Development of a daphnetin transdermal patch using chemical enhancer strategy: insights of the enhancement effect of Transcutol P and the assessment of pharmacodynamics

Serglycin secreted by late-stage nucleus pulposus cells is a biomarker of intervertebral disc degeneration

Intervertebral disc degeneration is a natural process during aging and a leading cause of lower back pain. Here, we generate a comprehensive atlas of nucleus pulposus cells using single-cell RNA-seq analysis of human nucleus pulposus tissues (three males and four females, age 41.14 ± 18.01 years). We identify fibrotic late-stage nucleus pulposus cells characterized by upregulation of serglycin expression which facilitate the local inflammatory response by promoting the infiltration of inflammatory cytokines and macrophages. Finally, we discover that daphnetin, a potential serglycin ligand, substantially mitigates the local inflammatory response by downregulating serglycin expression in an in vivo mouse model, thus alleviating intervertebral disc degeneration. Taken together, we identify late-stage nucleus pulposus cells and confirm the potential mechanism by which serglycin regulates intervertebral disc degeneration. Our findings indicate that serglycin is a latent biomarker of intervertebral disc degeneration and may contribute to development of diagnostic and therapeutic strategies.

Evaluation of Dose-Response Relationship of Permeation Enhancer Isopropyl Myristate Release on Drug Release: Release Enhancement Efficiency and Molecular Mechanism

The objective of this study is to investigate the dose-response relationship between various concentrations of permeation enhancers (PEs) and their ability to enhance drug release from a polymer matrix, utilizing an innovative parameter known as release enhancement efficiency (K). Additionally, the molecular mechanism underlying dynamic enhancement was also examined. Isopropyl myristate (IPM) was used as model enhancer and zolmitriptan (ZOL) was used as model drug to investigate dose-effect relationship in pressure sensitive adhesives (PSA). The release behavior of the PEs was determined by LC-MS/MS and verified by confocal laser scanning microscopy (CLSM). The enhancing effect of the PE on ZOL release was evaluated through in vitro release experiments and further validated by pharmacokinetics study. And the molecular mechanism was characterized with thermal analysis (DSC), Fourier transform infrared spectroscopy (FT-IR) and molecular dynamics simulation. K was 0.156, 0.286 and 0.279 at 3%, 6% and 9% IPM concentrations, indicating that the enhancement efficiency reached the maximum when the 6% IPM was applied. According to the mechanism research results, the fluidity of PSA increased linearly with the increase of IPM concentrations, but the interaction between IPM and ZOL reached its strongest point at 6%. In summary, the increase of K value (from 0 to 6% IPM content) was caused by the synergy of increased mobility of PSA and interaction (dipole-dipole and hydrogen-bond) among three components, and when the above two actions were in antagonistic, K no longer increased (6-9% IPM content).

Nephro-protective effect of Daphnetin in hyperoxaluria-induced rat renal injury via alterations of the gut microbiota

It is well proved that hyperoxaluria induces the renal injury and finally causes the end stage kidney disease. Daphnetin (coumarin derivative) already confirmed renal protective effect in renal model, but hyperoxaluria protective effect still unexplore. The objective of this research was to scrutinize the renal protective effect of daphnetin against ethylene glycol (GC)-induced hyperoxaluria via altering the gut microbiota. GC (1% v/v) was used for the induction of hyperoxaluria in the rats and the rats were received the oral administration of daphnetin (5, 10 and 15 mg/kg). The body and renal weight were assessed. Urine, renal, inflammatory cytokines, antioxidant, inflammatory parameters, and gut microbiota were appraised. Daphnetin effectually improved the body weight and reduced the renal weight. Its also remarkably boosted the magnesium, calcium, citrate level and suppressed the level of uric acid and oxalate formation. Daphnetin significantly (p < .001) ameliorate the level of urinary kidney injury molecule 1 (KIM-1), blood urea nitrogen (BUN), urea, serum creatinine (Scr), neutrophil gelatinase-associated lipocalin (NGAL) and uric acid along with inflammatory cytokines and inflammatory mediators. Daphnetin considerably repressed the malonaldehyde (MDA) level, protein carbonyl and improved the level of glutathione reductase (GR), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT). Daphnetin treatment considerably altered the microbial composition of different bacteria at phylum, genus and family level. Daphnetin significantly suppressed the Firmicutes relative abundance and boosted the Bacteroidetes relative abundance. Our result clearly indicated that daphnetin remarkably ameliorates the GC induced hyperoxaluria in rats via altering the oxidative stress, inflammatory reaction and gut microbiota. PRACTICAL APPLICATION: Nephrotoxicity is a serious health disease worldwide. We induce the renal toxicity in the experimental rats using the ethylene glycol and scrutinized the renal protective effect of daphnetin. Daphnetin considerably suppress the renal, urine parameters. For estimation the underlying mechanism, we estimated the gut microbiota in all group rats. Daphnetin remarkably altered the level of gut microbiota and suggesting the renal protective effect.

Development and Characterisation of a Topical Methyl Salicylate Patch: Effect of Solvents on Adhesion and Skin Permeation

The advent of skin patch formulation design and technology has enabled the commercialisation of methyl salicylate (MS) as a topical patch. However, the most fundamental aspect of skin permeation is unknown at present. The study aims to investigate the effect of solvent choice on the skin permeation of MS in a neat solvent system and patch formulation with an emphasis on patch adhesion. MS in six selected solvents (propylene glycol (PG), Transcutol^®, isopropyl myristate, Labrasol^®, Plurol^® oleique CC 497 and Maisine^® CC) was characterised and in vitro permeation studies were also performed. An ATR-FTIR analysis on solvent-treated skin was conudcted. Patch formulation was prepared and characterised for adhesion, in vitro drug release and skin permeation studies. The highest MS permeation was found in neat PG over 24 h (~90 μg/cm²) due to its strong skin protein conformation effect. Transcutol^® and isopropyl myristate showed better skin deposition and formulation retention, respectively. Nevertheless, PG enhanced the patch adhesion despite having a lower cumulative amount of MS permeated (~80 μg/cm²) as compared with Transcutol^® and Maisine^® (~110-150 μg/cm²). These two solvents, however, demonstrated better skin deposition and formulation retention but a lower patch adhesion. The unpredictable influence of the solvent on patch adhesion highlights the importance of the trade-off between patch adhesion and skin permeation during formulation design.

Sustainable and efficient skin absorption behaviour of transdermal drug: The effect of the release kinetics of permeation enhancer

At present, how the release kinetics of permeation enhancers affected their enhancement efficacy on drug skin absorption and its molecular mechanisms remained unclear. Herein, the release kinetics of permeation enhancer (Plurol Oleique CC (POCC)) which involved release percent (PR), release duration (RD) and release kinetic constant (k) and its enhancement efficacy on drug skin absorption were investigated with in vitro skin retention study and in vitro skin permeation study, respectively. POCC released from the acidic-drug loading patches followed with the Higuchi release model and had short RD (8-16 h), resulting in its unsustainable enhancement efficiency for acidic drugs. However, POCC released from the basic-drug loading patches followed with zero-order model with long RD (12-24 h), inducing a sustainable and efficient enhancement efficiency for basic drugs. The lower variance of an innovative parameter permeation enhancement coefficient (C_PE) represented the relatively sustainable and effective enhancement effect and was listed as followed: 0.20 (Zaltoprofen (ZPF)), 0.31 (Diclofenac (DCF)), 0.27 (Indomethacin (IMC)), 0.07 (Azasetron (AST)), 0.11 (Oxybutynin (OBN)) and 0.06 (Donepezil (DNP)). According to the results of FT-IR, MTDSC, ¹³C NMR spectra, molecular dynamics simulation, SAXS and Raman imaging, the Higuchi release model was caused by strong interaction between the acid drugs and pressure sensitive adhesive (PSA). This strong interaction induced faster diffusion speed of POCC from acidic-drug loading patches and make the swell degree of long periodicity phase (LPP) of stratum corneum (SC) lipids reached plateau early. The zero-order release model was because the weak interaction between basic drugs and PSA making most of POCC was still bound to PSA, which in turn lead to LPP swelled at a slow but sustainable process. In conclusion, zero-order release kinetic of POCC lead to sustainable and efficient penetration enhancement efficiency on basic drug, while the Higuchi release kinetic showed opposite effect for acidic drugs. A deep understanding of release kinetics of enhancer and its enhancement efficiency may drive the ideal selection of permeation enhancers and rational optimization of transdermal patches.

Design of a Long-Acting Rivastigmine Transdermal Delivery System: Based on Computational Simulation

The purpose of our study was using a computational simulation to develop a long-acting patch of rivastigmine (RVS). A range of patch formulations were screened including pressure sensitive adhesive (PSA), pharmaceutical excipients, and controlled release membranes using transfer simulation based on a mathematical model. Diffusion dynamics parameters for simulated operations were acquired through in vitro release tests (IVRT) and in vitro skin permeation tests (IVPT). The mechanism of controlled release was studied by FTIR (Fourier transform infrared), DSC (differential scanning calorimeter) and molecular docking. Results of a rat in vitro permeation profile showed excellent correlation with the in vivo deconvolution profile (R²=0.998). Experiments testified to transfer of RVS at a relatively uniform speed with high skin permeation (2531.2±142.46 μg/cm²) in 72 h. Pharmacokinetic data obtained in vivo also confirmed stable plasma concentrations over 72 h for the optimized patch, and significant prolongation of both T_max (11.20±1.79 h) and MRT_0-t (33.91±5.33 h). C_max was controlled with AUC_0-t (267.34±24.46 h ng/ml), which was closely comparable to parameters of a commercial Exelon® Patch. The successful development of a long-acting patch of RVS thus underscores the potential of computer aided design in a context of promnesic transdermal delivery. Graphical abstract.

A Systematic Quantitative Evaluation of Permeation Enhancement Window: Transdermal Permeation Enhancing Dynamics Establishment and Molecular Mechanisms Characterization of Permeation Enhancer

At present, transdermal permeation enhancing dynamics studies on permeation enhancers are still limited. In this study, these dynamics were established based on the content of enhancer Plurol Oleique CC in skin (C_POCC) and the increment of drug permeation amount (ΔQ). A new concept deemed "permeation enhancement window" (ΔC_POCC), comprised of a threshold dose (C^thr), maximal dose (C^max) and permeation enhancement efficiency (Eff) was used to evaluate the enhancement effect of POCC for different drugs. According to results of FT-IR, ATR-FTIR and DSC analyses, the higher CPOCC of patches containing acidic drugs vs. basic drugs resulted from their stronger interaction with pressure-sensitive adhesives, leading to more free POCC and a greater disturbing effect on stratum corneum (SC) lipids. Below C^thr, a longer lag phase for acidic drugs resulted from more POCC required to compete with ceramide. When CPOCC exceeded C^max by about 400 μg/g, plateau phases for all drugs were reached due to the upper limit of SC lipid fluidity, as confirmed by SAXS and Raman imaging. In summary, the differences in the permeation enhancement window for the test drugs resulted from the varied interaction strengths among POCC, drugs and adhesives, as well as changeable SC lipid fluidity.

Molecular perspective of efficiency and safety problems of chemical enhancers: bottlenecks and recent advances

Chemical penetration enhancer (CPE) is a preferred approach to improve drug permeability through the skin, due to its unique advantages of simple use and high compatibility. However, CPEs efficiency and safety problems frequently arise, which greatly restrains the further application in transdermal drug delivery systems (TDDS). To get access to the root of problems, the efficiency and safety of CPEs are reviewed especially from molecular perspectives, which include (1) the possible factors of CPEs low efficiency; (2) the possible contribution of CPEs in the evolution of safety problems such as skin irritation and allergic reaction; (3) the interactive relationship between CPEs efficiency and safety, as well as the bottlenecks of achieving their balance. More importantly, based on these, recent advances are summarized in improving efficiency or safety of CPEs, which offers a guidance of rationally selecting CPEs in future research.

Daphnetin inhibits spinal glial activation via Nrf2/HO-1/NF-κB signaling pathway and attenuates CFA-induced inflammatory pain

Daphnetin (7, 8-dihydroxycoumarin, DAPH), a coumarin derivative isolated from Daphne odora var., recently draws much more attention as a promising drug candidate to treat neuroinflammatory diseases due to its protective effects against neuroinflammation. However, itscontribution to chronic inflammatory pain is largely unknown. In the current work, we investigated the effects of DAPH in a murine model of inflammatory pain induced by complete Freund's adjuvant (CFA) and its possible underlying mechanisms. Our results showed that DAPH treatment significantly attenuated mechanical allodynia provoked by CFA. A profound inhibition of spinal glial activation, followed by attenuated expression levels of spinal pro-inflammatory cytokines, was observed in DAPH-treated inflammatory pain mice. Further study demonstrated that DAPH mediated negative regulation of spinal NF-κB pathway, as well as its preferential activation of Nrf2/HO-1 signaling pathway in inflammatory pain mice. This study, for the first time, indicated that DAPH might preventthe development of mechanical allodynia in mice with inflammatory pain. And more importantly, these data provide evidence for the potential application of DAPH in the treatment of chronic inflammatory pain.

Daphnetin exerts an anticancer effect by attenuating the pro-inflammatory cytokines

Leukemia is a malignant tissue-forming disease, which induces the overproduction of large numbers of immature blood cells entering the peripheral blood. It is well documented that inflammation plays a crucial role in the expansion of leukemia. Daphnetin has confirmed anti-inflammatory effects against various diseases. In this experimental study, we evaluated the anti-leukemia and anti-inflammatory effect of daphnetin against benzene-induced leukemia in rats and explored the underlying mechanism. Benzene was used for inducing leukemia in experimental rats. The rats were divided into different groups and the body weight, hematological parameters, bone marrow cells, cytokines, and inflammatory mediators were estimated. Reverse transcription polymerase chain reaction (RT-PCR) was used for estimating the messenger RNA (mRNA) expression of sphingosine-1-phosphate receptor-1. Daphnetin-treated rats showed upregulation of body weight compared to other groups. Moreover, Daphnetin reduced blasts in leukemic rats. It also altered hematological parameters such as red blood cells, white blood cells, lymphocytes, neutrophils, monocytes, eosinophils, monocytes, and basophils, respectively. Daphnetin-treated rats showed a reduction of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β (IL-1β), IL-2, IL-6, and inflammatory mediators including nuclear factor-κB. RT-PCR showed upregulated mRNA expression of sphingosine-1-phosphate receptor-1 of daphnetin-treated group rats compared to other groups. The current study showed that the anti-inflammatory effect of daphnetin against the benzene-induced leukemia via alteration of cytokines.

Preparation and in vitro and in vivo Study of Asiaticoside-Loaded Nanoemulsions and Nanoemulsions-Based Gels for Transdermal Delivery

Purpose

Asiaticoside (ASI), a compound of triterpene pentacyclic saponins, has apparently therapeutic efficacy on human hypertrophic scar. However, the characteristics of large molecular weight, low water solubility and poor lipophilicity do not favor the diffusion through the stratum corneum (SC). Therefore, it is expected that the development of a transdermally delivered formulation may enhance the permeability ratio (Qn) of ASI for its clinical application. In this study, we designed asiaticoside-loaded nanoemulsions (ASI-NEs) and nanoemulsions-based gels (ASI-NBGs) and studied their mechanism for transdermal delivery.

Methods

The preparation of ASI-NEs was optimized by simplex lattice design (SLD). The ex vivo transdermal penetration and the in vivo pharmacokinetics studies were studied, respectively. The skin irritation of ASI-NEs and ASI-NBGs was measured on normal and damaged skin in rabbits, and the transcutaneous mechanisms of ASI-NEs and ASI-NBGs were determined by HE stained and confocal laser scanning microscopy (CLSM).

Results

The mean particle size of ASI-NEs was 132±5.84nm. The ex vivo skin permeation study verified that the Qn of the optimized ASI-NEs and ASI-NBGs was about 13.65 times and 5.05 times higher than that of the ordinary ASI-G group. In vivo, the pharmacokinetics studies showed that ASI-NEs and ASI-NBGs reached the peak value in the skin quickly and maintained stable release for a long time with high bioavailability. ASI-NEs and ASI-NBGs were proved to be safe when applied for topical skin usage, and they could play a therapeutic role through the skin mainly by acting on the microstructure of the SC and by means of the skin adnexal pathways.

Conclusion

ASI-NEs and ASI-NBGs were effectively developed to overcome the barrier properties of the skin and show high drug penetration through the transdermal route. In addition, we found that ASI-NEs and ASI-NBGs are safe when applied through transdermal delivery system.

Rapid microneedle fabrication by heating and photolithography

Many fabrication methods for microneedle (MN) involve harsh conditions and long drying time. This study aims to fabricate a dissolving MN patch in a simple and efficient manner under mild conditions, using a combination of thermal and photo polymerisation. The MN patch was fabricated by pre-polymerisation of vinylpyrrolidone solution with heating followed by photolithography. The heating temperature and time of pre-polymer solution curing were optimized based on viscosity measurement. The MN properties including shape, size, skin penetration, dissolution, moisture absorption were determined. The fabricated MNs were sharp and consistent. The heated N-vinylpyrrolidone solution required less UV exposure time, thus reducing the total fabrication time. The percentage of MN penetration in human cadaver skin was more than 33.9%. The MN was dissolved within 1-2 min in water, or 40 min in saturated water vapor.