Catarina Pinto Reis

Review and current status of emulsion/dispersion technology using an internal gelation process for the design of alginate particles

Emulsification/internal gelation has been suggested as an alternative to extrusion/external gelation in the encapsulation of several compounds including sensitive biologicals such as protein drugs. Protein-loaded microparticles offer an inert environment within the matrix and encapsulation is conducted at room temperature in a media free of organic solvents. Recently, the concept of internal gelation has been applied to formulating nanoparticles as drug delivery systems. Emulsification/internal gelation technologies available for microparticles preparation, particularly that involving alginate polymer, are described as well as recent advances towards applications in nanotechnology. Those methods show great promise as a tool for the development of encapsulation processes, especially for the new field of nanotechnology using natural polymers.

Nanoparticle strategies for the oral delivery of insulin

Since its discovery, insulin remains the major treatment for Type 1 diabetes and many Type 2 diabetic patients, with insulin being administered parenterally. The oral route of insulin delivery, being the most comfortable, would also be the most physiologically advantageous in taking advantage of the portal–hepatic route of absorption. However, insulin is less absorbed by the intestinal mucosa and is rapidly degraded enzymatically in the gastrointestinal tract. Polymeric biodegradable and biocompatible nanoparticles have been developed. These nanoparticles protect insulin against degradation and facilitate the uptake of insulin (associated or not associated to the nanoparticles) through a paracellular or a transcellular pathway. In this review, the physicochemical characteristics of polymer composition, in vitro release kinetics and the biological effects of insulin-loaded nanoparticles in experimental diabetes and healthy animals are discussed.

Nanoparticulate biopolymers deliver insulin orally eliciting pharmacological response.

The aim of this study was to characterize and evaluate a novel oral insulin nanoparticulate system based on alginate-dextran sulfate core, complexed with a chitosan-polyethylene glycol-albumin shell. Insulin-loaded nanospheres (25, 50, 100 IU/kg) administered orally to diabetic rats reduced glycemia in a dose dependent manner. This effect lasted over 24 h with a maximal effect after 14 h. Nanospheres increased insulin plasma level and improved glycemic response to an oral glucose overload. After 4 days oral administration (50 IU/kg/day), the metabolic status of diabetic rats improved with a reduction in water intake, urine excretion and proteinuria. FITC-insulin-loaded nanospheres administered to an isolated intestinal loop were taken up by the intestinal mucosa. They strongly adhered to villus apical enterocytes and markedly labeled Peyers patches. It is concluded that nanospheres preserve insulin and exert an antidiabetic effect after oral administration. This is explained by a protective effect against proteolytic enzymes by the albumin coating, by the mucoadhesive properties of chitosan-polyethylene glycol, and by the possibility of chitosan reversibly altering tight junctions leading to an improved absorption of insulin. This formulation demonstrates beneficial effects on diabetic symptoms and will be of interest in the treatment of diabetes with oral insulin.

Polyelectrolyte Biomaterial Interactions Provide Nanoparticulate Carrier for Oral Insulin Delivery

Nanospheres are being developed for the oral delivery of peptide-based drugs such as insulin. Mucoadhesive, biodegradable, biocompatible, and acid-protective biomaterials are described using a combination of natural polyelectrolytes, with particles formulated through nanoemulsion dispersion followed by triggered in situ gel complexation. Biomaterials meeting these criteria include alginate, dextran, chitosan, and albumin in which alginate/dextran forms the core matrix complexed with chitosan and albumin coat. Smaller size and higher albumin-based acid-protective formulation was orally administered to diabetic rats and glucose reduction and physiological response analyzed. Insulin encapsulation efficiency was 90, 82, and 66% for uncoated, chitosan-coated, and albumin-chitosan-coated alginate nanospheres, respectively. The choice of coating polymer seems to influence insulin release profile and to be crucial to prevent peptic digestion. Physiological response following oral delivery showed that insulin albumin-chitosan-coated alginate nanospheres reduced glycemia ∼ 72% of basal values. Albumin serves as an important enteric coating providing acid- and protease protection enabling uptake of active drug following oral dosage.

Polymeric nanoparticles modified with fatty acids encapsulating betamethasone for anti-inflammatory treatment.

Topical glucocorticosteroids were incorporated into nanocarrier-based formulations, to overcome side effects of conventional formulations and to achieve maximum skin deposition. Nanoparticulate carriers have the potential to prolong the anti-inflammatory effect and provide higher local concentration of drugs, offering a better solution for treating dermatological conditions and improving patient compliance. Nanoparticles were formulated with poly-ϵ-caprolactone as the polymeric core along with stearic acid as the fatty acid, for incorporation of betamethasone-21-acetate. Oleic acid was applied as the coating fatty acid. Improvement of the drug efficacy, and reduction in drug degradation with time in the encapsulated form was examined, while administering it locally through controlled release. Nanoparticles were spherical with mean size of 300 nm and negatively charged surface. Encapsulation efficiency was 90%. Physicochemical stability in aqueous media of the empty and loaded nanoparticles was evaluated for six months. Drug degradation was reduced compared to free drug, after encapsulation into nanoparticles, avoiding the potency decline and promoting a controlled drug release over one month. Fourier transform infrared spectroscopy and thermal analysis confirmed drug entrapment, while cytotoxicity studies performed in vitro on human keratinocytes, Saccharomyces cerevisiae models and Artemia salina, showed a dose-response relationship for nanoparticles and free drug. In all models, drug loaded nanoparticles had a greater inhibitory effect. Nanoparticles increased drug permeation into lipid membranes in vitro. Preliminary safety and permeation studies conducted on rats, showed betamethasone-21-acetate in serum after 48 h application of a gel containing nanoparticles. No skin reactions were observed. In conclusion, the developed nanoparticles may be applied as topical treatment, after encapsulation of betamethasone-21-acetate, as nanoparticles promote prolonged drug release, increase drug stability in aqueous media, reducing drug degradation, and increase drug permeability through lipid membranes.

Hydrocortisone-loaded poly(ε-caprolactone) nanoparticles for atopic dermatitis treatment.

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects mostly young infants. The purpose of this research was to achieve a prolonged drug release and the reduction of side effects with hydrocortisone-loaded nanoparticles (NPs), for AD treatment. Poly(ε-caprolactone) (PCL) NPs were prepared by modified solvent displacement method and were characterized in terms of size, potential zeta, morphology, entrapment efficiency (EE), Fourier transform infrared (FT-IR) spectrometry and in vitro permeation studies using Franz cells. Toxicology of this nanosystem was also assessed. The obtained NPs EE showed an increased size and a more homogenous size distribution after loading and were negatively charged. EF was around 62%. In vitro release studies demonstrated a controlled release of drug from the NPs over time. FT-IR analysis showed the system stability for one week. Permeation studies revealed significant differences in the permeation of encapsulated and free hydrocortisone. In vitro toxicity studies showed no effect of drug toxicity after encapsulation. The study seems to indicate that encapsulation of hydrocortisone in PCL NPs could enable a faster control of the disease and a decrease in the side effects associated to the long-term application of corticosteroids.

Drug carriers for oral delivery of peptides and proteins: accomplishments and future perspectives

Effective formulation for peptide and protein delivery through the oral route has always been the critical effort with the advent of biotechnology. Stability, enzymatic degradation and ineffective absorption are common difficulties found for conventional dosage forms. As a result, new drug-delivery approaches are used to circumvent these limitations and enhance effective oral drug delivery. Some of these technologies have reached late stages of clinical trials and promising results will be available in the near future. This review covers, in general, the recent carriers reported in literature.

Toxicological assessment of orally delivered nanoparticulate insulin

Subacute toxicological assessment on diabetic rats was conducted after 15 days of daily oral administration of nanoparticulate insulin. Haematological and biochemical analyses were conducted on blood and urine, biopsies performed on organs and tissues, and histology analysed by optical microscopy. Insulin-loaded nanoparticles alone did not change liver or kidney functions. The increase of some hepatic parameters was attributed to diabetes physiopathology and to chemical inducement of diabetes and not to the nanoparticle composition since diabetic controls showed the same variations. In terms of kidney function, parameters such as urea nitrogen and creatinine, were also similar to normal rats with the exception of glycosuria. This single effect was due to diabetes physiopathology and the method of induction, and not to the nanoparticle composition, since non-dosed diabetic rats showed the same alteration. Even so, glycosuria levels of animals dosed with insulin-loaded nanoparticles were lower than control diabetic rats which may indicate an effective hypoglycaemic response. Nanoparticles did not exhibit toxicity in haematological parameters. Finally, organ histology was similar between dosed animals and normal rats with the exception of pancreas histology.

Bile acids and bile acid derivatives: use in drug delivery systems and as therapeutic agents

ABSTRACT Introduction: Bile acids are biological surfactants and signaling molecules with important paracrine and endocrine functions. The enterohepatic organotropism of bile acids turns these facial amphiphiles into attractive drug delivery systems for selective drug targeting to the liver or to enhance drug bioavailability by improving intestinal absorption and metabolic stability. Areas covered: Bile acid-based amphiphiles, in the form of mixed micelles, bilosomes, drug conjugates and hybrid lipid-polymer nanoparticles are critically discussed as delivery systems for anticancer drugs, antimicrobial agents and therapeutic peptides/proteins, including vaccines. Therapeutic applications of bile acid derivatives as cytotoxic and neuroprotective agents are also addressed. Expert opinion: Bile acids play an important role in modulating cancer therapy and novel derivatives with cytotoxic activity not restricted to the gastrointestinal tract can be expected. Selective toxicity targeting the bacterial membrane remains an attractive area of research for further development of bile acid-based bactericidal agents. On the other hand, the neuroprotective properties of some bile acids offer therapeutic potential in neurodegenerative disorders. Bile acid-based nanoparticles are also a growing research area due to the unique characteristics and tunable properties of these nanosystems. Therefore, multifaceted pharmaceutical and biomedical applications of bile salts are to be expected in the near future.

Nanotechnology as a promising strategy for alternative routes of insulin delivery.

Since its discovery, insulin has been used as highly specific and effective therapeutic protein to treat type 1 diabetes and later was associated to oral antidiabetic agents in the treatment of type 2 diabetes. Generally, insulin is administered parenterally. Although this route is successful, it still has several limitations, such as discomfort, pain, lipodystrophy at the injection sites and peripheral hyperinsulinemia, which may be the cause of side effects and some complications. Thus, alternative routes of administration have been developed, namely, those based on nanotechnologies. Nanoparticles, made of synthetic or natural materials, have been shown to successfully overcome the inherent barriers for insulin stability, degradation, and uptake across the gastrointestinal tract and other mucosal membranes. This review describes some of the many attempts made to develop alternative and more convenient routes for insulin delivery.