Biocompatible capsules and methods of making
Inventors
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-9770405-B1
Publication Date
2017-09-26
Expiration Date
2032-10-04
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Abstract
Embodiments of the invention include capsules for containing medical implants and delivery systems for release of active biological substances into a host body. Delivery systems comprise a capsule comprising an interior enclosed by walls, and a source of active biological substances enclosed within the capsule interior, wherein the active biological substances are free to diffuse across the capsule walls. The capsule walls comprise a continuous mesh of biocompatible fibers and a seal region where two capsule walls overlap. The interior of the capsule is substantially isolated from the medium surrounding the capsule, except for diffusion of at least one species of molecule between the capsule interior and the ambient medium, and prevents cell migration into or out of the capsule. Methods for preparing and using the capsules and delivery systems are provided.
Core Innovation
The invention provides capsules for containing medical implants and delivery systems for releasing active biological substances into a host body. These capsules comprise an interior enclosed by walls formed from a continuous mesh of biocompatible fibers, with a seal region where two capsule walls overlap. This seal is sufficiently continuous to prevent cell migration into or out of the capsule, allowing diffusion of molecules but isolating the interior from the host environment with respect to cells.
The problem addressed relates to limitations in transplantation of cells and tissues due to host immune rejection, as well as immune responses to implantable medical devices. Existing materials for immune shielding often provoke immune reactions or fibrotic scar formation, which obstruct pores necessary for nutrient and waste exchange. Previous methods using flat pieces of Bucky paper required seams and sutures that could compromise structural integrity and allow infiltration of immune cells.
The invention improves upon prior methods by providing a way to form three-dimensional capsules from a mesh of biocompatible fibers such as carbon nanotubes, without requiring stitching or additional materials for sealing. The capsules are formed using perforated molds that cause fibers to deposit conformally and form sealed containers by van der Waals forces and fiber entanglement alone. This allows manufacture of capsules with controlled porosity, shapes, and incorporation of additional functional elements like beads or interior scaffolds, providing enhanced immune shielding and controlled release or sensing of biological substances.
Claims Coverage
The patent includes one independent claim detailing a method for preparing a biocompatible capsule with multiple inventive features related to capsule formation, sealing, and component assembly.
Method for preparing biocompatible capsules using perforated molds
Provides a method involving immersing a perforated mold into a suspension of biocompatible fibers, withdrawing the suspending medium through the mold to form a tangled fiber mesh conforming to the mold shape, and removing the mold to produce capsule components.
Sealing capsule components by fiber overlap and van der Waals forces
Details sealing by forming at least one region of overlap between capsule components where fibers are in intimate contact, pressing them to bind by van der Waals forces, creating a smooth exterior and substantially isolating the capsule interior except for molecular diffusion.
Assembly of capsule components via differing diameters with overlap
Describes assembling capsule components of different diameters by inserting the smaller diameter component into the larger one, creating an overlap region sealed by van der Waals attraction without additional fasteners.
Insertion of biological or medical materials before sealing
Allows insertion of cells or medical devices into the capsule prior to sealing, enabling encapsulation of active biological substances or devices.
Use of various biocompatible fiber materials
Specifies that fibers include carbon nanotubes, carbon fibers, carbon nanofibers, graphene forms, and polysaccharides.
Orientation and layering of fibers during capsule formation
Permits controlling fiber orientation and incorporating distinct fiber types into one or more layers during formation for tailored capsule properties.
Incorporation of beads into the capsule structure
Includes embedding beads into one or more distinct fiber layers or into the capsule interior before sealing to augment capsule functionality or enable triggering.
Formation of interior fiber scaffolds
Allows incorporation of fibers into the capsule interior to form scaffolds supporting cell growth or tissue maintenance before sealing.
The independent claim collectively defines a method for forming biocompatible capsules by deposition of fiber meshes using perforated molds, sealing via fiber overlap and van der Waals interaction without additional materials, and assembly into sealed containers capable of housing cells, devices, or substances with control over fiber materials, orientation, layering, and incorporation of beads or interior scaffolds.
Stated Advantages
The capsules reduce the number of seams compared to prior methods, decreasing the chance of leakage or rupture and enhancing immune isolation of the contents.
Manufacturing with perforated molds allows a wider variety of capsule shapes and dimensions with improved efficiency and minimal manual intervention.
Sealing without sutures, glue, or clamps avoids introducing less biocompatible materials that could provoke immune responses, improving capsule biocompatibility.
Control over fiber orientation and layering optimizes mechanical properties, pore size, and overall capsule function for specific applications.
Incorporation of beads enables additional functionalities such as external triggering, imaging markers, or radiation treatment capability.
Documented Applications
Immune shielding and transplantation of cells or tissues for endocrinology such as islet cell transplantation for diabetes treatment.
Gene therapy using encapsulated genetically engineered cells producing therapeutic proteins like clotting factors.
Local delivery of chemotherapeutic agents for cancer treatment using sustained release compositions encapsulated within the capsules.
Encapsulation of antibody-producing cells near tumor sites for localized cancer immunotherapy.
Use as delivery systems for active biological substances including hormones, cytokines, growth factors, and other pharmacological agents.
Encapsulation of medical devices for implantation, including miniaturized devices such as osmotic pumps or pacemakers, with immune shielding and nonthrombogenic properties.
Biosensing applications by encapsulating sensors within capsules to monitor analyte concentrations like glucose in vivo.
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