Positive effect of alendronate on bone turnover in ovariectomised rats’ osteoporosis: comparison of transdermal lipid-based delivery with conventional oral administration

Hierarchically Released Liquid Metal Nanoparticles for Mild Photothermal Therapy/Chemotherapy of Breast Cancer Bone Metastases via Remodeling Tumor Stromal Microenvironment

Currently, the treatment strategy for bone metastasis is mainly to inhibit the growth of tumor cells and the activity of osteoclasts, while ignoring the influence of the tumor stromal microenvironment (TSM) on the progression of bone metastasis. Herein, a dual-target liquid metal (LM)-based drug delivery system (DDS) with favorable photothermal performance is designed to spatially program the delivery of multiple therapeutic agents to enhance the treatment of bone metastasis through TSM remodeling. Briefly, mesoporous silicon-coated LM is integrated into zeolitic imidazolate framework-8 (ZIF-8) with both bone-seeking and tumor-targeting capacities. Curcumin (Cur), a tumor microenvironment modulator, is encapsulated into ZIF-8, and doxorubicin (DOX) is enclosed inside mesoporous silicon. Specific accumulation of the LM-based DDS in bone metastases first relieves the tumor stroma by releasing Cur in response to the acidic tumor microenvironment and then releases DOX deep into the tumor under near-infrared light irradiation. The combined strategy of the LM-based DDS and mild photothermal therapy has been shown to effectively restrain cross-talk between osteoclasts and tumor cells by inhibiting the secretion of transforming growth factor-β, degrading extracellular matrix components, and increasing infiltration of CD4+ and CD8+ T cells, which provides a promising strategy for the treatment of bone metastases.

Insight into the Molecule Impact of Critical-Sized UHMWPE-ALN Wear Particles on Cells by the Alginate-Encapsulated Cell Reactor

Wear particles of ultra-high molecular weight polyethylene (UHMWPE) are inevitable during service as joint prosthesis, and particles ≤ 10 μm with critical size could cause serious osteolysis and aseptic loosening of joint prosthesis. The aim of this study is to adopt the alginate-encapsulated cell reactor to investigate the molecular impact of critical-sized wear particles of UHMWPE loaded with alendronate sodium (UHMWPE-ALN) on cells. Results showed that compared with UHMWPE wear particles, UHMWPE-ALN wear particles inhibited the proliferation of macrophages significantly after being co-cultured for 1, 4, 7, and 14 d. Furthermore, the released ALN promoted early apoptosis, suppressed the secretion of TNF-α and IL-6 of macrophages, and down-regulated relative gene expressions of TNF-α, IL-6, and IL-1β and RANK. In addition, compared with UHMWPE wear particles, UHMWPE-ALN wear particles promoted the ALP activity of osteoblasts, down-regulated the gene expression of RANKL, and up-regulated gene expression of osteoprotegerin. There were mainly two approaches of the effects of critical-sized UHMWPE-ALN wear particles on cells, one of which was cytology and the other was cytokine signal pathway. The former mainly affected the proliferation and activity of macrophages and osteoblasts. The latter would inhibit osteoclasts via cytokine and RANKL/RANK signal pathway. Thus, UHMWPE-ALN had the potential application in clinics to treat osteolysis induced by wear particles.

Strategies for transdermal drug delivery against bone disorders: A preclinical and clinical update

The transdermal drug delivery system is an exceptionally safe and well-tolerable therapeutic approach that has immense potential for delivering active components against bone-related pathologies. However, its use is limited in the current clinical practices due to the low skin permeability of most active drugs in the formulation. Thus, innovations in the methodologies of skin permeation enhancement techniques are suggested to overcome this limitation. Although various transdermal drug delivery systems are studied to date, there are insufficient studies comparing the therapeutic efficacy of transdermal delivery systems to oral delivery systems. Thus, creating a decision-making dilemma between oral or transdermal therapies. Therefore, a timely review is inevitable to develop a platform for future researchers to develop next-generation transdermal drug delivery strategies against skeletal diseases that must be convenient and cost-effective for the patients with improved therapeutic efficacy. Here, we will outline the most recent strategies that can overcome the choice limitation of the drug and enhance the transdermal adsorption of various types of drugs to treat bone disorders. For the first time, in this review paper, we will highlight the preclinical and clinical studies on the different transdermal delivery methods. Thus, providing insight into the current therapeutic approaches and suggesting new directions for the advancements in transdermal drug delivery systems against bone disorders.

Development of a Phosphoric Acid-Mediated Hyaluronic Acid Gel Sheet for Efficient Transdermal Delivery of Alendronate for Anti-Osteoporotic Therapy

For efficient transdermal delivery of alendronate (ALN) for anti-osteoporotic therapy, we developed a hyaluronic acid (HA) gel sheet that was prepared simply by enhancing HA noncovalent interactions using phosphoric acid and polyhydric alcohol (propanediol and glycerin). HA solution viscosity increased after addition of phosphoric acid, and the HA gel sheet formed after heated drying. The HA gel sheet could be converted to high viscosity state by addition of water. These results indicate that phosphoric acid enhances the noncovalent interactions of HA molecules. The HA gel sheet elicited no skin irritation over 7 days after a 24-h application. The permeation of ALN across rat and human skin was 109 and 7.17 µg/cm², respectively, up to 24 h after application of the ALN-loaded HA gel sheet, which is sufficient for clinical treatment of osteoporosis. The bioavailability of ALN in rats was ~20% after application of the ALN-loaded HA gel sheet, and plasma calcium levels were effectively reduced 3 days after sheet application. Furthermore, in a rat osteoporosis model, the reduction in tibial bone density was suppressed by treatment with the ALN-loaded HA gel sheet. These results indicate that our phosphoric acid-mediated HA gel sheet is a promising transdermal formulation for efficient ALN delivery.