In-vivo study of naltrexone hydrochloride release from an in-situ forming PLGA-PEG-PLGA system in the rabbit

In-vitro and in-vivo evaluation of sustained-release buprenorphine using in-situ forming lipid-liquid crystal gels

AIMS

Sustained-release systems reduce the incidence of drug side effects and the need for frequent drug consumption, thus increasing patient compliance with treatment. In this study, we aimed to produce sustained-release buprenorphine (BP) using lipid-liquid crystal gels.

MAIN METHODS

The three experimental groups in this study included: group I: lipid-liquid crystal formulation 5 (F5) containing BP, group II: BP-free F5, group III: BP solution in NMP, and group IV: control (no treatment). The formulations were injected subcutaneously into the rabbits' back neck.

KEY FINDINGS

The results showed that the time required to reach the drug's maximum concentration (T_max) was longer in group I than in group III. The maximum BP concentration (C_max) and the constants of the drug removal rate and drug absorption rate (K_a) were significantly higher in group III compared to group I. The half-life (t_1/2) of the drug in blood circulation was significantly longer in group I than in group III. Histopathological analysis revealed no histological abnormalities in the skin and heart in group I (BP-containing F5); however, mild hyperemia was observed in interstitial vessels in group III (BP-containing NMP). The kidney and liver tissues showed normal structure in the control group, as well as groups I and II. However, in the group receiving BP-containing NMP, significant congestion, tissue damage, necrosis, and fibrosis were observed in the kidney and liver.

SIGNIFICANCE

The results showed that the lipid-liquid crystal system can be used to design slow-release platforms for BP, minimizing the side effects associated with the use of its conventional forms.

The recent advancement in the PLGA-based thermo-sensitive hydrogel for smart drug delivery

To date, hydrogels have opened new prospects for potential applications for drug delivery. The thermo-sensitive hydrogels have the great potential to provide more effective and controllable release of therapeutic/bioactive agents in response to changes in temperature. PLGA is a safe FDA-approved copolymer with good biocompatibility and biodegradability. Recently, PLGA-based formulation have attracted a lot of interest for thermo-sensitive hydrogels. Thermo-sensitive PLGA-based hydrogels provide the delivery system with good spatial and temporal control, and have been widely applied in drug delivery. This review is focused on the recent progression of the thermo-sensitive and biodegradable PLGA-based hydrogels that have been reported for smart drug delivery to the different organs. Eventually, future perspectives and challenges of thermo-sensitive PLGA-based hydrogels are discussed briefly.

Lipid-liquid crystals for 2 months controlled risperidone release: In-vitro evaluation and pharmacokinetics in rabbits

In this study, a drug delivery system based on lipid liquid crystal (LLC) was developed for the long-term delivery of risperidone to improve psychological treatment. Optimal LLC formulation was achieved based on maximum release after 60 days with different ratios of phosphatidylcholine (PC) to sorbitol monooleate (PC: SMO), tween grade 80 (w/w %), and tocopherol acetate (TA) (w/w %) using the Box-Behnken method. In vitro and ex vivo studies, pharmacokinetics, and histopathological examination in rabbits were conducted to compare the optimal LLC with Risperdal CONSTA®. The optimum formulation containing the PC to SMO ratio of 58.6%, tween 0.82% w/w, and TA 3.6% w/w was selected because it had the highest drug release percentage (100%) during about two months. Polarized optical microscopy (POM) revealed H_II mesophase with a 2-dimensional structure. Cell culture also revealed moderate cytotoxicity for LLC-risperidone. Pharmacokinetic data displayed that the optimal LLC created a more consistent drug serum level within 60 days, and histopathology results demonstrated slight to moderate damage in rabbits' organs. Furthermore, the accelerated stability test confirmed optimum stability for LLC and risperidone. This study confirmed the better pharmacokinetic potentials of SMO-based LLC systems compared with Risperdal CONSTA®, which would promote patient compliance and obviate the difficulties of additional oral therapy.

Comparison of lipid liquid crystal formulation and Vivitrol® for sustained release of Naltrexone: In vitro evaluation and pharmacokinetics in rats

Camurus' FluidCrystal® injection depot is a lipid liquid crystal (LLC) phase formation-based method, comprising of glycerol dioleate (GDO) and soy phosphatidylcholine (SPC), together with minute quantities of N-methyl-2-pyrrolidone solvent (NMP). The present study aimed to develop a method for LLC using sorbitan monooleate (LLC-SMO) instead of GDO to prepare a one-month sustained-release formulation of naltrexone (NTX) that is applied for the treatment of autism and treating alcohol dependence. The optical characteristics of the LLC were assessed by polarizing light microscopy (PLM) to reveal the presence of lamellar, hexagonal, and cubic mesophases. Furthermore, in vitro release of NTX and NMP, degradation, pharmacokinetics, and histopathology of LLC-GDO and LLC-SMO in rats were evaluated and compared to those of Vivitrol®. The PLM images revealed that the structure of LLC-SMO is hexagonal, similar to LLC-GDO. The in vitro release of NTX and its pharmacokinetic results in rats indicted that the LLC-SMO system is more uniform than LLC-GDO and Vivitrol® during 35 days. Histopathological results of LLC-GDO and LLC-SMO confirmed the biocompatibility of our LLC delivery systems. Taken together these data demonstrate that the LLC-SMO-based method, was efficient enough to sustain the release of NTX in vitro and in vivo, confirming the biocompatible nature of this delivery system.

In-vitro Release Evaluation of Growth Hormone from an Injectable In-Situ Forming Gel Using PCL-PEG-PCL Thermosensitive Triblock

OBJECTIVE

An injectable long acting In-Situ Forming Gel (ISFG) of human Growth Hormone (hGH) was prepared by using triblock PCL-PEG-PCL (Mw 1500-1500-1500). Ring-Opening Polymerization (ROP) of triblock using microwave was applied.

METHODS

The BCA protein assay Kit was used to determine the concentration of hGH in the in-vitro release medium. Finally, Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) tests and Circular Dichroism (CD) spectrum were done to approve the stability of released hGH. The result of ROP demonstrated that the proportion of PCL to PEG accorded with the initial molar ratio of the monomers. The cross-section of the Surface Electron Microscopy (SEM) indicated the porous framework of the hydrogel could load the drug into its tridimensional matrixes structure. There is the low initial burst release of hGH from the supramolecular hydrogel.

RESULTS

The maximum in-vitro release of hGH was 71.2 % ± 1.5 that were due to hGH degrading after this time (21 days). The CD spectrum and SDS-PAGE results confirmed the stability of hGH during invitro release evaluation.

CONCLUSION

The results suggest that the sustained-release formulation using PCL-PEG-PCL can be applied to control the release of hGH.

New Biodegradable Poly(l-lactide)-Block-Poly(propylene adipate) Copolymer Microparticles for Long-Acting Injectables of Naltrexone Drug

In the present study, novel block copolymers of poly(l-lactide)-block-poly(propylene adipate) (PLLA-b-PPAd) were synthesized in two ratios, 90/10 and 75/25 w/w and were further investigated as long-acting injectable (LAI) polymeric matrices in naltrexone base microparticle formulations. The synthesized polymers were characterized by 1H-NMR, 13C-NMR, FTIR, XRD, TGA and DSC. NMR and FTIR spectroscopies confirmed the successful synthesis of copolymers while DSC showed that these are block copolymers with well-defined and separated blocks. Microparticles were prepared by single emulsification method and were further characterized. Nanoparticles in the range of 0.4-4.5 μm were prepared as indicated by SEM, with copolymers giving the lowest particle size. By XRD and DSC it was found that naltrexone was present in the amorphous state in its microparticles. Dissolution study showed a drug release extending over seven days, indicating that these novel PLLA-b-PPAd copolymers could be promising matrices for naltrexone's LAI formulations. It was evidenced that drug release depended on the copolymer composition. Model release studies showed that drug release is controlled by diffusion.

Structures and Applications of Thermoresponsive Hydrogels and Nanocomposite-Hydrogels Based on Copolymers with Poly (Ethylene Glycol) and Poly (Lactide-Co-Glycolide) Blocks

Thermoresponsive hydrogels showing biocompatibility and degradability have been under intense investigation for biomedical applications, especially hydrogels composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(lactic acid-co-glycolic acid) (PLGA) as first-line materials. Even though various aspects such as gelation behavior, degradation behavior, drug-release behavior, and composition effect have been studied for 20 years since the first report of these hydrogels, there are still many outputs on parameters affecting their gelation, structure, and application. In this review, the current trends of research on linear block copolymers composed of PEG and PLGA during the last 5 years (2014-2019) are summarized. In detail, this review stresses newly found parameters affecting thermoresponsive gelation, findings from structural analysis by simulation, small-angle neutron scattering (SANS), etc., progress in biomedical applications including drug delivery systems and regeneration medicine, and nanocomposites composed of block copolymers with PEG and PLGA and nanomaterials (laponite).

Antibiofilm Coatings Based on PLGA and Nanostructured Cefepime-Functionalized Magnetite

The aim of our study was to obtain and evaluate the properties of polymeric coatings based on poly(lactic-co-glycolic) acid (PLGA) embedded with magnetite nanoparticles functionalized with commercial antimicrobial drugs. In this respect, we firstly synthesized the iron oxide particles functionalized (@) with the antibiotic Cefepime (Fe₃O₄@CEF). In terms of composition and microstructure, the as-obtained powdery sample was investigated by means of grazing incidence X-ray diffraction (GIXRD), thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM and TEM, respectively). Crystalline and nanosized particles (~5 nm mean particle size) with spherical morphology, consisting in magnetite core and coated with a uniform and reduced amount of antibiotic shell, were thus obtained. In vivo biodistribution studies revealed the obtained nanoparticles have a very low affinity for innate immune-related vital organs. Composite uniform and thin coatings based on poly(lactide-co-glycolide) (PLGA) and antibiotic-functionalized magnetite nanoparticles (PLGA/Fe₃O₄@CEF) were subsequently obtained by using the matrix assisted pulsed laser evaporation (MAPLE) technique. Relevant compositional and structural features regarding the composite coatings were obtained by performing infrared microscopy (IRM) and SEM investigations. The efficiency of the biocompatible composite coatings against biofilm development was assessed for both Gram-negative and Gram-positive pathogens. The PLGA/Fe₃O₄@CEF materials proved significant and sustained anti-biofilm activity against staphylococcal and Escherichia coli colonisation.