Controlled Release: Mechanisms and Rates

STING-Pathway Inhibiting Nanoparticles (SPINs) as a Platform for Treatment of Inflammatory Diseases

Aberrant activation of the cyclic GMP-AMP synthase (cGAS)/Stimulator of Interferon Genes (STING) pathway has been implicated in the development and progression of a myriad of inflammatory diseases including colitis, nonalcoholic steatohepatitis, amyotrophic lateral sclerosis (ALS), and age-related macular degeneration. Thus, STING pathway inhibitors could have therapeutic application in many of these inflammatory conditions. The cGAS inhibitor RU.521 and the STING inhibitor H-151 have shown promise as therapeutics in mouse models of colitis, ALS, and more. However, these agents require frequent high-dose intraperitoneal injections, which may limit translatability. Furthermore, long-term use of systemically administered cGAS/STING inhibitors may leave patients vulnerable to viral infections and cancer. Thus, localized or targeted inhibition of the cGAS/STING pathway may be an attractive, broadly applicable treatment for a variety of STING pathway-driven ailments. Here we describe STING-Pathway Inhibiting Nanoparticles (SPINS)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with RU.521 and H-151-as a platform for enhanced and sustained inhibition of cGAS/STING signaling. We demonstrate that SPINs are equally or more effective at inhibiting type-I interferon responses induced by cytosolic DNA than free H-151 or RU.521. Additionally, we describe a SPIN formulation in which PLGA is coemulsified with poly(benzoyloxypropyl methacrylamide) (P(HPMA-Bz)), which significantly improves drug loading and allows for tunable release of H-151 over a period of days to over a week by varying P(HPMA-Bz) content. Finally, we find that all SPIN formulations were as potent or more potent in inhibiting cGAS/STING signaling in primary murine macrophages, resulting in decreased expression of inflammatory M1-like macrophage markers. Therefore, our study provides an in vitro proof-of-concept for nanoparticle delivery of STING pathway inhibitors and positions SPINs as a potential platform for slowing or reversing the onset or progression of cGAS/STING-driven inflammatory conditions.

Chitosan-Based Particulate Carriers: Structure, Production and Corresponding Controlled Release

The state of the art in the use of chitosan (CS) for preparing particulate carriers for drug delivery applications is reviewed. After evidencing the scientific and commercial potentials of CS, the links between targeted controlled activity, the preparation process and the kinetics of release are detailed, focusing on two types of particulate carriers: matrix particles and capsules. More precisely, the relationship between the size/structure of CS-based particles as multifunctional delivery systems and drug release kinetics (models) is emphasized. The preparation method and conditions greatly influence particle structure and size, which affect release properties. Various techniques available for characterizing particle structural properties and size distribution are reviewed. CS particulate carriers with different structures can achieve various release patterns, including zero-order, multi-pulsed, and pulse-triggered. Mathematical models have an unavoidable role in understanding release mechanisms and their interrelationships. Moreover, models help identify the key structural characteristics, thus saving experimental time. Furthermore, by investigating the close relation between preparation process parameters and particulate structural characteristics as well as their effect on release properties, a novel "on-demand" strategy for the design of drug delivery devices may be developed. This reverse strategy involves designing the production process and the related particles' structure based on the targeted release pattern.

Advances and trends in encapsulation of essential oils

There is a huge concern regarding the potential carcinogenic and mutagenic risks associated with the usage of synthetic chemicals as preservatives in various consumer products such as food and pharmaceutical formulations. In this aspect, there is a need for the development of alternative natural preservatives to replace these synthetic chemicals. More recently, naturally occurring essential oils have emerged as popular ingredients owing to their unique characteristics like antioxidant and antimicrobial activity, to enrich and enhance the functional properties of consumer products. However, due to their high volatility and hydrophobicity, their functionality is lost and their incorporation in aqueous products is challenging. One of the promising strategies to overcome this challenge is encapsulation which involves the entrapment of the essential oil inside a biocompatible material for its controlled release and increased bioavailability. Also, the choice of encapsulation method depends on the component to be encapsulated and the shell material. In this review, encapsulation in various colloidal systems that facilitate the potential delivery of essential oils is discussed. The focus is on encapsulation techniques along with their advantages and disadvantages, encapsulation efficiency, and in vitro release studies.

Transethosomal Gel for the Topical Delivery of Celecoxib: Formulation and Estimation of Skin Cancer Progression

The topical delivery of therapeutics is a promising strategy for managing skin conditions. Cyclooxygenase-2 (COX-2) inhibitors showed a possible target for chemoprevention and cancer management. Celecoxib (CXB) is a selective COX-2 inhibitor that impedes cell growth and generates apoptosis in different cell tumors. Herein, an investigation proceeded to explore the usefulness of nano lipid vesicles (transethosomes) (TES) of CXB to permit penetration of considerable quantities of the drug for curing skin cancer. The prepared nanovesicles were distinguished for drug encapsulation efficiency, vesicle size, PDI, surface charge, and morphology. In addition, FT-IR and DSC analyses were also conducted to examine the influence of vesicle components. The optimized formulation was dispersed in various hydrogel bases. Furthermore, in vitro CXB release and ex vivo permeability studies were evaluated. A cytotoxicity study proceeded using A431 and BJ1 cell lines. The expression alteration of the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene and DNA damage and fragmentation using qRT-PCR and comet assays were also investigated. Optimized CXB-TES formulation was spherically shaped and displayed a vesicle size of 75.9 ± 11.4 nm, a surface charge of -44.7 ± 1.52 mV, and an entrapment efficiency of 88.8 ± 7.2%. The formulated TES-based hydrogel displayed a sustained in vitro CXB release pattern for 24 h with an enhanced flux and permeation across rat skin compared with the control (free drug-loaded hydrogel). Interestingly, CXB-TES hydrogel has a lower cytotoxic effect on normal skin cells compared with TES suspension and CXB powder. Moreover, the level of expression of the CDKN2A gene was significantly (p ≤ 0.01, ANOVA/Tukey) decreased in skin tumor cell lines compared with normal skin cell lines, indicating that TES are the suitable carrier for topical delivery of CXB to the cancer cells suppressing their progression. In addition, apoptosis demonstrated by comet and DNA fragmentation assays was evident in skin cancer cells exposed to CXB-loaded TES hydrogel formulation. In conclusion, our results illustrate that CXB-TES-loaded hydrogel could be considered a promising carrier and effective chemotherapeutic agent for the management of skin carcinoma.

A novel nasal co-loaded loratadine and sulpiride nanoemulsion with improved downregulation of TNF-α, TGF-β and IL-1 in rabbit models of ovalbumin-induced allergic rhinitis

PURPOSE

The work aimed to develop a co-loaded loratadine and sulpiride nasal nanoemulsion for allergic rhinitis management.

METHODS

Compatibility studies were conducted adopting differential scanning calorimetry and Fourier transform infrared spectroscopy. Nanoemulsion formulations were prepared using soybean lecithin, olive oil and tween 80. Sodium cholate and glycerol were employed as co-surfactants. Nanoemulsions were assessed for viscosity, pH, droplet size, polydispersity index, zeta potential, electrical conductivity, entrapment, In vitro drug release and corresponding kinetics. Stability of the selected formulation was investigated. The biological effectiveness was evaluated in rabbit models of ovalbumin-induced allergic rhinitis by measuring TNF-α, TGF-β and IL-1.

RESULTS

Compatibility studies revealed absence of drug/drug interactions. Nanoemulsions exhibited > 90% entrapment efficiency. The selected nanoemulsion demonstrated small droplet size (85.2 ± 0.2 nm), low PDI (0.35 ± 0.0) and appropriate Zeta Potential (-23.3 ± 0.2) and stability. It also displayed enhanced in vitro drug release following the Higuashi Diffusion and Baker-Lonsdale models. The mean relative mRNA expression of TNF-α, IL-1 and TGF-β significantly decreased from 9.59 ± 1.06, 4.15 ± 0.02 and 4.15 ± 0.02 to 1.28 ± 0.02, 1.93 ± 0.06 and 1.56 ± 0.02 respectively after treatment with the selected nanoemulsion formulation.

CONCLUSION

The results reflected a promising potent effect of the combined loratadine and sulpiride nasal nanoemulsion in managing the symptoms of allergic rhinitis.

Micronutrients encapsulation by starch as an enhanced efficiency fertilizer

Developing different paths to achieve sustainable agriculture is no longer an option; it is a necessity. EEF materials are alternatives to improve the efficacy of the agrochemicals in the soil and plant, reducing wasting and environmental contamination. The present work aims to develop EEF materials based on starch and micronutrients, considering few works address EEFs materials with micronutrients. Monoelementary dispersions of gelatinized starch with micronutrients (Fe, Cu, Mn) were spray-dried and thermally, structurally, and morphologically characterized. We evaluated water-medium nutrient release, release kinetics, and the swelling degree. Different micronutrients affect morphology, size distribution, swelling degree, release, kinetics, and interaction between polymer-nutrient. Bigger particle sizes achieved a higher swelling degree, which led to decreased micronutrient release in the water. The Peppas-Sahlin model mainly ruled the release kinetics (fitted to all the materials). This result confirmed our hypothesis that a swelling starch delays the release.

A New Approach for Dry Eye Management By Mucoadhesive In situ Gel of Vitamin B12: Formulation, In vitro and In vivo Assessment

The commitment of the existent study was to develop a mucoadhesive in situ gel systems of vitamin B12 for the management of dry eye disease. The gels were prepared using pluronic F-127 and either of chitosan, carbapol 971P, sodium alginate, or hydroxy propyl methyl cellulose. Drug-excipients compatibility was investigated by means of differential scanning calorimetry and Fourier transform infrared spectroscopy. The gels were characterized for pH, clarity, gelling capacity, viscosity, and adhesion. In vitro release of vitamin B12 from the selected gels was investigated. In vivo effectiveness of the selected gel was determined in rabbit models using Schirmer's and fluorescein tests. The compatibility studies revealed the possibility of incidence of drug/polymer interaction in some formulations. F2-containing pluronic F127 and hydroxypropyl methyl cellulose showed the most appropriate physical characterization and in vitro release profile. The prepared gels showed prolonged drug release with drug release mechanism of combined diffusion and erosion. The in vivo study revealed good effectiveness of the prepared mucoadhesive in situ gel system of vitamin B12 in the treatment of dry eye disease that was comparable to that of the marketed drops.

New Acaciin-Loaded Self-Assembled Nanofibers as MPro Inhibitors Against BCV as a Surrogate Model for SARS-CoV-2

BACKGROUND

SARS-COVID-2 has recently been one of the most life-threatening problems which urgently needs new therapeutic antiviral agents, especially those of herbal origin.

PURPOSE

The study aimed to load acaciin (ACA) into the new self-assembled nanofibers (NFs) followed by investigating their possible antiviral effect against bovine coronavirus (BCV) as a surrogate model for SARS-COV-2.

METHODS

ACA was identified using 1H-NMR and DEPT-Q 13C-NMR spectroscopy, the molecular docking study was performed using Autodock 4 and a modification of the traditional solvent injection method was applied for the synthesis of the biodegradable NFs. Different characterization techniques were used to inspect the formation of the NFs, which is followed by antiviral investigation against BCV as well as MTT assay using MDBK cells.

RESULTS

Core/shell NFs, ranging between 80-330 nm with tiny thorn-like branches, were formed which attained an enhanced encapsulation efficiency (97.5 ± 0.53%, P<0.05) and a dual controlled release (a burst release of 65% at 1 h and a sustained release up to >24 h). The antiviral investigation of the formed NFs revealed a significant inhibition of 98.88 ± 0.16% (P<0.05) with IC50 of 12.6 µM against BCV cells.

CONCLUSION

The results introduced a new, time/cost-saving strategy for the synthesis of biodegradable NFs without the need for electric current or hazardous cross-linking agents. Moreover, it provided an innovative avenue for the discovery of drugs of herbal origin for the fight against SARS-CoV-2 infection.

Formulation and Optimization of Nanospanlastics for Improving the Bioavailability of Green Tea Epigallocatechin Gallate

The present study aimed to investigate the potential of nanospanlastics for boosting the bioavailability of epigallocatechin gallate (EGCG). EGCG has valuable effects like anti-inflammation, anti-oxidation, and anti-tumorigenesis. Unfortunately, it has a low oral bioavailability due to its limited permeation and poor stability. To overcome these pitfalls, EGCG was fabricated as a nanospanlastic. Nanospanlastics are flexible nanovesicles that are composed of surfactants and edge activators (EAs). EAs improve the deformability of spanlastics by acting as a destabilizing factor of their vesicular membranes. EGCG-loaded spanlastics were prepared by an ethanol injection method, according to 2³ factorial design, to explore the impact of different independent variables on entrapment efficiency (EE%), % drug released after 12 h (Q_12h), and particle size (PS). In vitro characterization, ex vivo intestinal permeation test, and pharmacokinetic study of the optimized formula were performed. A newly developed RP-HPLC technique was adopted for the estimation of EGCG. The optimized formula (F4) demonstrated more prolonged drug release and a significant improvement in the EE%, permeability, deformability and stability than the corresponding niosomes. The pharmacokinetic study investigated that F4 had a more sustained drug release and a higher bioavailability than the conventional niosomes and free drugs. Nanospanlastics could be a promising approach for improving the bioavailability of EGCG.

Modeling the release of food bioactive ingredients from carriers/nanocarriers by the empirical, semiempirical, and mechanistic models

The encapsulation process has been utilized in the field of food technology to enhance the technofunctional properties of food products and the delivery of nutraceutical ingredients via food into the human body. The latter application is very similar to drug delivery systems. The inherent sophisticated nature of release mechanisms requires the utilization of mathematical equations and statistics to predict the release behavior during the time. The science of mathematical modeling of controlled release has gained a tremendous advancement in drug delivery in recent years. Many of these modeling methods could be transferred to food. In order to develop and design enhanced food controlled/targeted bioactive release systems, understanding of the underlying physiological and chemical processes, mechanisms, and principles of release and applying the knowledge gained in the pharmaceutical field to food products is a big challenge. Ideally, by using an appropriate mathematical model, the formulation parameters could be predicted to achieve a specific release behavior. So, designing new products could be optimized. Many papers are dealing with encapsulation approaches and evaluation of the impact of process and the utilized system on release characteristics of encapsulated food bioactives, but still, there is no deep insight into the mathematical release modeling of encapsulated food materials. In this study, information gained from the pharmaceutical field is collected and discussed to investigate the probable application in the food industry.

Vitamin B12 buccoadhesive tablets: auspicious non-invasive substitute for intra muscular injection: formulation, in vitro and in vivo appraisal

Attempting to prepare a convenient bioavailable formulation of vitamin B₁₂ (cyanocobalamin), 17 tablet formulations were prepared by direct compression. Different concentrations of hydroxypropyl methyl cellulose (HPMC), carbopol 971p (CP971p), and chitosan (Cs) were used. The tablets were characterized for thickness, weight, drug content, hardness, friability, surface pH, in vitro drug release, and mucoadhesion. Kinetic analysis of the release data was conducted. Vitamin B₁₂ bioavailability from the optimized formulations was studied on rabbits by the aid of enzyme-linked immunosorbent assay. Neurotone^® I.M. injection was used for comparison. HPMC (F1-F4), CP971p (F5-F8), and HPMC/CP971p (F12-F15)-based formulations showed acceptable mechanical properties. The formulated tablets showed maximum swelling indices of 232 ± 0.13. The surface pH values ranged from 5.3 ± 0.03 to 6.6 ± 0.02. Bioadhesive force ranged from 66 ± 0.6 to 150 ± 0.5 mN. Results showed that CP971p-based tablets had superior in vitro drug release, mechanical, and mucoadhesive properties. In vitro release date of selected formulations were fitted well to Peppas model. HPMC/CP971p-based formulations showed bioavailability up to 2.7-folds that of Neurotone^® I.M. injection.

Effect of lipid and cellulose based matrix former on the release of highly soluble drug from extruded/spheronized, sintered and compacted pellets

Background

The study was to develop an extended release (ER) encapsulated and compacted pellets of Atenolol using hydrophobic (wax based and polymeric based) and high viscosity grade hydrophilic matrix formers to control the release of this highly water soluble drug by extrusion/spheronization (ES). Atenolol is used for cardiovascular diseases and available as an immediate release (IR) tablet dosage form. The lipids, Carnauba wax (CW), Glyceryl monostearate (GMS) and cellulose based i.e. Hydroxypropyl methylcellulose (HPMC) and Ethyl cellulose (EC) were used in preparing Atenolol ER pellets. Thermal sintering and compaction techniques were also applied to control the burst release of Atenolol.

Method

For this purpose, thirty-six trial formulations (F1-F36) were designed by Response Surface Methodology (RSM), using Design-Expert 10 software, keeping (HPMC K4M, K15 M & K100 M), (EC 7FP, 10FP & 100FP), waxes (GMS, & CW), their combinations, sintering temperature and duration, as input variables. Dissolution studies were performed in pH, 1.2, 4.5 and 6.8 dissolution media. Drug release kinetics using different models such as zero order, first order, Korsmeyer-Peppas, Hixon Crowell, Baker-Lonsdale and Higuchi kinetics were studied with the help of DDsolver, an excel based add-in program.

Results

The formulations F35 and F36 showed compliance with Korsmeyer-Peppas Super case II transport model (R² = 0.975–0.971) in dissolution medium pH 4.5. No drug excipient interaction observed by FTIR. Stereomicroscopy showed that sintered combination pellets, (F35), were highly spherical (AR = 1.061, and sphericity = 0.943). The cross-sectional SEM magnification (at 7000X) of F34 and F35 showed dense cross-linking. The results revealed that the optimized formulations were F35 (sintered pellets) and F36 (compacted pellets) effectively controlling the drug release for 12 h.

Conclusion

Extended-release encapsulated, and compacted pellets were successfully prepared after the combination of lipids CW (10%) and GMS (20%) with EC (10FP 20% & 100FP 20%). Sintering and compaction, in addition, stabilized the system and controlled the initial burst release of the drug. Extended release (ER) Atenolol is an effective alternative of IR tablets in controlling hypertension and treating other cardiovascular diseases.

Fluorouracil-Loaded Gold Nanoparticles for the Treatment of Skin Cancer: Development, in Vitro Characterization, and in Vivo Evaluation in a Mouse Skin Cancer Xenograft Model

Fluorouracil (5-FU) is an antimetabolite drug used in the treatment of various malignancies, such as colon and skin cancers. However, its systemic administration results in severe side effects. Topical 5-FU delivery for the treatment of skin cancer could circumvent these shortcomings, but it is limited by the drug poor permeability through the skin. To enhance 5-FU efficacy against skin cancer and reduce its systemic side effects, it was loaded into a gold nanoparticle (GNP)-based topical delivery system. 5-FU was loaded onto GNPs capped with CTAB through ionic interactions between 5-FU and CTAB. GNPs were prepared at different 5-FU/CTAB molar ratios and evaluated using different techniques. GNP stability and drug release were studied as a function of salt concentration and solution pH. Optimum 5-FU/CTAB-GNPs were incorporated into gel and cream bases, and their ex vivo permeability was evaluated in mice dorsal skin. The in vivo anticancer efficacy of the same preparations was evaluated in A431 tumor-bearing mice. The GNPs had spherical shape and a size of ∼16-150 nm. Maximum 5-FU entrapment was achieved at 5-FU/CTAB molar ratio of 1:1 and pH 11.5. Drug release from GNPs was sustained and pH-dependent. 5-FU GNP gel and cream had around 2-fold higher permeability through mice skin compared with free 5-FU gel and cream formulations. Further, in vivo studies in a mouse model having A431 skin cancer cells implanted in the subcutaneous space showed that the GNP gel and cream achieved 6.8- and 18.4-fold lower tumor volume compared with the untreated control, respectively. These results confirm the potential of topical 5-FU/CTAB-GNPs to enhance drug efficacy against skin cancer.

Investigation of Dissolution Behavior HPMC/Eudragit®/Magnesium Aluminometasilicate Oral Matrices Based on NMR Solid-State Spectroscopy and Dynamic Characteristics of Gel Layer

Burst drug release is often considered a negative phenomenon resulting in unexpected toxicity or tissue irritation. Optimal release of a highly soluble active pharmaceutical ingredient (API) from hypromellose (HPMC) matrices is technologically impossible; therefore, a combination of polymers is required for burst effect reduction. Promising variant could be seen in combination of HPMC and insoluble Eudragits^® as water dispersions. These can be applied only on API/insoluble filler mixture as over-wetting prevention. The main hurdle is a limited water absorption capacity (WAC) of filler. Therefore, the object of this study was to investigate the dissolution behavior of levetiracetam from HPMC/Eudragit^®NE matrices using magnesium aluminometasilicate (Neusilin^® US2) as filler with excellent WAC. Part of this study was also to assess influence of thermal treatment on quality parameters of matrices. The use of Neusilin^® allowed the application of Eudragit^® dispersion to API/Neusilin^® mixture in one step during high-shear wet granulation. HPMC was added extragranularly. Obtained matrices were investigated for qualitative characteristics, NMR solid-state spectroscopy (ssNMR), gel layer dynamic parameters, SEM, and principal component analysis (PCA). Decrease in burst effect (max. of 33.6%) and dissolution rate, increase in fitting to zero-order kinetics, and paradoxical reduction in gel layer thickness were observed with rising Eudragit^® NE concentration. The explanation was done by ssNMR, which clearly showed a significant reduction of the API particle size (150-500 nm) in granules as effect of surfactant present in dispersion in dependence on Eudragit^®NE amount. This change in API particle size resulted in a significantly larger interface between these two entities. Based on ANOVA and PCA, thermal treatment was not revealed as a useful procedure for this system.

Model for Microcapsule Drug Release with Ultrasound-Activated Enhancement

Microbubbles and microcapsules of silane-polycaprolactone (SiPCL) have been filled with a fluorescent acridium salt (lucigenin) as a model for a drug-loaded delivery vehicle. The uptake and delivery were studied and compared with similar microbubbles and microcapsules of silica/mercaptosilica (S/M/S). Positively charged lucigenin was encapsulated through an electrostatic mechanism, following a Type I Langmuir isotherm as expected, but with an additional multilayer uptake that leads to a much higher loading for the SiPCL system (∼280 μg/2.4 × 10⁹ microcapsules compared with ∼135 μg/2.4 × 10⁹ microcapsules for S/M/S). Whereas the lucigenin release from the S/M/S bubbles and capsules loaded below the solubility limit is consistent with diffusion from a monolithic structure, the SiPCL structures show distinct release patterns; the Weibull function predicts a general trend for diffusion from normal Euclidean space at short times tending toward diffusion out of fractal spaces with increasing time. As a slow release system, the dissolution time (T_d) increases from 1 to 2 days for the S/M/S and for the low concentration, loaded SiPCl vehicles to ∼10 days for the high loaded microcapsules. However, T_d can be reduced on insonation to 2 days, indicating the potential to gain control over the local enhanced release with ultrasound. This was tested for a docetaxel model and its effect on C4-2B prostate cancer cells, showing improved cell toxicity for concentrations below the normal EC₅₀ in solution.

Gold nanoparticles capped with benzalkonium chloride and poly (ethylene imine) for enhanced loading and skin permeability of 5-fluorouracil

OBJECTIVE

To enhance 5-fluorouracil (5-FU) permeability through the skin by loading onto gold nanoparticles (GNPs) capped with two cationic ligands, benzalkonium chloride (BC) or poly (ethylene imine) (PEI). Whereas 5-FU has excellent efficacy against many cancers, its poor permeability through biological membranes and several adverse effects limit its clinical benefits. BC and PEI were selected to stabilize GNPs and to load 5-FU through ionic interactions.

METHODS

5-FU/BC-GNPs and 5-FU/PEI-GNPs were prepared at different 5-FU/ligand molar ratios and different pH values and were evaluated using different techniques. GNPs stability was tested as a function of salt concentration and storage time. 5-FU release from BC- and PEI-GNPs was evaluated as a function of solution pH. Ex vivo permeability studies of different 5-FU preparations were carried out using mice skin.

RESULTS

5-FU-loaded GNPs size and surface charge were dependent on the 5-FU/ligand molar ratios. 5-FU entrapment efficiency and loading capacity were dependent on the used ligand, 5-FU/ligand molar ratio and solution pH. Maximum drug entrapment efficiency of 59.0 ± 1.7% and 46.0 ± 1.1% were obtained for 5-FU/BC-GNPs and 5-FU/PEI-GNPs, respectively. 5-FU-loaded GNPs had good stability against salinity and after storage for 4 months at room temperature and at 4 °C. In vitro 5-FU release was pH- and ligand-dependent where slower release was observed at higher pH and for 5-FU/BC-GNPs. 5-FU permeability through mice skin was significantly higher for drug-loaded GNPs compared with drug-ligand complex or drug aqueous solution.

CONCLUSION

Based on these results, BC- and PEI-GNPs might find applications as effective topical delivery systems of 5-FU.

Mechanistic Approach to Understanding the Influence of USP Apparatus I and II on Dissolution Kinetics of Tablets with Different Operating Release Mechanisms

This article provides an analysis of dissolution kinetics associated with formulations subjected to different dissolution methods with the purpose of revealing credible direction on selection of apparatus type and hydrodynamics on in vitro drug release profiles using three different formulations. The dissolution kinetics of immediate release (IR) and controlled release (CR) ibuprofen tablets under different hydrodynamic conditions were determined, and potential existence of any correlation between USP apparatus I and II were analyzed using adequate kinetic models. Two types of CR tablets based on PEO (polyethylene oxide-N80) and HPMC (hydroxypropyl methylcellulose- K100M) polymers were prepared. Marketed ibuprofen 200-mg IR tablets were also used. Dissolution studies were carried out using USP 34 apparatuses I and II methods at stirring speed of 100 and 50 rpm in 900 mL phosphate buffer, pH 7.2 at 37°C. The drug release profiles for each formulation was determined and statistically analyzed using model-dependent, model-independent (f ₂ ), and ANOVA methods. No significant dissolution differences existed between IR tablets, whereas CR tablets were significantly impacted by apparatus types and hydrodynamics. PEO matrices displayed higher sensitivity to hydrodynamics relative to HPMC matrices, and differences in dissolution profiles were confirmed by ANOVA and boxplot analysis. It is concluded that in the case of CR systems, selection of apparatus type and adherence to the monograph specifications and hydrodynamic conditions is critical, while for IR tablets, both apparatus types and agitation rates had no significant impact on drug release rate, suggesting the possibility of apparatus interchangeability if desired.

The influence of thermal treatment and type of insoluble poly(meth)acrylates on dissolution behavior of very soluble drug from hypromellose matrix tablets evaluated by multivariate data analysis

Hypromellose matrices exhibit extended burst effect immediately after contact with aqueous medium, especially when a water-soluble drug is incorporated. The objective of this study was to reduce burst effect and maintain complete dissolution of a very soluble levetiracetam over 12 h period from hypromellose K4M matrices to obtain zero-order kinetics. Desired changes were achieved by applying water dispersions of insoluble Eudragits^® (NE, NM, RL, RS) as a granulation liquid to the drug/microcrystalline cellulose mixture during high-shear granulation (non-thermal treated set) and consequently by thermally treating granules or final tablets (TT), respectively. Applying Eudragit^® water dispersions to the drug/microcrystalline cellulose mixture was recognized as an effective method of significantly reducing the burst release (25.4-33.7%) of levetiracetam in comparison with a reference sample without Eudragit^®. Multivariate data analysis showed that the addition of Eudragit^® reduced burst effect, increased fitting with zero-order kinetics, and supported matrix erosion as the supplementary mechanism to predominant diffusion. Moreover, resulting PCA sub-model revealed the addition of Eudragit^® RL and thermal treatment of tablets to be the most suitable method of all. For a 12 h dissolution profile, characterized by low burst effect and drug release close to 100% at the 12th hour, sample RL_TT was the most suitable.

Evaluation of the Thermosensitive Release Properties of Microspheres Containing an Agrochemical Compound

The purpose of this study was to develop a deeper understanding of the key physicochemical parameters involved in the release profiles of microsphere-encapsulated agrochemicals at different temperatures. Microspheres consisting of different polyurethanes (PUs) were prepared using our previously reported solventless microencapsulation technique. Notably, these microspheres exhibited considerable differences in their thermodynamic characteristics, including their glass transition temperature (T_g), extrapolated onset temperature (T_o) and extrapolated end temperature (T_e). At test temperatures below the T_o of the PU, only 5-10% of the agrochemical was rapidly released from the microspheres within 1 d, and none was released thereafter. However, at test temperatures above the T_o of the PU, the rate of agrochemical release gradually increased with increasing temperatures, and the rate of release from the microspheres was dependent on the composition of the PU. Taken together, these results show that the release profiles of the microspheres were dependent on their thermodynamic characteristics and changes in their PU composition.

Novel Design of Microreservoir-Dispersed Matrices for Drug Delivery Formulations: Drug Release from Polybutadiene- and Poly (ethylene oxide)-Based Segmented Polyurethanes in Relation to Their Microdomain Structures

Drug release from monolithic devices of segmented polyether-poly- (urethane-urea) (PEUU)s based on 1,2-polybutadiene (PBD) and poly(ethylene oxide) (PEO) as their soft segments was examined in relation to their micro domain structures. Physical characterization of these PEUU films was carried out in terms of their thermal properties, dynamic mechanical properties, and water structure in water swollen PEUU films. These results reveal that the ter nary microdomain structures are composed of PBD, PEO, and hard segments. The drug release profiles of these PEUU devices are strongly affected by the physicochemical nature of soft segment matrices in PEUUs. The PEUUs with high PEO content exhibited slow and steady (zero-ordered) release of drug in contrast with those with low PEO content from which drug release was en tirely restricted. This result indicates the importance of a matrix to perform the function not only as a drug reservoir but also a transport channel. The solu bility parameters of both constituent segments and the drug must be realized for regulated drug release from microdomain-structured polymeric devices.

α,β-Poly(N-Hydroxyethyl)-DL-Aspartamide Hydrogels as Drug Delivery Devices

α,β-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) was exposed to gamma radiation to obtain micromatrices able to swell in an aqueous medium. Crosslinked PHEA was loaded with an anti-inflammatory drug, 4-biphenylacetic acid (BPAA) and the drug dispersion in the network was investigated by X-ray analysis. The BPAA loaded PHEA microparticles were also characterized by dimensional analysis, which showed the presence of quasispherical shapes. The drug release from PHEA hydrogel was studied in vitro in a pH 1.1 (simulated gastric juice) and in a pH 7.4 buffer solution, respectively. The experimental data indicate that an anomalous delivery occurs, but Fickian diffusion through swollen PHEA hydrogel seems to be the predominant release mechanism. The interactions between PHEA microparticles and dimyristoil-phosphatidylcholine (DMPC) liposomes, chosen as biomembrane model, were studied by a differential scanning calorimetry (DSC) technique. The calorimetric results show that the cross-linked PHEA network does not interact with the DMPC liposomes.

Poly(Glyceryl Methacrylate) Hydrogels - Effect of Composition and Crosslinking Density on Structure and Release of Dextran as a Model Macromolecule

A series of hydrogels based on glyceryl methacrylate (pGMA) were prepared with different ratios of ethylene glycol dimethacrylate (EGDMA) and ethyl methacrylate (EMA) in order to vary the degree of crosslinking and the degree of hydrophobicity of the matrices, respectively. The swelling be haviour and the crosslinking density of the hydrogels were characterized and the structure was determined by scanning electron microscopy and porosime try. FITC-dextran (molecular weight 20,000) was imbibed into the gels and the release rate studied. It was found that the initial rate of release and the total amount of dextran release varied as an inverse function of crosslinking and monomer concentration, but as a linear function of EMA concentration.

Review : Biodegradable Microcapsular Drug Delivery Systems: Manufacturing Methodology, Release Control and Targeting Prospects

An overview of the subject of biodegradable microcapsular drug delivery systems is presented from a polymer chemist's viewpoint. Various polymerization and microencapsulation techniques (including emulsion polymerization, interfacial polycondensation, suspension crosslinking, coacer vation/phase separation and solvent evaporation/extraction) suitable for the preparation of biodegradable microcapsules based on proteins, polysaccharides, polyesters, polyamides, or cyanoacrylates are described. Drug release from biodegradable microcapsules is discussed, and examples are presented to illus trate how the rate of drug release can be controlled by adjusting parameters such as microcapsule size, porosity, and crosslinking. Prospects of site-specific chemotherapy by means of passive and active targeting of microcapsular drug carriers are also analyzed.

Localized rosuvastatin via implantable bioerodible sponge and its potential role in augmenting bone healing and regeneration

OBJECTIVE

Statins proved potential bone healing properties. Rosuvastatin is a synthetic, hydrophilic, potent and highly efficacious statin. In the current work, an attempt was investigated to develop, evaluate various bioerodible composite sponges enclosing rosuvastatin and explore their potential in augmenting bone healing and regeneration.

METHOD

Twelve lyophilized sponge formulae were prepared adapting a 4¹.3¹ full factorial design. Xanthan gum, polycarbophil, Carbopol® and sodium alginate were investigated as anionic polymers, each at three chitosan:anionic polymer ratios (1:3, 1:1, 3:1). The formula of choice was implanted in fractured rat femora.

RESULTS

Visual and microscopic examination showed flexible homogenous porous structures with considerable bending ability. Polyelectrolyte complex formation was proved by DSC and FT-IR for all chitosan/anionic combinations except with xanthan gum where chitosan probably bound to the drug rather than xanthan gum. Statistical analysis proved that anionic polymer type and chitosan: polymer ratio, as well as, their interactions, exhibited significant effects on the release parameters at p ≤ 0.05. The optimum chitosan/anionic polymer complexation ratios were 3:1 for polycarbophil and 1:1 for Carbopol and alginate. The release at these ratios followed Fiction diffusion while other ratios had anomalous diffusion. Imwitor® 900K and HPMC K100M were added as release retarardants for further release optimization. The formula of choice was implanted in fractured rat femora. Histopathological examination revealed advanced stages of healing in treated femora compared to control ones.

CONCLUSION

Biodegradable sponges for local rosuvastatin delivery proved significantly enhanced wound healing and regeneration properties to fractured bones.

Chitosan crosslinked microparticles with encapsulated polyphenols: Water sorption and release properties

Chitosan–glutaraldehyde microparticles were produced by emulsion crosslinking method to be used as drug delivery system for polyphenols from Thymus serpyllum L. aqueous extract. The effect of preparation conditions, chitosan concentration (1.5–3% w/v), and glutaraldehyde/chitosan (GA/Ch) mass ratio (0.15–1.20) on water and polyphenols transport properties was investigated. Swelling ratio of dry particles (68–230 µm) in water ranged from 280% to 530%, depending on the formulation. The decrease in swelling was observed with increased GA/Ch mass ratio (i.e. crosslinking degree) at the same chitosan concentration, or with increased chitosan concentration at the same GA/Ch mass ratio. The increase in GA/Ch mass ratio was also manifested by increased particle compactness i.e. decreased size and reduced surface roughness. The sorption capacity for polyphenols seems to be a complex interplay of swelling behaviour and interactions chitosan–glutaraldehyde–polyphenols identified by Fourier transmission infrared analysis. An increase in crystallinity of chitosan was observed upon crosslinking with glutaraldehyde and encapsulation of polyphenols, as observed by X-ray diffraction analysis. The results obtained from release kinetics of selected polyphenolic compounds (caffeic acid, rosmarinic acid, total flavonoids, and total phenol content) showed that polyphenols were released at a lower amount (2–4 times) in water, but more rapidly (45–120 min) in comparison with the release in gastric followed by intestinal simulated fluid (SGF-SIF) (120–240 min). The experimental results of the time-dependent swelling in water and polyphenols release in both, water and SGF-SIF, were analyzed with several mathematical models. The results depicted Fickian diffusion as the water transport mechanism. In the case of polyphenols, only empirical Weibull model could be suggested for describing release kinetics.

Photomechanically Controlled Encapsulation and Release from pH-Responsive and Photoresponsive Microcapsules

Poly(acrylic acid)/azobenzene microcapsules were obtained through distillation precipitation polymerization and the selective removal of silica templates by hydrofluoric acid etching. The uniform, robust, and monodisperse microcapsules, confirmed by transmission electron microscopy and scanning electron microscopy, had reversible photoisomerization under ultraviolet (UV) and visible light. Under UV irradiation, azobenzene cross-linking sites in the main chain transformed from the trans to cis isomer, which induced the shrinkage of microcapsules. These photomechanical effects of azobenzene moieties were applied to the encapsulation and release of model molecules. After loading with rhodamine B (RhB), the release behaviors were completely distinct. Under steady UV irradiation, the shrinkage adjusted the permeability of the capsule, providing a novel way to encapsulate RhB molecules. Under alternate UV/visible light irradiation, a maximal release amount was reached due to the continual movement of shell networks by cyclic trans-cis photoisomerization. Also, microcapsules had absolute pH responsiveness. The diffusion rate and the final release percentage of RhB both increased with pH. The release behaviors under different irradiation modes and pH values were in excellent agreement with the Baker-Lonsdale model, indicating a diffusion-controlled release behavior. Important applications are expected in the development of photocontrolled encapsulation and release systems as well as in pH-sensitive materials and membranes.

Chitosan nanoparticles for the linear release of model cationic Peptide

PURPOSE

The present study is focused on the development of a model drug delivery system (DDS) based on Chitosan (CS) nanoparticles using Renin substrate I (RSI) as model agent. RSI shares the main chemical-physical features of several biologically active antimicrobial peptides (AMPs). AMPs have a great therapeutic potential that is hampered by their lability in the biological fluids and as such they are perfect candidates for DDS. The development studies of quality DDS loaded with AMPs would require highly sensitive and specific quantification assays. The use of RSI allowed for the fine-tuning and optimization of the formulation parameters to promote the hydrophobic interactions between CS and the cationic peptide, favour the loading of the active ingredient and enhance the release properties of the carrier.

METHODS

RSI was encapsulated in chitosan NPs by mean of ionic gelation and a chromogenic enzymatic essay was carried out for the release kinetics evaluation.

RESULTS

The developed formulations displayed almost 100% of encapsulation efficacy, low burst percentages, and a linear release of the model peptide. A release model was created showing a direct dependence on both the amount of RSI and NPs radius.

CONCLUSIONS

Although CS has always been formulated with negatively charged active agents (e.g. oligonucleotides or anionic proteins), the use of ionotropic gelation in presence of a small cationic active agent promoted the formation of "core-shell" NPs. The described model, with tuneable linear release rates, appears eligible for further exploitation such as the loading of therapeutically active AMPs.

Tailored beads made of dissolved cellulose--investigation of their drug release properties

In the frame of this work, we have investigated drug entrapping and release abilities of new type of porous cellulose beads (CBs) as a spherical matrix system for drug delivery. For that purpose, CBs prepared with three different methods were used as drug carriers and three compounds, anhydrous theophylline (Thp), riboflavin 5'-phosphate sodium (RSP) and lidocaine hydrochloride monohydrate (LiHCl) were used as model drug substances. The loading procedure was carried out by immersing swollen empty beads into the solutions of different concentrations of model drugs. The morphology of empty and loaded beads was examined using a field emission scanning electron microscopy (FE-SEM). Near-infrared (NIR) imaging was performed to identify the drug distributions on and within the loaded CBs. The drug amount incorporated into CBs was examined spectrophotometrically and in vitro drug release studies were performed to determine the drug release rates. The results of FE-SEM and chemical NIR imaging analyses revealed that incorporated drug were distributed on the surface and but also within the internal structure of the CBs. Physical properties of CBs and solubility of model drugs had effect on loading efficacy. Also, the drug release rates were controlled by solubility of model drugs (diffusion controlled release). In conclusion, CBs from dissolved cellulose show promise in achieving controlled drug delivery.

Production of slow-released nitrogen fertilizer from urine

Human excreta, especially urine is rich in nitrogen that can be utilized for agricultural purposes, while the slow-release fertilizer allows effective utilization of nutrients in agricultural production. The direct formation of slow-release fertilizer--methylene urea--from urine was being proposed in this study. The experiments were tried to prove formation of methylene urea from human urine, and to investigate the effect of pH and salt concentration on the reaction rate. The synthetic urine and real urine were used for the urea source of the reaction. As a result, the precipitates were prepared from synthetic urine, while the small molecule fractions generated then they grew into precipitate. The nuclear magnetic resonance, infrared spectroscopy, element analyses showed the precipitates in synthetic urine were the same compound found in the urea solution, which was methylene urea. The reaction rate was high at low pH value. The reaction rate in the buffer solution was lower than the synthetic urine at the same pH, because some salts may work as a catalyst. The urea concentration reduction rate in real urine showed the same trend with synthetic urine at the same pH, while the precipitation was quite similar to methylene urea.

Preparation and characterization of hydrophilic composites AA/EPMA loaded with hydroxyapatite

Copolymeric composites of acrylamide (AA) and 2,3-epoxypropyl methacrylate (EPMA) with hydroxyapatite (HA) load were studied. Swelling studies reports an anomalous or non-Fickian behavior following a good fitting to a pseudo second order mathematical treatment (α = 0.05, p < 0.0001). The composites showed a strong dependence on pH, related with the variations in the swelling behavior. The addition of load induces a diminution of swelling capacity and an increase of diametric tensile strength (DTS) ranging between 20 and 90 kPa. The calorimetric experiments showed two steps at 78°C and 255°C assigned to water loss and samples Tg. The drug control released was adjusted to a two-term equation obtaining a diffusion coefficient around 10(-5) cm(2) /s. The samples showed a significant bioactivity in vitro and it was certified by SEM, EDS and surface area calculus.

Evaluation of dense polylactic acid/beta-tricalcium phosphate scaffolds for bone tissue engineering

Advances in biomaterial fabrication have introduced numerous innovations in designing scaffolds for bone tissue engineering. Often, the focus has been on fabricating scaffolds with high and interconnected porosity that would allow for cellular seeding and tissue ingrowth. However, such scaffolds typically lack the mechanical strength to sustain in vivo ambulatory stresses in models of load bearing cortical bone reconstruction. In this study, we investigated the microstructural and mechanical properties of dense PLA and PLA/beta-TCP (85:15) scaffolds fabricated using a rapid volume expansion phase separation technique, which embeds uncoated beta-TCP particles within the porous polymer. PLA scaffolds had a volumetric porosity in the range of 30 to 40%. With the embedding of beta-TCP mineral particles, the porosity of the scaffolds was reduced in half, whereas the ultimate compressive and torsional strength were significantly increased. We also investigated the properties of the scaffolds as delivery vehicles for growth factors in vitro and in vivo. The low-surface porosity resulted in sub optimal retention efficiency of the growth factors, and burst release kinetics reflecting surface coating rather than volumetric entrapment, regardless of the scaffold used. When loaded with BMP2 and VEGF and implanted in the quadriceps muscle, PLA/beta-TCP scaffolds did not induce ectopic mineralization but induced a significant 1.8-fold increase in neo vessel formation. In conclusion, dense PLA/beta-TCP scaffolds can be engineered with enhanced mechanical properties and potentially be exploited for localized therapeutic factor delivery.

Characterization of drug release from liposomal formulations in ocular fluid

The successful application of liposomes in topical ophthalmic drug delivery requires knowledge of vesicle stabilization in the presence of tear fluid. The release of procaine hydrochloride (PCH) from large unilamellar liposomes in the presence of simulated tear fluid was studied in vitro as a function of bilayer lipid content and tear protein composition. Reverse-phase evaporation vesicles were prepared from egg phosphatidylcholine, stearylamine or dicetyl phosphate, and cholesterol. The relationship between lipid composition and encapsulation efficiency, vesicle size, drug leakage upon storage at 4 degrees C, and the release of PCH-loaded liposomes was studied. The encapsulation efficiency was found to be dependent upon the lipid composition used in the liposome preparation. In particular, phosphatidylcholine vesicles containing cholesterol and/or charged lipids had a lower entrapment efficiency than liposomes prepared with phosphatidylcholine alone. However, the drug release rate was reduced significantly by inclusion of cholesterol and/or charged lipids in the liposomes. The release kinetics of the entrapped agent seemed to be a biphasic process and the drug-release in both simulated tear fluid (STF) and pH 7.4 phosphate buffered saline (PBS) solutions followed pseudo first-order kinetics in the early stage of the release profile. The drug-release appeared to be diffusion and/or partition controlled. Drug release from liposomes into STF, pH 7.4 PBS, and five different modified tear formulations was also evaluated. While serum-induced leakage is attributed to high-density lipoprotein-mediated destabilization, it was determined that lactoferrin might be the protein component in tear fluid that has the primary influence on the liposome-entrapped drug release rate. Five local anesthetics, benoxinate, proparacaine, procaine, tetracaine, and benzocaine were entrapped in liposomal vesicles by a reverse-phase evaporation (REV) technique. The release of these structurally similar topical anesthetics entrapped in positively charged liposomes (egg phosphatidylcholine, stearylamine, and cholesterol in a 7:2:1 molar ratio) was evaluated in a simulated tear fluid and pH 7.4 phosphate buffered saline solution. The liposomes appeared to be useful carriers for these drugs to retard their in vitro release in tear fluid and perhaps sustain or control their release in the eye for better therapeutic efficacy. An analysis of the release data demonstrated that for this series of drugs, drug partition coefficient has the largest effect on release rate, with molecular weight exhibiting a smaller effect. Release rate was found to decrease with increased lipophilicity or increased molecular weight.

Development and evaluation of hydrophilic colloid matrix of famotidine tablets

The objective of the present study was to develop a once-daily sustained-release (SR) matrix tablet of famotidine. Nine different formulations (F1-F9) were prepared by direct compression method using Avicel PH101 as filler/binder in the range of 41-27% in F1-F3, 18-22% in F4-F7, and 16-18% in F8-F9 and hydroxypropyl methylcellulose (4,000 cps) as hydrophilic matrix was used in F1-F3 from 19% to 30%, around 40% in F4-F7, and 42-45% in F8-F9. Talc and Aerosil were added in the ratio of 0.7-1.2%. The tablets were subjected to various physical parameters including weight variation test, hardness, thickness, diameter, friability, and in vitro release studies. Assay was also performed according to the USP 30 NF 25 procedure. The results of the physical parameters and assay were found to be within the acceptable range. In vitro dissolution results indicated that formulation F4-F7, having around 40% of rate control polymer, produced a SR pattern throughout 24 h. F1-F3 showed drug release at a faster rate, while F8-F9 released much slower, i.e., <80% in 24 h. Model-dependent and model-independent methods were used for data analysis and the best results were observed for F4 in zero order (r(2) = 0.984) and F6 in Korsmeyer and Higuchi (r(2) = 0.992 and 0.988). The parameter n indicated anomalous diffusion, while beta in Weibull showed a parabolic curve with higher initial slope. The f(2) similarity test was performed taking F4 as a reference formulation. Only the F5-F7 formulations were similar to the reference formulation F4. The mean dissolution time was around 10 h for the successful formulation.