Shaohua Ma

Synergic effect of magnetic nanoparticles on the electrospun aligned superparamagnetic nanofibers as a potential tissue engineering scaffold

In this study, aligned nanofibers have been fabricated by magnetic electrospinning, through the incorporation of magnetic nanoparticles (MNPs) into poly(lactic-co-glycolide) (PLGA) nanofibers. We further optimized the magnetic electrospinning process by systematically investigating the influence of the MNP and its content on the alignment of nanofibers. The biological effect of the aligned magnetic-electrospun nanofibers has been investigated by culturing C2C12 myoblasts on different nanofibers. The results indicated that the cells migrated and extended along the fiber arrangement. Because of the synergic effect of the magnetic nanoparticles on the nanofibers, the cells adhesion and proliferation is much more enhanced in our aligned nanofibers than the traditional ones in this experiment. Therefore, the magnetic-electrospun nanofibers could be a good candidate for an aligned tissue engineering scaffold.

Hollow superparamagnetic PLGA/Fe 3O 4 composite microspheres for lysozyme adsorption

Uniform hollow superparamagnetic poly(lactic-co-glycolic acid) (PLGA)/Fe(3)O(4) composite microspheres composed of an inner cavity, PLGA inner shell and Fe(3)O(4) outer shell have been synthesized by a modified oil-in-water (O/W) emulsion-solvent evaporation method using Fe(3)O(4) nanoparticles as a particulate emulsifier. The obtained composite microspheres with an average diameter of 2.5 μm showed excellent monodispersity and stability in aqueous medium, strong magnetic responsiveness, high magnetite content (>68%), high saturation magnetization (58 emu g(-1)) and high efficiency in lysozyme adsorption.

Polyacrylic acid brushes grafted from P(St-AA)/Fe3O4 composite microspheres via ARGET-ATRP in aqueous solution for protein immobilization

Recently, the atom transfer radical polymerization (ATRP) of acrylic monomers in many reaction systems has been successfully accomplished. However, its application in aqueous solution is still a challenging task. In this work, polyacrylic acid (PAA) brushes with tunable length were directly grafted from P(St-AA)/Fe3O4 composite microspheres in aqueous solution via an improved method, activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). This reaction was carried out in environment-friendly solvent. As well, this method overcame the sensitivity of the catalyst. Due to the strong coordination interaction of carboxyl groups, PAA brushes were employed for immobilizing gold nanoparticles, which were prepared via the in situ reduction of chloroauric acid. The PAA brushes modified magnetic composite microspheres decorating with gold nanoparticles were efficient for specific immobilization and separation of bovine serum albumin (BSA) from aqueous solution under the external magnetic field.

Double-sided coordination assembly: superparamagnetic composite microspheres with layer-by-layer structure for protein separation

Double-sided coordination assembly via a two-step ligand exchange reaction was introduced to synthesize superparamagnetic poly(styrene-co-acrylic acid)/Fe3O4/polyacrylic acid (P(St-AA)/Fe3O4/PAA) composite microspheres for the first time. In the two-step ligand exchange reaction, the coordination interaction of carboxyl groups with the iron replaced the hydrogen bonding between triethylene glycol (TEG) and the Fe3O4 nanoparticles, resulting in the attachment of the Fe3O4 nanoparticles onto the surface of P(St-AA) colloidal template and the coating of monomeric AA onto the surface of Fe3O4 nanoparticles. The obtained P(St-AA)/Fe3O4/PAA composite microspheres showed excellent uniformity, high saturation magnetization, stability and efficient protein separation capacity. The equilibrium adsorption capacity of P(St-AA)/Fe3O4/PAA microspheres for lysozyme was as high as 1800 mg g−1. Functionalized with nitrilotriacetate-Ni2+ (NTA-Ni2+), such composite microspheres could efficiently and selectively capture polyhistidine-tagged glutathione-S-transferase (His-tagged-GST) from cell lysate.

Polydopamine-based superparamagnetic molecularly imprinted polymer nanospheres for efficient protein recognition

A new strategy for synthesis of superparamagnetic molecularly imprinted polymer nanospheres (MIPNSs) for efficient protein recognition is described here. Homogeneous hydroxyl group functionalized Fe3O4/polymethyl methacrylate (PMMA) composite nanospheres were prepared using improved miniemulsion polymerization. Uniform superparamagnetic MIPNSs were obtained via self-polymerization of dopamine (DA) on the surface of Fe3O4/PMMA composite nanospheres in the presence of lysozyme (lyz) template. The as-synthesized Fe3O4/PMMA/PDA MIPNSs had average diameters of 180 nm, high saturation magnetization and a good magnetic response. The lyz-imprinted Fe3O4/PMMA/PDA MIPNSs exhibited specific recognition and efficient adsorption capacity toward lyz template. The amount of lyz adsorbed onto the lyz-imprinted Fe3O4/PMMA/PDA MIPNSs was about 4 times greater than that of the Fe3O4/PMMA/PDA non-imprinted polymer nanospheres (NIPNSs) and about 14, 5, and 5 times greater than that of BSA, BHb, and cyt C, respectively.

Ligand‐Free Fe3O4/CMCS Nanoclusters with Negative Charges for Efficient Structure‐Selective Protein Adsorption

The easy and effective capture of a single protein from a complex mixture is of great significance in proteomics and diagnostics. However, adsorbing nanomaterials are commonly decorated with specific ligands through a complicated and arduous process. Fe3 O4 /carboxymethylated chitosan (Fe3 O4 /CMCS) nanoclusters are developed as a new nonligand modified strategy to selectively capture bovine hemoglogin (BHB) and other structurally similar proteins (i.e., lysozyme (LYZ) and chymotrypsin (CTP)). The ligand-free Fe3 O4 /CMCS nanoclusters, in addition to their simple and economical two-step preparation process, possess many merits, including uniform morphology, high negative charges (-27 mV), high saturation magnetization (60 emu g(-1) ), and high magnetic content (85%). Additionally, the ligand-free Fe3 O4 /CMCS nanoclusters are found to selectively capture BHB in a model protein mixture even within biological samples. The reason for selective protein capture is further investigated from nanomaterials and protein structure. In terms of nanomaterials, it is found that high negative charges are conducive to selectively adsorb BHB. In consideration of protein structure, interestingly, the ligand-free magnetic nanoclusters display a structure-selective protein adsorption capacity to efficiently capture other proteins structurally similar to BHB, such as LYZ and CTP, showing great potential of the ligand-free strategy in biomedical field.

Synthesis of amphipathic superparamagnetic Fe3O4 Janus nanoparticles via a moderate strategy and their controllable self-assembly

Recently, amphipathic Janus Fe3O4 nanoparticles, with distinct hydrophilic and hydrophobic “faces”, have attracted tremendous attention. However, conventional synthesis methods for these nanoparticles either influenced the superparamagnetism of Fe3O4 nanoparticles or failed to endow Fe3O4 nanoparticles evident amphipathy, and thus as-prepared amphipathic Janus Fe3O4 nanoparticles hardly reveal remarkable self-assembly properties. To address these critical issues, a versatile strategy that combines activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP) and Pickering emulsions is proposed here to synthesize amphipathic Janus Fe3O4 nanoparticles for the first time. Owing to the masterly integration all of the unique features of ARGET-ATRP and Pickering emulsions, Janus Fe3O4 nanoparticles with high saturation magnetization and diverse self-assembly behaviors in different solvents are successfully prepared in a gentle, simple and highly controllable reaction condition. Furthermore, these Janus Fe3O4 nanoparticles exhibit prominent emulsification in toluene–water model system as their superior amphipathy. These emulsions could not only maintain excellent stability even in an extremely low usage of Janus Fe3O4 nanoparticles, but also be easily separated by an external magnetic field because of the intrinsic superparamagnetism of Fe3O4. The result implies that the as-received Janus Fe3O4 nanoparticles may have extensive application prospects in oil purification from oil–water compounds. This synthesis strategy likewise could be a guidance to synthesize similar Janus materials.

Superparamagnetic nanocomposites based on surface imprinting for biomacromolecular recognition.

A combination strategy of moderate self-polymerization and assembly technique was proposed to fabricate superparamagnetic surface imprinted nanocomposites (SSINs) for efficient protein recognition. Homogeneous Fe3O4/Poly (methyl methacrylate) (PMMA)/Poly (dihydroxyphenylacetic acid) (PDOPA) SSINs were obtained via self-polymerization of DOPA on the surface of Fe3O4/PMMA nanospheres in the presence of lysozyme (Lyz) as a template. The Lyz-imprinted Fe3O4/PMMA/PDOPA SSINs possessed average diameters of 200nm, high magnetic content, high saturation magnetization, as well as excellent specific recognition capacity toward Lyz template, exhibiting their great potential for biomacromolecular recognition.

Polyethylene Glycol-Functionalized Magnetic Fe3O4/P(MMA-AA) Composite Nanoparticles Enhancing Efficient Capture of Circulating Tumor Cells

Circulating tumor cells (CTCs) played a significant role in early diagnosis and prognosis of carcinomas, and efficient capture of CTCs was highly desired to provide important and reliable evidence for clinical diagnosis. In present work, we successfully synthesized functional magnetic Fe3O4/P(MMA-AA) composite nanoparticles (FCNPs) inspired by a counterbalance concept for recognition and capture of CTCs. This counterbalance, composed of polyethylene glycol (PEG) suppressing cell adhesion and anti-epithelial-cell-adhesion-molecule (anti-EpCAM) antibody targeting tumor cells, could both enhance the specific capture of tumor cells and reduce unspecific adhesion of normal cells. The study showed that the PEG density on the surface of the FCNPs affected the specificity of the materials, and a density of ca. 15% was efficient for reducing the unspecific adhesion. After incubation with the mixture of HepG2 cells and Jurkat T cells, the FCNPs reached a capture efficiency as high as about 86.5% of the cancer cells, suggesting great potential on detection of CTCs in the diagnoses and prognoses of cancer metastasis.

Protein Adsorption: Ligand-Free Fe3O4/CMCS Nanoclusters with Negative Charges for Efficient Structure-Selective Protein Adsorption (Small 17/2016)

Ligand-free negatively charged magnetic nanoclusters are first presented for effective structure-selective protein adsorption by F. Lan, Z. Gu and co-workers on page 2344. The nanoclusters could selectively capture bovine hemoglobin as well as structurally similar proteins (e.g., lysozyme, chymotrypsin) from model proteins and even biological samples due to their highly negative charge, exhibiting their great potential as candidates for practical bio-separation applications.