using glycerol as the carbon source, was employed as a coating material for magnetic particles (MPs), which were subsequently functionalized with an artificial ligand for the capture of antibodies. The performance of the modified MPs (MP-EPS-22/8) for antibody purification was investigated using direct magnetic separation alone or combined with an aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and dextran. In direct magnetic capturing, and using pure protein solutions of human immunoglobulin G (hIgG) and bovine serum albumin (BSA), MP-EPS-22/8 bound 120 mg hIgG g(-1) MPs, whereas with BSA only 10 ± 2 mg BSA g(-1) MPs was achieved. The hybrid process combining both the ATPS and magnetic capturing leads to a good performance for partitioning of hIgG in the desired phase as well as recovery by the magnetic separator. The MPs were able to bind 145 mg of hIgG g(-1) of particles which is quite high when compared with direct magnetic separation. The theoretical maximum capacity was calculated to be 410 ± 15 mg hIgG adsorbed g(-1) MPs with a binding affinity constant of 4.3 × 10(4) M(-1). In multiple extraction steps, the MPs bound 92% of loaded hIgG with a final purity level of 98.5%. The MPs could easily be regenerated, recycled and re-used for five cycles with only minor loss of capacity. FucoPol coating allowed both electrostatic and hydrophobic interactions with the antibody contributing to enhance the specificity for the targeted products.

Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeLn)(3/4+)-γ-Fe2O3) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeLn)(3/4+)-γ-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)(3/4+)-γ-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)(3/4+)-γ-Fe2O3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H2O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes.

Synthesis, characterization, and application of Fe3O4@SiO2–NH2 nanoparticles

Synthesis of Fe₃O₄@SiO₂–NH₂ nanoparticles by a mild and time-saving method and the application in separation of ovotransferrin were studied.

Glycosaminoglycan-targeted iron oxide nanoparticles for magnetic resonance imaging of liver carcinoma

To develop an efficient probe for targeted magnetic resonance (MR) imaging of liver carcinoma, the surface modification of superparamagnetic iron oxide nanoparticles (SPIONs) was carried out by conjugating a naturally-occurring glycosaminoglycan with specific biological recognition to human hepatocellular liver carcinoma (HepG2) cells. These modified SPIOs have good water dispersibility, superparamagnetic property, cytocompatibility and high magnetic relaxivity for MR imaging. When incubated with HepG2 cells, they demonstrated significant cellular uptake and specific accumulation, as confirmed by Prussian blue staining and confocal microscopy. The in vitro MR imaging of HepG2 cells and in vivo MR imaging of HepG2 tumors confirmed their effectiveness for targeted MR imaging of liver carcinoma.

Application of iron magnetic nanoparticles in protein immobilization

Due to their properties such as superparamagnetism, high surface area, large surface-to-volume ratio, easy separation under external magnetic fields, iron magnetic nanoparticles have attracted much attention in the past few decades. Various modification methods have been developed to produce biocompatible magnetic nanoparticles for protein immobilization. This review provides an updated and integrated focus on the fabrication and characterization of suitable magnetic iron nanoparticle-based nano-active materials for protein immobilization.

Preparation and characterization of pH- and temperature-responsive nanocomposite double network hydrogels

A methodology is described for the preparation of pH- and temperature-responsive double network (DN) hydrogels with poly(N-isopropylacrylamide) (PNIPAM) as a tightly crosslinked 1st network, polyacrylic acid (PAA) as a loosely crosslinked 2nd network and graphene oxide (GO) as an additive. GO sheets were first prepared via an oxidation reaction and then dispersed in NIPAM aqueous solution via silanization. Free-radical polymerization of NIPAM was carried out at 20 °C in a water bath, and then subjected to UV light, leading to the formation of pH- and temperature-responsive PNIPAM/AA/GO DN hydrogels. The effects of GO sheets and AA contents on various physical properties were investigated. Results show that PNIPAM/AA/GO hydrogels undergo a large volumetric change in response to temperature. It also exhibits significantly fast swelling/deswelling compared with conventional PNIPAM hydrogel. Moreover, the PNIPAM/AA/GO hydrogels have a much better mechanical property than the conventional PNIPAM hydrogels.

Atomic force microscopy and analytical ultracentrifugation for probing nanomaterial protein interactions

Upon contact with the human body, nanomaterials are known to interact with the physiological surroundings, especially with proteins. In this context, we explored analytical methods to provide biologically relevant information, in particular for manufactured nanomaterials as produced by the chemical industry. For this purpose, we selected two batches of SiO(2) nanoparticles as well as four batches of CeO(2) nanoparticles, each of comparably high chemical purity and similar physicochemical properties. Adsorption of serum proteins and bovine serum albumin (BSA) was quantified by SDS-PAGE in combination with densitometry and further investigated by atomic force microscopy (AFM) and analytical ultracentrifugation (AUC). The protein adsorption to SiO(2) nanoparticles was below the limit of detection, regardless of adjusting pH or osmolality to physiological conditions. In contrast, the four CeO(2) nanomaterials could be classified in two groups according to half-maximal protein adsorption. Measuring the work of adhesion and indention by AFM for the BSA-binding CeO(2) nanomaterials revealed the same classification, pointing to alterations in shape of the adsorbed protein. The same trend was also reflected in the agglomeration behavior/dispersibility of the four CeO(2) nanomaterials as revealed by AUC. We conclude that even small differences in physicochemical particle properties may nevertheless lead to differences in protein adsorption, possibly implicating a different disposition and other biological responses in the human body. Advanced analytical methods such as AFM and AUC may provide valuable additional information in this context.

Bovine serum albumin adsorption to iron-oxide coated sands can change microsphere deposition mechanisms

Particulate colloids often occur together with proteins in sewage-impacted water. Using Bovine Serum Albumin (BSA) as a surrogate for protein in sewage, column experiments investigating the capacity of iron-oxide coated sands to remove latex microspheres from water revealed that microsphere attenuation mechanisms depended on antecedent BSA coverage. Dual pulse experiment (DPE) results suggested that where all BSA was adsorbed, subsequent multiple pore volume microsphere breakthrough curves reflected progressively reduced colloid deposition rates with increasing adsorbed BSA content. Modeling colloid responses suggested adsorption of 1 μg BSA generated the same response as blockage by between 7.1 × 10(8) and 2.3 × 10(9) deposited microspheres. By contrast, microsphere responses in DPEs where BSA coverage of the deposition sites approached/reached saturation revealed the coated sand maintained a finite capacity to attenuate microspheres, even when incapable of further BSA adsorption. Subsequent microsphere breakthrough curves demonstrated the matrix's colloid attenuation capacity progressively increased with continued microsphere deposition. Experimental findings suggested BSA adsorption on the sand surface approaching/reaching saturation generated attractive deposition sites for colloids, which became progressively more attractive with further colloid deposition (filter ripening). Results demonstrate that adsorption of a single type of protein may either enhance or inhibit colloid mobility in saturated porous media.

Selective recognition and separation of nucleosides using carboxymethyl-β-cyclodextrin functionalized hybrid magnetic nanoparticles

A novel magnetic nanoadsorbent (CMCD-APTS-MNPs) containing the superparamagnetic and molecular recognition properties was synthesized by grafting carboxymethyl-β-cyclodextrin (CM-β-CD) on 3-aminopropyltriethoxysile (APTS) modified Fe(3)O(4) nanoparticles. The feasibility of using CMCD-APTS-MNPs as magnetic nanoadsorbent for selective adsorption of adenosine (A) and guanosine (G) based on inclusion and molecular recognition was demonstrated. The as-synthesized magnetic nanoparticles were characterized by TEM, FTIR and TGA analyses. The effects of pH and initial nucleoside concentrations on the adsorption behavior were studied. The complexation of CMCD-APTS-MNPs with both nucleosides was found to follow the Langmuir adsorption isotherm. The CMCD-APTS-MNPs showed a higher adsorption ability and selectivity for G than A under identical experimental conditions, which results from the ability of selective binding and recognition of the immobilized CM-β-CD towards G. The driving force of the separation between G and A is through the different weak interaction with grafted CM-β-CD, i.e., hydrogen bond interaction, which is evidenced by different inclusion equilibrium constants and FTIR analyses of inclusion complexes between grafted cyclodextrin and the guest molecules. Our results indicated that this nanoadsorbent would be a promising tool for easy, fast and selective separation, analysis of nucleosides and nucleotides in biological samples.

Physicochemical properties and inhibition effect on iron deficiency anemia of a novel polysaccharide-iron complex (LPPC)

Porphyran (P) was extracted from red algae Porphyra by boiling water. A novel polysaccharide-iron complex (LPPC) was prepared under the alkaline condition by adding a ferric chloride solution to the low molecular weight porphyran (LP) solution. Physicochemical properties and inhibition effect on iron deficiency anemia of this complex were studied. The content of iron(III) in the complex is 21.57% determined with iodometry. The results indicate that LPPC was product required. The complex can increase red blood cell count (RBC), hemoglobin (Hb), Serum iron (SI), spleen index, spleen mass and mass of mice with iron deficiency anemia (IDA). Although the structure and deeper mechanisms on hemolytic anemia of LPPC should be further studied, LPPC is hoped to be developed as a late-model iron supplement which has a synergism on anemia.

Development of peptide and protein nanotherapeutics by nanoencapsulation and nanobioconjugation

The targeted delivery of therapeutic peptide by nanocarriers systems requires the knowledge of interactions of nanomaterials with the biological environment, peptide release, and stability of therapeutic peptides. Therapeutic application of nanoencapsulated peptides are increasing exponentially and >1000 peptides in nanoencapsulated form are in different clinical/trial phase. This review covers current scenario of therapeutic protein and peptides encapsulation on polymer to metallic nanocarriers including methods of protein encapsulation, peptide bioconjugation on nanoparticles, stability enhancement of encapsulated proteins and its biomedical applications.

Interaction of metal oxide nanoparticles with lung surfactant protein A

The alveolar lining fluid (ALF) covering the respiratory epithelium of the deep lung is the first biological barrier encountered by nanoparticles after inhalation. We here report for the first time significant differences for metal oxide nanoparticles to the binding of surfactant protein A (SP-A), the predominant protein component of ALF. SP-A is a physiologically most relevant protein and provides important biological signals. Also, it is involved in the lung's immune defence, controlling e.g. particle binding, uptake or transcytosis by epithelial cells and macrophages. In our study, we could prove different particle-protein interaction for eight different nanoparticles, whereas particles of the same bulk material revealed different adsorption patterns. In contrast to other proteins as bovine serum albumin (BSA), SP-A does not seem to significantly deagglomerate large agglomerates of particles, indicating different adsorption mechanisms as in the well-investigated model protein BSA. These findings may have important consequences for biological fate and toxicological effects of inhaled nanomaterials.

In situ crosslinkable hydrogel formed from a polysaccharide-based hydrogelator

In situ crosslinkable hydrogel formed from an amphiphilic amylopectin-based hydrogelator in aqueous solution was investigated with respect to its viscoelasticity, structure as well as protein encapsulation and release. Different from the physical hydrogel formed from an aqueous amylopectin system of sufficiently high concentration, such a hydrogel could be formed rapidly at room temperature and exhibit enhanced viscoelastic properties, mechanical strength, and shear thinning behavior. In addition, it has a more complex network structure with a higher fractal dimension due to intermolecular hydrophobic interactions and macromolecular chain entanglements. By circular dichroism analyses and in vitro release experiments, this hydrogel material was found to have a great potential as new matrix for the entrapment and sustained release of bovine serum albumin.

Magnetic particle-based hybrid platforms for bioanalytical sensors

Biomagnetic nano and microparticles platforms have attracted considerable interest in the field of biological sensors due to their interesting physico-chemical properties, high specific surface area, good mechanical stability and opportunities for generating magneto-switchable devices. This review discusses recent advances in the development and characterization of active biomagnetic nanoassemblies, their interaction with biological molecules and their use in bioanalytical sensors.

Superparamagnetic iron oxide nanoparticles encapsulated in biodegradable thermosensitive polymeric micelles: toward a targeted nanomedicine suitable for image-guided drug delivery

Superparamagnetic iron oxide nanoparticles (SPIONs) have been receiving great attention lately due to their various biomedical applications, such as in MR imaging and image guided drug delivery. However, their systemic administration still remains a challenge. In this study, the ability of biodegradable thermosensitive polymeric micelles to stably encapsulate hydrophobic oleic-acid-coated SPIONs (diameter 5-10 nm) was investigated, to result in a system fulfilling the requirements for systemic administration. The micelles were composed of amphiphilic, thermosensitive, and biodegradable block copolymers of poly(ethylene glycol)-b-poly[N-(2-hydroxypropyl) methacrylamide dilactate] (mPEG-b-p(HPMAm-Lac2)). The encapsulation was performed by addition of one volume of SPIONs in THF to nine volumes of a cold aqueous mPEG-b-p(HPMAm-Lac2) solution (0 degrees C; below the cloud point of the polymer), followed by rapid heating of the resulting mixture to 50 degrees C, to induce micelle formation ("rapid heating" procedure). Dynamic light scattering (DLS) measurements revealed that approximately 200 nm particles (PDI=0.2) were formed, while transmission electron microscopy (TEM) analysis demonstrated that clusters of SPIONs were present in the core of the micelles. A maximum loading of 40% was obtained, while magnetic resonance imaging (MRI) scanning of the samples demonstrated that the SPION-loaded micelles had high r2 and r2* relaxivities. Furthermore, the r2* values were found to be at least 2-fold higher than the r2 values, confirming the clustering of the SPIONs in the micellar core. The particles showed excellent stability under physiological conditions for 7 days, even in the presence of fetal bovine serum. This, together with their ease of preparation and their size of approximately 200 nm, makes these systems highly suitable for image-guided drug delivery.