Iron oxide labelling of human mesenchymal stem cells in collagen hydrogels for articular cartilage repair

Ferrous/Ferric Ions Crosslinked Type II Collagen Multifunctional Hydrogel for Advanced Osteoarthritis Treatment

Osteoarthritis (OA) is a highly prevalent and intricate degenerative joint disease affecting an estimated 500 million individuals worldwide. Collagen-based hydrogels have sparked immense interest in cartilage tissue engineering, but substantial challenges persist in developing biocompatible and robust crosslinking strategies, as well as improving their effectiveness against the multifaceted nature of OA. Herein, a novel discovery wherein the simple incorporation of ferrous/ferric ions enables efficient dynamic crosslinking of type II collagen, leading to the development of injectable, self-healing hydrogels with 3D interconnected porous nanostructures, is unveiled. The ferrous/ferric ions crosslinked type II collagen hydrogels demonstrate exceptional physical properties, such as significantly enhanced mechanical strength, minimal swelling ratios, and remarkable resistance to degradation, while also exhibiting extraordinary biocompatibility and bioactivity, effectively promoting cell proliferation, adhesion, and chondrogenic differentiation. Additionally, the hydrogels reveal potent anti-inflammatory effects by upregulating anti-inflammatory cytokines while downregulating pro-inflammatory cytokines. In a rat model of cartilage defects, these hydrogels exhibit impressive efficacy, substantially accelerating cartilage tissue regeneration through enhanced collagen deposition and increased proteoglycan secretion. The innovative discovery of the multifunctional role of ferrous/ferric ions in endowing type II collagen hydrogels with a myriad of beneficial properties presents exciting prospects for developing advanced biomaterials with potential applications in OA.

An Updated Review on Advances in Hydrogel-Based Nanoparticles for Liver Cancer Treatment

More than 90% of all liver malignancies are hepatocellular carcinomas (HCCs), for which chemotherapy and immunotherapy are the ideal therapeutic choices. Hepatocellular carcinoma is descended from other liver diseases, such as viral hepatitis, alcoholism, and metabolic syndrome. Normal cells and tissues may suffer damage from common forms of chemotherapy. In contrast to systemic chemotherapy, localized chemotherapy can reduce side effects by delivering a steady stream of chemotherapeutic drugs directly to the tumor site. This highlights the significance of controlled-release biodegradable hydrogels as drug delivery methods for chemotherapeutics. This review discusses using hydrogels as drug delivery systems for HCC and covers thermosensitive, pH-sensitive, photosensitive, dual-sensitive, and glutathione-responsive hydrogels. Compared to conventional systemic chemotherapy, hydrogel-based drug delivery methods are more effective in treating cancer.

The immunogenic reaction and bone defect repair function of ε-poly-L-lysine (EPL)-coated nanoscale PCL/HA scaffold in rabbit calvarial bone defect

Tissue engineering is a promising strategy for bone tissue defect reconstruction. Immunogenic reaction, which was induced by scaffolds degradation or contaminating microorganism, influence cellular activity, compromise the efficiency of tissue engineering, or eventually lead to the failure of regeneration. Inhibiting excessive immune response through modulating scaffold is critical important to promote tissue regeneration. Our previous study showed that ε-poly-L-lysine (EPL)-coated nanoscale polycaprolactone/hydroxyapatite (EPL/PCL/HA) composite scaffold has enhanced antibacterial and osteogenic properties in vitro. However, the bone defect repair function and immunogenic reaction of EPL/PCL/HA scaffolds in vivo remains unclear. In the present study, three nanoscale scaffolds (EPL/PCL/HA, PCL and PCL/HA) were transplanted into rabbit paraspinal muscle pouches, and T helper type 1 (Th1), T helper type 2 (Th2), T helper type 17 (Th17), and macrophage infiltration were analyzed after 1 week and 2 weeks to detect their immunogenic reaction. Then, the different scaffolds were transplanted into rabbit calvarial bone defect to compare the bone defect repair capacities. The results showed that EPL/PCL/HA composite scaffolds decreased pro-inflammatory Th1, Th17, and type I macrophage infiltration from 1 to 2 weeks, and increased anti-inflammatory Th2 infiltration into the regenerated area at 2 weeks in vivo, when compared to PCL and PCL/HA. In addition, EPL/PCL/HA showed an enhanced bone repair capacity compared to PCL and PCL/HA when transplanted into rabbit calvarial bone defects at both 4 and 8 weeks. Hence, our results suggest that EPL could regulate the immunogenic reaction and promote bone defect repair function of PCL/HA, which is a promising agent for tissue engineering scaffold modulation.

Magnetic Nanodiscs-A New Promising Tool for Microsurgery of Malignant Neoplasms

Magnetomechanical therapy is one of the most perspective directions in tumor microsurgery. According to the analysis of recent publications, it can be concluded that a nanoscalpel could become an instrument sufficient for cancer microsurgery. It should possess the following properties: (1) nano- or microsized; (2) affinity and specificity to the targets on tumor cells; (3) remote control. This nano- or microscalpel should include at least two components: (1) a physical nanostructure (particle, disc, plates) with the ability to transform the magnetic moment to mechanical torque; (2) a ligand-a molecule (antibody, aptamer, etc.) allowing the scalpel precisely target tumor cells. Literature analysis revealed that the most suitable nanoscalpel structures are anisotropic, magnetic micro- or nanodiscs with high-saturation magnetization and the absence of remanence, facilitating scalpel remote control via the magnetic field. Additionally, anisotropy enhances the transmigration of the discs to the tumor. To date, four types of magnetic microdiscs have been used for tumor destruction: synthetic antiferromagnetic P-SAF (perpendicular) and SAF (in-plane), vortex Py, and three-layer non-magnetic-ferromagnet-non-magnetic systems with flat quasi-dipole magnetic structures. In the current review, we discuss the biological effects of magnetic discs, the mechanisms of action, and the toxicity in alternating or rotating magnetic fields in vitro and in vivo. Based on the experimental data presented in the literature, we conclude that the targeted and remotely controlled magnetic field nanoscalpel is an effective and safe instrument for cancer therapy or theranostics.

Superparamagnetic Iron Oxide Particles (VSOPs) Show Genotoxic Effects but No Functional Impact on Human Adipose Tissue-Derived Stromal Cells (ASCs)

Adipose tissue-derived stromal cells (ASCs) represent a capable source for cell-based therapeutic approaches. For monitoring a cell-based application in vivo, magnetic resonance imaging (MRI) of cells labeled with iron oxide particles is a common method. It is the aim of the present study to analyze potential DNA damage, cytotoxicity and impairment of functional properties of human (h)ASCs after labeling with citrate-coated very small superparamagnetic iron oxide particles (VSOPs). Cytotoxic as well as genotoxic effects of the labeling procedure were measured in labeled and unlabeled hASCs using the MTT assay, comet assay and chromosomal aberration test. Trilineage differentiation was performed to evaluate an impairment of the differentiation potential due to the particles. Proliferation as well as migration capability were analyzed after the labeling procedure. Furthermore, the labeling of the hASCs was confirmed by Prussian blue staining, transmission electron microscopy (TEM) and high-resolution MRI. Below the concentration of 0.6 mM, which was used for the procedure, no evidence of genotoxic effects was found. At 0.6 mM, 1 mM as well as 1.5 mM, an increase in the number of chromosomal aberrations was determined. Cytotoxic effects were not observed at any concentration. Proliferation, migration capability and differentiation potential were also not affected by the procedure. Labeling with VSOPs is a useful labeling method for hASCs that does not affect their proliferation, migration and differentiation potential. Despite the absence of cytotoxicity, however, indications of genotoxic effects have been demonstrated.

Nanotextured silk fibroin/hydroxyapatite biomimetic bilayer tough structure regulated osteogenic/chondrogenic differentiation of mesenchymal stem cells for osteochondral repair

OBJECTIVES

Articular cartilage plays a vital role in bearing and buffering. Injured cartilage and subchondral bone repair is a crucial challenge in cartilage tissue engineering due to the peculiar structure of osteochondral unit and the requirement of osteogenic/chondrogenic bi-directional differentiation. Based on the bionics principle, a nanotextured silk fibroin (SF)-chondroitin sulphate (CS)/hydroxyapatite (HAp) nanowire tough bilayer structure was prepared for osteochondral repair.

METHODS

The SF-CS/HAp membrane was constructed by alcohol-induced β-sheet formation serving as the physical crosslink. Its osteochondral repairing capacity was evaluated by culturing bone marrow mesenchymal stem cells (BMSCs) in vitro and constructing a rat osteochondral defect model in vivo.

RESULTS

The bilayer SF-CS/HAp membrane with satisfactory mechanical properties similar to natural cartilage imitated the natural osteochondral unit structural layers and exerted the function of bearing and buffering timely after in vivo implantation. SF-CS layer upregulated the expression of chondrogenesis-related genes of BMSCs by surface nanotopography and sustained release CS. Meanwhile, nanotextured HAp layer assembled with nanowire endowed the membrane with an osteogenic differentiation tendency for BMSCs. In vivo results proved that the biomimetic bilayer structure dramatically promoted new cartilage formation and subchondral bone remodelling for osteochondral defect model after implantation.

CONCLUSIONS

The SF-CS/HAp biomimetic bilayer membrane provides a promising strategy for precise osteochondral repair.

Toxicity and Functional Impairment in Human Adipose Tissue-Derived Stromal Cells (hASCs) Following Long-Term Exposure to Very Small Iron Oxide Particles (VSOPs)

Magnetic nanoparticles (NPs), such as very small iron oxide NPs (VSOPs) can be used for targeted drug delivery, cancer treatment or tissue engineering. Another important field of application is the labelling of mesenchymal stem cells to allow in vivo tracking and visualization of transplanted cells using magnetic resonance imaging (MRI). For these NPs, however, various toxic effects, as well as functional impairment of the exposed cells, are described. The present study evaluates the influence of VSOPs on the multilineage differentiation ability and cytokine secretion of human adipose tissue derived stromal cells (hASCs) after long-term exposure. Human ASCs were labelled with VSOPs, and the efficacy of the labelling was documented over 4 weeks in vitro cultivation of the labelled cells. Unlabelled hASCs served as negative controls. Four weeks after labelling, adipogenic and osteogenic differentiation was histologically evaluated and quantified by polymerase chain reaction (PCR). Changes in gene expression of IL-6, IL-8, VEGF and caspase 3 were determined over 4 weeks. Four weeks after the labelling procedure, labelled and unlabelled hASCs did not differ in the gene expression of IL-6, IL-8, VEGF and caspase 3. Furthermore, the labelling procedure had no influence on the multidifferentiation ability of hASC. The percentage of labelled cells decreased during in vitro expansion over 4 weeks. Labelling with VSOPs and long-term intracellular disposition probably have no influence on the physiological functions of hASCs. This could be important for the future in vivo use of iron oxide NPs.

Preparation of Injectable Composite Hydrogels by Blending Poloxamers with Calcium Carbonate-Crosslinked Sodium Alginate

The effects of calcium carbonate-crosslinked sodium alginate on poloxamer hydrogels have been investigated. The mechanical strength, degradability, and thermal stability of hydrogels were characterized. The chemical and physical crosslinking in the composite hydrogels has resulted in an improvement of the compressive strength and elasticity of the hydrogels. These mixed hydrogels showed improved mechanical properties, elasticity, and stability as well as environmental responsiveness and injectability.

Aptamers Increase Biocompatibility and Reduce the Toxicity of Magnetic Nanoparticles Used in Biomedicine

Aptamer-based approaches are very promising tools in nanomedicine. These small single-stranded DNA or RNA molecules are often used for the effective delivery and increasing biocompatibility of various therapeutic agents. Recently, magnetic nanoparticles (MNPs) have begun to be successfully applied in various fields of biomedicine. The use of MNPs is limited by their potential toxicity, which depends on their biocompatibility. The functionalization of MNPs by ligands increases biocompatibility by changing the charge and shape of MNPs, preventing opsonization, increasing the circulation time of MNPs in the blood, thus shielding iron ions and leading to the accumulation of MNPs only in the necessary organs. Among various ligands, aptamers, which are synthetic analogs of antibodies, turned out to be the most promising for the functionalization of MNPs. This review describes the factors that determine MNPs’ biocompatibility and affect their circulation time in the bloodstream, biodistribution in organs and tissues, and biodegradation. The work also covers the role of the aptamers in increasing MNPs’ biocompatibility and reducing toxicity.

Mussel-Inspired Tough Hydrogel with In Situ Nanohydroxyapatite Mineralization for Osteochondral Defect Repair

Repairing osteochondral defects is a considerable challenge because it involves the breakdown of articular cartilage and underlying bone. Traditional hydrogels with a homogenized single-layer structure cannot fully restore the function of osteochondral cartilage tissue. In this study, a mussel-inspired hydrogel with a bilayer structure is developed to repair osteochondral defects. The hydrogel is synthesized by simultaneously polymerizing two layers using a one-pot method. The resulting upper and lower gelatin methacryloyl-polydopamine hydrogel layers are used as cartilage and subchondral bone repair layers, respectively. Polydopamine-induced hydroxyapatite in situ mineralization takes place in the lower layer to mimic the structure of subchondral bone. The bilayer hydrogel exhibits good mechanical properties for the synergistic effect of covalent and noncovalent bonds, as well as nanoreinforcement of mineralized hydroxyapatite. To improve the tissue-inducibility of hydrogels, transforming growth factor β₃ is immobilized in the upper layer to induce cartilage regeneration, while bone morphogenetic protein 2 is immobilized in the lower layer to induce bone regeneration. Bone and cartilage repair performance of the hydrogel is examined by implantation into a full-thickness cartilage defect of a rabbit knee joint. The bilayer-structure hydrogel promotes regeneration of osteochondral tissue, thus providing a new option for repair of osteochondral defects.

Viscoelasticity in natural tissues and engineered scaffolds for tissue reconstruction

Viscoelasticity of living tissues plays a critical role in tissue homeostasis and regeneration, and its implication in disease development and progression is being recognized recently. In this review, we first explored the state of knowledge regarding the potential application of tissue viscoelasticity in disease diagnosis. In order to better characterize viscoelasticity with local resolution and non-invasiveness, emerging characterization methods have been developed with the potential to be supplemented to existing facilities. To understand cellular responses to matrix viscoelastic behaviors in vitro, hydrogels made of natural polymers have been developed and the relationships between their molecular structure and viscoelastic behaviors, are elucidated. Moreover, how cells perceive the viscoelastic microenvironment and cellular responses including cell attachment, spreading, proliferation, differentiation and matrix production, have been discussed. Finally, some future perspective on an integrated mechanobiological comprehension of the viscoelastic behaviors involved in tissue homeostasis, cellular responses and biomaterial design are highlighted. STATEMENT OF SIGNIFICANCE: Tissue- or organ-scale viscoelastic behavior is critical for homeostasis, and the molecular basis and cellular responses of viscoelastic materials at micro- or nano-scale are being recognized recently. We summarized the potential applications of viscoelasticity in disease diagnosis enabled by emerging non-invasive characterization technologies, and discussed the underlying mechanism of viscoelasticity of hydrogels and current understandings of cell regulatory functions of them. With a growing understanding of the molecular basis of hydrogel viscoelasticity and recognition of its regulatory functions on cell behaviors, it is important to bring the clinical insights on how these characterization technologies and engineered materials may contribute to disease diagnosis and treatment. This review explains the basics in characterizing viscoelasticity with our hope to bridge the gap between basic research and clinical applications.

Long-Term Impact of Zinc Oxide Nanoparticles on Differentiation and Cytokine Secretion of Human Adipose-Derived Stromal Cells

Zinc oxide nanoparticles (ZnO-NPs) are widely utilized, for example in manufacturing paints and in the cosmetic industry. In addition, there is raising interest in the application of NPs in stem cell research. However, cytotoxic, genotoxic and pro-inflammatory effects were shown for NPs. The aim of this study was to evaluate the impact of ZnO-NPs on cytokine secretion and differentiation properties of human adipose tissue-derived stromal cells (ASCs). Human ASCs were exposed to the subtoxic concentration of 0.2 µg/mL ZnO-NPs for 24 h. After four weeks of cultivation, adipogenic and osteogenic differentiation procedures were performed. The multi-differentiation potential was confirmed histologically and using polymerase chain reaction (PCR). In addition, the gene expression of IL-6, IL-8, vascular endothelial growth factor (VEGF) and caspase 3 was analyzed. Over the course of four weeks after ZnO-NPs exposure, no significant differences were detected in the gene expression of IL-6, IL-8, VEGF and caspase 3 compared to non-exposed cells. The differentiation was also not affected by the ZnO-NPs. These findings underline the fact, that functionality of ASCs is likely to be unaffected by ZnO-NPs, despite a long-term disposition of NPs in the cells, supposing that the starting concentration was safely in the non-toxic range. This might provide important information for single-use nanomedical applications of ZnO-NPs.

Ex vivo MRI cell tracking of autologous mesenchymal stromal cells in an ovine osteochondral defect model

BACKGROUND

Osteochondral injuries represent a significant clinical problem requiring novel cell-based therapies to restore function of the damaged joint with the use of mesenchymal stromal cells (MSCs) leading research efforts. Pre-clinical studies are fundamental in translating such therapies; however, technologies to minimally invasively assess in vivo cell fate are currently limited. We investigate the potential of a MRI- (magnetic resonance imaging) and superparamagnetic iron oxide nanoparticle (SPION)-based technique to monitor cellular bio-distribution in an ovine osteochondral model of acute and chronic injuries.

METHODS

MSCs were isolated, expanded and labelled with Nanomag, a 250-nm SPION, and using a novel cell-penetrating technique, glycosaminoglycan-binding enhanced transduction (GET). MRI visibility thresholds, cellular toxicity and differentiation potential post-labelling were assessed in vitro. A single osteochondral defect was created in the medial femoral condyle in the left knee joint of each sheep with the contralateral joint serving as the control. Cells, either GET-Nanomag labelled or unlabelled, were delivered 1 week or 4.5 weeks later. Sheep were sacrificed 7 days post implantation and immediately MR imaged using a 0.2-T MRI scanner and validated on a 3-T MRI scanner prior to histological evaluation.

RESULTS

MRI data demonstrated a significant increase in MRI contrast as a result of GET-Nanomag labelling whilst cell viability, proliferation and differentiation capabilities were not affected. MRI results revealed evidence of implanted cells within the synovial joint of the injured leg of the chronic model only with no signs of cell localisation to the defect site in either model. This was validated histologically determining the location of implanted cells in the synovium. Evidence of engulfment of Nanomag-labelled cells by leukocytes is observed in the injured legs of the chronic model only. Finally, serum c-reactive protein (CRP) levels were measured by ELISA with no obvious increase in CRP levels observed as a result of P21-8R:Nanomag delivery.

CONCLUSION

This study has the potential to be a powerful translational tool with great implications in the clinical translation of stem cell-based therapies. Further, we have demonstrated the ability to obtain information linked to key biological events occurring post implantation, essential in designing therapies and selecting pre-clinical models.

Cellular toxicity of silicon carbide nanomaterials as a function of morphology

Silicon carbide has been shown to be biocompatible and is used as a coating material for implanted medical devices to prevent biofilms. Silicon carbide nanomaterials are also promising in cell tracking due to their stable and strong luminescence, but more comprehensive studies of this material on the nanoscale are needed. Here, we studied the toxicity of silicon carbide nanomaterials on human mesenchymal stem cells in terms of metabolism, viability, adhesion, proliferation, migration, oxidative stress, and differentiation ability. We compared two different shapes and found that silicon carbide nanowires are toxic to human mesenchymal stem cells but not to cancer cell lines at the concentration of 0.1 mg/mL. Control silicon carbide nanoparticles were biocompatible to human mesenchymal stem cells at 0.1 mg/mL. We studied the potential mechanistic effect of silicon carbide nanowires on human mesenchymal stem cells' phenotype, cytokine secretion, and gene expression. These findings suggest that the toxic effect of silicon carbide nanomaterials to human mesenchymal stem cells are dependent on morphology.

Very small superparamagnetic iron oxide nanoparticles: Long-term fate and metabolic processing in atherosclerotic mice

We investigated the biotransformation of very small superparamagnetic iron oxide nanoparticles (VSOP) in atherosclerotic LDLR^-/- mice. Transmission electron microscopy revealed an uptake of VSOP not only by macrophages but also by endothelial cells in liver, spleen, and atherosclerotic lesions and their accumulation in the lysosomal compartment. Using magnetic particle spectroscopy (MPS), we show that the majority of VSOP's superparamagnetic iron was degraded within 28 days. MPS spectrum shape indicated changes in the magnetic properties of VSOP during the biodegradation process. Experiments with primary murine bone marrow derived macrophages, primary murine liver sinusoidal endothelial cells, and primary human aortic endothelial cells demonstrated that loading with VSOP induced a differential response of cellular iron homeostasis mechanisms with increased levels of ferritin and iron transport proteins in macrophages and increased levels of ferritin in endothelial cells.

Magnetic field and nano-scaffolds with stem cells to enhance bone regeneration

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy.

Noninvasive imaging of nanoparticle-labeled transplant populations within polymer matrices for neural cell therapy

AIM

To develop a 3D neural cell construct for encapsulated delivery of transplant cells; develop hydrogels seeded with magnetic nanoparticle (MNP)-labeled cells suitable for cell tracking by MRI.

MATERIALS & METHODS

Astrocytes were exogenously labeled with MRI-compatible iron-oxide MNPs prior to intra-construct incorporation within a 3D collagen hydrogel.

RESULTS

A connective, complex cellular network was clearly observable within the 3D constructs, with high cellular viability. MNP accumulation in astrocytes provided a hypointense MRI signal at 24 h & 14 days.

CONCLUSION

Our findings support the concept of developing a 3D construct possessing the dual advantages of (i) support of long-term cell survival of neural populations with (ii) the potential for noninvasive MRI-tracking of intra-construct cells for neuroregenerative applications.

In Vivo Tracking of Human Adipose-derived Mesenchymal Stem Cells in a Rat Knee Osteoarthritis Model with Fluorescent Lipophilic Membrane Dye

In order to support the clinical application of human adipose-derived mesenchymal stem cell (haMSC) therapy for knee osteoarthritis (KOA), we examined the efficacy of cell persistence and biodistribution of haMSCs in animal models. We demonstrated a method to label the cell membrane of haMSCs with lipophilic fluorescent dye. Subsequently, intra-articular injection of the labeled cells in rats with surgically induced KOA was monitored dynamically by an in vivo imaging system. We employed the lipophilic carbocyanines DiD (DilC18 (5)), a far-red fluorescent Dil (dialkylcarbocyanines) analog, which utilized a red laser to avoid excitation of the natural green autofluorescence from surrounding tissues. Furthermore, the red-shifted emission spectra of DiD allowed deep-tissue imaging in live animals and the labeling procedure caused no cytotoxic effects or functional damage to haMSCs. This approach has been shown to be an efficient tracking method for haMSCs in a rat KOA model. The application of this method could also be used to determine the optimal administration route and dosage of MSCs from other sources in pre-clinical studies.

Biofabrication and spectral characterization of silver nanoparticles and their cytotoxic studies on human CD34 +ve stem cells

Biosynthesis of plant-mediated silver nanoparticles is gaining significant importance due to environmentally safe ‘green method’ and it is an efficient alternative method. In the present study, silver nanoparticles were synthesized by using root extract of Glycyrrhiza glabra an important medicinal plant. The AgNPs are characterized by spectral analysis; the surface plasmon resonance (SPR) peak of AgNPs showed maximum absorption at 445 nm. Fourier-transform infrared spectroscopy (FT-IR) data show that the O–H hydroxyl groups, carboxylic acids, ester and ether groups and C–O stretching of alcohols have been utilized in the formation of AgNPs. The X-ray powder diffraction (XRD) data reveal that the AgNPs are face-centered cubic (fcc) in structure. The size was determined by particle size analyzer and atomic force microscope (AFM); the results reveal that AgNPs were spherical in shape and the average grain size is determined as 41.5–46.5 nm. Transmission electron microscopy (TEM) micrographs obtained show that AgNPs were roughly spherical and well dispersed with the sizes ranging from 10 to 45 nm ± 5 nm. The biofabricated AgNPs are extremely stable due to its high negative zeta potential −34.1 mV which indicates that the nanoparticles are polydispered in nature. The cytotoxic studies of AgNPs on human CD34 +ve stem cells in microcarrier culture reveal excellent growth at different concentrations of biosynthesized AgNPs. This is the first report of microcarrier culture of CD34 +ve stem cells on biosynthesized AgNPs.

Gadolinium functionalized carbon dots for fluorescence/magnetic resonance dual-modality imaging of mesenchymal stem cells

The development of multimodal nanoprobes is of great importance in nanomedicine because it integrates the advantages of each imaging modality and offers a significantly enhanced diagnostic effect. In this work, gadolinium(iii) functionalized fluorescent carbon dots (Gd-CDs) are synthesized by means of a one-step hydrothermal approach. As a fluorescent nanomaterial, the obtained Gd-CDs exhibit strong and stable fluorescence with excitation-independent emission behavior. Moreover, as an MRI contrast agent, the Gd-CDs exhibited a longitudinal relaxation rate of 6.06 mM^-1 s^-1, which is significantly higher than that of the commercially available MRI agent Gadovist (4.24 mM^-1 s^-1). In addition, the cellular experiment reveals that Gd-CDs promote the proliferation of human mesenchymal stem cells (hMSCs), which is tracked by the fluorescence/Magnetic Resonance dual-modality imaging of hMSCs by the Gd-CDs.

Stem cell labeling with iron oxide nanoparticles: impact of 3D culture on cell labeling maintenance

AIM

We aimed to analyze the suitability of nanoparticles (M4E) for safe human mesenchymal stem cell (hMSC) labeling and determined cell labeling maintenance in 2D and 3D culture.

MATERIALS & METHODS

We investigated cell-particle interaction and the particles' impact on cell viability, growth and proliferation. We analyzed cell labeling maintenance in 2D and 3D culture invasively and noninvasively.

RESULTS

M4E do not affect cell viability, growth and proliferation and do not cause chromosomal aberrations. Cell labeling maintenance is up to five-times higher in 3D conditions compared with 2D culture.

CONCLUSION

M4E allow safe hMSC labeling and noninvasive identification. Our hMSC-loaded, 3D tissue-engineered construct could serve as a graft for regenerative therapies, in which M4E-labeled hMSCs can migrate to their target.

Autonomous magnetic labelling of functional mesenchymal stem cells for improved traceability and spatial control in cell therapy applications

Mesenchymal stem cells (MSCs) represent a valuable resource for regenerative medicine treatments for orthopaedic repair and beyond. Following developments in isolation, expansion and differentiation protocols, efforts to promote clinical translation of emerging cellular strategies now seek to improve cell delivery and targeting. This study shows efficient live MSC labelling using silica‐coated magnetic particles (MPs), which enables 3D tracking and guidance of stem cells. A procedure developed for the efficient and unassisted particle uptake was shown to support MSC viability and integrity, while surface marker expression and MSC differentiation capability were also maintained. In vitro, MSCs showed a progressive decrease in labelling over increasing culture time, which appeared to be linked to the dilution effect of cell division, rather than to particle release, and did not lead to detectable secondary particle uptake. Labelled MSC populations demonstrated magnetic responsiveness in vitro through directed migration in culture and, when seeded onto a scaffold, supporting MP‐based approaches to cell targeting. The potential of these silica‐coated MPs for MRI cell tracking of MSC populations was validated in 2D and in a cartilage repair model following cell delivery. These results highlight silica‐coated magnetic particles as a simple, safe and effective resource to enhance MSC targeting for therapeutic applications and improve patient outcomes. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

Labeling of mesenchymal stem cells for MRI with single-cell sensitivity

Sensitive cell detection by magnetic resonance imaging (MRI) is an important tool for the development of cell therapies. However, clinically approved contrast agents that allow single-cell detection are currently not available. Therefore, we compared very small iron oxide nanoparticles (VSOP) and new multicore carboxymethyl dextran-coated iron oxide nanoparticles (multicore particles, MCP) designed by our department for magnetic particle imaging (MPI) with discontinued Resovist^® regarding their suitability for detection of single mesenchymal stem cells (MSC) by MRI. We achieved an average intracellular nanoparticle (NP) load of >10 pg Fe per cell without the use of transfection agents. NP loading did not lead to significantly different results in proliferation, colony formation, and multilineage in vitro differentiation assays in comparison to controls. MRI allowed single-cell detection using VSOP, MCP, and Resovist^® in conjunction with high-resolution T2*-weighted imaging at 7 T with postprocessing of phase images in agarose cell phantoms and in vivo after delivery of 2,000 NP-labeled MSC into mouse brains via the left carotid artery. With optimized labeling conditions, a detection rate of ~45% was achieved; however, the experiments were limited by nonhomogeneous NP loading of the MSC population. Attempts should be made to achieve better cell separation for homogeneous NP loading and to thus improve NP-uptake-dependent biocompatibility studies and cell detection by MRI and future MPI. Additionally, using a 7 T MR imager equipped with a cryocoil resulted in approximately two times higher detection. In conclusion, we established labeling conditions for new high-relaxivity MCP, VSOP, and Resovist^® for improved MRI of MSC with single-cell sensitivity.

Silk protein-based hydrogels: Promising advanced materials for biomedical applications

Hydrogels are a class of advanced material forms that closely mimic properties of the soft biological tissues. Several polymers have been explored for preparing hydrogels with structural and functional features resembling that of the extracellular matrix. Favourable material properties, biocompatibility and easy processing of silk protein fibers into several forms make it a suitable material for biomedical applications. Hydrogels made from silk proteins have shown a potential in overcoming limitations of hydrogels prepared from conventional polymers. A great deal of effort has been made to control the properties and to integrate novel topographical and functional characteristics in the hydrogel composed from silk proteins. This review provides overview of the advances in silk protein-based hydrogels with a primary emphasis on hydrogels of fibroin. It describes the approaches used to fabricate fibroin hydrogels. Attempts to improve the existing properties or to incorporate new features in the hydrogels by making composites and by improving fibroin properties by genetic engineering approaches are also described. Applications of the fibroin hydrogels in the realms of tissue engineering and controlled release are reviewed and their future potentials are discussed.

STATEMENT OF SIGNIFICANCE

This review describes the potentiality of silk fibroin hydrogel. Silk Fibroin has been widely recognized as an interesting biomaterial. Due to its properties including high mechanical strength and excellent biocompatibility, it has gained wide attention. Several groups are exploring silk-based materials including films, hydrogels, nanofibers and nanoparticles for different biomedical applications. Although there is a good amount of literature available on general properties and applications of silk based biomaterials, there is an inadequacy of extensive review articles that specifically focus on silk based hydrogels. Silk-based hydrogels have a strong potential to be utilized in biomedical applications. Our work is an effort to highlight the research that has been done in the area of silk-based hydrogels. It aims to provide an overview of the advances that have been made and the future course available. It will provide an overview of the silk-based hydrogels as well as may direct the readers to the specific areas of application.

2-Amino-2-deoxy-glucose conjugated cobalt ferrite magnetic nanoparticle (2DG-MNP) as a targeting agent for breast cancer cells

In this study, 2-amino-2-deoxy-glucose (2DG) was conjugated to COOH modified cobalt ferrite magnetic nanoparticles (COOH-MNPs), which were designed to target tumor cells as a potential targetable drug/gene delivery agent for cancer treatment. According to our results, it is apparent that, 2DG labeled MNPs were internalized more efficiently than COOH-MNPs under the same conditions in all cell types (MDA-MB-231 and MCF-7 cancer and MCF-10A normal breast cells) (p<0.001). Moreover, the highest amount of uptake was observed in MDA-MB-231, followed by MCF-7 and normal MCF-10A cells for both MNPs. The apoptotic effects of 2DG-MNPs were further evaluated, and it was found that apoptosis was not induced at low concentrations of 2DG-MNPs in all cell types, whereas dramatic cell death was observed at higher concentrations. In addition, the gene expression levels of four drug-metabolizing enzymes, two Phase I (CYP1A1, CYP1B1) and two Phase II (GSTM3, GSTZ1) were also increased with the high concentrations of 2DG-MNPs.

Stem Cell Tracking with Nanoparticles for Regenerative Medicine Purposes: An Overview

Accurate and noninvasive stem cell tracking is one of the most important needs in regenerative medicine to determine both stem cell destinations and final differentiation fates, thus allowing a more detailed picture of the mechanisms involved in these therapies. Given the great importance and advances in the field of nanotechnology for stem cell imaging, currently, several nanoparticles have become standardized products and have been undergoing fast commercialization. This review has been intended to summarize the current use of different engineered nanoparticles in stem cell tracking for regenerative medicine purposes, in particular by detailing their main features and exploring their biosafety aspects, the first step for clinical application. Moreover, this review has summarized the advantages and applications of stem cell tracking with nanoparticles in experimental and preclinical studies and investigated present limitations for their employment in the clinical setting.

Iron Oxide as an MRI Contrast Agent for Cell Tracking

Iron oxide contrast agents have been combined with magnetic resonance imaging for cell tracking. In this review, we discuss coating properties and provide an overview of ex vivo and in vivo labeling of different cell types, including stem cells, red blood cells, and monocytes/macrophages. Furthermore, we provide examples of applications of cell tracking with iron contrast agents in stroke, multiple sclerosis, cancer, arteriovenous malformations, and aortic and cerebral aneurysms. Attempts at quantifying iron oxide concentrations and other vascular properties are examined. We advise on designing studies using iron contrast agents including methods for validation.

Magnetic Nanoparticles Labeled Mesenchymal Stem Cells: A Pragmatic Solution toward Targeted Cancer Theranostics

Mesenchymal stem cells (MSCs) have gained much interest to be used as targeting vehicle in cancer therapy due to the intrinsic tumor-homing behavior associated with them. In this scenario, superparamagnetic nanoparticles are emerging as an ideal probe for noninvasive cell tracking for different stem cell applications. In the study, it is demonstrated that the formulated aqueous dispersible glyceryl monooleate coated magnetic nanoparticles (MNPs) can act as a better labeling and efficient tracking agent without affecting the inherent properties of MSCs. The MNPs-MSCs facilitate the stem cell tracking by magnetic resonance imaging at a very low cell number having high T₂ relaxivity and potentiates the use of MNPs-MSCs as a prospective diagnostic tool. Most importantly, the homing of MNPs-MSCs toward inflammation site, subcutaneous prostate tumor (small as well as large tumor), and in orthotopic prostate tumor suggests the clinical relevance of the system. In addition, intraperitoneal delivery of MNPs-MSCs shows enhanced tumor accumulation and less sequestration in liver as revealed by in vivo imaging and histological studies. The results here demonstrate that MNPs-MSCs may prove as a better targeted delivery agent for early diagnosis of tumors even of smaller size.

Superparamagnetic iron oxide nanoparticles as a means to track mesenchymal stem cells in a large animal model of tendon injury

The goal of this study was to establish an SPIO-based cell-tracking method in an ovine model of tendonitis and to determine if this method may be useful for further study of cellular therapies in tendonitis in vivo. Functional assays were performed on labeled and unlabeled cells to ensure that no significant changes were induced by intracellular SPIOs. Following biosafety validation, tendon lesions were mechanically (n = 4) or chemically (n = 4) induced in four sheep and scanned ex vivo at 7 and 14 days to determine the presence and distribution of intralesional cells. Ovine MSCs labeled with 50 µg SPIOs/mL remained viable, proliferate, and undergo tri-lineage differentiation (p < 0.05). Labeled ovine MSCs remained detectable in vitro in concentrated cell numbers as low as 10 000 and in volumetric distributions as low as 100 000 cells/mL. Cells remained detectable by MRI at 7 days, as confirmed by correlative histology for dually labeled SPIO+/GFP+ cells. Histological evidence at 14 days suggested that SPIO particles remained embedded in tissue, providing MRI signal, although cells were no longer present. SPIO labeling has proven to be an effective method for cell tracking for a large animal model of tendon injury for up to 7 days post-injection. The data obtained in this study justify further investigation into the effects of MSC survival and migration on overall tendon healing and tissue regeneration.

BMSCs laden injectable amino-diethoxypropane modified alginate-chitosan hydrogel for hyaline cartilage reconstruction

We developed an injectable hydrogel composed of amino-diethoxypropane modified alginate and chitosan, and also investigated bone marrow mesenchy + mal stromal cells (BMSCs) laden hydrogel for cartilage reconstruction in vitro and in vivo.

Evaluation of the effects of boron nitride nanotubes functionalized with gum arabic on the differentiation of rat mesenchymal stem cells

The biocompatibility of boron nitride nanotubes with rat mesenchymal stem cells has been evaluated in terms of cell proliferation and differentiation.

Pre-clinical characterization of tissue engineering constructs for bone and cartilage regeneration

Pre-clinical animal models play a crucial role in the translation of biomedical technologies from the bench top to the bedside. However, there is a need for improved techniques to evaluate implanted biomaterials within the host, including consideration of the care and ethics associated with animal studies, as well as the evaluation of host tissue repair in a clinically relevant manner. This review discusses non-invasive, quantitative, and real-time techniques for evaluating host-materials interactions, quality and rate of neotissue formation, and functional outcomes of implanted biomaterials for bone and cartilage tissue engineering. Specifically, a comparison will be presented for pre-clinical animal models, histological scoring systems, and non-invasive imaging modalities. Additionally, novel technologies to track delivered cells and growth factors will be discussed, including methods to directly correlate their release with tissue growth.

Dose-response of superparamagnetic iron oxide labeling on mesenchymal stem cells chondrogenic differentiation: a multi-scale in vitro study

Aim

The aim of this work was the development of successful cell therapy techniques for cartilage engineering. This will depend on the ability to monitor non-invasively transplanted cells, especially mesenchymal stem cells (MSCs) that are promising candidates to regenerate damaged tissues.

Methods

MSCs were labeled with superparamagnetic iron oxide particles (SPIO). We examined the effects of long-term labeling, possible toxicological consequences and the possible influence of progressive concentrations of SPIO on chondrogenic differentiation capacity.

Results

No influence of various SPIO concentrations was noted on human bone marow MSC viability or proliferation. We demonstrated long-term (4 weeks) in vitro retention of SPIO by human bone marrow MSCs seeded in collagenic sponges under TGF-β1 chondrogenic conditions, detectable by Magnetic Resonance Imaging (MRI) and histology. Chondrogenic differentiation was demonstrated by molecular and histological analysis of labeled and unlabeled cells. Chondrogenic gene expression (COL2A2, ACAN, SOX9, COL10, COMP) was significantly altered in a dose-dependent manner in labeled cells, as were GAG and type II collagen staining. As expected, SPIO induced a dramatic decrease of MRI T2 values of sponges at 7T and 3T, even at low concentrations.

Conclusions

This study clearly demonstrates (1) long-term in vitro MSC traceability using SPIO and MRI and (2) a deleterious dose-dependence of SPIO on TGF-β1 driven chondrogenesis in collagen sponges. Low concentrations (12.5–25 µg Fe/mL) seem the best compromise to optimize both chondrogenesis and MRI labeling.

In vivo magnetic resonance imaging of type I collagen scaffold in rat: improving visualization of bladder and subcutaneous implants

Noninvasive monitoring of implanted scaffolds is important to understand their behavior and role in tissue engineering, in particular to follow their degradation and interaction with host tissue. Magnetic resonance imaging (MRI) is well suited for this goal, but its application is often hampered by the low contrast of scaffolds that are prepared from biomaterials such as type I collagen. The aim of this study was to test iron oxide particles incorporation in improving their MRI contrasts, and to follow their degradation and tissue interactions. Scaffolds with and without iron oxide particles were implanted either subcutaneously or on the bladder of rats. At predetermined time points, in vivo MRI were obtained and tissues were then harvested for histology analysis and transmission electron microscopy. The result showed that the incorporation of iron oxide particles improved MRI contrast of the implants, providing information on their location, shapes, and degradation. Second, the host tissue reaction to the type I collagen implants could be observed in both MRI and histology. Finally, MRI also revealed that the degradation and host tissue reaction of iron particles-loaded scaffolds differed between subcutaneous and bladder implantation, which was substantiated by histology.

Different cell responses induced by exposure to maghemite nanoparticles

Recent advances in nanotechnology have permitted the development of a wide repertoire of inorganic magnetic nanoparticles (NPs) with extensive promise for biomedical applications. Despite this remarkable potential, many questions still arise concerning the biocompatible nature of NPs when in contact with biological systems. Herein, we have investigated how controlled changes in the physicochemical properties of iron oxide NPs at their surface (i.e., surface charge and hydrodynamic size) affect, first, their interaction with cell media components and, subsequently, cell responses to NP exposure. For that purpose, we have prepared iron oxide NPs with three different coatings (i.e., dimercaptosuccinic acid - DMSA, (3-aminopropyl)triethoxysilane - APS and dextran) and explored the response of two different cell types, murine L929 fibroblasts and human Saos-2 osteoblasts, to their exposure. Interestingly, different cell responses were found depending on the NP concentration, surface charge and cell type. In this sense, neutral NPs, as those coated with dextran, induced negligible cell damage, as their cellular internalization was significantly reduced. In contrast, surface-charged NPs (i.e., those coated with DMSA and APS) caused significant cellular changes in viability, morphology and cell cycle under certain culture conditions, as a result of a more active cellular internalization. These results also revealed a particular cellular ability to detect and remember the original physicochemical properties of the NPs, despite the formation of a protein corona when incubated in culture media. Overall, conclusions from these studies are of crucial interest for future biomedical applications of iron oxide NPs.

Whole body tracking of superparamagnetic iron oxide nanoparticle-labelled cells--a rheumatoid arthritis mouse model

Introduction

The application of mesenchymal stem cells (MSCs) in treating rheumatoid arthritis (RA) has been made possible by the immunosuppressive and differentiation abilities of these cells. A non-invasive means of assessing cell integration and bio-distribution is fundamental in evaluating the risks and success of this therapy, thereby enabling clinical translation. This paper defines the use of superparamagnetic iron oxide nanoparticles (SPIONs) in conjunction with magnetic resonance imaging (MRI) to image and track MSCs in vivo within a murine model of RA.

Methods

Murine MSCs (mMSCs) were isolated, expanded and labelled with SiMAG, a commercially available particle. In vitro MRI visibility thresholds were investigated by labelling mMSCs with SiMAG with concentrations ranging from 0 to 10 μg/ml and resuspending varying cell doses (10³ to 5 × 10⁵ cells) in 2 mg/ml collagen prior to MR-imaging. Similarly, in vivo detection thresholds were identified by implanting 3 × 10⁵ mMSCs labelled with 0 to 10 μg/ml SiMAG within the synovial cavity of a mouse and MR-imaging. Upon RA induction, 300,000 mMSCs labelled with SiMAG (10 μg/ml) were implanted via intra-articular injection and joint swelling monitored as an indication of RA development over seven days. Furthermore, the effect of SiMAG on cell viability, proliferation and differentiation was investigated.

Results

A minimum particle concentration of 1 μg/ml (300,000 cells) and cell dose of 100,000 cells (5 and 10 μg/ml) were identified as the in vitro MRI detection threshold. Cell viability, proliferation and differentiation capabilities were not affected, with labelled populations undergoing successful differentiation down osteogenic and adipogenic lineages. A significant decrease (P < 0.01) in joint swelling was measured in groups containing SiMAG-labelled and unlabelled mMSCs implying that the presence of SPIONs does not affect the immunomodulating properties of the cells. In vivo MRI scans demonstrated good contrast and the identification of SiMAG-labelled populations within the synovial joint up to 7 days post implantation. This was further confirmed using histological analysis.

Conclusions

We have been able to monitor and track the migration of stem cell populations within the rheumatic joint in a non-invasive manner. This manuscript goes further to highlight the key characteristics (biocompatible and the ability to create significant contrast at realistic doses within a clinical relevant system) demonstrated by SiMAG that should be incorporated into the design of a new clinically approved tracking agent.

Imaging challenges in biomaterials and tissue engineering

Biomaterials are employed in the fields of tissue engineering and regenerative medicine (TERM) in order to enhance the regeneration or replacement of tissue function and/or structure. The unique environments resulting from the presence of biomaterials, cells, and tissues result in distinct challenges in regards to monitoring and assessing the results of these interventions. Imaging technologies for three-dimensional (3D) analysis have been identified as a strategic priority in TERM research. Traditionally, histological and immunohistochemical techniques have been used to evaluate engineered tissues. However, these methods do not allow for an accurate volume assessment, are invasive, and do not provide information on functional status. Imaging techniques are needed that enable non-destructive, longitudinal, quantitative, and three-dimensional analysis of TERM strategies. This review focuses on evaluating the application of available imaging modalities for assessment of biomaterials and tissue in TERM applications. Included is a discussion of limitations of these techniques and identification of areas for further development.

Imaging of VSOP labeled stem cells in agarose phantoms with susceptibility weighted and T2* weighted MR Imaging at 3T: determination of the detection limit

OBJECTIVES

This study aimed to evaluate the detectability of stem cells labeled with very small iron oxide particles (VSOP) at 3T with susceptibility weighted (SWI) and T2* weighted imaging as a methodological basis for subsequent examinations in a large animal stroke model (sheep).

MATERIALS AND METHODS

We examined ovine mesenchymal stem cells labeled with VSOP in agarose layer phantoms. The experiments were performed in 2 different groups, with quantities of 0-100,000 labeled cells per layer. 15 different SWI- and T2*-weighted sequences and 3 RF coils were used. All measurements were carried out on a clinical 3T MRI. Images of Group A were analyzed by four radiologists blinded for the number of cells, and rated for detectability according to a four-step scale. Images of Group B were subject to a ROI-based analysis of signal intensities. Signal deviations of more than the 0.95 confidence interval in cell containing layers as compared to the mean of the signal intensity of non cell bearing layers were considered significant.

RESULTS

GROUP A

500 or more labeled cells were judged as confidently visible when examined with a SWI-sequence with 0.15 mm slice thickness. Group B: 500 or more labeled cells showed a significant signal reduction in SWI sequences with a slice thickness of 0.25 mm. Slice thickness and cell number per layer had a significant influence on the amount of detected signal reduction.

CONCLUSION

500 VSOP labeled stem cells could be detected with SWI imaging at 3 Tesla using an experimental design suitable for large animal models.

Reconstruction of cartilage with clonal mesenchymal stem cell-acellular dermal matrix in cartilage defect model in nonhuman primates

OBJECTIVE

Articular cartilage defects are commonly associated with trauma, inflammation and osteoarthritis. Mesenchymal stem cell (MSC)-based therapy is a promising novel approach for repairing articular cartilage. Direct intra-articular injection of uncommitted MSCs does not regenerate high-quality cartilage. This study explored utilization of a new three-dimensional, selected chondrogenic clonal MSC-loaded monkey acellular dermal matrix (MSC-ADM) scaffold to repair damaged cartilage in an experimental model of knee joint cartilage defect in Cynomolgus monkeys.

METHODS

MSCs were characterized for cell size, cell yield, phenotypes, proliferation and chondrogenic differentiation capacity. Chondrogenic differentiation assays were performed at different MSC passages by sulfated glycosaminoglycans (sGAG), collagen, and fluorescence activated cell sorter (FACS) analysis. Selected chondrogenic clonal MSCs were seeded onto ADM scaffold with the sandwich model and MSC-loaded ADM grafts were analyzed by confocal microscopy and scanning electron microscopy. Cartilage defects were treated with normal saline, clonal MSCs and clonal MSC-ADM grafts, respectively. The clinical parameters, and histological and immunohistochemical examinations were evaluated at weeks 8, 16, 24 post-treatment, respectively.

RESULTS

Polyclonal and clonal MSCs could differentiate into the chondrogenic lineage after stimulation with suitable chondrogenic factors. They expressed mesenchymal markers and were negative for hematopoietic markers. Articular cartilage defects were considerably improved and repaired by selected chondrogenic clonal MSC-based treatment, particularly, in MSC-ADM-treated group. The histological scores in MSC-ADM-treated group were consistently higher than those of other groups.

CONCLUSION

Our results suggest that selected chondrogenic clonal MSC-loaded ADM grafts could improve the cartilage lesions in Cynomolgus monkey model, which may be applicable for repairing similar human cartilage defects.

DiI labeling of human adipose-derived stem cells: evaluation of DNA damage, toxicity and functional impairment

INTRODUCTION

Adipose tissue-derived stem cells (ASCs) have become the primary focus of tissue engineering research. To understand their functions and behavior in in vitro and in vivo models, it is mandatory to track the implanted cells and distinguish them from the resident or host cells. A common labeling method is the use of fluorescent dyes, e.g. the lipophilic carbocyanine dye, DiI. This study aimed to analyze potential DNA damage, toxicity and impairment of the functional properties of human ASCs after labeling with DiI.

METHODS

Cytotoxicity was measured using the MTT assay and DNA damage was determined by means of the comet assay. Potential apoptotic effects were determined using the annexin V-propidium iodide test. Differentiation potential was evaluated by trilineage differentiation procedures in labeled and unlabeled ASCs. Proliferation as well as migration capability was analyzed, and the duration and stability of DiI labeling in ASCs during in vitro expansion was observed over a period of 35 days.

RESULTS

DiI labeling did not cause genotoxic effects 15, or 30 min or 24 h after the labeling procedure, and there were no cytotoxic effects until 72 h afterwards. No impairment of proliferation or migration capability or differentiation potential could be determined. However, after 35 days, only 37% of labeled cells could be detected using the fluorescence microscope, which indicates a decrease in staining stability during in vitro expansion.

CONCLUSION

DiI is a convenient method for ASCs labeling which causes no toxic effects and does not impair the proliferation, migration or differentiation potential of ASCs after the labeling procedure.

Induced clustered nanoconfinement of superparamagnetic iron oxide in biodegradable nanoparticles enhances transverse relaxivity for targeted theranostics

PURPOSE

Combined therapeutic and diagnostic agents, "theranostics" are emerging valuable tools for noninvasive imaging and drug delivery. Here, we report on a solid biodegradable multifunctional nanoparticle that combines both features.

METHODS

Poly(lactide-co-glycolide) nanoparticles were engineered to confine superparamagnetic iron oxide contrast for magnetic resonance imaging while enabling controlled drug delivery and targeting to specific cells. To achieve this dual modality, fatty acids were used as anchors for surface ligands and for encapsulated iron oxide in the polymer matrix.

RESULTS

We demonstrate that fatty acid modified iron oxide prolonged retention of the contrast agent in the polymer matrix during degradative release of drug. Antibody-fatty acid surface modification facilitated cellular targeting and subsequent internalization in cells while inducing clustering of encapsulated fatty-acid modified superparamagnetic iron oxide during particle formulation. This induced clustered confinement led to an aggregation within the nanoparticle and, hence, higher transverse relaxivity, r2 , (294 mM(-1) s(-1) ) compared with nanoparticles without fatty-acid ligands (160 mM(-1) s(-1) ) and higher than commercially available superparamagnetic iron oxide nanoparticles (89 mM(-1) s(-1) ).

CONCLUSION

Clustering of superparamagnetic iron oxide in poly(lactide-co-glycolide) did not affect the controlled release of encapsulated drugs such as methotrexate or clodronate and their subsequent pharmacological activity, thus highlighting the full theranostic capability of our system.