Oral delivery and fate of poly(lactic acid) microsphere-encapsulated interferon in rats

Forms and Methods for Interferon's Encapsulation

Interferons (IFNs) are cytokines involved in the immune response that act on innate and adaptive immunity. These proteins are natural cell-signaling glycoproteins expressed in response to viral infections, tumors, and biological inducers and constitute the first line of defense of vertebrates against infectious agents. They have been marketed for more than 30 years with considerable impact on the global therapeutic protein market thanks to their diversity in terms of biological activities. They have been used as single agents or with combination treatment regimens, demonstrating promising clinical results, resulting in 22 different formulations approved by regulatory agencies. The 163 clinical trials with currently active IFNs reinforce their importance as therapeutics for human health. However, their application has presented difficulties due to the molecules' size, sensitivity to degradation, and rapid elimination from the bloodstream. For some years now, work has been underway to obtain new drug delivery systems to provide adequate therapeutic concentrations for these cytokines, decrease their toxicity and prolong their half-life in the circulation. Although different research groups have presented various formulations that encapsulate IFNs, to date, there is no formulation approved for use in humans. The current review exhibits an updated summary of all encapsulation forms presented in the scientific literature for IFN-α, IFN-ß, and IFN-γ, from the year 1996 to the year 2021, considering parameters such as: encapsulating matrix, route of administration, target, advantages, and disadvantages of each formulation.

Novel Delivery Systems for Interferons

Interferons, IFNs, are among the most widely studied and clinically used biopharmaceuticals. Despite their invaluable therapeutic roles, the widespread use of IFNs suffers from some inherent limitations, mainly their relatively short circulation lifespan and their unwanted effects on some non-target tissues. Therefore, both these constraints have become the central focus points for the research efforts on the development of a variety of novel delivery systems for these therapeutic agents with the ultimate goal of improving their therapeutic end-points. Generally, the delivery systems currently under investigation for IFNs can be classified as particulate delivery systems, including micro- and nano-particles, liposomes, minipellets, cellular carriers, and non-particulate delivery systems, including PEGylated IFNs, other chemically conjugated IFNs, immunoconjugated IFNs, and genetically conjugated IFNs. All these strategies and techniques have their own possibilities and limitations, which should be taken into account when considering their clinical application. In this article, currently studied delivery systems/techniques for IFN delivery have been reviewed extensively, with the main focus on the pharmacokinetic consequences of each procedure.

Absorption of interferon alpha from patches in rats

Interferon alpha (IFN-alpha), patch preparations composed of three layers, water-insoluble backing layer, drug containing layer with absorption enhancer and surface layer containing pH-dependent polymer were prepared. As absorption enhancer, three surfactants, Gelucire44/14 (Lauroyl macrogol-32 glycerides), Labrasol (Caprylocaproyl macrogol-8 glycerides) and HCO-60 (polyoxyethylated hydrogenerated castor oil) were used in preparing IFN-alpha patch preparations. The intestinal absorption of IFN-alpha was studied after the administration of test patch preparations into the rat jejunum, 50,000 IU/kg. The serum IFN-alpha levels were measured by an ELISA method and both C(max) and AUC were determined as the index of absorption of IFN-alpha. Gelucire44/14 preparation including Pharmasol for the stable solidification showed the higher C(max), 7.66 +/- 0.82 IU/ml, and AUC, 12.85 +/- 1.49 IU h/ml, than Labrasol (6.51 +/- 0.89 and 8.30 +/- 1.34 IU h/ml) and HCO-60 (6.02 +/- 1.14, 7.53 +/- 1.84 IU h/ml) preparations, respectively. By comparing to the AUC obtained after s.c. injection of the same dose of IFN-alpha to rats, bioavailability (BA) was estimated to be 7.8% in Gelucire44/14 preparation. In vitro release study showed that the T50%s, the time when half of the formulated IFN-alpha is released from the patches, were 3.4 +/- 0.1 min for HCO-60, 7.8 +/- 0.1 min for Gelucire44/14 and 11.4 +/- 0.1 min for Labrasol preparations. To study the effect of absorption site, Gelucire44/14 preparation was administered into the rat duodenum and ileum. However, there were not significant differences on AUC among the three absorption sites. By reducing the IFN-alpha dose from 50,000 to 25,000 IU/kg, the serum IFN-alpha levels vs time profile showed a tendency of dose-dependency. When the histological examination of small intestinal mucosa was carried out in this study, the small intestinal mucosa after the Gelucire44/14 patches administered and before it was administered, could not recognize impaired. From these results, the usefulness of oral patch system for the oral delivery of IFN-alpha has been proved in rats.

Percutaneous absorption of interferon-alpha by self-dissolving micropiles

To ascertain the pharmaceutical usefulness of self-dissolving micropiles (SDMPs) containing interferon (IFN), two types of SDMPs were prepared using chondroitin sulfate and dextran as the base. After percutaneous administration of 5000 IU/kg IFN-alpha2b SDMP to rats, serum IFN levels were measured for 6 h. The peak serum IFN level, maximum drug concentration (Cmax), and the time when serum IFN level reaches to Cmax, time to reach maximum concentration (Tmax), were 8.2+/-0.5 IU/ml and 1.2+/-0.1 h, respectively, for chondroitin SDMP. For dextran SDMP, Cmax and Tmax were 3.1+/-0.4 IU/ml and 3.3+/-0.3 h, respectively. AUC of chondroitin SDMP was 1.5 times greater than that of dextran SDMP. Bioavailabilities (BAs) of IFN were 378.3% for chondroitin SDMP and 255.9% for dextran SDMP that were larger than 100%. The BA of IFN from subcutaneous (s.c.) injection solution was 320.9%. The relative BAs of IFN SDMPs against s.c. injection solution were 117.8% for chondroitin SDMP and 79.9% dextran SDMP. An in vitro release experiment suggested the faster release rate of IFN from chondroitin SDMP, 57.3% at 5 min, than dextran SDMP, 32.6% at 5 min. Chondroitin SDMP containing IFN showed good stability for 3 months and no damage to the administered rat skin.

Hydrophilic biodegradable microspheres of interferon-alpha and its pharmacokinetics in mice

The goal of this research was to prepare a kind of hydrophilic sustained release microspheres of interferon-alpha (IFN-alpha), alginate-chitosan microspheres (ACM) of IFN, and investigate its pharmacokinetics in mice. Alginate microspheres of IFN-alpha were first prepared by an emulsion method and further incubated in chitosan to form IFN-ACM. The influences of isopropanol, bovine serum albumin (BSA), and pH adjustment by isoelectric point of IFN were studied. The optimized IFN-ACM was obtained with smooth and round morphology, size of 2.18 +/- 0.43 microm and entrapment efficiency of 40%. All the concentrations of IFN-alpha were determined by IFN assay kits. Finally the pharmacokinetics of IFN-ACM suspension was studied in ICR mice by intramuscular (I.M.) routes. Compared with IFN solution, C(max) of IFN-ACM reduced 2.3-fold, and time to achievement of maximum serum concentrations (T(max)) increased 4-fold. Meanwhile the area under the concentration-time curve (AUC) was the same as that of solution. The concentration-time profiles presented the prolonged serum levels of IFN from IFN-ACM.

Nanoparticles as potential oral delivery systems of proteins and vaccines: a mechanistic approach

Peptides and proteins remain poorly bioavailable upon oral administration. One of the most promising strategies to improve their oral delivery relies on their association with colloidal carriers, e.g. polymeric nanoparticles, stable in gastrointestinal tract, protective for encapsulated substances and able to modulate physicochemical characteristics, drug release and biological behavior. The mechanisms of transport of these nanoparticles across intestinal mucosa are reviewed. In particular, the influence of size and surface properties on their non-specific uptake or their targeted uptake by enterocytes and/or M cells is discussed. Enhancement of their uptake by appropriate cells, i.e. M cells by (i) modeling surface properties to optimize access to and transport by M cells (ii) identifying surface markers specific to human M cell allowing targeting to M cells and nanoparticles transcytosis is illustrated. Encouraging results upon in vivo testing are reported but low bioavailability and lack of control on absorbed dose slow down products development. Vaccines are certainly the most promising applications for orally delivered nanoparticles.

Particle uptake by Peyer's patches: a pathway for drug and vaccine delivery

Particle uptake by Peyer's patches offers the possibility of tailoring vaccines that can be delivered orally. However, particle uptake by the follicle-associated epithelium in the gastrointestinal tract depends on several different factors that are the physicochemical properties of the particles, the physiopathological state of the animal, the analytical method used to evaluate the uptake and finally the experimental model. These parameters do not allow a clear idea about the optimal conditions to target the Peyer's patches. The goal of this review is to clarify the role of each factor in this uptake.

A novel method for removing residual acetone from gelatin microspheres

PURPOSE

To develop a method for removing residual acetone from gelatin microspheres.

METHODS

Free-flowing gelatin microspheres were either heated under vacuum or subjected to a stream of humidified air in a specially designed apparatus for removal of the residual acetone. To understand the removal mechanism, hygroscopic and thermal properties of the microspheres were examined.

RESULTS

Heating the gelatin microspheres under vacuum did not reduce the acetone level below 2%, but the use of humidified air under fluidizing condition reduced the residual acetone in gelatin microspheres by an additional two orders of magnitude. The rate of acetone removal was a strong function of the relative humidity (RH) of the air stream; higher RH accelerated acetone removal. Other variables influencing the acetone removal rate are the mean particle diameter and the linear velocity of the humidified air. Under high relative humidities, significant amounts of moisture were absorbed into gelatin microspheres, reducing their glass transition temperature below 25 degrees C.

CONCLUSION

The residual acetone in gelatin microspheres can be efficiently removed when exposed to air of high RH. Mechanisms of water-dependent acetone removal are proposed.