Release Profiles Of Model Drug Research Articles

Stimulus-responsive polymeric micelles for the light-triggered release of drugs

Ethyl cellulose macroinitiator was firstly synthesized by direct acylation of ethyl cellulose with 2-bromopropionyl bromide in a room temperature. And a light-responsive triblock copolymer of ethyl cellulose-g-poly(2-hydroxyethyl methacrylate)-g-poly(spiropyran ether methacrylate) (EC-g-PHEMA-g-PSPMA) was prepared by atom transfer radial polymerization. The amphiphilic structure of the copolymer enabled it to aggregate into spherical micelles in aqueous solution with an average diameter of 100nm. The micelles exhibited light-responsive performance because of the SPMA monomer. The hydrophobic side chain of PSPMA became hydrophilic under UV light, which decreased the average size of the micelles. Additionally, the diameters of the micelles can be recovered when subsequently irradiated with visible light. The loading and light-triggered release profiles of model drugs were also investigated, and results showed that the release behavior can be controlled by changing the light wavelength.

Multidrug release based on microneedle arrays filled with pH-responsive PLGA hollow microspheres

This work presents an approach to codelivering transdermally two model drugs, Alexa 488 and Cy5, in sequence, based on a system of polyvinylpyrrolidone microneedles (PVP MNs) that contain pH-responsive poly(d,l-lactic-co-glycolic acid) hollow microspheres (PLGA HMs). The MN system provides the green fluorescence of Alexa 488 in PVP MNs, the red fluorescence of the DiI-labeled PLGA shell of HMs, and the cyan fluorescence of Cy5 in their aqueous core. Combined together, the prepared MN arrays support the localization of the HMs and the monitoring of the release profiles of model drugs within the skin tissues. The key component of this system is NaHCO3, which can be easily incorporated into HMs. After HMs are treated with an acidic solution (simulating the skin pH environment), protons (H+) can rapidly diffuse through the free volume in the PLGA shells to react with NaHCO3 and form a large number of CO2 bubbles. This effect generates pressure inside the HMs and creates pores inside their PLGA shells, releasing the encapsulated Cy5. Test MNs were strong enough to be inserted into rat skin without breaking. The PVP MNs were significantly dissolved within minutes, and the first model drug Alexa 488, together with HMs, were successfully deposited into the tissues. Once in the acidic environment of the skin, the released HMs started to release Cy5 and continued to spread throughout the neighboring tissues, in a second step of the release of the drug. This approach can be used clinically to codeliver sequentially and transcutaneously a broad range of drugs.

Synthesis and characterization of molecularly imprinted polymer of N-maleoylchitosan-grafted-2-acrylamido-2-methylpropanesulfonic acid and its controlled delivery and recognition of bovine serum albumin

In this study a novel molecularly imprinted polymer matrix, namely protein-imprinted N-maleoylchitosan-grafted-2-acrylamido-2-methylpropanesulfonic acid polymer (MIP) matrix was prepared by using bovine serum albumin (BSA) as a template. The characteristics of the MIP were investigated using FTIR, SEM, XRD and Zeta Potential Analyses. The effects of monomer to template ratio, cross linking density, porogen, pH and ionic strength on the loading of BSA into the MIP were investigated. The adsorption studies showed that the MIP exhibits good recognition for BSA, as compared to non-imprinted polymer (NIP). The experimental adsorption isotherms of BSA onto MIP and NIP were determined and well fitted by Sips model with a maximum binding capacity of 113.51 mg g−1 for MIP and 76.39 mg g−1 for NIP. A pseudo-second-order kinetic model adequately described the kinetic rate in comparison to a pseudo-first-order model. In vitro release profiles of model drug from the MIP were investigated in physiological buffered solution using a UV/vis spectrophotometer. In addition, the drug release mechanism was analyzed by fitting the amount of drug released into Peppa's potential equation.

Preparation of Fast Dissolving Films for Oral Dosage from Natural Polysaccharides.

Fast-dissolving films (FDFs) were prepared from natural polysaccharides, such as pullulan, without heating, controlling the pH, or adding other materials. The release profiles of model drugs from the films were investigated. In the absence of a drug, the casting method and subsequent evaporation of the solvent resulted in the polysaccharide forming a circular film. The presence of drugs (both their type and concentration) affected film formation. The thickness of the film was controllable by adjusting the concentration of the polysaccharide, and regular unevenness was observed on the surface of 2% pullulan film. All films prepared with polysaccharides readily swelled in dissolution medium, released the incorporated compound, and subsequently disintegrated. The release of dexamethasone from the films was complete after 15 min, although this release rate was slightly slower than that of pilocarpine or lidocaine. Therefore, FDFs prepared from polysaccharides could be promising candidates as oral dosage forms containing drugs, and would be expected to show drug dissolution in the oral cavity.

A drug-loaded gel based on polyelectrolyte complexes of poly (acrylic acid) with poly (vinylpyrrolidone) and chitosan

A drug-loaded gel (CSPP) based on ionic crosslinked chitosan (CS) and polyelectrolyte complexes of poly (acrylic acid) (PAA) with poly (vinylpyrrolidone) (PVP) was prepared by dropping CS solution containing suitable amount of PVP into PAA and trisodium citrate co-existing gelling solution. The surface and cross-section morphology of the gel was observed using scanning electron microscopy, and the observation showed that the CSPP gel had more compact structure than CS gel. In vitro release profiles of model drug from the CSPP gel, which was prepared under different conditions, were investigated in simulative gastric fluid (pH 1.8) using an UV/vis spectrophotometer. The results showed that the rapid release of the model was restrained due to the complex of PVP and PAA, and the CSPP gel could serve as a suitable candidate in drug delivery system such as the site-specific controlled release of the drug in stomach. In addition, the release mechanism of drug was analyzed by fitting the amount of drug released into Peppa's potential equation.

Use of Silk Protein, Sericin, as a Sustained-Release Material in the Form of a Gel, Sponge and Film

To evaluate the usability of silk protein (sericin, SC) as a sustained-release material, the physicochemical properties of SC and the release profiles of model drugs from SC gel, sponge and film were studied. Heat aids the dissolution of SC. The molecular weight of SC tended to decrease as the heating temperature and heating time increased. The gel and sponge formed by SC were moldable and consisted of high molecular weight SC polymers (250 kDa and about 400 kDa). SC film was easily broken and exhibited elastic distortion. The addition of moisture-retaining plasticizer (glycerin and sorbitol) improved the film-forming characteristics of SC. The results suggested that SC is practical as a moldable gel and sponge, and as a tensible film. To evaluate the release profiles of small molecules, fluorescein isothiocyanate-dextran ((1) FD4, 4 kDa and (2) FD70, 70 kDa) were used as two model drugs with significantly different molecular weights, and fluorescein isothiocyanate-albumin ((3) FA, 66 kDa) was used as a charged drug. Each was formulated in SC gel, sponge and film. In each preparation, the release rate of the model drugs tended to be FA<FD70<FD4. FA, which has a large molecular weight and negative charge, was released for the longest period of time (≥1 week) from each preparation. The results suggest that SC is usable as an aqueous sustained-release material for high molecular weight drugs. Furthermore, if the drug is charged, its release can be sustained for an extended time.

Chitosan derivatives alter release profiles of model compounds from calcium phosphate implants

The aim of the current study was to evaluate the impact of chitosan derivatives, namely N-octyl-chitosan and N-octyl- O-sulfate chitosan, incorporated in calcium phosphate implants to the release profiles of model drugs. The rate and extent of calcein (on M.W. 650 Da) ED, and FITC-dextran (M.W. 40 kDa) on in vitro release were monitored by fluorescence spectroscopy. Results show that calcein release is affected by the type of chitosan derivative used. A higher percentage of model drug was released when the hydrophilic polymer N-octyl-sulfated chitosan was present in the tablets compared with the tablets containing the hydrophobic polymer N-octyl-chitosan. The release profiles of calcein or FD from tablets containing N-octyl- O-sulfate revealed a complete release for FD after 120 h compared with calcein where 20% of the drug was released over the same time period. These results suggest that the difference in the release profiles observed from the implants is dependent on the molecular weight of the model drugs. These data indicate the potential of chitosan derivatives in controlling the release profile of active compounds from calcium phosphate implants.

The role of polymer/drug interactions on the sustained release from poly(dl-lactic acid) tablets

Abstract The release profiles of model drugs (propranolol HCl, diclofenac sodium, salicylic acid and sulfasalazine) from low molecular weight poly( d , l -lactic acid) [ d , l -PLA] tablets immersed in buffer solutions were investigated in an attempt to explore the mechanism of the related phenomena. It was confirmed that drug release is controlled by diffusion through the polymer matrix and by the erosion of the polymer. The pH of the surrounding medium influences the drug solubility as well as swelling and degradation rate of the polymer and therefore the overall drug release process. Physicochemical interaction between d , l -PLA and drug is an additional factor which influences the degree of matrix swelling and therefore its porosity and diffusion release process. Propranolol HCl shows extended delivery time at both examined pH values (5.4 and 7.4) and especially at pH 7.4 where release was accomplished in 190 days, most probably due to its decreased solubility at higher pH values. The acidic drugs gave shorter delivery times especially at pH 7.4. A slower drug release rate and more extended delivery time at pH 7.4 in comparison with that at pH 5.4 was recorded for tablets loaded with diclofenac sodium and salicylic acid. The opposite effect was observed with samples loaded with propranolol HCl.

Preparation, Characterization and Biodegradation Characteristics of Poly(adipic anhydride‐ co ‐ D , L ‐lactide)

Poly(adipic anhydride-co-D,L-lactide) (P(AA-LA)) has been synthesized by ring-opening polymerization of adipic anhydride (AA) and D,L-lactide (LA) using stannous octoate as catalyst in bulk and in solution. The copolymers were characterized by IR, nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry. The physical properties can be tailored by varying the copolymer compositions, and showed low glass transition temperature, melting temperature and good solubility in common solvents. In vitro tests showed that after rapid weight loss in the first day, a constant degradation rate was observed. The release profiles of model drugs, bovine serum albumin and norethindrone over 16 days followed closely that of the degradation of copolymers containing higher amounts of AA (AA > 64mol%), suggesting that the release mechanism was controlled predominantly by surface erosion. However, a large deviation from the close correlation of polymer degradation and drug release was observed for copolymers containing lower amounts of AA (< 30 mol%). These materials may be useful in protein delivery systems.