A novel pH-responsive hydrogel based on carboxymethyl cellulose/2-hydroxyethyl acrylate for transdermal delivery of naringenin

Recent advances in celluloses and their hybrids for stimuli-responsive drug delivery

The limitations of existing drug delivery systems (DDS) such as non-specific bio-distribution and poor selectivity have led to the exploration of a variety of carrier platforms to facilitate highly desirable and efficient drug delivery. Stimuli-responsive DDS are one of the most versatile and innovative approach to steer the compounds to the intended sites by exploiting their responsiveness to a range of various triggers. Preparation of stimuli-responsive DDS using celluloses and their derivatives offer a remarkable advantage over conventional polymer materials. In this review, we highlight on state-of-art progress in developing cellulose/cellulose hybrid stimuli-responsive DDS, which covers the preparation techniques, physicochemical properties, basic principles and, mechanisms of stimuli effect on drug release from various types of cellulose based carriers, through recent innovative investigations. Attention has been paid to endogenous stimuli (pH, temperature, redox gradient and ionic-strength) responsive DDS and exogenous stimuli (light, magnetic field and electric field) responsive DDS, where the cellulose-based materials have been extensively employed. Furthermore, the current challenges and future prospects of these DDS are also discussed at the end.

Novel Enhanced Therapeutic Efficacy of Dapoxetine HCl by Nano-Vesicle Transdermal Gel for Treatment of Carrageenan-Induced Rat Paw Edema

The aim of this was to develop a well-balanced, replaceable, and patient non-infringing innovative transdermal drug delivery system "nano-vesicle transdermal gel" (NVTG) approaches for inhibiting inflammation. To consummate this objective, we developed a skin permeation nanogel system containing surface active agent along with ethanol. Carbopol 971p, hydroxypropyl methyl cellulose (HPMC K15M), and chitosan were used to fabricate the nanogels. The nanogel system was evaluated for pH, content uniformity, spreadability, rheological studies, in vitro skin permeation, and drug release. Carbapol 971p with the desired in vitro skin permeation was utilized to investigate skin irritation test and effects on inflammation using acute inflammatory paw edema models. Moreover, in vivo pharmacokinetic study was assessed. pH of this nanogels was found within the range of 6.1-7.2, whereas the viscosity was found 310.13 to 6361 cps. The ex vivo skin permeation gels showed permeation flux range, 5.9 ± 0.80 to 17.92 ± 1.13 μg/cm² h. The highest permeation flux (17.92 ± 1.13 μg/cm² h) was observed, which was 3.14-folds higher than that of the plain DH gel (10.72 ± 0.84 μg/cm² h. Additionally, from toxicological study, no obvious signs of toxicity such as skin irritation (of laboratory rats) were identified. The in vivo anti-inflammatory behavior in carrageenan-induced rats showed comparatively higher inhibition of rat paw edema swelling by the prepared nanogel compared to that of the plain DH gel and marketed ibuprofen over 6 h. The amount of drug accumulated in the skin after topical application was much higher than oral application. In conclusion, developed NVTG formulation loaded with dapoxetine HCl (DH) offers new opportunities for creating novel therapeutic modality for inflammation patients with fewer adverse effects.

Fabrication and characterization of a novel semi-interpenetrating network hydrogel based on sodium carboxymethyl cellulose and poly(methacrylic acid) for oral insulin delivery

In this research, pH-sensitive semi-interpenetrating polymer network hydrogels based on sodium carboxymethyl cellulose and poly(methacrylic acid) were synthesized using free radical polymerization and semi-interpenetrating polymer network approach for oral administration of insulin. The chemical structure and thermal stability of the hydrogels were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis measurements. The interior morphology was observed by scanning electron microscopy and the inner structure exhibited a porous honeycomb-like shape. The investigations on the swelling properties of hydrogels revealed their ability to response to pH value change. The in vitro release behavior of insulin was pH dependent and the release of insulin was much lower at pH 1.2 compared to pH 6.8. In vitro cytotoxicity assay indicated that the hydrogels were noncytotoxic to HeLa cells. A sustained reduction in blood glucose level was observed after oral administration of insulin-loaded hydrogel to diabetic rats at 75 IU/kg. These results indicated that the hydrogel would be a promising vehicle for oral insulin delivery systems.

Lappaconitine trifluoroacetate contained polyvinyl alcohol nanofibrous membranes: Characterization, biological activities and transdermal application

Lappaconitine (LA), a potent analgesic drug extracted from the root of natural aconitum species, has been clinically used for years because of its effectiveness and non-addictive properties. However, it is mainly limited in oral and intravenous administration in the form of Lappaconitine Hydrobromide (LAH). In this work, Lappaconitine trifluoroacetate (LAF), a new derivative of LA, was successfully obtained by introducing organofluorine group to LA. This new compound had a lower toxicity (LD₅₀ of 21.14 mg·kg^-1), improved analgesic effect and longer half-life (T_1/2 of 2.24 h) when compared with LAH. Moreover, in vitro transdermal permeation (J_ss of 206.82 μg·cm^-2·h^-1) of LAF was 30.54% higher than that of LAH, means that LAF can be conveniently used for transdermal drug delivery (TDD). Therefore, drug membranes with PVA solution (10 wt%) containing LAF in various amounts were fabricated by electrospinning. The in vitro release tests confirmed that up to 81.43% of LAF in the PVA/LAF nanofibrous membranes could be released in 72 h, accompanied by significant analgesic effect when compared with the blank control group. In conclusion, the prepared LAF-loaded membrane is a novel formulation for the treatment of chronic and long-term pain.

Solvation-Controlled Elastification and Shape-Recovery of Cellulose Nanocrystal-Based Aerogels

Aerogels based on rod-like cellulose nanocrystals (CNCs) have been used in anisotropic materials, adsorbents and sensors, whereas they also suffer a low elasticity, leading to hard handling/processing in practical applications. Inspired by the sea cucumber, which transits from rigid to flexible when its cross-link network of collagen fibers is weakened by stiparin inhibitor, we cross-linked the CNCs with flexible poly ethylene glycol (PEG) to prepare an aerogel owning variable mechanical properties in different environments. This aerogel not only had a chemical-bond cross-link network, but also an H-bond one, which could be easily weakened by water. The results showed that the obtained CNC/PEG aerogel owned a high modulus of 0.80 MPa in a dry state and transited to an elastic state (modulus is 0.87 kPa) in a wet state. In the dry state, the shape change of the CNC/PEG aerogel could not recover when the strain was over 10%, when in the wet state the shape change could be reversible. Interestingly, the irreversible strain in the dry state could further transit to reversible in the wet state, and the wet aerogel could then transit back to rigid after freeze-drying. The mechanism study proved that this recovery came from the solvation-controlled weakening of the H-bond network between PEG and CNC. This work offered a simple but useful design of stimulation-response aerogels that can conduce to an elastification and shape recovery.

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

We discuss prospects for halloysite nanotubes, vaterite crystals and nanocellulose to enter the market of biomaterials for drug delivery and tissue engineering, and their potential for economically viable production from abundant natural sources.

Meglumine-based supra-amphiphile self-assembled in water as a skin drug delivery system: Influence of unfrozen bound water in the system bioadhesiveness

Hexagonal liquid crystals and supramolecular polymers from meglumine-based supra-amphiphiles were developed as drug delivery systems to be applied on the skin. The influence of fatty acid unsaturation on the structure and mechanical properties was evaluated. Moreover, we have investigated the system biocompatibility and how the type of water could influence its bioadhesive properties. Meglumine-oleic acid (MEG-OA) was arranged as hexagonal liquid crystals at 30-70 wt% water content, probably due to its curvature and increased water solubility. Meglumine-stearic acid (MEG-SA) at 10-80 wt% water content self-assembled as a lamellar polymeric network, which can be explained by the low mobility of MEG-SA in water due to hydrophobic interactions between fatty acid chains and H-bonds between meglumine and water molecules. Both systems have shown suitable mechanical parameters and biocompatibility, making them potential candidates to encapsulate therapeutic molecules for skin delivery. Moreover, a strong positive correlation between the amount of unfrozen bound water in meglumine-based systems and the bioadhesion properties was observed. This work shows that a better understanding of the physicochemical properties of a drug delivery system is extremely important for the correlation with the desired biological response and, thus, improve the product performance for biomedical applications.

Mechanism investigation of ethosomes transdermal permeation

Ethosomes are widely used to promote transdermal permeation of both lipophilic and hydrophilic drugs, but the mechanism of interaction between the ethosomes and the skin remains unclear. In this work, it was exploded with several technologies and facilities. Firstly, physical techniques such as attenuated total reflectance fourier-transform infrared and laser confocal Raman were used and the results indicated that the phospholipids configuration of stratum corneum changes from steady state to unstable state with the treatment of ethosomes. Differential scanning calorimetry reflected the thermodynamics change in stratum corneum after treatment with ethosomes. The results revealed that the skin of Bama mini-pigs, which is similar to human skin, treated by ethosomes had a relatively low T_m and enthalpy. Scanning electron microscopy and transmission electron microscopy showed that the microstructure and ultrastructure of stratum corneum was not damaged by ethosomes treatment. Furthermore, confocal laser scanning microscopy revealed that lipid labeled ethosomes could penetrate the skin via stratum corneum mainly through intercellular route, while during the process of penetration, phospholipids were retained in the upper epidermis. Cell experiments confirmed that ethosomes were distributed mainly on the cell membrane. Further study showed that only the drug-loaded ethosomes increased the amount of permeated drug. The current study, for the first time, elucidated the mechanistic behavior of ethosomes in transdermal application from molecular configuration, thermodynamic properties, ultrastructure, fluorescent labeling and cellular study. It is anticipated that the approaches and results described in the present study will benefit for better design of drug-loaded ethosomes.

Fabrication of alginate-based stimuli-responsive, non-cytotoxic, terpolymric semi-IPN hydrogel as a carrier for controlled release of bovine albumin serum and 5-amino salicylic acid

Herein, we report a functionalized alginate(Alg)-based terpolymeric semi-interpenetrating (semi-IPN) hydrogel, synthesized via free radical polymerization for the delivery of bovine albumin serum (BSA) and 5-amino salicylic acid (5-ASA). To improve mechanical properties, and to modulate surface morphology of Alg, 2-hydroxyethyl acrylate (HEA) was grafted on alginate and then crosslinked using poly(ethylene glycol) diacrylate (PEGDA). The probable structure and compositions of the synthesized semi-IPN terpolymer were identified by FTIR, ¹H-HR-MAS NMR, and TGA analyses. Achievement of equilibrium swelling state (ESS) and higher elastic modulus values confirmed terpolymer gel formation in aqueous media. Differences in the ESS of the prepared gel at pH 2.5 and 7.4 signify its stimuli-responsive behaviour. The influence of PEGDA on swelling, mechanical properties, surface morphology, cell viability and proliferation, and BSA and 5-ASA delivery were characterized. SEM images show that higher % PEGDA resulted in smaller sized pores in the gel network. Texture analyses demonstrate that hardness, adhesiveness and chewiness of the gel were enhanced at higher PEGDA concentrations. Increases in PEGDA concentration also induced increases in osteoblastic cell viability and higher rates of cell proliferation compared with gels containing lower concentrations of PEGDA. The release results indicate that the gels containing higher concentrations of PEGDA more sustainably release BSA and 5-ASA at 5 days and 30 h, respectively. The experimental data revealed that the synthesized terpolymeric semi-IPN hydrogel may have useful biomedical applications, especially as a carrier of protein (BSA), or 5-ASA (a therapeutic option for conditions of the colon such as Crohn's Disease and Ulcerative Colitis).