Oral administration of active pharmaceutical ingredients is desirable because it is easy, safe, painless, and can be performed by patients, resulting in good medication adherence. The mucus layer in the gastrointestinal (GI) tract generally acts as a barrier to protect the epithelial membrane from foreign substances; however, in the absorption process after oral administration, it can also disturb effective drug absorption by trapping it in the biological sieve structured by mucin, a major component of mucus, and eliminating it by mucus turnover. Recently, functional nanocarriers (NCs) have attracted much attention due to their immense potential and effectiveness in the field of oral drug delivery. Among them, NCs with mucopenetrating and mucoadhesive properties are promising dosage options for controlling drug absorption from the GI tracts. Mucopenetrating and mucoadhesive NCs can rapidly deliver encapsulated drugs to the absorption site and/or prolong the residence time of NCs close to the absorption membrane, providing better medications than conventional approaches. The surface characteristics of NCs are important factors that determine their functionality, owing to the formation of various kinds of interactions between the particle surface and mucosal components. Thus, a deeper understanding of surface modifications on the biopharmaceutical characteristics of NCs is necessary to develop the appropriate mucosal drug delivery systems (mDDS) for the treatment of target diseases. This review summarizes the basic information and functions of the mucosal layer, highlights the recent progress in designing functional NCs for mDDS, and discusses their performance in the GI tract.

Oral dosage is the most commonly used and preferred method of drug administration due to its several advantages, including non-invasiveness, patient adherence, and ease of use. However, oral bioavailability can be influenced by several factors, such as drug solubility and mucosal permeability in the gastrointestinal tract, sometimes leading to poor and/or inconsistent absorption. In particular, low aqueous solubility presents a significant challenge in achieving adequate oral bioavailability and therapeutic effectiveness for many pharmaceutical compounds. Attempts to overcome these limitations have focused on deeper understanding of the physicochemical, biochemical, and biological barriers that limit overall drug bioavailability. To ensure better and stable pharmacokinetic behavior of orally administered drugs, various formulation strategies have been developed to enhance solubility, dissolution rate, membrane permeability, and overall oral bioavailability. This review article explores recent advancements in formulation techniques aimed at improving the biopharmaceutical properties of orally administered drugs. The challenges and development aspects of oral dosage forms are also addressed.

We developed dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of the Mo₂ core. A 2,4,6-triisopropylbenzoate-supported Mo₂ complex acts as a catalyst for radical addition reactions of polyhaloalkanes to 1-alkenes and cyclopentene, while amidinate- and guanidinate-supported Mo₂ clusters are effective catalysts for the radical polymerization reaction of methyl methacrylate.

In this study, we developed stabilized astaxanthin (AX) nanoparticles (sNP/AX) to improve the physicochemical properties, oral bioavailability, and hepatoprotection of AX. A flash nanoprecipitation technique was used with a multi-inlet vortex mixer to prepare the sNP/AX. Vitamins E (VE) and C (VC) were used as co-stabilizers with poloxamer 407 as a stabilizer to inhibit the oxidative degradation of AX during sNP/AX formation and storage. VC stabilized AX in the aqueous phase during the preparation, whereas VE markedly improved the storage stability of sNP/AX, as evidenced by the AX contents remaining at 94 and 81% after 12 weeks of storage at 4 °C and 25 °C, respectively. The mean sNP/AX diameter was 215 nm, which resulted in higher AX release properties than those of crystalline AX. Rats, orally administered sNP/AX (33.2 mg AX/kg), exhibited higher systemic exposure to AX, whereas oral absorption in the crystalline AX group was negligible. In the rat hepatic injury model, oral pretreatment with sNP/AX (33.2 mg AX/kg) markedly attenuated hepatic damage, as shown by the histopathological analysis and reduced levels of plasma biomarkers for hepatic injury. These findings suggest that strategically including antioxidative additives in the sNP/AX has the potential to improve the physicochemical and nutraceutical properties of AX.