Modulation of the clinically accessible gelation time using glucono-d-lactone and pyridoxal 5'-phosphate for long-acting alginate in situ forming gel injectable

The purpose of this study was to design alginate in situ forming gel (ISFG) injectable with clinically acceptable gelation time and controlled release of hydrophobic drug. Milled or unmilled paliperidone palmitate (PPP) was used. The gelation time was controlled by varying the ratios of glucono-d-lactone (GDL) and pyridoxal 5'-phosphate (PLP) in prefilled alginate solution mixtures (ASMs) containing PPP, CaCO₃, GDL and PLP for clinically acceptable injectability. However, the gelation time was varied by the alginate type (M/G ratio), storage condition, and drug solubilizers. This ISFG exhibited 32.15 kPa of the maximal compressive stress without causing pain and stiffness. The ISFG containing conically milled PPP released PPP in a controlled manner without exhibiting any initial burst release for 4 weeks. The current alginate ISFG injectable using new combination of PLP and GDL could be used to deliver long-acting injectable drugs.

Doxycycline hyclate-loaded in situ forming gels composed from bleached shellac, Ethocel, and Eudragit RS for periodontal pocket delivery

Polymeric material plays an important role as a matrix former in the modulation of drug release of antimicrobial-loaded in situ forming gel (ISG) for efficient periodontitis treatment. This study was conducted to compare three polymers, namely bleached shellac (BS), Ethocel (EC) and Eudragit RS (ERS), as matrix formers of doxycycline hyclate (DH)-loaded solvent exchange-induced ISG. All prepared ISGs, except 25% EC ISG, exhibited the Newtonian flow behaviour. Transformation from solution into matrix-like was achieved rapidly within 5 min. Increasing the amount of these polymers extended the release of DH. DH-loaded EC and ERS ISG systems exhibited high antimicrobial activity, and all ISGs were effective in inhibiting the growth of Staphylococcus aureus, Escherichia coli, Streptococcus mutans, Porphyromonas gingivalis and Candida albicans. By comparison, the DH-loaded ERS ISG, through the solvent exchange mechanism, was found to be ease in injection with low viscosity and sustained the release with higher concentration, meanwhile, it also exhibited interesting in vitro degradability and antimicrobial activities. Therefore, the DH-loaded ERS ISG exhibited a potential use for localized periodontal drug delivery system for the treatment periodontitis.

Meloxicam-loaded solvent exchange-induced in situ forming beta-cyclodextrin gel and microparticle for periodontal pocket delivery

The in situ forming system has attracted attention for periodontitis treatment owing to its sustainable drug release localisation at a periodontal pocket. Given its low aqueous solubility, beta-cyclodextrin (β-CD) may serve as a matrix former of solvent exchange-induced in situ forming gel (ISG) and microparticle (ISM). Meloxicam (Mex)-loaded-β-CD ISG and ISM were prepared using β-CD in dimethyl sulphoxide (ISG) as the internal phase and camellia oil comprising 5% glyceryl monostearate as the external phase (ISM). Mex-loaded β-CD systems comprising 40% β-CD were easily injected via a 24-gauge needle. During solvent exchange with phosphate buffer saline (pH 6.8), the highly concentrated β-CD ISG promoted the phase inversion of β-CD aggregates into matrix-like. Upon exposure to aqueous phase, the ISM system comprising 40% β-CD transformed into microparticles and extended the drug release to 7 days with minimised initial burst release following Fickian diffusion. Moreover, the potential degradability was evident from the high weight loss. High maximum deformation force with high viscous character initiated the slow diffusion rate of the solvent from the ISM system. Therefore, 40% β-CD ISM is a potential local Mex-controlled release system of anti-inflammatory drug for periodontitis treatment.

Injectable in situ forming gel based on lyotropic liquid crystal for persistent postoperative analgesia

Local anesthetics have been widely used for postoperative analgesia. However, multiple injections or local infiltration is required due to the short half-lives of local anesthetics after single injection, which results in poor compliance and increasing medical expense. In this study, an in situ forming gel (ISFG) based on lyotropic liquid crystal was developed to deliver bupivacaine hydrochloride (BUP) for long-acting postoperative analgesia. BUP-ISFG was designed to be administrated as a precursor solution which would spontaneously transform into gel with well-defined internal nanostructures for sustained drug release at the site of administration when exposed to physiological fluid. A lamellar-hexagonal-cubic phase transition occurred during the in situ gelation. The lamellar phase of the precursor solution endows it with low viscosity for good syringeability while the unique nanostructures of hexagonal and cubic phases of the in situ gel provide sustained drug release. Persistent analgesia effect in vivo was achieved with BUP-ISFG, and the plasma BUP concentration was found to be steadier compared to commercially available BUP for injection. In addition, the ISFG displayed acceptable biocompatibility and good biodegradability. The findings are positive about ISFG as a sustained release system for persistent postoperative analgesia.

STATEMENT OF SIGNIFICANCE

To address the issue of insufficient postoperative analgesia associated with short half-lives of local anesthetics after single injection, an in situ forming gel (ISFG) based on lyotropic liquid crystal was developed to deliver bupivacaine hydrochloride (BUP) for postoperative analgesia over three days. The results demonstrated that persistent analgesia effect in vivo was achieved with single injection of BUP-ISFG, and the plasma BUP concentration was found to be steadier compared to commercially available BUP injection. The BUP-ISFG possessed a lamellar-hexagonal-cubic phase transition with corresponding crystal change in 3D nanostructure during the in situ gelation. The relationship between crystal nanostructure and carrier function, might provide some insights to the design and clinical applications of the drug delivery systems based on lyotropic liquid crystal.

Role of clove oil in solvent exchange-induced doxycycline hyclate-loaded Eudragit RS in situ forming gel

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Role of clove oil (CO) in doxycycline hyclate (DH)-loaded Eudragit RS (ERS) in situ forming gel (ISG) was investigated.

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CO could solubilize ERS and increase the viscosity of ISG and also minimize DH burst release with sustainable DH release.

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ISGs comprising CO could expel through the 27-gauge needle and transform into matrix depot in simulated crevicular fluid.

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Antimicrobial activities against all test bacterias were increased when increasing CO and N-methyl pyrrolidone (NMP) ratio.

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DH-loaded ERS ISG comprising CO could be used as a local drug delivery system for periodontitis treatment.

Solvent exchange induced in situ forming gel (ISG) is the promising drug delivery system for periodontitis treatment owing to the prospect of maintaining an effective high drug level in the gingival crevicular fluid. In the present study, the influence of clove oil (CO) on the characteristics of doxycycline hyclate (DH)-loaded ISG comprising Eudragit RS (ERS) was investigated including viscosity/rheology, syringeability, in vitro gel formation/drug release, matrix formation/solvent diffusion and antimicrobial activities. CO could dissolve ERS and increase the viscosity of ISG and its hydrophobicity could also retard the diffusion of solvent and hinder the drug diffusion; thus, the minimization of burst effect and sustained drug release were achieved effectively. All the prepared ISGs comprising CO could expel through the 27-gauge needle for administration by injection and transform into matrix depot after exposure to the simulated gingival crevicular fluid. The antimicrobial activities against Staphylococcus aureus, Escherichia coli, Streptococcus mutans and Porphyromonas gingivalis were increased when the ratio of CO and N-methyl pyrrolidone (NMP) was decreased from 1:1 to 1:10 owing to higher diffusion of DH except that for C. albicans was increased as CO amount was higher. Therefore, CO could minimize the burst while prolonging the drug release of DH-loaded ERS ISG for use as a local drug delivery system for periodontitis treatment.

Study of an injectable in situ forming gel for sustained-release of Ivermectin in vitro and in vivo

The purpose of this study was to develop an in situ forming gel based on SAIB-PLA composite matrix depot for sustained release of Ivermectin. The burst release and cumulative release were significantly reduced with the increased content of solvents and the minimum burst release and cumulative release were found in formulations with NMP. With the addition of PLA in the NMP based gel, burst release and cumulative release were reduced. When concentration of IVM raised from 1% to 2% and 4%, cumulative release was 2.4-2.9 and 3.1-3.7 times that of 1%. The optimal prescription displayed a slow in vitro release rate with 10.46% burst release and 80% cumulative release in 80 days. Pharmacokinetic results indicate that the effective blood concentration of the gel could be maintained up to 110-120 days, t1/2λz of the gels was (24.37 ± 1.71) days and MRT was (32.86 ± 0.91) days.

Solvent exchange-induced in situ forming gel comprising ethyl cellulose-antimicrobial drugs

Solvent-exchanged in situ forming gel is a drug delivery system which is in sol form before administration. When it contacts with the body fluid, then the water miscible organic solvent dissipates and water penetrates into the system, leading the polymer precipitation as in situ gel at the site of injection. The aim of this research was to study the parameters affecting the gel properties, drug release and antimicrobial activities of the in situ forming gels prepared from ethyl cellulose (EC) dissolved in N-methyl pyrrolidone (NMP) to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The gel appearance, pH, viscosity, rheology, syringeability, gel formation, rate of water diffusion into the gels, in vitro degradation, drug release behavior and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyrommonas gingivalis were determined. Increasing the amount of EC increased the viscosity of system while still exhibiting Newtonian flow and increased the work of syringeability whereas decreased the releasing of drug. The system transformed into the rigid gel formation after being injected into the simulated gingival crevicular fluid. The developed systems containing 5% w/w antimicrobial agent showed the antimicrobial activities against all test bacteria. Thus the developed solvent exchange-induced in situ forming gels comprising EC-antimicrobial drugs exhibited potential use for periodontitis treatment.