Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Reexamination Certificate
2001-09-05
2004-11-23
Naff, David M. (Department: 1651)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
C424S094100, C435S176000, C435S180000, C436S525000, C436S531000, C514S002600, C530S402000, C530S811000, C530S815000
Reexamination Certificate
active
06821529
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT
No Federally sponsored research and development was used in making this invention.
BACKGROUND OF THE INVENTION
Since they were first reported by Nuzzo and Allara in 1983, self-assembled monolayers (SAMs) composed of sulfur-terminated organic molecules adsorbed on and adherent to gold surfaces have shown broad utility in lubrication, electrochemistry, electronic and vibrational spectroscopy, photochemistry, diagnostics, the modification of biochemical membranes, catalysis, drug delivery, and facile modification of the absorptive properties of surfaces. (R. G. Nuzzo and D. L. Allara. Adsorption of bifunctional organic disulfides on gold surfaces. J. Am. Chem. Soc. 1983; 105: 4481-4483.) More recently, organic modifications of gold surfaces by SAMs have proven to be successful in nanotechnological biosensor applications, e.g., in commercially available chips for biomolecular interaction analysis with surface plasmon resonance. (S. L{haeck over (o)}fås, B. Johnsson, K. Tegendahl, and I. R{haeck over (o)}nnberg. Colloids Surf. B 1993; 1: 83-89.)
For example, Dijksma and coworkers have reported that an electrochemical immunosensor composed of self-assembled monolayers of cysteine or N-acetylcysteine on gold electrodes is useful for the detection of interferon-&ggr; at the attomolar level. (M. Dijksma, B. Kamp, J. C. Hoogvliet, and W. P. van Bennekom. Development of an electrochemical immunosensor for direct detection of interferon-&ggr; at the attomolar level. Analyt. Chem. 2001; 73: 901-907.) Similarly, Darder and coworkers have found that horseradish peroxidase retained its activity when immobilized onto a gold surface via a 3-thiopropionate tether and was useful as a peroxide biosensor. (M. Darder, K. Takeda, F. Pariente, E. Lorenzo, and H. D. Abruña. Dithiobissuccinimidyl propionate as an anchor for assembling peroxidases at electrodes surfaces and its application in a H
2
O
2
biosensor. Analyt. Chem. 1999; 71: 5530-5537.)
Likewise, poly- and oligo(ethylene glycols) (PEGs or OEGs, respectively; Structure 1, where R
1
is MeO or HO and R
2
is OH) have found widespread use in a variety of biotechnological and commercial applications, including the preparation of surfactants, ion-conducting materials, and conjugates of low and high molecular weight molecules. Investigators have found that these glycols provide good anchors for biological and non-biological receptor/reporter molecules or for ligands for biological and non-biological chelation or binding sites. Moreover, both PEGs and OEGs are known to reduce the nonspecific binding of proteins and other bioactive molecules to the surface to which they are conjugated. PEG and OEG derivatives are ideal for these applications because they are inexpensive, water soluble, stable, nonantigenic and non-immunogenic, and commercially available in a wide range of molecular weight distributions.
R
1
—CH
2
CH
2
O—(CH
2
CH
2
O)
x
—CH
2
CH
2
—R
2
Structure 1
In addition, conjugation with more highly branched and dendritic poly- and oligo(ethylene glycols) has been reported to be useful for improving the stability of protein drugs. [(a) D. C. Tully and J. M. J. Frechet. Dendrimers at surfaces and interfaces: chemistry and applications. Chem. Commun. 2001; 1229-1239. (b) I. Fuke, T. Hayashi, Y. Tabata, and Y. Ikada. Synthesis of poly(ethylene glycol) derivatives with different branchings and their use for protein modification. J. Controlled Release 1994; 30: 27-34. (c) J. M. Harris, F. M. Veronese, P. Caliceti, and O. Schiavon, U.S. Pat. No. 5,932,462.]
The broad utility of both classes of reagents (i.e., SAMs and PEGS or OEGS) suggests that synergistic benefits would obtain if libraries of reagents were available that combined the beneficial attributes of a SAM with those a PEG or OEG and exhibited additional features, such as the presence of reactive or activated groups at one end of each PEG or OEG chain. This combination of attributes would enable attachment of one terminus of such a combined SAM-forming-OEG reagent to a metal surface, yielding a SAM-OEG reagent, and attachment of a biological or non-biological receptor, ligand or reporter moiety at each of the other activated or reactive termini of the combined SAM/OEG reagent. The literature reports that describe examples of combined SAM/OEG reagents are limited to disclosures of methods of synthesis of OEG conjugates of linear alkyl monothiols and the effects of structure on the stability and physico-chemical properties of the reagents and the SAMs formed from them. (S. Svedhem, C-A. Hollander, J. Shi, P. Konradsson, B. Liedberg, and S. C. T. Svensson. Synthesis of a series of oligo(ethylene glycol)-terminated alkanethiol amides designed to address structure and stability of biosensing surfaces. J. Org. Chem. 2001; 66: 4494-4503.) Thus, the known reagents are limited to alkyl monothiols that lack an activated or reactive terminus at the end of the OEG chain and other desirable attributes that would enhance their utility.
Clearly, significant biotechnological advances in a spectrum of areas would be possible if activated or reactive, oligo(ethylene glycol)-terminated reagents and OEG-terminated reagents conjugated with a biological or non-biological receptor, ligand or reporter moiety useful for preparing self-assembled monolayers on gold were available. The present invention addresses this need.
SUMMARY OF THE INVENTION
The invention is based upon the recognition that the availability of activated or reactive, oligo(ethylene glycol)-terminated dithiolane compositions suitable for use in preparing self-assembled monolayers on a metal would enable significant advances in the biotechnological arts.
Thus, the invention provides highly versatile tethers suitable for immobilization on a metal backbone, wherein one segment of the tether is a linear or branched oligo(ethylene glycol) residue and the other segment of the tether is an alkyl-substituted 1,2-dithiolane. Further, one terminus of each oligo(ethylene glycol) residue is activated or reactive, enabling the preparation of conjugates of the oligo(ethylene glycol)-terminated dithiolane compositions that are also suitable for immobilization on a metal backbone.
One embodiment of the present invention comprises linear or branched oligo(ethylene glycol)-terminated 3-alkyl-1,2-dithiolanes having the formula:
wherein m is from about 3 to about 20; n is from 2 to about 6; OEG is shorthand for a linear oligoether having the general structure —(CH
2
CH
2
O)
x
— wherein x is from 2 to about 100, or for a branched oligoether wherein each branch comprises a linear oligoether having this general structure; one terminus of the OEG residue is covalently joined to the terminus of the alkyl side chain of the dithiolane by a linker L, wherein L is N, O, S, P, or an amide or hydrazide group; and each of the other termini of the OEG residue is a reactive or activated substituent Z that can be joined covalently to a biological or non-biological, ligand, sequestering, or reporter moiety. Examples of suitable reactive or activated substituents Z include an amino, guanidino, sulfhydryl, or activated ester moiety; a substituent that is reactive toward nucleophilic displacement, such as chloride, bromide, iodide, tosylate, tresylate, or mesylate; a group that is reactive toward nucleophilic addition, such as cyanate, isocyanate, thiocyanate, isothiocyanate, maleimide, oxirane, thiirane, or azirane; a carbonyl group; or a hydroxyl group.
A preferred embodiment comprises oligo(ethylene glycol)-terminated thioctic acid derivatives having the formula:
wherein n is from 2 to about 6; the symbol OEG is a linear oligoether having the general structure —(OCH
2
CH
2
)
x
— and x is from 2 to about 100, or is a branched oligoether wherein each branch comprises a linear oligoether having this general structure; one terminus of the OEG residue is covalently joined to the alkyl side chain of thioctic acid by a linker L, wherein L is amide or hydrazi
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