Immobilization of Retinoic Acid by Cationic Polyelectrolytes

Abstract

Retinoic acid was immobilized by precipitating its complexes with cationic polyelectrolytes from aqueous solution. Polyelectrolytes with different architectures, such as poly(ionene-6,3 bromide), poly(dimethyldiallylammonium chloride), and poly(N-methyl-4-vinylpyridinium chloride), form self-assembling complexes containing retinoic acid (70% (w/w)). All these complexes are thermodynamically stable and can be processed into mesomorphously ordered films with interesting physical properties. In contrast to the brittle crystalline retinoic acid the complexes with polyelectrolytes are highly deformable viscoelastic materials. All materials show lamellar mesophase structures; their T g value strongly depends on the polyelectrolyte. It is suggested that these materials have great potential as pharmaceutical agents as well as models for the investigation and the mimicking of chromophores in visual pigments and photosynthetic bacteria. The properties of the complexes are examined by X-ray diffraction, differential scanning calorimetry, polarization optical microscopy, UV−vis spectroscopy, and stress−strain measurements.

Self-assembled, pH-sensitive retinoate nanostructures ionically complexed with PEG-grafted cationic polyelectrolytes

“…However, the lifetime of retinoic acids in the blood gradually decreases after prolonged treatment, and thus, efficient delivery systems are required to maximize the pharmaceutical efficacy of retinoic acids. Multiple systems have been suggested for the solubilization and delivery of retinoic acids, including complexation with proteins [8] or cationic polyelectrolytes [9][10][11][12], encapsulation within liposomes or nanoparticles [13][14][15], and chemical conjugation [16]. Through co-crystallization, retinoic acids can be complexed with thyroxine-binding transthyretin, which is a natural retinol-binding protein having a high affinity for retinoic acids.…”

“…However, the practical application of this technique is limited due to its complicated and expensive processes. As a simple and inexpensive alternative to the use of natural proteins, Thünemann and his colleagues reported the use of cationic polyelectrolytes to form the ionic complexes with retinoic acids [9][10][11][12]. This approach is based on the polyion complex between oppositely charged polyelectrolytes and ionic amphiphiles in aqueous media [17].…”

Biodegradable Hyaluronic Acid/N‐Carboxyethyl Chitosan/Protein Ternary Complexes as Implantable Carriers for Controlled Protein Release

“…Polyelectrolyte/ionic drug complexes have been designed and investigated as erodible carriers for controlled delivery of low‐molecular weight (MW) ionic drugs 7–11. This type of systems has the advantage of delivering low‐MW ionic drugs at a pseudo zero‐order thereby overcoming the problems associated with earlier polyelectrolyte hydrogels (e.g., Fickian release kinetics with severe tailing toward the end of drug release) 7.…”

Chemical immobilization of retinoic acid within poly(ε‐caprolactone) nanoparticles based on drug–polymer bioconjugates

“…10 That is the reason why developing a delivery carrier is a major problem in administrating retinoids as a pharmacological agent. Several methods to produce a delivery carrier for retinoic acid (RA) have been reported: complexation with transthyretin (a natural RBP carrier protein), 11 complexation with cationic polyelectrolytes, [12][13][14][15][16] and encapsulation within liposomes or nanoparticles. [17][18][19] Complexation of retinoids with transthyretin is a technique to mimic nature's strategy.…”

“…However, this technique is an expensive and complicated process. As an alternative approach, Thü nemann et al [12][13][14][15] proposed a different and less expensive strategy for the immobilization of RA: the complexation of RA with cationic polyelectrolytes. This approach is based on the formation of ordered structures in solution, which can occur by ionically binding RA to a polyelectrolyte via self-assembly.…”