Not Applicable
Rudimentary bio-molecules such as proteins and polysaccharides, which usually have nanometer dimensions, achieve several levels of functionality in biological processes. Particles with nanometric dimensions (5-50 nm) therefore should be able to probe cellular phenomena, such as cellular trafficking. Nanoparticles intended for use in biology are generally classified as nano-biomaterials. At present, the ability to produce un-agglomerated individualized nanoparticles below 50 nm is a daunting task. A critical factor determining final aggregation of nanoparticles is stabilization of the particle at a particular pH range (generally physiological, pH 7.4) in the media of interest. Since particles smaller than 50 nm possess extremely high surface area (hence surface energy) colloidal stability remains a problem. This high surface energy leads to an “energy-driven,” uncontrolled aggregation which is highly unfavorable. As the fraction of atoms on the surface of a spherical particle, roughly 10 nm, becomes approximately 50% of the total, control over aggregation becomes even more critical. Organic molecules, adsorbed or chemisorbed on the surface of the nanoparticle can be used to control size. These absorbed molecules can further serve as linkers, facilitating the binding of various biocompatible moieties depending on the function required by a specific application (see, for example, Lebugle et al., 2006, Yang, et al., 2008, and Aissa, et al., 2009). Functional nano-biomaterials, in addition to being an appropriate size and displaying minimal toxicity should also posses certain qualities to effectively be used for biological applications. These qualities are:
The combination of these characteristics coupled with suitable particle size tuned for the application make nanoparticles highly versatile for a large number of biological and other applications. Ideally, the combination of selectivity and tuned luminescent and magnetic properties results in the simultaneous ability to detect, target, and manipulate nanoparticles.
All patents, patent applications, provisional patent applications and publications referred to or cited herein, are incorporated by reference in their entirety to the extent they are not inconsistent with the teachings of the specification.
The invention involves the synthesis of calcium-phosphate based nanoparticles (CAPNP) which are simultaneously intrinsically magnetic and fluorescent, and extrinsically surface modified to serve an attachment function. This is achieved by doping calcium phosphates during colloidal synthesis resulting in 10 nm particles that are stable in aqueous media and importantly at physiological pH. The synthesis is simple (with a high potential for scale up and production) and enables in one step the production of several modified CAPNPs. These magnetically, electronically and optically enhanced nanoparticle dispersions are synthesized similarly by introducing metal dopants into the base crystal lattice during synthesis. The biologically benign and chemically stable nature of this material make these nanoparticles ideal candidates for controlled biomedical imaging and biochemical sensing, and as cellular delivery vehicles. Coupled with this is the fact that surfaces of these particles can be conveniently functionalized and can be linked to a host of other agents (molecules) to achieve several other levels of functionality, such as self-assembly, cellular and tissue specificity and prolonged turn over time in vivo.
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Colloidally stable apatite nanoparticles (10-20 nm) with the intrinsic ability to exhibit fluorescent and super-paramagnetic properties simultaneously possess the potential for interaction, are easy to track and detect, are easily manipulated, and are versatile tools for many applications.
Generally, the nanoparticles of the subject invention are synthesized by equilibrating a calcium ion source, or salt thereof. An appropriate calcium ion chelator is added to the equilibrated solution. An appropriate chelator is one that chelates Ca2+ ions such that the free energy reduction associated with the chelation does not exceed the free energy reduction associated with the formation of the apatite phase. Finally, a phosphate source is added to begin nanoparticle formation. Molar concentrations of calcium to phosphate should be about 10:6. The pH of the calcium phosphate solution is adjusted to from about 8.0 to about 9.0 and an amorphous calcium phosphate precursor gel is formed. As the gel ages calcium hydroxyl-carbonated apatite nanoparticles are formed. An effective amount of a metal ion is added to the base crystal lattice during formation to impart magnetic and luminescent properties to the nanoparticles. In a particularly preferred embodiment, iron is added during synthesis at about 5 molar to about 40 molar percent. In another preferred embodiment, neodymium is added to the nanoparticles during synthesis at about 5 molar to about 30 molar percent.
The following examples are offered to further illustrate but not limit both the compositions and the methods of the present invention. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted.
A preferred embodiment of the nanoparticles of the subject invention are synthesized as follows:
A preferred embodiment of the metal doped apatite nanoparticles of the subject invention are synthesized as follows:
The nanoparticles from Example 1 were examined using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) and size distribution as determined by these techniques confirmed a 10-20 nm size range for these apatite particles. The particles were more spheroidal (
The iron (Fe) and neodymium (Nd) substituted particles (Example 2) were also analyzed similarly and FESEM and FTIR spectroscopy results indicated that the size range and chemical structure of these doped apatite nanoparticles were similar to the undoped samples. The doped nanoparticles exhibited variation in their absorbance profiles (example for Nd—HA is shown in
These easy to synthesize particles can be used for detection and treatment-based therapies with higher levels of control greatly impacting health care in the near future. Spheriodal metal-ion doped neodymium (Nd), samarium (Sm), iron (Fe) and copper (Cu) multi-functional apatite nanoparticles (
Transmission electron microscopy studies show that the nano-apatite particles of the subject invention interact with bacteria in a specific manner; and accumulated at the ends, as apposed to the sides, of the organism (
Further, application potential for the subject nanoparticles include, but are not limited to, tunable contrast dyes for MRI, as well as candidates for externally controllable nano-detection devices. Nanoparticles with individual properties, synthesized through various physical and chemical processing routes, are currently available however the combination of intrinsic multi-functionality has not been demonstrated thus far from single or even multiple doping ions. The realization of these properties are also linked to the physiochemical and crystallographic properties of the calcium-hydroxy carbonate-apatite which allow for a substantial metal ion substitution before the apatite structure is compromised. Other than being colloidally stable, achieved through a molecular capping technique during early nucleation and growth, the same surface carboxylate moieties can facilitate the surface functionalization of the nano-apatite particles with other simple linkers (e.g. amine, thiol, etc.) or more complex molecules such as biotin.
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.
This application claims the benefits of U.S. Provisional Application No. 61/104,652 filed Oct. 10, 2008, the disclosure of which is hereby incorporated by reference in its entirety including all figures, tables and drawings.
This invention was made in part with Government support under Grant No. B28026 awarded by the National Science Foundation. The government has certain rights in the invention.
Number | Date | Country | |
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61104652 | Oct 2008 | US |