scholarly journals Development of Intranasal Levothyroxine Powder Delivery for Hypothyroidism

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A828-A829
Author(s):  
Syed Ali Imran ◽  
Obinna Esomchukwu ◽  
Remigius Agu
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Surface Morphology ◽  
Freeze Drying ◽  
Significant Proportion ◽  
In Vitro Release ◽  
X Ray ◽  
Freeze Dried ◽  
Vitro Release

Abstract Background: Hypothyroidism affects 3-5% of the general population with oral levothyroxine (LT4) being the predominant replacement therapy. However, significant proportion of hypothyroid patients are unable to absorb oral replacement leading to therapeutic failure and may require injectable thyroxine. Objectives: To develop non-invasive, less costly, and patient-friendly LT4 nasal delivery alternative using mucoadhesive polymers: chitosan and hydroxypropylmethylcellulose (HPMC). Methods: Six nasal LT4 formulations were developed with either chitosan or hydroxypropyl methylcellulose as mucoadhesive. The formulations were prepared through freeze-drying by varying the drug to polymer ratio (1:1, 1:3, and 1:5). The percentage drug yield was calculated by analyzing the weight of the formulation pre- and post-freeze drying. HPLC analysis was conducted to determine the amount of LT4 loaded in each formulation. Furthermore, the surface morphology, particle size, zeta potential, differential scanning calorimetry, X-ray diffraction as well as the in vitro release were assessed to determine the physicochemical properties and release characteristics of the formulations, respectively. Results: Both percentage drug loading and yield were > 70% for all the formulations. The freeze-dried formulations displayed a compact needle-like surface morphology. LT4-chitosan formulations, 1:1, 1:3, and 1:5 had mean particle size of 2.45 ± 0.88 µm, 2.76 ± 1.38 µm, and 1.59 ± 0.27 µm, respectively. Mean particle sizes for 1:1, 1:3, and 1:5 LT4-HPMC formulations were 0.56 ± 0.02 µm, 0.22 ± 0.06 µm, and 0.46 ± 0.04 µm. Zeta potential for LT4-chitosan formulation 1:1, 1:3, and 1:5 were -18.7 ± 1.00 mV, -16.2 ± 0.79 mV, and -19.17 ± 1.01 mV, respectively. LT4-HPMC 1:1, 1:3, and 1:5 formulations had zeta charges of -11.66 ± 3.16 mV, -6.06 ± 3.92 mV, and -9.53 ± 1.68 mV, respectively. Differential calorimetric analysis confirmed drug-polymer integration in all formulations, and X-ray powder diffraction showed both chitosan and HPMC formulations as crystalline configuration. The formulations with the highest in vitro release were LT4-HPMC 1:3 and LT4-chitosan 1:5. Conclusions: Results of this study suggest that both chitosan and HPMC can be used as sustained release polymers for the intranasal delivery of LT4.

scholarly journals SELF-ASSEMBLED CHITOSAN NANOPARTICLES FOR PERCUTANEOUS DELIVERY OF CAFFEINE: PREPARATION, CHARACTERIZATION AND IN VITRO RELEASE STUDIES

2018 ◽  
Vol 10 (4) ◽  
pp. 172 ◽  
Author(s):  
Nik Amanina Farhanah Abu Hassan ◽  
Shariza Sahudin ◽  
Zahid Hussain ◽  
Mumtaz Hussain ◽  
Mumtaz Hussain
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Zeta Potential ◽  
Surface Charge ◽  
Process Parameters ◽  
In Vitro Release ◽  
Freeze Dried ◽  
Release Studies ◽  
Vitro Release

Objective: Chitosan (CS)–tripolyphosphate (TPP)–nanoparticles (NPs) have been extensively studied during the past few decades due to their well-recognized applicability in various fields. The present study attempts to optimise the development of these nanoparticles to enhance the percutaneous delivery of caffeine.Methods: CS-TPP-NPs were prepared via ionic cross-linking of CS and TPP and were characterized. The influence of several formulation conditions (CS: TPP mass ratio and concentration of caffeine) and process parameters (stirring speed, stirring time and ultra-sonication time) on the colloidal characteristics of CS-TPP-NPs were investigated and the resulting nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and x-ray diffraction (XRD) analyses. Physicochemical properties, including particle size, zeta potential and polydispersity index (PDI) were examined, and in vitro release studies were conducted to ascertain the release profile of caffeine from the nanoparticles. In addition, the colloidal stability of the prepared NPs was also assessed on storage.Results: Process parameters appeared to exert a significant effect on the physicochemical characteristics of the CS-TPP-NPs. The CS-TPP-NPs prepared under optimum conditions (CS concentration of 0.2 mg/ml, CS: TPP volume ratio of 25:12 ml, stirred at 700 rpm for 60 min, with 0.97 mg/ml caffeine concentration and treatment with low ultra-sonication for 30 min) had shown a mean particle size of ~143.43±1.69 nm, zeta potential of+43.13±1.10 mV, PDI of ~0.30±0.01. A drug loading capacity and encapsulation efficiency of 48.89% and 60.69%, respectively, were obtained. Cumulative release study for drug-loaded CS-NPs was significantly (p<0.001, paired t-test) higher (58.7% caffeine released) compared to control formulation (41.5% caffeine released) after 72 h. Stability studies conducted for 28 d showed that caffeine-loaded CS-NPs degraded much quicker when stored at 25 ⁰C than 4 ⁰C. It was also noted that caffeine-loaded CS-NPs in the freeze-dried form were unstable as the surface charge of nanoparticles dropped from positive zeta potential to-3.55 mV within 2 d at 4 ⁰C and at 25 ⁰C, surface charge dropped to-3.16 mV within 14 d of the experiment.Conclusion: Chitosan (CS)–tripolyphosphate (TPP)–nanoparticles (NPs) appear to be a promising strategy to achieve sustained percutaneous delivery of caffeine.

Optimization and Characterization of Aqueous Micellar Formulations for Ocular Delivery of an Antifungal Drug, Posaconazole

2020 ◽  
Vol 26 (14) ◽  
pp. 1543-1555 ◽  
Author(s):  
Meltem E. Durgun ◽  
Emine Kahraman ◽  
Sevgi Güngör ◽  
Yıldız Özsoy
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Size Distribution ◽  
Encapsulation Efficiency ◽  
Fungal Infections ◽  
In Vitro Release ◽  
Pluronic F127 ◽  
Glycol Succinate ◽  
Vitro Release

Background: Topical therapy is preferred for the management of ocular fungal infections due to its superiorities which include overcoming potential systemic side effects risk of drugs, and targeting of drugs to the site of disease. However, the optimization of effective ocular formulations has always been a major challenge due to restrictions of ocular barriers and physiological conditions. Posaconazole, an antifungal and highly lipophilic agent with broad-spectrum, has been used topically as off-label in the treatment of ocular fungal infections due to its highly lipophilic character. Micellar carriers have the potential to improve the solubility of lipophilic drugs and, overcome ocular barriers. Objective: In the current study, it was aimed optimization of posaconazole loaded micellar formulations to improve aqueous solubility of posaconazole and to characterize the formulations and to investigate the physical stability of these formulations at room temperature (25°C, 60% RH), and accelerated stability (40°C, 75% RH) conditions. Method: Micelles were prepared using a thin-film hydration method. Pre-formulation studies were firstly performed to optimize polymer/surfactant type and to determine their concentration in the formulations. Then, particle size, size distribution, and zeta potential of the micellar formulations were measured by ZetaSizer Nano-ZS. The drug encapsulation efficiency of the micelles was quantified by HPLC. The morphology of the micelles was depicted by AFM. The stability of optimized micelles was evaluated in terms of particle size, size distribution, zeta potential, drug amount and pH for 180 days. In vitro release studies were performed using Franz diffusion cells. Results: Pre-formulation studies indicated that single D-ɑ-tocopheryl polyethylene glycol succinate (TPGS), a combination of it and Pluronic F127/Pluronic F68 are capable of formation of posaconazole loaded micelles at specific concentrations. Optimized micelles with high encapsulation efficiency were less than 20 nm, approximately neutral, stable, and in aspherical shape. Additionally, in vitro release data showed that the release of posaconazole from the micelles was higher than that of suspension. Conclusion: The results revealed that the optimized micellar formulation of posaconazole offers a potential approach for topical ocular administration.

scholarly journals pH-Responsive Liposomes of Dioleoyl Phosphatidylethanolamine and Cholesteryl Hemisuccinate for the Enhanced Anticancer Efficacy of Cisplatin

Pharmaceutics ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 129
Author(s):  
Hassan Shah ◽  
Asadullah Madni ◽  
Muhammad Muzamil Khan ◽  
Fiaz-ud-Din Ahmad ◽  
Nasrullah Jan ◽  
...  
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Release Rate ◽  
In Vitro Release ◽  
Chemotherapeutic Agents ◽  
Ph Responsive ◽  
Scanning Calorimetry ◽  
Cholesteryl Hemisuccinate ◽  
Vitro Release

The current study aimed to develop pH-responsive cisplatin-loaded liposomes (CDDP@PLs) via the thin film hydration method. Formulations with varied ratios of dioleoyl phosphatidylethanolamine (DOPE) to cholesteryl hemisuccinate (CHEMS) were investigated to obtain the optimal particle size, zeta potential, entrapment efficiency, in vitro release profile, and stability. The particle size of the CDDP@PLs was in the range of 153.2 ± 3.08–206.4 ± 2.26 nm, zeta potential was −17.8 ± 1.26 to −24.6 ± 1.72, and PDI displayed an acceptable size distribution. Transmission electron microscopy revealed a spherical shape with ~200 nm size. Fourier transform infrared spectroscopic analysis showed the physicochemical stability of CDDP@PLs, and differential scanning calorimetry analysis showed the loss of the crystalline nature of cisplatin in liposomes. In vitro release study of CDDP@PLs at pH 7.4 depicted the lower release rate of cisplatin (less than 40%), and at a pH of 6.5, an almost 65% release rate was achieved compared to the release rate at pH 5.5 (more than 80%) showing the tumor-specific drug release. The cytotoxicity study showed the improved cytotoxicity of CDDP@PLs compared to cisplatin solution in MDA-MB-231 and SK-OV-3 cell lines, and fluorescence microscopy also showed enhanced cellular internalization. The acute toxicity study showed the safety and biocompatibility of the developed carrier system for the potential delivery of chemotherapeutic agents. These studies suggest that CDDP@PLs could be utilized as an efficient delivery system for the enhancement of therapeutic efficacy and to minimize the side effects of chemotherapy by releasing cisplatin at the tumor site.

scholarly journals FORMULATION OF POLYMERIC NANOSUSPENSION CONTAINING PRAMIPEXOLE DIHYDROCHLORIDE AND HESPERIDIN FOR IMPROVED TREATMENT OF PARKINSON’S DISEASES

2018 ◽  
Vol 11 ◽  
Author(s):  
Somasundaram I
Keyword(s):  
Particle Size ◽  
Drug Release ◽  
Zeta Potential ◽  
In Vitro Release ◽  
Entrapment Efficiency ◽  
Burst Release ◽  
Drug Content ◽  
Pramipexole Dihydrochloride ◽  
Vitro Release

Aims and Objectives: The present study is to formulate the nanosuspension containing a hydrophilic drug pramipexole dihydrochloride and hesperidin and to increase the drug entrapment efficiency.Methods: Hesperidin and pramipexole dihydrochloride loaded in chitosan nanosuspension is prepared by ionic gelation method using chitosan and tripolyphosphate. There was no incompatibility observed between the drug and polymer through Fourier transform infrared and differential scanning calorimetric. Various other parameters such as particle size, zeta potential, scanning electron microscope, drug content, drug entrapment efficiency, and in vitro release have been utilized for the characterization of nanoparticles.Results and Discussion: The average size of particle is 188 nm; zeta potential is 46.7 mV; drug content of 0.364±0.25 mg/ml; entrapment efficiency of 72.8% is obtained with HPN3 formulation. The PHC1 shows the highest drug release followed by PHC2 due to low concentration of polymer and PHC4 and PHC5 show less drug release due to high concentration of polymer. The in vitro release of PHC3 is 85.2%, initial the burst release is shown which is approximately 60% in 8 h; then, slow release later on drastic reduction in release rate is shown in 24 h. The in vivo study histopathological report confers the effective protective against rotenone induces Parkinson’s.Conclusion: PHC3 was chosen as the best formulation due to its reduced particle size and controlled release at optimum polymer concentration which may be used to treat Parkinson’s disease effectively..

ROSUVASTATIN CALCIUM LOADED CHITOSAN NANOPARTICLES: PREPARATION EVALUATION AND IN VITRO RELEASE STUDIES

2020 ◽  
pp. 95-102
Author(s):  
SUVARNA G. BHOKARE ◽  
RAJENDRA P. MARATHE
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Sustained Release ◽  
Sodium Tripolyphosphate ◽  
Chitosan Nanoparticles ◽  
In Vitro Release ◽  
Particle Diameter ◽  
Vitro Release ◽  
Rosuvastatin Calcium

Objective: The objective of the present study was to develop sustained release biodegradable polymeric nanoparticles of rosuvastatin calcium. Methods: Nanoparticles were prepared by modified ionotropic gelation method using 3² full factorial designs. From the preliminary trials, the constraints for independent variables X1 (concentration. of chitosan) and X2 (concentration. of sodium tripolyphosphate) have been fixed. Factors included concentration of chitosan and sodium tripolyphosphate, have been examined to investigate effect on particle size, encapsulation efficiency, zeta potential, % release, scanning electron microscopy, Fourier transfer infrared study and X-ray diffraction and release study of rosuvastatin calcium nanoparticles. 0 Results: The prepared nanoparticles were white, free-flowing and spherical in shape. The infrared spectra showed stable character of rosuvastatin calcium in the drug-loaded nanoparticles and revealed the absence of drug polymer interactions. The chitosan nanoparticles have a particle diameter ranging approximately 114.5±3.61 to 724±.2.51 nm and a zeta potential-13.12 to-52.63 mV. The in vitro release behavior from all the drug loaded batches were found to follow first order and provided sustained release over a period of 10 h. The Zeta potential of all the batches were in the range of-13.12 to-52.63 mv. The release profiles of all batches were very well fitted by Korsmeyer Peppas model. Conclusion: The best-fit release kinetics was achieved with Korsmeyer peppas model. The release of rosuvastatin calcium was influenced by the drug to polymer ratio and particle size. These results indicate that rosuvastatin calcium nanoparticles could be effective in sustaining drug release for a prolonged period.

scholarly journals Preparation of Curcumin Solid Lipid Nanoparticles Loaded with Flower-Shaped Lactose for Lung Inhalation and Preliminary Evaluation of Cytotoxicity In Vitro

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Nan Li ◽  
Xu Li ◽  
Peng Cheng ◽  
Ping Yang ◽  
Pengcheng Shi ◽  
...  
Keyword(s):  
Particle Size ◽  
Solid Lipid Nanoparticles ◽  
Freeze Drying ◽  
Drug Loading ◽  
In Vitro Release ◽  
Dry Powder Inhaler ◽  
Lipid Nanoparticles ◽  
Solid Lipid ◽  
Vitro Release

The purpose of this study is to design a flower-shaped lactose loaded curcumin solid lipid nanoparticles dry powder inhaler and characterize it to improve the solubility and dissolution rate of curcumin in lung. Curcumin solid lipid nanoparticles (Cur-SLNs) were prepared by solvent evaporation method, and then they were micronized by freeze-drying technology. Finally, Cur-SLN micropowder obtained by freeze-drying was mixed with flower-shaped lactose (FL) at a ratio of 2 : 1 and then passed through a 200-mesh sieve to obtain Cur-SLN-FL powder. Tween-80 was selected as the surfactant to inhibit the aggregation of drug solid lipid nanoparticles. Under the optimum conditions, the solid lipid nanoparticles (SLN) were relatively spherical, with an average particle size of 14.7 nm, narrow distribution, Zeta potential of −22.5 mV, encapsulation efficiency of 90.21%, and drug loading of 8.56%. According to the particle size, PI, Zeta potential, drug loading (LC%), encapsulation efficiency (EE%), morphology, and in vitro release characteristics, the prescription of solid lipid nanoparticles was screened. Dry powder inhaler (DPI) was characterized by differential scanning calorimetry, scanning electron microscopy, particle size, density, and in vitro release performance. Its cytotoxicity to mouse fibroblasts (L929) and human normal lung epithelial cells (BEAS-2B) in vitro was investigated, and its safety for pulmonary inhalation was preliminarily determined. FTIR analysis shows that the micronized Cur-SLN-FL has the same chemical structure as FL. FTIR and DSC analysis confirmed that the characteristic absorption peak of curcumin was not found in Cur-SLN-FL, showing similar structure to SLN and FL. In addition, curcumin was coated in solid lipid nanoparticles to make powder mist, which increased its drug loading, kept its aerodynamic particle size (4.03 ± 0.40) μm, and significantly improved its drug release performance in artificial lung fluid. In vitro cytotoxicity test results confirmed that Cur-SLN-FL was less toxic to BEAS-2B cells than L929 cells. Therefore, curcumin was prepared into solid lipid nanoparticles by emulsion evaporation-low temperature solidification method and then micronized and mixed with FL to prepare curcumin solid lipid nanoparticle powder mist loaded with flower-shaped lactose. The process is simple and feasible, and it has better safety performance for lung cells, which is expected to become a safe and effective delivery system for pulmonary inhalation drugs.

scholarly journals Formulation and Evaluation of Nanoemulsion using Tazarotene and Curcumin

2021 ◽  
pp. 807-815
Author(s):  
Parmita Phaugat ◽  
Suchitra Nishal ◽  
Aparna Khansili
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Ternary Phase Diagram ◽  
In Vitro Release ◽  
Tween 80 ◽  
High Energy ◽  
Oral Route ◽  
Topical Formulation ◽  
Vitro Release

Aims: To formulate and evaluate nanoemulsion of Tazarotene and Curcumin Study Design: Ultrsonication Methods. Place and Duration of Study, Sample: Swami Dayanand Postgraduate Institute of Pharmaceuticals Sciences, University of Health Sciences, Rohtak; 2020-2021 Methodology: Oleic acid, tween 80, and propylene glycol were selected as oil, surfactant, and co-surfactant, respectively. The ratio of oil: surfactant: co-surfactant was selected based on a ternary phase diagram using the aqueous titration method. The selected ratio was employed to develop eight formulations of Tazarotene-curcumin by ultra-sonication. The formulations (F1-F8) were characterized using several physicochemical methods like pH, viscosity, particle size distribution, zeta potential, drug content, and in vitro release. The optimized formulation was selected based on the results of characterization. Results: The formulations (F1-F8) were formulated by using the ultrasonication (high energy) method. The optimized formulation possessed particle size 121, 0.382 PDI, and -20.1 zeta potential. The in vitro release of F6 was found to be 90.9 ± 3.1 at 24 hours. It also passed the thermodynamic stability tests. Conclusion: The current investigations conclude that Tazarotene-curcumin nanoemulsion can be used as an alternative to the oral route of tazarotene and is also useful in reducing the adverse effects associated with oral. The physicochemical evaluation of the formulation showed that the nanoemulsion had the necessary properties for a topical formulation.

scholarly journals Formulation and Quality Control Tests for Nanoemulsion of Tofacitinib: A Novel Approach

2021 ◽  
pp. 224-234
Author(s):  
Suchitra Nishal ◽  
Vikas Jhawat ◽  
Parmita Phaugat ◽  
Rohit Dutt
Keyword(s):  
Rheumatoid Arthritis ◽  
Particle Size ◽  
Adverse Effects ◽  
Zeta Potential ◽  
In Vitro Release ◽  
High Energy ◽  
Janus Kinase ◽  
Oral Dosage ◽  
Vitro Release

Background: Tofacitinib (TFB) is a pioneer JAK (Janus kinase) inhibitor mainly employed to treat rheumatoid arthritis. It has proven efficacy for the treatment of rheumatoid arthritis in the oral dosage form. Oral TFB exhibited several toxic effects. Current research aims to develop a topical formulation of TFB to achieve effective treatment without any adverse effects. Study Design: Ultrsonication Methods. Place and Duration of Study: Sample: Swami Dayanand Postgraduate Institute of Pharmaceuticals Sciences, University of Health Sciences, Rohtak; 2020-2021. Methods: Oleic acid, tween 80, and propylene glycol were selected as oil, surfactant, and co-surfactant, respectively. The ratio of oil:surfactant:co-surfactant was selected based on a ternary phase diagram using the aqueous titration method. The selected ratio was employed to develop eight formulations of TFB by ultra-sonication. The formulations (F1-F8) were characterized using several physicochemical methods like pH, viscosity, particle size distribution, zeta potential, drug content, and in vitro release. Results: The formulations (F1-F8) were formulated by using the ultrasonication (high energy) method. The optimized formulation selected on the basis of characterization methods for instance, F8 possessed particle size 127.4 nm, and -18.4 (mV) zeta potential. The in vitro release of F8 was found to be 88.1 ± 2.5% at 24 hours. It also passed the thermodynamic stability tests. Conclusion:  The current investigations conclude that tofacitinib-nanoemulsion (TFB-NE) can be used as an alternative to the oral route of TFB and is also useful in reducing the adverse effects associated with oral TFB.

Formulation and Evaluation of Mefloquine Hydrochloride Nanoparticles

2014 ◽  
Vol 7 (1) ◽  
pp. 2377-2386
Author(s):  
Dilip Kumar Gupta ◽  
B K Razdan ◽  
Meenakshi Bajpai
Keyword(s):  
Particle Size ◽  
Sustained Release ◽  
In Vitro Release ◽  
Entrapment Efficiency ◽  
Taste Masking ◽  
Diffusion Method ◽  
Drug Entrapment Efficiency ◽  
Resistant Strains ◽  
Vitro Release

The present study deals with the formulation and evaluation of mefloquine hydrochloride nanoparticles. Mefloquine is a blood schizonticidal quinoline compound, which is indicated for the treatment of mild-to-moderate acute malarial infections caused by mefloquine-susceptible multi-resistant strains of P. falciparum and P. vivax. The purpose of the present work is to minimize the dosing frequency, taste masking toxicity and to improve the therapeutic efficacy by formulating mefloquine HCl nanoparticles. Mefloquine nanoparticles were formulated by emulsion diffusion method using polymer poly(ε-caprolactone) with six different formulations. Nanoparticles were characterized by determining its particle size, polydispersity index, drug entrapment efficiency, drug content, particle morphological character and drug release. The particle size ranged between 100 nm to 240 nm. Drug entrapment efficacy was >95%. The in-vitro release of nanoparticles were carried out which exhibited a sustained release of mefloquine HCl from nanoparticles up to 24 hrs. The results showed that nanoparticles can be a promising drug delivery system for sustained release of mefloquine HCl.

Preparation, Characterization and In-vitro release of Piroxicam-loaded Solid Lipid Nanoparticles

2010 ◽  
Vol 3 (3) ◽  
pp. 1136-1146
Author(s):  
V K Verma ◽  
Ram A
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Solid Lipid Nanoparticles ◽  
In Vitro Release ◽  
Entrapment Efficiency ◽  
Lipid Nanoparticles ◽  
Diffusion Method ◽  
Solid Lipid ◽  
Vitro Release

 Solid lipid nanoparticles (SLNs) of piroxicam where produced by solvent emulsification diffusion method in a solvent saturated system. The SLNs where composed of tripamitin lipid, polyvinyl alcohol (PVAL) stabilizer, and solvent ethyl acetate. All the formulation were subjected to particle size analysis, zeta potential, drug entrapment efficiency, percent drug loading determination and in-vitro release studies. The SLNs formed were nano-size range with maximum entrapment efficiency. Formulation with 435nm in particle size and 85% drug entrapment was subjected to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for surface morphology, differential scanning calorimetry (DSC) for thermal analysis and short term stability studies. SEM and TEM confirm that the SLNs are nanometric size and circular in shape. The drug release behavior from SLNs suspension exhibited biphasic pattern with an initial burst and prolong release over 24 h. 

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