Gastro-protective protein-silica nanoparticles formulation for oral drug delivery: In vitro release, cytotoxicity and mitochondrial activity.

Our contribution aims to provide an efficient solution to one of the major challenges of oral delivery of gastro-sensitive drugs, namely preventing their premature release and degradation in the gastric fluid in order to maximize the absorption in the small intestine. Our results show that a pH-responsive protein, i.e., succinylated ß-lactoglobulin (BL), together with the key attributes of mesoporous silica nanoparticles (MSNs), can synergetically reduce the release of the gastro-sensitive drug, omeprazole (OMP), in acidic pH and enhance the dissolution in intestinal pH conditions. Two families of MSNs were synthesized, MCM-48-based and dendritic-type MSNs, and both materials were additionally functionalized with trimethylsilyl groups to produce a hydrophobic surface that can further modulate the interaction of the MSNs with the succinylated protein in the nanoformulation. The methyl-functionalization of the MSNs also impacted on the physical state of the confined OMP and consequently on its release in near neutral pH. Our cytotoxicity screening revealed no particular mitochondrial dysfunction originating from the MSNs. Moreover, upon progressive release of the drug confined into dendritic-type MSNs, the cytotoxicity against tumorigenic and non-tumorigenic cells (Caco-2 and HCEC) was significantly lower in comparison to the drug pre-dissolved in DMSO.

Smart Protein-Based Formulation of Dendritic Mesoporous Silica Nanoparticles: Toward Oral Delivery of Insulin.

Oral insulin administration still represents a paramount quest that almost a century of continuous research attempts did not suffice to fulfill. Before pre-clinical development, oral insulin products have first to be optimized in terms of encapsulation efficiency, protection against proteolysis, and intestinal permeation ability. With the use of dendritic mesoporous silica nanoparticles (DMSNs) as an insulin host and together with a protein-based excipient, succinylated ß-lactoglobulin (BL), pH-responsive tablets permitted the shielding of insulin from early release/degradation in the stomach and mediated insulin permeation across the intestinal cellular membrane. Following an original in vitro cellular assay based on insulin starvation, direct cellular fluorescent visualization has evidenced how DMSNs could ensure the intestinal cellular transport of insulin.

Evaluation of mesoporous silica nanoparticles for oral drug delivery - current status and perspective of MSNs drug carriers.

The oral pathway is considered as the most common method for drug administration, although many drugs, especially the highly pH- and/or enzymatic biodegradable peptide drugs, are very difficult to formulate and achieve a good intestinal absorption. Efficient systematic absorption of an active substance, delivered via oral ingestion, is only achievable if the drug (1) is substantially present as a solution in the gastrointestinal tract, (2) is able to penetrate through the intestinal mucus, (3) overcomes the different gastrointestinal barriers, and (4) provides an effective therapeutic dose. Therefore, optimization of oral bioavailability of poorly-soluble drugs still remains a significant challenge for the pharmaceutical industry. Even though numerous conventional drug carriers have successfully solved some of the issues related to oral delivery of poorly-soluble drugs, only few of them met commercialization requirements. These drawbacks have led the scientific world to reconsider its approaches toward targeted drug delivery systems and researchers started looking for alternative vectorized carriers. In this area, nanoparticle-based materials have several significant advantages over free and non-formulated drugs. For example, nanosized porous silica carriers allow for more sustained and controlled drug release or improved oral bioavailability. Thus, in the present review, we will highlight the most important features of nanostructured silica drug carriers, such as particle size, particle shape, surface roughness or surface functionalization, and underline the key advantages of these nanosupports. In particular, this article will discuss recent progress and challenges in the area of mesoporous silica nanocarriers used for oral drug delivery. Additional emphasis will be set on the biological and chemical features of the gastrointestinal tract as well as currently tested nanoformulations and strategies to avoid drug degradation in the gastrointestinal environment.

In vitro gastric survival of commercially available probiotic strains and oral dosage forms.

Although the intestinal microbial community is still incompletely understood, there is strong evidence of the benefits of using probiotics to address some medical states or conditions. As a result, the probiotics oral supplements market has exploded during the last few years. However, while their sensitivity to gastric juices, acidic pH and bile is well known, most of these oral forms would not guarantee any survival of the strains in such conditions. In this work, we have studied the resistance to simulated gastric juices of several commercially available probiotics products. These included sixteen strains and ten oral forms such as enteric/non-enteric capsules/tablets and microencapsulated strains. Results demonstrated that all tested strains showed high sensitivity to acidic conditions and suggested that most of these microorganisms would not show any viability when immersed in the stomach at fasting. Most probiotics oral forms did not provide any protection to strains, unless these forms presented strong enteric protection. Consequently, the efficacy of non-enteric products to fully provide to the patient the benefits related to the consumption of probiotics supplement would be strongly questionable. This study underlines the chasm between the current opinion about probiotics protection needs and the products proposed by many companies in the dietary supplements area.

Characterization of a food-based enteric coating for capsules and its compatibility with an alternative sealing method.

Efficiency of a new protein-based enteric coating for capsules was studied. Coating physical-chemical properties were compared to those obtained from a well-known methacrylate-based enteric coating (Eudragit). Swelling in simulated gastric fluid (SGF) was 20 times higher than for Eudragit films. Mechanical properties (elastic modulus, elongation and puncture strength at break) were comparable to those measured from a standard Eudragit formulation. Pilot-scale coating trials were performed following three methods: using a standard spray-gun configuration, using a HPC-based seal-coat prior to enteric coating and using an "inverted" spray-gun configuration. The effect of these methods on capsules sealing and in vitro gastric performance was studied. In vitro tests were performed following the two USP official methods: disintegration and dissolution. Inverted gun configuration and HPC-sealing showed the highest sealing efficiency and the best in vitro performance. Capsules with a weight gain of 14-16% generally passed all USP tests (no disintegration evidence after 60 min in SGF; release below 10% after 2h of experiments in SGF). However, in some cases, slight differences between results obtained from dissolution and disintegration tests were pointed out. This work demonstrates the potential of a protein-based enteric coating and underlines the importance of capsules sealing.

Protein based tablets as reversible gelling systems for delayed release applications.

Succinylated ß-lactoglobulin (S-ß-lg) was previously shown to be efficient as new excipient for the formation of enteric tablets, suitable for several applications including probiotics delivery. This work investigates the mechanisms leading to S-ß-lg tablets delayed release. Release kinetics were evaluated in vitro. Fourier transformed infra red spectroscopy (FTIR) was used to visualize the effect of dissolution medium on matrix tablet surface. Results demonstrated that tablets release in simulated gastric fluids (SGF) might be due to water/drug diffusion through an in situ formed gel layer, as revealed by FTIR data. As SGF penetrated the tablet, regardless of protein succinylation rate (50% or 100%), molecular rearrangements occurred, allowing the development of an important band located in the 1621-1623 cm(-1) region. This band was characteristic of the formation of protein intermolecular ß-sheets. The gel was showed to be reversible in intestinal conditions, allowing delayed release. While the molecular structure of the gel layer was not depending on protein succinylation rate, it appeared that 100% S-ß-lg tablets showed slower release. This low release was probably related to 100% S-ß-lg lower solubility, lower charge density, and their ability to form stronger intermolecular hydrogen bonds. This work highlights proteins potential for the conception of controlled drug delivery systems.

ß-Lactoglobulin tablets as a suitable vehicle for protection and intestinal delivery of probiotic bacteria.

The use of succinylated ß-lactoglobulin as a novel functional tablet excipient for the protection of probiotic bacteria against the adverse gastric conditions and their delivery in the intestine was studied. Tablets were produced by direct compression of a dry mixture of Bifidobacterium longum HA-135 and the tested excipient. The results showed that tablets made of native ß-lg did not ensure cell survival while grafting carboxylic acid groups on the protein revealed to be an innovative method to create a gastroresistant matrix that could allow the survival of up to 10(8)CFU and 10(7)CFU after 1h and 2h gastric incubation, respectively. When compared to other polymers, succinylated ß-lg promoted the best survival both upon compression and after simulated gastric passage. The proportion of succinylated ß-lg in the formulation could be lowered to 60% without modifying the protective ability of the matrix. Additionally, the tablets proved to be stable over a period of 3 months when refrigerated. Succinylated ß-lg tablets are an interesting vehicle for the protection of acid-sensitive bacteria during transit in the upper gastro-intestinal tract.