Novel composite fiber structures to provide drug/protein delivery for medical implants and tissue regeneration

Drug-Eluting Medical Textiles: From Fiber Production and Textile Fabrication to Drug Loading and Delivery

Drug-eluting medical textiles have recently gained great attention to be used in different applications due to their cost effectiveness and unique physical and chemical properties. Using various fiber production and textile fabrication technologies, fibrous constructs with the required properties for the target drug delivery systems can be designed and fabricated. This review summarizes the current advances in the fabrication of drug-eluting medical textiles. Different fiber production methods such as melt-, wet-, and electro-spinning, and textile fabrication techniques such as knitting and weaving are explained. Moreover, various loading processes of bioactive agents to obtain drug-loaded fibrous structures with required physicochemical and morphological properties, drug delivery mechanisms, and drug release kinetics are discussed. Finally, the current applications of drug-eluting fibrous systems in wound care, tissue engineering, and transdermal drug delivery are highlighted.

Biomaterials-based nanofiber scaffold: targeted and controlled carrier for cell and drug delivery

Nanofiber scaffold formulations (diameter less than 1000 nm) were successfully used to deliver the drug/cell/gene into the body organs through different routes for an effective treatment of various diseases. Various fabrication methods like drawing, template synthesis, fiber-mesh, phase separation, fiber-bonding, self-assembly, melt-blown, and electrospinning are successfully used for fabrication of nanofibers. These formulations are widely used in various fields such as tissue engineering, drug delivery, cosmetics, as filter media, protective clothing, wound dressing, homeostatic, sensor devices, etc. The present review gives a detailed account on the need of the nanofiber scaffold formulation development along with the biomaterials and techniques implemented for fabrication of the same against innumerable diseases. At present, there is a huge extent of research being performed worldwide on all aspects of biomolecules delivery. The unique characteristics of nanofibers such as higher loading efficiency, superior mechanical performance (stiffness and tensile strength), controlled release behavior, and excellent stability helps in the delivery of plasmid DNA, large protein drugs, genetic materials, and autologous stem-cell to the target site in the future.

Highly porous drug-eluting structures: from wound dressings to stents and scaffolds for tissue regeneration

For many biomedical applications, there is need for porous implant materials. The current article focuses on a method for preparation of drug-eluting porous structures for various biomedical applications, based on freeze drying of inverted emulsions. This fabrication process enables the incorporation of any drug, to obtain an "active implant" that releases drugs to the surrounding tissue in a controlled desired manner. Examples for porous implants based on this technique are antibiotic-eluting mesh/matrix structures used for wound healing applications, antiproliferative drug-eluting composite fibers for stent applications and local cancer treatment, and protein-eluting films for tissue regeneration applications. In the current review we focus on these systems. We show that the release profiles of both types of drugs, water-soluble and water-insoluble, are affected by the emulsion's formulation parameters. The former's release profile is affected mainly through the emulsion stability and the resulting porous microstructure, whereas the latter's release mechanism occurs via water uptake and degradation of the host polymer. Hence, appropriate selection of the formulation parameters enables to obtain desired controllable release profile of any bioactive agent, water-soluble or water-insoluble, and also fit its physical properties to the application.

Structure-property effects of novel bioresorbable hybrid structures with controlled release of analgesic drugs for wound healing applications

Over the last decades, wound dressings have developed from the traditional gauze dressing to tissue-engineered scaffolds. A wound dressing should ideally maintain a moist environment at the wound surface, allow gas exchange, act as a barrier to micro-organisms and remove excess exudates. In order to provide these characteristics, we developed and studied bioresorbable hybrid structures which combine a synthetic porous drug-loaded top layer with a spongy collagen sublayer. The top layer, prepared using the freeze-drying of inverted emulsions technique, was loaded with the analgesic drugs ibuprofen or bupivacaine, for controlled release to the wound site. Our investigation focused on the effects of the emulsion's parameters on the microstructure and on the resulting drug-release profile, as well as on the physical and mechanical properties. The structure of the semi-occlusive top layer enables control over vapor transmission, in addition to strongly affecting the drug release profile. Release of the analgesic drugs lasted from several days to more than 100 days. Higher organic:aqueous phase ratios and polymer contents reduced the burst release of both drugs and prolonged their release due to a lower porosity. The addition of reinforcing fibers to this layer improved the mechanical properties. Good binding of the two components, PDLGA and collagen, was achieved due to our special method of preparation, which enables a third interfacial layer in which both materials are mixed to create an "interphase". These new PDLGA/collagen structures demonstrated a promising potential for use in various wound healing applications.

Controlled release of analgesic drugs from porous bioresorbable structures for various biomedical applications

Pain is one of the most common patient complaints encountered by health professionals and remains the number one cause of absenteeism and disability. In the current study, analgesic-eluting bioresorbable porous structures prepared using the freeze-drying of inverted emulsions technique were developed and studied. These drug-eluting structures can be used for coating fibers or implants, or for creating standalone films. They are ideal for forming biomedically important structures that can be used for various applications, such as wound dressings that provide controlled release of analgesics to the wound site in addition to their wound dressing role. Our investigation focused on the effects of the inverted emulsion's parameters on the shell microstructure and on the resulting drug-release profile of ibuprofen and bupivacaine. The release profiles of ibuprofen formulations exhibited a diffusion-controlled pattern, ranging from several days to 21 days, whereas bupivacaine formulations exhibited an initial burst release followed by a three-phase release pattern over a period of several weeks. Higher organic to aqueous phase ratios and higher polymer contents reduced the burst release of both drugs and prolonged their release due to lower porosity. Overall, the drug-eluting porous structures loaded with either ibuprofen or bupivacaine demonstrated a promising potential for use in various applications that require pain relief.

Novel biodegradable composite wound dressings with controlled release of antibiotics: microstructure, mechanical and physical properties

Wound dressings aim to restore the milieu required for skin regeneration and protect the wound from environmental threats, including penetration of bacteria. The dressings should be easy to apply and remove and maintain a moist healing environment. In this study, novel biodegradable composite wound dressings based on a polyglyconate mesh and a porous PDLGA binding matrix were developed and studied. These novel dressings were prepared by dip-coating woven meshes in inverted emulsions, followed by freeze-drying. Their investigation focused on the microstructure, mechanical and physical properties, and the release profile of the antibiotic drug ceftazidime from the binding matrix. The mechanical properties of our wound-dressing structures were found to be superior, combining relatively high tensile strength and ductility, which changed only slightly during 3 weeks of incubation in an aqueous medium. The parameters of the inverted emulsion, the organic-aqueous phase ratio, and the type of surfactant used for stabilizing the emulsion were found to affect the microstructure of the binding matrix and the resulting properties, i.e., water absorbance, water vapor transmission rate, and drug-release profile from the binding matrix. Appropriate selection of these parameters can yield composite structures that have the desired physical properties and drug release behavior. Thus, these unique structures are potentially very useful as burn and ulcer dressings.

DRUG-ELUTING BIORESORBABLE STENTS FOR VARIOUS APPLICATIONS

A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. Metallic coronary stents were first introduced to prevent arterial dissections and to eliminate vessel recoil and intimal hyperplasia associated with percutaneous transluminal coronary angioplasty. The stent application range has expanded as more experience was gained, and encouraging results have been obtained in the treatment of vascular diseases. Stents are currently used for support of additional body conduits, including the urethra, trachea, and esophagus. The rationale for bioresorbable stents is the support of a body conduit only during its healing process. The stent mass and strength decrease with time, and the mechanical load is gradually transferred to the surrounding tissue. Bioresorbable stents also enable longer term delivery of drugs to the conduit wall from an internal reservoir and abolish the need for a second surgery to remove the device. The present review describes recent advances in bioresorbable stents, focusing on drug-eluting bioresorbable stents for various applications. Controlled release of an active agent from a stent can be used to enhance healing of the surrounding tissues, to increase the implant's biocompatibility, as well as to help cure certain diseases. Because a lot of research in this field has been done by us, examples for these functions are described based mainly on developments in our laboratories.