Diffusion of anti-tumor drugs through membranes from hydrophilic methacrylate gels

Flexible polymeric patch based nanotherapeutics against non-cancer therapy

Flexible polymeric patches find widespread applications in biomedicine because of their biological and tunable features including excellent patient compliance, superior biocompatibility and biodegradation, as well as high loading capability and permeability of drug. Such polymeric patches are classified into microneedles (MNs), hydrogel, microcapsule, microsphere and fiber depending on the formed morphology. The combination of nanomaterials with polymeric patches allows for improved advantages of increased curative efficacy and lowered systemic toxicity, promoting on-demand and regulated drug administration, thus providing the great potential to their clinic translation. In this review, the category of flexible polymeric patches that are utilized to integrate with nanomaterials is briefly presented and their advantages in bioapplications are further discussed. The applications of nanomaterials embedded polymeric patches in non-cancerous diseases were also systematically reviewed, including diabetes therapy, wound healing, dermatological disease therapy, bone regeneration, cardiac repair, hair repair, obesity therapy and some immune disease therapy. Alternatively, the limitations, latest challenges and future perspectives of such biomedical therapeutic devices are addressed.

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The most explored polymeric patches, such as microneedle, hydrogel, microsphere, microcapsule, and fiber are summarized.

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Polymeric patches integrated with a diversity of nanomaterials are systematically overviewed in non-cancer therapy.

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The future prospective for the development of polymeric patch based nanotherapeutics is discussed.

Poly(Glyceryl Methacrylate) Hydrogels - Effect of Composition and Crosslinking Density on Structure and Release of Dextran as a Model Macromolecule

A series of hydrogels based on glyceryl methacrylate (pGMA) were prepared with different ratios of ethylene glycol dimethacrylate (EGDMA) and ethyl methacrylate (EMA) in order to vary the degree of crosslinking and the degree of hydrophobicity of the matrices, respectively. The swelling be haviour and the crosslinking density of the hydrogels were characterized and the structure was determined by scanning electron microscopy and porosime try. FITC-dextran (molecular weight 20,000) was imbibed into the gels and the release rate studied. It was found that the initial rate of release and the total amount of dextran release varied as an inverse function of crosslinking and monomer concentration, but as a linear function of EMA concentration.

In vitro diffusion in polyacrylamide embedded agarose microbeads

125I Sodium iodide, 125I insulin, 125I albumin, and 111indium IGG were employed to investigate release from, and penetration of different sized molecules into agarose/polyacrylamide microcapsules. The microcapsules were formed by photopolymerization of an acrylamide solution round agarose beads. The indium-chelated antibody gave a particular low background count. The different release times were explained in terms of differences in diffusion coefficient. By retarding in vitro penetration of antibodies, these microcapsules could be of value for the encapsulation of living cells in bioartificial organs.

Synthetic hydrogels as drug delivery systems

Hydrogels are widely studied materials for the preparation of sustained release drug dosage forms. Their soft, tissue-like consistency and their high biocompatibility in a number of applications make them promising candidates for this purpose. The water and the polymer in the gel form intricate structures and much research has been devoted to the elucidation of these structures, and of the interactions involved in their formation. Simple, drug-loaded hydrogels normally give a matrix-type delivery profile, in which the release rate is proportional to the square root of time; a number of approaches has been used to change this profile to other types of delivery, for instance to zero-order release. A number of in vivo tests using hydrogel delivery systems has given favourable results.

Mass transport properties of co(polyether)polyurethane membranes I: Preparation and characterization

A series of polyurethane copolymers containing polyethylene glycol 600, 1000, or 1540 was synthesized, purified by reprecipitation, and cast into clear, tough, flexible membranes using the solution method. The weight average molecular weight of each polymer was estimated by gel permeation chromatography. The ability of the various polymers to absorb water was measured and increased with the increasing molecular weight of the polyethylene-glycol. The ability of the copolymer membranes to hold a pH gradient decreased with increasing polyethylene glycol molecular weight.

Release characteristics of dibucaine dispersed in konjac gels

A possible use of konjac gel for sustained release of drugs was examined in a monolithic system containing dibucaine. Dibucaine was dispersed in the gel which was prepared by gelation of the konjac flour in a borax solution at 60 degrees. The cumulative amount of the drug released plotted against the square root of time was linear in the monolithic system. This relationship was in agreement with that expected from the theoretical equation for planar configuration. The mechanism of the release of the drug from the gel may be considered to be leaching of the drug by the permeating fluid. The release profile from dried konjac gel was similar to that from undried gel, but that from unwarmed gel showed a deviation from linearity although sustained release was similarly obtained.

Progestin permeation through polymer membranes IV: Mechanism of steroid permeation and functional group contributions to diffusion through hydrogel films

Hydrogel films were prepared from hydroxyethyl methacrylate, both with (Film II) and withouth (Film I) 5.25 mole% of ethylene glycol dimethacrylate. Permeation, diffusion, and partition coefficients for progesterone, testosterone, nandrolone, norethindrone, 17 alpha-hydroxyprogesterone, estradiol, and hydrocortisone were determined. A solute permeation model was proposed based on the separation of a domain (B) composed of "bulk-like" water and a doman (A) composed of polymer, interfacial water, and bound water present in the films. The separate contributions from the "pore" and "solution-diffusion" mechanisms to the total permeability were calculated from the model. Steroid permeabilities through Films I and II were analyzed in accordance with this model. Permeation of Film II occurred via the solution-diffusion mechanism. Permeation of Film I occurred predominately by the pore mechanism with a small contribution (approximate 20%) from the solution-diffusion mechanism. The latter contribution was dependent on the solubility of the solute within the A domains of the hydrogel film. Functional group contributions to permeation of Film II were ascribed to either steric or hydrogen bonding effects.

Progestin permeation through polymer membranes III: Polymerization solvent effect on progesterone permeation through hydrogel membranes

Hydrogels prepared from poly(hydroxyethyl methacrylate) are biocompatible and highly permeable to low molecular weight solutes. Permeation rates can be varied by altering the cross-linker concentration or using copolymers; the latter are chosen to alter the hydrogel equilibrium hydration. These factors suggest that hydrogels are good candidates for controlled-release drug delivery devices. Hydrogels may be synthesized using various temperatures, initiators (nature and concentration), and solvents (nature and concentration). This study demonstrated that progesterone permeation through poly(hydroxyethyl methacrylate) films is independent of polymerization solvent (nature and concentration) for the solvents, water, ethanol, and tert-butyl alcohol. The importance of hydrogel equilibrium hydration in progesterone permeation is emphasized.

Progestin permeation through polymer membranes I: diffusion studies on plasma-soaked membranes

The potential of several commercially available polymeric materials for use in controlled-release drug delivery devices was investigated. Progesterone was used as a model hydrophobic drug. The progesterone permeation rates through polydimethylsiloxane, two polyether urethanes, a hydroxyethyl methacrylate, a polyether urethan--polydimethylsiloxane blend, and a cellulosic membrane were determined. The permeabilities were obtained on nonsoaked membranes and on membranes soaked in plasma for varying times. The purpose of the plasma soaks was to examine the effects of lipid absorption and degradative processes within the membrane on progesterone permeability. This study identified several polymers that show potential for use in controlled-release drug delivery devices. The plasma treatment studies showed that several polymers may not be acceptable. The plasma soak studies were interpreted in terms of the mechanisms of drug permeation through the membranes.

Progestin permeation through polymer membranes II: diffusion studies on hydrogel membranes

The potential use of hydrogels in controlled-release drug delivery systems for contraceptive steroids was investigated. The permeabilities, diffusion coefficients, and partition coefficients for progesterone were determined for hydrogels made from hydroxyethyl methacrylate containing varying amounts of ethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate. In addition, copolymers of hydroxyethyl methacrylate with methoxyethyl methacrylate and methoxyethoxyethyl methacrylate were investigated. The results were interpreted in terms of the mechanisms of permeation of progesterone through the hydrogels. This study showed that progesterone permeated these membranes primarily through loose pores in the hydrogel network except at high concentrations of the cross-linker, ethylene glycol dimethacrylate, where dissolution and diffusion of the progesterone in the polymer network was the dominant mechanism.

Porous hydrophilic polymer: good and bad news in the orthopedic application of cruciate ligament substitution

In the configuration used, the Hydron sponge did not enhance the ingrowth of bone into the Dacron for prosthesis anchorage. In fact, the presence of the Hydron seemed to retard such ingrowth, even though there was bony incorporation of portions of the Hydron polymer. Fixation was more rigid when Dacron was implanted bare. Hydron sponge does not appear to remain intact within a joint. It would not seem suitable for intra-articular protection of a prosthesis or local delivery of antibiotics here. We did not search further for the polymer in the regional lymph nodes. Hydron sponge is capable of eleciting an unusual phenomenon of woven bone formation. This is "good news" for its potential, but realization of such potential will certainly require additional study. Double and triple interval fluorochrome labelling would be especially helpful in further studying the localization and rate of this bone formation.