Preparation and use of silver sulfadiazine-immobilized fillers

Abstract

Silver sulfadiazine-immobilized inorganic fillers are described, and their synthesis is presented. The fillers are believed to have utility in dental composites and dental adhesives to achieve potent, long-term, and none-leaching antimicrobial effects.

Claims

1. A composition of matter, comprising: a particulate glass substrate modified as follows: ##STR00003## wherein X is Cl or ##STR00004##

2. The composition of matter of claim 1, comprising ##STR00005## wherein X is ##STR00006##

3. The composition of matter of claim 1, wherein said particulate glass substrate comprises a glass comprising BaO.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The objects and features of the invention can be better understood with reference to the drawings described below, and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views.

(2) FIG. 1 is a reaction scheme for preparing a glass substrate with (3-aminopropyl)trimethoxysilane (APTMS).

(3) FIG. 2 is an FTIR spectrum of A-Glass, or amine-functionalized glass as produced by the reaction scheme of FIG. 1.

(4) FIG. 3 is a schematic reaction of A-Glass-CyCl with sulfadiazine to produce reaction product A-Glass-CyCl-SD.

(5) FIG. 4 is an FTIR spectrum of A-Glass-CyCl-SD.

(6) FIG. 5A is an image of A-Glass-CyCl-SD treated with chlorine bleach.

(7) FIG. 5B is an image of A-Glass-CyCl-SD treated with chlorine bleach and then with KI.

(8) FIG. 6 is a reaction scheme for preparing a silver sulfadiazine-inorganic filler conjugate A-Glass-CyCl-SD-Ag according to principles of the invention.

(9) FIG. 7 is an SEM-EDS spectrum of A-Glass-CyCl-SD-Ag.

DETAILED DESCRIPTION

(10) The invention creates silver sulfadiazine-immobilized inorganic fillers, and uses the resulting fillers in dental composites and dental adhesives to achieve potent, long-term, and none-leaching antimicrobial effects. In the examples that follow, glass is recited as a substrate material. It is believed that other biologically-inert inorganic materials may also be used as suitable particulate substrates in place of glass. In various embodiments, the methods of the invention include the following steps:

(11) Sulfadiazine is covalently attached onto conventional inorganic fillers (such as glass powders) used in dental composites. This can be achieved by chemically modifying the filler surfaces to introduce reactive groups onto the filler surfaces, and then reacting the new functional groups with the amino groups on sulfadiazine to form covalent linkage. The resulting sulfadiazine-filler conjugates are believed to be novel. The following examples show how this can be done.

(12) Preparation of Amine Modified Glass (A-Glass):

(13) FIG. 1 is a reaction scheme for preparing a glass substrate with (3-aminopropyl)trimethoxysilane (APTMS). As shown in FIG. 1, in one embodiment 8.0 g glass powder was reacted with 12.0 ml (3-aminopropyl)trimethoxysilane in a reaction medium comprising mixed with 100 ml cyclohexane and 3.2 ml n-propyl amine. The reaction was allowed to proceed at room temperature for 2 h. The solvent was then removed under vacuum and keep the sample in oven at 100 C. for 2 h. The samples were washed with cyclohexane 3 times under ultracentrifugation to remove unattached APTMS and other side products. Finally the sample was dried under vacuum. The glass is illustrated in the lower right corner of FIG. 1 as silicate glass having approximately 33% BaO content. It is believed that the reaction of the (3-aminopropyl)trimethoxysilane with the glass occurs at hydroxyl moieties in the glass surface.

(14) The amine functionalization at the glass surface was confirmed by FTIR as shown in FIG. 2. FIG. 2 is an FTIR spectrum of A-Glass, or amine-functionalized glass as produced by the reaction scheme of FIG. 1.

(15) The Reaction of Cyanuric Chloride with the Amine-Modified Glass to Prepare A-Glass-CyCl

(16) Cyanuric chloride is an organic compound with the formula (NCCl).sub.3 and the chemical structure

(17) ##STR00001##

(18) Place 4 g amine modified glass (A-Glass) into a 3-neck round bottom flask. Add 80 ml acetone and stir the solution for 15 min at 0-5 C. After proper dispersion of A-Glass in acetone, add 1.970 g (10.3 m mol) cyanuric chloride. After mixing, add Na.sub.2CO.sub.3 solution (1.280 g in 35 ml water), and continue the reaction at 0-5 C. for 1 h and then at 30 C. for 2 h. Wash the product (A-Glass-CyCl) with acetone 3 times and dry it under vacuum.

(19) Reaction of Sulfadiazine with the Cyanuric Chloride Treated Amine Modified Glass (A-Glass-CyCl-SD)

(20) Sulfadiazine is a sulfonamide antibiotic having the chemical structure

(21) ##STR00002##

(22) 3 g of A-Glass-CyCl were added to 80 ml DMSO, and 1.5732 g sulfadiazine (SD) was added, followed by the addition of aqueous Na.sub.2CO.sub.3 solution (0.7417 g in 50 ml DI water) dropwise over the period of 30 min. After reaction at 60 C. for 5 h, the temperature was increased to 100 C. for the next 3 h. The reaction was then continued at room temperature overnight. The products were washed with 2 times with DMSO and then 3 times with DI water, and dried under vacuum.

(23) FIG. 3 is a schematic reaction of A-Glass-CyCl with sulfadiazine to produce reaction product A-Glass-CyCl-SD.

(24) The reaction product A-Glass-CyCl-SD is confirmed by FTIR analysis and KI test.

(25) FIG. 4 is an FTIR spectrum of A-Glass-CyCl-SD.

(26) The KI Test

(27) Treat a small amount of modified glass powder A-Glass-CyCl-SD with 1:30 dilute chlorine bleach at room temperature (RT) for 1 h. After treatment, filter it and wash with DI water thoroughly to remove unreacted chlorine bleach. Dry the powder at RT and treat it with 5% aqueous solution of KI. There is a color change from white to yellow-brown spontaneously as shown in FIG. 5A and FIG. 5B.

(28) FIG. 5A is an image of A-Glass-CyCl-SD treated with chlorine bleach.

(29) FIG. 5B is an image of A-Glass-CyCl-SD treated with chlorine bleach and then with KI.

(30) Preparation of Silver Sulfadiazine-Inorganic Filler Conjugates

(31) Silver sulfadiazine-inorganic filler conjugates are prepared. This is accomplished by reacting sulfadiazine-filler conjugates as described above with a source that can provide silver, e.g., silver nitrate aqueous solution. The sulfadiazine will form a complex with the silver cations, leading to the formation of silver sulfadiazine-inorganic filler conjugates, which are believed never to have been reported before. The following example shows how this can be done.

(32) Silver Salt of Modified Glass (A-Glass-CyCl-SD-Ag)

(33) Put 2.5 g of A-Glass-CyCl-SD in 60 ml DI water in a small beaker under magnetic stirring. Add 0.65 g AgNO.sub.3, and stir the mixture at room temperature under dark overnight. After the reaction, wash the sample with DI water 6 times to remove un-attached silver.

(34) FIG. 6 is a reaction scheme for preparing a silver sulfadiazine-inorganic filler conjugate A-Glass-CyCl-SD-Ag

(35) The surface functionalization was confirmed by SEM-EDS and the results are shown in FIG. 7.

(36) FIG. 7 is an SEM-EDS spectrum of A-Glass-CyCl-SD-Ag.

(37) The silver content attached to modified glass powder was also confirmed by inductively coupled plasma atomic emission spectrometric analysis. This analysis was outsourced from an external laboratory.

(38) Antimicrobial dental composites and/or dental adhesives are prepared. This is achieved by adding silver sulfadiazine-inorganic filler conjugates into the dental composites or dental adhesive formulations to replace the conventional inorganic fillers totally or partially, and follow the conventional preparation methods to produce antimicrobial dental composites and/or dental adhesives. These composites or adhesives that contain silver sulfadiazine-inorganic filler conjugates to produce antimicrobial functions have never been reported.

(39) In the preparation of resin composite, 49.5% bis-glycidylmethacrylate (bisGMA), 49.5% triethylene glycidyldimethacrylate (TEGDMA), 0.2% camphor quinone (CQ) and 0.8% 4-ethyl dimethylamino benzoate (4-EDMAB) were used as the resin parts (30% by weight), and glass powders were used as fillers (70% by weight). The control discs contained 100% of the original commercial glass to make up the 70% filler weight. For the antimicrobial discs, 2%, 5%, 10%, of the original glass was replaced by the silver glass powder (A-Glass-CyCl-SD-Ag).

(40) The prepared composite mixture was placed in a custom made mold of 6.0 mm in diameter and 1.0 mm in height. A blue LED light at the wavelength 395-480 nm with 1000 mW/cm.sup.2 of intensity was focused on the composite mixtures for 100 seconds to cure the resins.

(41) After curing, the resin discs were used for the following antimicrobial tests. The bacteria, S. mutans, were grown and harvested following ATCC's recommendations. In a typical test, 2.5 l bacteria solution with 10.sup.6-10.sup.7 CFU of the bacteria were placed on a disc, which was covered by another identical disc to make a sandwich. After 30 min of contact, the discs were placed in 1 ml PBS solution and vortexed for 60 seconds to wash out all the bacteria attached to the disks. The solution was serially diluted, and each dilution was placed on agar plates for incubation at 37 C. with 95% air and 5% CO.sub.2 for 24 h. Colony forming units (CFUs) on the agar plates were counted. We found that from the control disc, as high as 10.sup.6 CFU/cm.sup.2 of bacteria could be recovered. From the discs with 10% of the silver glass, no any bacteria could be recovered, demonstrating powerful antimicrobial effects.

(42) It is believed that the non-leaching properties of the anti-microbial agents are novel. The antimicrobial agents are covalently bound onto fillers, and will not leach away.

(43) In addition, the compositions described are expected to provide potent antimicrobial activity, be safe to use, and suffer no discoloration: Silver has potent antimicrobial effects and is safe to use. Thus, prior studies have used silver nano particles for dental applications. However, in the earlier applications, silver was easily oxidized and changed its appearance to a black color, which limited the acceptance of such materials as dental composites and dental adhesives. In the present invention, silver is bound onto the filler and forms coordination complexes with sulfadiazine. The resulting silver-sulfadiazine has the same efficacy and safety, yet it is white, and does not change to black. It is believed that this property will significantly improve the acceptance.

(44) In the present invention, the antimicrobial agents are covalently bound onto conventional fillers. The appearance and handling characteristics of the resulting fillers will not be significantly altered. From the users' (dentists') point of view, no new monomers or new nano fillers are used, and they can still use the instruments and procedures they are most familiar with in their clinics. This ease of use (and use as a substitute material in presently available application/treatment methods) is believed to be a further help for the acceptance of the resulting products.

(45) The compositions of the invention are believed to be useful in dental composites, dental adhesives, and other related applications. It is believed that the present invention provides a novel solution for a long-standing problem in dental (and possibly other medical) technology.

(46) Theoretical Discussion

(47) Although the theoretical description given herein is thought to be correct, the operation of the devices described and claimed herein does not depend upon the accuracy or validity of the theoretical description. That is, later theoretical developments that may explain the observed results on a basis different from the theory presented herein will not detract from the inventions described herein.

(48) Any patent, patent application, patent application publication, journal article, book, published paper, or other publicly available material identified in the specification is hereby incorporated by reference herein in its entirety. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material explicitly set forth herein is only incorporated to the extent that no conflict arises between that incorporated material and the present disclosure material. In the event of a conflict, the conflict is to be resolved in favor of the present disclosure as the preferred disclosure.

(49) While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be affected therein without departing from the spirit and scope of the invention as defined by the claims.