Large-scale synthesis of monodisperse ultrasmall metal ferrite nanoparticles as well as understanding the correlations between chemical composition and MR signal enhancement is critical for developing next-generation, ultrasensitive T magnetic resonance imaging (MRI) nanoprobes. Herein, taking ultrasmall MnFeO nanoparticles (UMFNPs) as a model system, we report a general dynamic simultaneous thermal decomposition (DSTD) strategy for controllable synthesis of monodisperse ultrasmall metal ferrite nanoparticles with sizes smaller than 4 nm. The comparison study revealed that the DSTD using the iron-eruciate paired with a metal-oleate precursor enabled a nucleation-doping process, which is crucial for particle size and distribution control of ultrasmall metal ferrite nanoparticles. The principle of DSTD synthesis has been further confirmed by synthesizing NiFeO and CoFeO nanoparticles with well-controlled sizes of ∼3 nm. More significantly, the success in DSTD synthesis allows us to tune both MR and biochemical properties of magnetic iron oxide nanoprobes by adjusting their chemical composition. Beneficial from the Mn dopant, the synthesized UMFNPs exhibited the highest r relaxivity (up to 8.43 mM s) among the ferrite nanoparticles with similar sizes reported so far and demonstrated a multifunctional T MR nanoprobe for in vivo high-resolution blood pool and liver-specific MRI simultaneously. Our study provides a general strategy to synthesize ultrasmall multicomponent magnetic nanoparticles, which offers possibilities for the chemical design of a highly sensitive ultrasmall magnetic nanoparticle based T MRI probe for various clinical diagnosis applications.

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With the increasing occurrence of vascular diseases and poor long-term patency rates of current small diameter vascular grafts, it becomes urgent to pursuit biomaterial as scaffold to mimic blood vessel morphologically and mechanically. In this study, novel human-like collagen (HLC, produced by recombinant E. coli)/chitosan tubular scaffolds were fabricated by cross-linking and freeze-drying process. The scaffolds were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and tensile test, respectively. Human venous fibroblasts were expanded and seeded onto the scaffolds in the density of 1 x 10(5) cells/cm(2). After a 15-day culture under static conditions, the cell-polymer constructs were observed using SEM, confocal laser scanning microscopy (CLSM), histological examination, and biochemical assays for cell proliferation and extracellular matrix production (collagen and glycosaminoglycans). Furthermore, the scaffolds were implanted into rabbits' livers to evaluate their biocompatibility. The results indicated that HLC/chitosan tubular scaffolds (1) exhibited interconnected porous structure; (2) achieved the desirable levels of pliability (elastic up to 30% strain) and stress of 300 +/- 16 kPa; (3) were capable of enhancing cell adhesion and proliferation and ECM secretion; (4) showed superior biocompatibility. This study suggested the feasibility of HLC/chitosan composite as a promising candidate scaffold for blood vessel tissue engineering.

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