Preparation and Evaluation of Enteric-Coated Chitosan Derivative-Based Microparticles Loaded with Salmon Calcitonin as an Oral Delivery System

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

Composite Separable Microneedles for Transdermal Delivery and Controlled Release of Salmon Calcitonin for Osteoporosis Therapy

A composite separable microneedles (MNs) system consisting of silk fibroin (SF) needle tips and hyaluronic acid (HA) base is developed for transdermal delivery of salmon calcitonin (sCT) for therapy of osteoporosis. Poly(ethylene glycol) (PEG) is used to modulate the conformation structure of SF to achieve controllable sustained release of sCT. The prepared MNs can effectively penetrate the skin stratum corneum. After application to the skin, the HA base is dissolved within 2 min, allowing these SF drug depots to be implanted into the skin for controllable sustained release of sCT. The release kinetics of sCT can be controlled by regulating the conformation of SF with PEG and the interaction between sCT peptide and SF proteins. Compared with traditional needle injection, delivery of sCT using optimized HA-PEG/SF MNs shows better trabecular bone repair for ovariectomized-induced osteoporosis in mice. The proposed MNs system provides a new noninjection strategy for therapy of osteoporosis.

Oral delivery of protein and peptide drugs: from non-specific formulation approaches to intestinal cell targeting strategies

The past few years has witnessed a booming market of protein and peptide drugs, owing to their superior efficiency and biocompatibility. Parenteral route is the most commonly employed method for protein and peptide drugs administration. However, short plasma half-life protein and peptide drugs requires repetitive injections and results in poor patient compliance. Oral delivery is a promising alternative but hindered by harsh gastrointestinal environment and defensive intestinal epithelial barriers. Therefore, designing suitable oral delivery systems for peptide and protein drugs has been a persistent challenge. This review summarizes the main challenges for oral protein and peptide drugs delivery and highlights the advanced formulation strategies to improve their oral bioavailability. More importantly, major intestinal cell types and available targeting receptors are introduced along with the potential strategies to target these cell types. We also described the multifunctional biomaterials which can be used to prepare oral carrier systems as well as to modulate the mucosal immune response. Understanding the emerging delivery strategies and challenges for protein and peptide drugs will surely inspire the production of promising oral delivery systems that serves therapeutic needs in clinical settings.

Spatiotemporally controlled calcitonin delivery: Long-term and targeted therapy of skeletal diseases

Bone is a connective tissue that support the entire body and protect the internal organs. However, there are great challenges on curing intractable skeletal diseases such as hypercalcemia, osteoporosis and osteoarthritis. To address these issues, calcitonin (CT) therapy is an effective treatment alternative to regulate calcium metabolism and suppress inflammation response, which are closely related to skeletal diseases. Traditional calcitonin formulation requires frequent administration due to the low bioavailability resulting from the short half-life and abundant calcitonin receptors distributed through the whole body. Therefore, long-term and targeted calcitonin delivery systems (LCDS and TCDS) have been widely explored as the popular strategies to overcome the intrinsic limitations of calcitonin and improve the functions of calcium management and inflammation inhibition in recent years. In this review, we first explain the physiological effects of calcitonin on bone remodeling: (i) inhibitory effects on osteoclasts and (ii) facilitated effects on osteoblasts. Then we summarized four strategies for spatiotemporally controlled delivery of calcitonin: micro-/nanomedicine (e.g. inorganic micro-/nanomedicine, polymeric micro-/nanomedicine and supramolecular assemblies), hydrogels (especially thermosensitive hydrogels), prodrug (PEGylation and targeting design) and hybrid biomaterials. Subsequently, we discussed the application of LCDS and TCDS in treating hypercalcemia, osteoporosis, and arthritis. Understanding and analyzing these advanced calcitonin delivery applications are essential for future development of calcitonin therapies toward skeletal diseases with superior efficacy in clinic.

Transdermal Delivery of Salmon Calcitonin Using a Dissolving Microneedle Array: Characterization, Stability, and In vivo Pharmacodynamics

Salmon calcitonin (sCT) is a polypeptide drug, possessing the ability to inhibit osteoclast-mediated bone resorption. Just like other bioactive macromolecules, sCT is generally administered to the patients by either injection for poor compliance or through nasal spray for low bioavailability, which limits its use as therapeutic drugs. In the present study, to overcome the limitations of the conventional routes, two new dissolving microneedle arrays (DMNAs) based on transdermal sCT delivery systems were developed, namely sCT-DMNA-1 (sCT/Dex/K90E) and sCT-DMNA-2 (sCT/Dex-Tre/K90E) with the same dimension, meeting the requirements of suitable mechanical properties. An accurate and reliable method was established to determine the needle drug loading proportion in sCT-DMNAs. The stability study exhibited that the addition of trehalose could improve the stability of sCT in DMNA under high temperature and humidity. Further, in vivo pharmacodynamic study revealed that DMNA patch could significantly enhanced relative bioavailability to approximately 70%, and the addition of trehalose was found to be beneficial for sCT transdermal delivery. Therefore, sCT-DMNA is expected to replace traditional dosage form, providing a secure, efficient, and low-pain therapeutic strategy for bone disorders.