Cubic Liquid Crystalline Gels Based on Glycerol Monooleate for Intra-articular Injection

Cubic liquid crystals containing propolis flavonoids as in situ thermo-sensitive hydrogel depots for periodontitis treatment: Preparation, pharmacodynamics and therapeutic mechanisms

Propolis has a long ethnopharmacological history for oral periodontal diseases treatment. Propolis flavonoids are main active components for anti-inflammation and tissue protection. However, the intractable dissolution properties of propolis flavonoids and complex oral environment pose great challenges for periodontal delivery. In addition, the therapeutic mechanism as well as the therapeutic correlation of inflammation resolution and tissue regeneration remain unclear for propolis flavonoids. In this study, we constructed an in situ thermosensitive depot systems using total flavonoids from propolis-loaded cubic liquid crystals (TFP-CLC) hydrogel for periodontal delivery. TFP-CLC inhibited inflammatory cell infiltration, reactive oxygen species and the expression of inflammatory cytokines of NF-κB and IL-1β. In addition, alveolar bone and collagen were significantly regenerated after TFP-CLC administration according to micro-CT and immunohistochemistry. Mechanism studies suggested that TFP-CLC alleviated inflammation and promoted alveolar bone repair via regulating TLR4/MyD88/NF-κB p65 and RANK/NF-κB signaling pathways, respectively. Correlation analysis further confirmed that the inflammatory resolution produced by TFP-CLC could accelerate periodontal tissue regeneration. In summary, TFP-CLC is a promising multifunctional in situ thermo-sensitive hydrogel depots for periodontitis treatment.

A Novel Molecular Reservoir Based on Reverse Self-Assembled Liquid Crystals - A New Strategy for Prolonging the Duration in Action of Analgesics

PURPOSE

The aim of this study was to develop liquid crystal (LC) precursors to obtain novel long-acting analgesics for injection based on depot systems and compare the difference between the cubic and hexagonal precursors in delivering Diclofenac sodium (DS).

METHODS

Diclofenac sodium liquid crystal precursor injections were prepared and characterized, followed by in vitro release, pharmacodynamic, and pharmacokinetic studies.

RESULTS

The optimal formulations were prepared with a ratio of Phytantriol/ethanol/water as 76:19:5 for cubic LC precursors, and a ratio of Phytantriol/ethanol/water/Vitamine-E acetate as 72:18:5:5 for hexagonal, both loading various drug dosages (2.5%, 3.75% and 5%), respectively. Polarized light microscopy and small angle diffraction confirmed that the precursors were isotropic fluids and transformed into gels with Pn3m or HII framework in water. Rheological studies have shown that precursors belong to Newtonian fluids and gels to pseudoplastic fluids. The release showed that the DS in the commercial injection (DS-inj) was completely liberated within 6 h, whereas only 46.55% and 49.73% of the DS in 2.5% cubic precursors and 2.5% hexagonal precursors were freed, respectively. Pharmacodynamic studies have shown that cubic, hexagonal and DS-inj raised the pain threshold in mice by 169.4%, 157.3% and 113.79%, respectively. The mean retention times of DS in cubic and hexagonal were 3.16 and 2.67 times longer than DS-inj, respectively, according to pharmacokinetic results.

CONCLUSION

In conclusion, cubic and hexagonal are both promising analgesic sustained release formulations. In addition, based only on the current comparison, cubic seems to have a better long-acting effect.

Recent Advancements in Drug Delivery of Sinomenine, A Disease-Modifying Anti-Rheumatic Drug

Sinomenine (SIN) is a benzyltetrahydroisoquinoline-type alkaloid isolated from the dried plant root and stem of Sinomenium acutum (Thumb.) Rehd.et Wils, which shows potent anti-inflammatory and analgesic effects. As a transforming disease-modifying anti-rheumatic drug, SIN has been used to treat rheumatoid arthritis over twenty-five years in China. In recent years, SIN is also in development for use against other disorders, including colitis, pain, traumatic brain injury, and uveitis. However, its commercial hydrochloride (SIN-HCl) shows low oral bioavailability and certain allergic reactions in patients, due to the release of histamine. Therefore, a large number of pharmaceutical strategies have been explored to address these liabilities, such as prolonging release behaviors, enhancing skin permeation and adsorption for transdermal delivery, targeted SIN delivery using new material or conjugates, and co-amorphous technology. This review discusses these different delivery strategies and approaches employed to overcome the limitations of SIN for its efficient delivery, in order to achieve improved bioavailability and reduced side effects. The potential advantages and limitations of SIN delivery strategies are elaborated along with discussions of potential future SIN drug development strategies.

In Situ Swelling Formulation of Glycerol-Monooleate-Derived Lyotropic Liquid Crystals Proposed for Local Vaginal Application

Hydrogels have been extensively investigated to identify innovative formulations that can fulfill all the necessary purposes to improve local vaginal therapy through the mucosa. Herein, we propose in situ-forming lyotropic liquid crystals (LLCs) derived from a cheap and GRAS (generally recognized as safe) ingredient as an intravaginal delivery system. The system consists of a precursor solution loaded with sertaconazole nitrate as a model drug, which is able to easily swell in a stable three-dimensional structure by absorbing simulated vaginal fluid. Under polarized light microscopy the precursor solution and the formed phase of LLCs showed the typical textures belonging to anisotropic and an isotropic mesophases, respectively. A deep rheological investigation by Kinexus^® Pro proved the stability and strength of the cubic phase, as well as its potential in mucoadhesion. In vitro degradation studies showed a slow matrix erosion, consistent with data obtained from lipophilic drug release studies in simulated vaginal fluid. Therefore, the suggested cubic phase based on lyotropic liquid crystals could represent a valid proposal as a vaginal drug delivery system due to its characteristics of resistance, adhesion and the possibility of providing a slow and controlled release of drugs directly at the administration site.

Hexagonal liquid crystalline system containing Cinnamaldehyde for enhancement of skin permeation of Sinomenine hydrochloride

Sinomenine hydrochloride (SH) is usually applied to treat rheumatoid arthritis (RA) with severe side effect due to oral administration. Cinnamaldehyde (CA) as essential oil possesses anti-RA effect and can facilitate transdermal penetration. Hence, this study developed hexagonal liquid crystalline (HII) gels to deliver two components (SH and CA) across the skins. HII gels were prepared and characterized by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS) and rheology. Moreover, in vitro drug release behavior and ex vivo skin permeation were investigated. Finally, Fourier transform infrared spectral analysis (FTIR) and confocal laser scanning microscopy (CLSM) were used to explore the skin penetration mechanism. PLM and SAXS showed that the inner structure of the gels was HII phase. The addition of lipophilic or hydrophilic molecule slowed down one another's release and the release model was dominated by Fickian diffusion (n< 0.43). Furthermore, in vitro permeation studies indicated that appropriate CA could improve the skin permeability of SH. FTIR and CLSM suggested that infiltration occurred due to disruption of the lipid bilayer structure and increased fluidity of the skin. In conclusion, HII gels and CA exhibited a penetration-promoting effect for transdermal applications in SH.

Investigation of diclofenac release and dynamic structural behavior of non-lamellar liquid crystal formulations during in situ formation by UV-Vis imaging and SAXS

In situ formation of high viscous inverse lyotropic non-lamellar liquid crystalline phases is a promising approach for sustained drug delivery in the joint. The in situ forming process on exposure of two diclofenac-loaded preformulations to aqueous media was characterized with respect to depot size and shape, initial release and structural transitions using UV-Vis imaging and spatially and time-resolved synchrotron small-angle X-ray scattering (SAXS). The preformulations consisted of 10 % (w/w) ethanol, 10 % (w/w) water and a binary lipid mixture of glycerol monooleate (GMO):1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DOPG) or GMO:medium chain triglycerides (MCT). Upon injection of preformulations into an employed injection-cell containing excess of bio-relevant medium, rapid generation of liquid crystalline depots was observed. UV-Vis images and constructed 2D SAXS maps of the injection-cell showed depots with different shapes and sizes, and features with high nanostructural heterogeneity. More extensive swelling of the GMO:DOPG-based preformulation was observed compared to the GMO:MCT-based preformulation. The UV image analysis found that a higher amount of diclofenac was released in the image area after 20 h from the GMO:MCT-depot compared to the GMO:DOPG-depot. The injection-cell setup employing UV-Vis imaging and synchrotron SAXS constitutes an attractive approach for evaluating the in situ forming processes of liquid crystalline depots.

In Situ Liquid Crystal Gel as a Promising Strategy for Improving Ocular Administration of Dexamethasone: Preparation, Characterization, and Evaluation

The purpose of this study was to design an in situ liquid crystal gel (ISLG) as an ophthalmic drug delivery system for dexamethasone (DEX) to enhance its eye retention and ocular bioavailability. The in situ liquid crystal gels (ISLGs) were prepared using a phytantriol/PEG400/water (65:30:5, w/w) ternary system. Polarized light microscope (PLM), small-angle X-ray scattering (SAXS), and rheology analysis confirmed that the internal structure of the preparations was Pn3m cubic phase liquid crystal gels with pseudoplastic fluid properties. Meanwhile, in vitro release behavior of the preparations conforms to the Higuchi equation. Corneal penetration experiments showed that compared with DEX sodium phosphate eye drops, DEX-ISLGs(F2) produced a 5.45-fold increase in the P_app value, indicating a significant enhancement of corneal penetration. In addition, in vivo experiments have confirmed that the ISLGs have better biocompatibility and longer retention time in the cornea. Simultaneously, corneal hydration level, eye irritation experiments, and histological observations proved the safety of the preparations. Pharmacokinetic studies have shown that the ISLG could maintain the DEX concentration in aqueous humor for at least 12 h after administration, which significantly improves the bioavailability of the drug. Collectively, these results indicated that ISLG would be a potential drug carrier for the treatment of diabetic retinopathy (DR).

Physicochemical Evaluation and Pharmacodynamics of Itraconazole-loaded Liquid Crystal Precursor for Vaginal Delivery

PURPOSE

To develop liquid crystal (LC) precursor that can be used as a novel vaginal delivery system for Itraconazole (ITZ) and evaluate its pharmacodynamics. Methods: The LC precursor was prepared by using phytantriol (PYT) as lipid matrix and N, N-dimethylformamide (DMAC) as solvent. Swelling studies were performed to assess the phase conversion ability. The formulations were characterized by crossed polarized light microscopy (CPLM), small-angle X-ray scatterin (SAXS). Moreover, the rheological and in vitro drug release behavior were investigated. Then the vaginal retention time of ITZ in the optimal prescription was evaluated. Finally, the pharmacodynamics studies of the ITZ-loaded LC precursor were performed in a mouse model of vulvovaginal candidiasis (VVC). Results: The LC precursor could transform to LC gels after administration into the vagina. Based on PLM and SAXS, the LC gels, formed after phase-conversion, were cubic LC. The LC precursor was Non-Newtonian, while the LC gels exhibited a pseudo-plastic fluid behavior. In vitro release results revealed that F2 (68.0 %) had a higher cumulative drug release than that of F1 (59.17 %) at 72 h. Most of the LC gels could be retained in the vagina of mice for 24 - 36 h. Pharmacodynamics studies showed that there was only mild inflammation or no inflammatory stimulation in the control group. The ITZ-loaded LC precursor significantly improved the symptoms of vaginitis in mice and had a better therapeutic effect than that of positive control group. Conclusions: The ITZ-loaded LC precursor would be a promising formulation for vaginal drug delivery.

Self-assembled lyotropic liquid crystal gel for osteoarthritis treatment via anti-inflammation and cartilage protection

Osteoarthritis (OA) is a chronic joint disease with occurrence of articular inflammation and cartilage degeneration. An ideal drug delivery system for effective treatment of OA should integrate inflammation alleviation with cartilage protection. Herein, a lyotropic liquid crystal (LLC) precursor co-loading hyaluronic acid (HA) and celecoxib, formulated as the HLC precursor, was developed for the combined therapeutic efficacy. The in situ gelling property of the HLC precursor effectively prolongs drug retention in the articular cavity to achieve a long-term anti-inflammation effect. Based on the rheological tests, HLC gel with a cubic lattice structure endows it with a spring-like effect to buffer joint shock and shows great potential in providing cartilage protection by resisting mechanical destruction, lubricating joint, and decomposing intensive stress (about 50%). Meanwhile, the pharmacodynamics study on the OA-induced SD rats demonstrated that HLC gel was the most effective to reduce inflammation levels and to protect the cartilage against abrasion and degeneration. Furthermore, the in vivo degradation behavior and the intra-articular irritation results of LLC/HLC gel demonstrated that it was biodegradable and biocompatible. These results collectively demonstrated that HLC gel with anti-inflammation and cartilage protection performance provides a useful approach to treat OA.

Spatially and time-resolved SAXS for monitoring dynamic structural transitions during in situ generation of non-lamellar liquid crystalline phases in biologically relevant media

Formation of high viscous inverse lyotropic liquid crystalline phases in situ upon exposure of low viscous drug-loaded lipid preformulations to synovial fluid provides a promising approach for design of depot formulations for intra-articular drug delivery. Rational formulation design relies on a fundamental understanding of the synovial fluid-mediated dynamic structural transitions occurring at the administration site. At conditions mimicking the in vivo situation, we investigated in real-time such transitions at multiple positions by synchrotron small-angle X-ray scattering (SAXS) combined with an injection-cell. An injectable diclofenac-loaded quaternary preformulation consisting of 72/8/10/10% (w/w) glycerol monooleate/1,2-dioleoyl-glycero-3-phospho-rac-(1-glycerol)/ethanol/water was injected into hyaluronic acid solution or synovial fluid. A fast generation of a coherent drug depot of inverse bicontinuous Im3m and Pn3m cubic phases was observed. Through construction of 2D spatial maps from measurements performed 60 min after injection of the preformulation, it was possible to differentiate liquid crystalline rich- and excess hyaluronic acid solution- or synovial fluid-rich regimes. Synchrotron SAXS findings confirmed that the exposure of the preformulation to the media leads to alterations in structural features in position- and time-dependent manners. Effects of biologically relevant medium composition on the structural features, and implications for development of formulations with sustained drug release properties are highlighted.

Targeted drug-delivery systems in the treatment of rheumatoid arthritis: recent advancement and clinical status

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that is characterized by synovial inflammation, cellular infiltration in joints which leads to progressive joint destruction and bone erosion. RA is associated with many comorbidities including pulmonary disease, rheumatoid nodules and can have a pessimistic impact on quality of life. The current therapies of RA treatment comprise conventional, small molecule and biological antirheumatic drugs. Their utility as therapeutic agents is limited because of poor absorption, rapid metabolism and adverse effects (dose-escalation, systemic toxicity, lack of selectivity and safety). To overcome these limitations, the novel drug delivery systems are being investigated. This review has compiled currently approved therapies along with emerging advanced drug-delivery systems for RA treatment. Further, active targeting of therapeutic agents to inflamed joints via folate receptor, CD44, angiogenesis, integrins and other provided an improved therapeutic efficacy in the treatment of RA.

Thermoresponsive Hyalomer intra-articular hydrogels improve monoiodoacetate-induced osteoarthritis in rats

Osteoarthritis (OA) is characterized by degenerative knees, fingers and hip joints. In OA joints, the concentration and polymerization of hyaluronic acid (HA) are changed; affecting the viscosity of the synovial fluid. Replenishing HA synovial fluid content, along with an anti-inflammatory drug could be a cost-effective strategy. As free drugs are rapidly cleared out of the synovial fluid, we aimed to prepare Hyalomer in situ forming gel for intra-articular (IA) injection. Hyalomer contains poloxamer 407 (PX) as thermogelling agent, HA, and diclofenac potassium (DK) as an anti-inflammatory. Hyalomer formulations were prepared and characterized in terms of sol-gel transition, gelation time, in vitro release and 3-month stability. The selected Hyalomer formula was injected IA in OA rat model, in comparison to its individual components. The optimized Hyalomer formulation showed 25% DK release after 24 h and 40% after 4 days. The gelation time was 40 ± 2.08 s and gelation temperature was 26 ± 1.87 °C. Hyalomer maintained the percentage drug release and DK content after 3-months storage. In OA rats, Hyalomer showed the highest anti-nociceptive and anti-edematous effect. Both radiography and histopathology revealed regenerated cartilage profile in Hyalomer-treated group. combining IA HA and diclofenac in thermoresponsive gel represents a promising therapeutic alternative for OA.

The Effect of Prescription on the Framework of Lipid Matrix and In Vitro Properties

PURPOSE

To clarify the inner framework and relative properties in vitro of Lyotropic liquid crystal (LLC) based on various prescriptions by using hydrophilic sinomenine hydrochloride (SH) and lipophilic cinnamaldehyde (CA) as model drugs.

METHODS

Phase structures were checked by polarized light microscopy (PLM) and small-angle X-ray scattering (SAXS). Rheological studies and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis were carried out to reveal their molecular interactions. In vitro release and skin permeation were conducted by Franz diffusion cell.

RESULTS

PLM and SAXS showed double diamond cubic crystal. All the samples displayed characteristics of non-Newtonian fluid, and the molecular interactions increased with the reducing water. ATRFTIR showed that the strongest strength of hydrogen bond emerged in the formulation with 32% water. Released SH of S2 and S3 arrived over 80%, while S1 only reached 45%, and that of CA was about 23%. Water-rich prescription gave higher percutaneous penetration for hydrophilic drugs, whereas no significant difference existed in CA permeation.

CONCLUSION

Proportion of Phytantriol to water determined the LLC assembling and affected the dissolving status of hydrophilic substance, thereby impacting on the location sites of guest molecular interactions among the substances, rheology properties, and finally the release and penetration behavior in vitro. Adjusting the basic prescription was the key to obtain satisfactory percutaneous delivery and stability for LLC carrying multi-therapeutic agents.

Self-assembled hexagonal liquid crystalline gels as novel ocular formulation with enhanced topical delivery of pilocarpine nitrate

The aim of this paper was to develop hexagonal liquid crystalline (H_II) gels that can be used as a novel ocular delivery system for pilocarpine nitrate (PN). H_II gels were prepared by a vortex method using phytantriol/triglyceride/water (71.15: 3.85: 26, w/w) ternary system. The gels were characterized by crossed polarized light microscopy, small-angle X-ray scattering, differential scanning calorimetry and rheology. And, in vitro drug release behavior and ex vivo corneal permeation were investigated. Finally, preocular residence time evaluation, eye irritation test, histological examination and miotic tests were studied in vivo and compared with carbopol gel. Based on various characterization techniques, the inner structure of the gels were H_II mesophase and exhibited a pseudoplastic fluid behaviour. In vitro release results revealed that PN could be released continuously from H_II gel over a period of 24 h. The ex vivo apparent permeability coefficient of H_II gel was 3.15-fold (P < 0.01) higher than that of the Carbopol gel. Compared with Carbopol gel, H_II gel displayed longer residence time on the eyeballs surface using fluorescent labeling technology. Furthermore, the H_II gel caused no ocular irritation was estimated by corneal hydration levels, Draize test and histological inspection. Additionally, in vivo miotic study showed that H_II gel had a remarkably long-lasting decrease in the pupil diameter of rabbits. In conclusion, H_II gels would be a promising sustained-release formulation for ocular drug delivery.

A Novel Phytantriol-Based Lyotropic Liquid Crystalline Gel for Efficient Ophthalmic Delivery of Pilocarpine Nitrate

The purpose of this paper was to investigate the potential of liquid crystalline (LC) gels for ophthalmic delivery, so as to enhance the bioavailability of pilocarpine nitrate (PN). The gels were prepared by a vortex method using phytantriol and water (in the ratio of 73:27 w/w). Their inner structures were confirmed by crossed polarized light microscopy, small-angle X-ray scattering, attenuated total reflectance-Fourier transform infrared spectrum, and rheology. The in vitro release studies revealed that PN could keep sustained release from the gels over a period of 12 h. The ex vivo apparent permeability coefficient of the gels demonstrated a 3.83-folds (P < 0.05) increase compared with that of eye drops. The corneal hydration levels of the gel maintained in the normal range of 79.46 ± 2.82%, hinting that the gel could be considered non-damaging and safe to the eyes. Furthermore, in vivo residence time evaluation suggested that a better retention performance of LC gel was observed in rabbit's eyes compared to eye drops. In vivo ocular irritation study indicated that LC gel was nonirritant and might be suitable for various eye applications. In conclusion, LC gels might represent a potential ophthalmic delivery strategy to overcome the limitations of eye drops.

Characterization of Lipid-Based Lyotropic Liquid Crystal and Effects of Guest Molecules on Its Microstructure: a Systematic Review

Liquid crystals (LCs) are conventionally divided into thermotropic or lyotropic, based on the organization and sequence of the controlled molecular system. Lipid-based lyotropic liquid crystal (LLC), such as lamellar (Lα), bicontinuous cubic (Q_II), or hexagonal (H_II) phases, have attracted wide interest in the last few decades due to their practical potential in diverse applications and notable structural complexity. Various guest molecules, such as biopharmaceuticals, chemicals, and additives, can be solubilized in either aqueous or oily phase. And the LLC microstructure can be altered to affect the rate of drug release eventually. To utilize these microstructural variations to adjust the drug release in drug delivery system (DDS), it is crucial to understand the structure variations of the LLC caused by different types of guest molecules. Therefore, in this article, we review the effect of guest molecules on lipid-based LLC microstructures. In particular, we focus on the different characterization methods to evaluate this change caused by guest substances, such as polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), self-diffusion nuclear magnetic resonance (SD-NMR), and so on.