Gelatin: is a collection of high molecular weight peptides produced by hydrolysis of collagen usually isolted from bovine or porcine skin. Gelatin is obtained by the partial hydrolysis of collagen dervied from skin, white connective tissue and bones of animals. The top 4 sources are cohide splits, bones, pork skin and fish skin. There are no plant sources of gelatin. Hydrolyzed gelatin does not gel (hydrolyzed gelatin has had its gelling function enzymatically removed). Apart from its uses in therapeutic implants and device coatings, it is widely used as a stabilizer for therapeutic vaccines. For example, hydrolyzed gelatin is used as a stabilizer in the live attenuated measles, mumps and rubella virus vaccine (MMR vaccine). Natural gelatin preparations are very heterogeneous, consisting of a wide distribution of polypeptide sizes of varying isoelectric points and gelling properties. Gelatin derived from an acid-treated precurosr is known as Type A, and gelatin dervied from an alkali-treated precursor is known as Type B.
As is well known, when gelatin is solubilized in warm or hot aqueous solutions, the molcules ahve little organization. However, as a gelatin solution is allowed to cool, the gelatin molcules intertwine into a three dimensional matrix and the fixcosity of the solution increases. At a characteristic set temperature, a phase transformation changes the flowable solution into a non-flowable gel. The set time, set temperature and density of the resulting non-flowable mass are dependent on several factors including concentraiton of gelatin, the MW and the intrinsic viscosity of the gelatin molecules and on the pH of the composition. (McKay, US2007/0128249).
Gelatin is produced from collagen by acid (Ypte A) or alkaline (Type B) hydroysis and thermal denaturation of the collagen fibers. With heaing, the triple helix of the hydrolyzed collagen unfolds, and the protein becomes soluble. Cooling of the protein, now referred to as gelatin, causes partial re-folding of the helix and results in a network of helical junctions. At a critical point determiend by such factors as protein concentration, temperature, and ionic strenght of the solvent, the network is extensive enough to form a gel. These gels are thermoreversible gels, and their properties have been extensively studied (Bishop, US 5,834, 232).
Gelatin with other composition
Gelatin + antifungal/antibacterial ointments: Lin (US 2007/0065504) discloses a solid dosage from that can take the form of a soft gelatin capsul containing antifungal and antibacterail ointments designed to melt within a body cavity such as the rectum or vagina.
Gelatin/collagen + translutaminase: Bishop (US 5,834,232) discloses a method of preparing a cross linked protein gel by adding a transglutaminase such as factor XIII to a composition of a temperature sensitive gel forming protein such as gelatin or collagen. In one embodiment, the composition is in the form of an aqueous solution and in another embodiment the composition is in the form of a gel.
Gelatin + cross-linking agent + bioactive material: Yoo (US2011/0212501) disclsoes a 3 dimensional multi-layered hydrogel such as collagen or gelatin with bioactive agents such as antibodies and cells. A first nebulized layer of a cross-linking agent is first applied on a substrate, a hydrogen precursor is then applied on top fo the first corss-linking material such that the hydrogen precursor cross-links upon contact with the nebulized layer of cross-lining material to form a partically corss linked gel, a second nebulized layer of cross linking agent is applied on top of the partially corss-linked getl thereby promoting completing corss linking of the hydrogel layer.
Gelatin + Osteogenic factor: McKay (US 2007/0128249) discloses an osteogenic paste compsotion made with a substance such as gelatin, hyaluronic acid and/or carboxymethyl cellulose with an effective amount of an osteogenic fact effective for the induction and support of new bone growth in a primate. In use, the composition is implanted at a site at which bone growth is desired. In the case of compositions which are flowable at temperatures higher than the body temperature of the mammal in which they are to be implanted, yet which transition to a non-flowable mass at or near such body temperature, the composition is heated to a temperature at which it is flowable, but which will not denature any osteogenic factor present, molded or shaped to the shape of the desired new bone, cooled to a temperature sufficient to transition the osteogenic implant material into a non-flowable mass either in situe or implanted at the site of desired new bone formation.
Applications:
Gelatin has been extensively used in food products (e.g., gelatin desserts) (US 2,196,146). Hydrogels have also been used extensively for encapsulating various proteins such as interferon (US 2007/0248674), vaccine delivery (US 2005/0255121) wound dressing (US 6458386) and as a means to inhibit protein aggregation (US 2007/0190047). Hydrogels have also been used extensively for controlled drug delivery (US2008/0057128).