Synthesis and characterization of poly N-isopropylacrylamide-co-acrylic acid and their binary blend films properties

In past decades, the combination of polymers to obtain blends in film shapes has been a very effective strategy to meet the needs of the increasingly demanding market. In this sense, pH- and thermo-sensitive (PHT) polymers have recently drawn the attention of researchers for their countless applications. However, binary mixtures of typical PHTs like polyacrylic acid (p-AAc) and poly-N-isopropylacrylamide (p-NIPAm) were unable to form films. In this sense, it was hypothesized that NIPAm copolymerized with AAc monomers can yield blends with virtually the same functional group composition of binary mixtures of p-NIPAm and p-AAc homopolymers but with different properties of film formation. For this, a copolymeric radical synthesis and the subsequent analytical studies were complemented to get a broad description of these materials. P-NIPAm and p-AAc homopolymers and different proportions of copolymers p-NIPAm-co-AAc were obtained and thoroughly characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Size Exclusion Chromatography (SEC), acid-basic titration, and rotational rheology. Among the samples, the solutions of p-AAc with p-NIPAm and p-NIPAm-co-AAc copolymers with a higher proportion of NIPAm units (0.8 and 0.6 NIPAm/AAc) precipitated as interpolymer complexes. Since it was expected, the combination with p-NIPAm-co-AAc 40/60 copolymer, which has a higher proportion of AAc groups and pH sensitivity, allowed obtaining blends suitable for the preparation of films. Furthermore, despite the fact that the combinations of p-NIPAm-co-AAc 40/60 with p-NIPAm-co-AAc 80/20 or p-NIPAm were successful, the mechanical properties of the films are worse compared to the other blends, leaving this issue open for subsequent studies.

Interpolymer Complexes Based on Carbopol® and Poly(2-ethyl-2-oxazoline) as Carriers for Buccal Delivery of Metformin

Introduction. Buccal drug delivery has a number of advantages over oral administration: ease of application, good blood supply to the buccal mucosa, drug can enter the systemic circulation directly, avoiding the "first pass effect through the liver", and are not exposed to the acidic environment of the gastric juice and the destructive action of digestive enzymes. The use of interpolymer complexes (IPCs) makes it possible not only to ensure adhesion to the mucosal membranes of the oral cavity, but also to achieve a prolonged release of drugs.Aim. Development of carriers based on interpolymer complexes using Carbopol® 971 NF (C971) and poly(2-ethyl-2-oxazoline) (POZ) of different molecular weights for buccal delivery of metformin (MF).Materials and methods. The study of IPC adhesion was carried out using a TA.XTplus texture analyzer (Stable Micro Systems, UK); mucin compacts with a diameter of 13 mm were used as a substrate; these were prepared by compressing porcine gastric mucin powder using a manual hydraulic press for IR spectroscopy (PerkinElmer, USA) at a pressure of 2.45 MPa. The study of the swelling capacity was carried out by placing polymer matrices in an artificial saliva medium, with constant thermostating at a temperature of 37.0 ± 0.5 °C for 5 hours. The study of the release of MF from the matrices based on IPC was carried out using a DFZ II apparatus (Erweka, Germany) according to the Flow Through Cell method (USP IV) with cells for tablets (22.6 mm) and adaptors for ointments, creams and gels in a medium simulating saliva. The concentration of MF in the samples from the dissolution tests was determined with UV-spectrophotometry (Lambda, PerkinElmer, USA) at 232.8 nm.Results and discussion. In a comparative study of the mucoadhesive properties of polymer samples, IPC compacts showed a mucoadhesion capacity comparable to that of poly(2-ethyl-2-oxazoline); at the same time, compacts from physical mixtures (PM) and C971 are inferior in terms of the separation force to IPC samples, however, POZes dissolve in an artificial saliva medium, that is, they are not suitable as dosage forms for buccal delivery. For 5 hours of the experiment to assess the swelling capacity, the IPC matrices did not change significantly, which can ensure their comfortable use as carriers for buccal delivery. When evaluating the release of metformin from polymer matrices (with weight ratio MF/IPC 1: 0.5), the most complete release (more than 90 %) is observed from both IPC matrices compared to matrices of PM and individual polymers.Conclusion. Polycomplex matrix systems based on C971-POZ (50 kDa) and C971-POZ (500 kDa) are suitable for buccal delivery of metformin.

Microstructural Transition of Poly(vinyl alcohol)-based Aerogels in the Present of Interpolymer Complexes

The interpolymer interactions play a vital role of determining the microstructure and the properties of polymer aerogels. In terms of Poly (vinyl alcohol) (PVA) aerogels, the conformation and behaviour of...

Interpolymer Complexes of Eudragit® Copolymers as Novel Carriers for Colon-Specific Drug Delivery

Interpolymer complexes (IPC) based on Eudragit® EPO and Eudragit® S100 were investigated as potential carriers for oral controlled drug delivery to the colon. IPC samples were prepared by mixing copolymer solutions in organic solvents (ethanol, isopropanol:acetone mixture (60:40, % v/v) and tetrahydrofuran). According to the data of elemental analysis, FTIR-spectroscopy, X-ray photoelectron spectroscopy and thermal analysis these IPCs have excess of anionic copolymer (Eudragit® S100) in their structure; they are stabilized by hydrogen and ionic intermacromolecular bonds and do not include free copolymer domains. IPC have pH-independent swelling properties in the media mimicking gastrointestinal tract (GIT) conditions and provide colon-specific delivery of indomethacin in buffer solutions (pH 1.2; 5.8; 6.8; 7.4) and in biorelevant media (fasted state simulated gastric fluid, fasted state simulated intestinal fluid—version 2 and fasted stated simulated colonic fluid).