This review summarizes recent advances in synthesis routes for quickly and reliably making and functionalizing magnetic nanoparticles for applications in biomedicine. We put special emphasis on describing synthetic strategies that result in the production of nanosized materials with well-defined physical and crystallochemical characteristics as well as colloidal and magnetic properties. Rather than grouping the information according to the synthetic route, we have described methods to prepare water-dispersible equiaxial magnetic nanoparticles with sizes below about 10 nm, sizes between 10 and 30 nm and sizes around the monodomain–multidomain magnetic transition. We have also described some recent examples reporting the preparation of anisometric nanoparticles as well as methods to prepare magnetic nanosized materials other than iron oxide ferrites, for example Co and Mn ferrite, FePt and manganites. Finally, we have described examples of the preparation of multicomponent systems with purely inorganic or organic–inorganic characteristics.

A simple procedure is used to prepare anisometric iron oxide nanoparticlesexhibiting superparamagnetic behavior. The figure shows the nanorod/nanorice morphology of these novel structures. Superparamagnetism is engineered in these structures by favoring thermally activated processes by adopting small particle sizes, introducing defects, and doping with cations. Positively and negatively charged particles are obtained by varying the surface coating.

We present a method to produce superparamagnetic iron oxide/silica nanocomposites that have a large BET surface area, a high pore volume, and at least one pore size population centered at around or larger than 10 nm. By means of this methodology, which is based on nanocasting techniques, we are able to not only prepare mesoporous iron oxide/silica nanocomposites with adequate pore sizes and magnetic properties for enzyme immobilization but also explore various phenomena associated with the characteristics of the magnetic mesoporous matrixes. Magnetic nanocomposites that have a ordered mesostructured porosity, a high BET surface area, and a high pore volume display a better distribution of their magnetic components and superior magnetic properties than magnetic nanocomposites with a disordered mesostructured porosity and low BET surface area. The applicability of this kind of composites for the immobilization and magnetic separation of biomolecules has been clearly demonstrated in the case of lysozyme.

The individual and co-operative properties of inorganic and hybrid superparamagnetic colloidal nanocomposites that satisfy all the requirements of magnetic carriers in the biosciences and/or catalysis fields are been studied. Essential to the success of this study is the selection of suitable synthetic routes (aerosol and nanocasting) that allow the preparation of materials with different matrix characteristics (carbon, silica, and polymers with controlled porosity). These materials present magnetic properties that depend on the average particle size and the degree of polydispersity. Finally, the analysis of the co-operative behavior of samples allows for the detection of signatures of clustering, which are closely related to the textural characteristics of samples and the methodology used to produce the magnetic carriers.

Development of nanosized materials to enhance the image contrast between the normal and diseased tissue and/or to indicate the status of organ functions or blood flow is essential in nuclear magnetic resonance imaging (MRI). Here we describe a contrast agent based on a new iron oxide design (superparamagnetic iron oxide clusters embedded in antiferromagnetic iron oxide porous nanorods). We show as a proof-of-concept that aqueous colloidal suspensions containing these particles show enhanced-proton relaxivities (i.e., enhanced MRI contrast capabilities). A remarkable feature of this new design is that large scale production is possible since aqueous-based routes are used, and porosity and iron oxide superparamagnetic clusters are directly developed from a single phase. We have also proved with the help of a simple model that the physical basis behind the increase in relaxivities lies on both the increase of dipolar field (interactions within iron oxide clusters) and the decrease of proton-cluster distance (porosity favors the close contact between protons and clusters). Finally, a list of possible steps to follow to enhance capabilities of this contrast agent is also included (partial coating with noble metals to add extra sensing capacity and chemical functionality, to increase the amount of doping while simultaneously carrying out cytotoxicity studies, or to find conditions to further decrease the size of the nanorods and to enhance their stability).

No abstract

Porous magnetic nanorods with sizes readily modulated and high water affinity are prepared via a water-in-oil/water solvothermal method.

In vitro effects of 635-nmdiode laser irradiation on the lipidic inclusions and the cellular fat distribution were observed in situ on a selected multilocular adipose cell in culture by an effective laser power of 3 . 1 6 mW. Selected microscopic field was 12 times sequentially irradiated, using 100 seconds exposures, a free spot of 5 mm and effective energy density of 1.6 Jcm2 per exposure. Same field was irradiated 24 times using a beam spot of 10 mm, 0.4 Jcm2. Digital microphotograph sequences permit to observe and follow changes in fat distribution. Results show changes in fat vesicles. Microscopic follow-up shows an almost empty vacuole 15 hours after irradiation, the cell was empty after 42 hours, and dies after 52 hours.