Electrospin polymer nanofibers are gaining increasing importance in tissue engineering, wound dressing and drug delivery. Here, we present a thorough rheological study of polymer solutions in the bulk and at the interface to find correlations between those properties and the electrospinnability of the solutions and the morphology of the resultant nanofibers. Our results indicate that blended solutions of chitosan or alginate with polyethylene oxide (PEO) are appropriate for electrospinning when they form conductive, unstructured fluids displaying plasticity, rather than elasticity, in the bulk and at the interface. The interfacial rheological parameters are three orders of magnitude lower than those in the bulk. We demonstrated for the first time that interfacial, rather than bulk rheological parameters show improved correlation and can be used to predict the success of the electrospinning process. Using the interfacial parameters of samples with homologous compositions, different groups of solutions can be identified that form smooth nanofibers. However, rheological parameters of the bulk and at the interface provide complementary information. The bulk parameters are determined by polymer concentration and directly affect jet initiation, while the interfacial behaviour determines the continuation of the jet and fibre formation. We propose that interfacial parameters are indispensible tools for the design of electrospinning experiments.
COBISS.SI-ID: 3248753
The preparation of microcapsules with a self-microemulsifying system (SMES) core using a vibrating nozzle technology was improved with regard to process reproducibility and core phase retention. The microcapsule shell was optimized for composition of the alginate-pectin (A/P) ratio and hydrophilic filling agent content. The best-shaped microcapsules with highest encapsulation efficiency for furosemide-loaded SMES were obtained from the shell-formation phase with an A/P ratio of 25:75, containing 10% lactose, which was hardened through a one-step process. Fluid bed-dried microcapsules were examined for their release characteristics and swelling behavior of the polymeric matrix. Incorporation of hydrophilic filling agents in the shell-formation phase was shown to be successful in limiting the leakage of the core phase during the microcapsule production and drying processes. Moreover, the addition of different fillers also allows the drug release profile from Ca-alginate/pectinate microcapsules with a self-microemulsifying core to be modified.
COBISS.SI-ID: 3292017
To treat ophthalmic diseases like glaucoma or inflammatory disorders topically applied ophthalmic formulations such as eye drops are usually used. In addition, novel ophthalmic implants releasing drug substances locally into different parts of the eye are available today. In the work presented here, the permeability coefficients of selected drugs (ciprofloxacin hydrochloride, lidocaine hydrochloride, timolol maleate) for ophthalmic tissues were determined using side-by-side diffusion chambers (so-called Ussing chambers). Sclera, conjunctiva, cornea, choroidea-retina-complex and a complex of conjunctiva-sclera-choroidea-retina were excised from fresh porcine, rabbit and bovine eyes. In the porcine eye tissues the highest Papp values were obtained for conjunctiva with the exception of lidocaine. Therefore, it can be estimated that a certain amount of drug diffuses or is transported through conjunctiva after application. The Papp values for sclera were also higher than those for cornea and even more, the surface area of sclera which is available for drug absorption is much larger than that of cornea when applying an implant. The obtained permeability coefficients for sclera and conjunctiva indicate that the administration of periocular implants can be an alternative to topically applied formulations. The complexes of the tissues were a significantly (p ( 0.01) stronger barrier to the investigated substances than the separated tissues. Distinct differences in permeability coefficients between the investigated animal tissues were observed. Overall the highest Papp values for all mounted tissues were obtained with the rabbit, followed by porcine and bovine eyes. Because of these distinct interspecies differences one must be very careful when selecting the proper animal model for the permeability experiments.
COBISS.SI-ID: 3370353
The absorption and bioavailability of drugs can be substantially affected by the transit of dosage forms through the gastrointestinal (GI) tract. Gastric emptying is one of the most critical parameters contributing to this inter- and intra-individual GI transit variability. It is especially important for the delayed release dosage forms whose release depends on the local environment and begins when the dosage form passes pylorus and comes into contact with higher pH medium in small intestine. The purpose of our research work was to predict the in vivo dissolution from enteric coated pellets for population and establish a good in vitro/in vivo correlation (IVIVC) with mean in vivo absorption profiles, obtained in a pharmacokinetic study under fasting conditions. The dissolution tests were carried out on a USP 4 flow-through cell with enteric coated pellets containing an acid-labile drug and formulated as orodispersible tablets. Using several residence times in an acidic medium, we simulated the gastric emptying of the pellets and the exposure of different fractions of the pellets to the gastric medium for different periods of time. The amount of drug released decreased with the increasing time of exposure to the acidic medium due to the drugʼs degradation. The mean in vivo dissolution profiles, which were predicted on the basis of experimentally determined dissolution profiles and mathematical model of pelletsʼ gastric emptying, gave a very good IVIVC with the mean in vivo absorption profiles.
COBISS.SI-ID: 3286385
Objectives: Firstly, to assess paracetamol-related counselling. Secondly, to evaluate the patientʼs approach as a determinant of counselling and to test the acceptability of the simulated patient method in Slovenian pharmacies. Methods: The simulated patient methodology was used in 17 community pharmacies. Three scenarios related to selfmedication for headaches were developed and used in all participating pharmacies. Two scenarios were direct product requests: scenario 1: a patient with an uncomplicated short-term headache; scenario 2: a patient with a severe, longduration headache who takes paracetamol for too long and concurrently drinks alcohol. Scenario 3 was a symptom-based request: a patient asking for medicine for a headache. Pharmacy visits were audio recorded and scored according to predetermined criteria arranged in two categories: counselling content and manner of counselling. The acceptability of the methodology used was evaluated by surveying the participating pharmacists. Results: The symptom-based request was scored significantly better (a mean 2.17 out of a possible 4 points) than the direct product requests (means of 1.64 and 0.67 out of a possible 4 points for scenario 1 and 2, respectively). The most common information provided was dosage and adverse effects. Only the symptom-based request stimulated spontaneous counselling. No statistically significant differences in the duration of the consultation between the scenarios were found. There were also no significant differences in the quality of counselling between the Masters of Pharmacy and Pharmacy Technicians. The acceptability of the simulated patient method was not as high as in other countries. Conclusion: The assessment of paracetamol-related counselling demonstrates room for practice improvement.
COBISS.SI-ID: 3368817