Non-degradable microparticles containing a hydrophilic and/or a lipophilic drug: preparation, characterization and drug release modeling

Distinguishing nanoparticle drug release mechanisms by asymmetric flow field-flow fractionation

This research demonstrates the development, application, and mechanistic value of a multi-detector asymmetric flow field-flow fractionation (AF4) approach to acquire size-resolved drug loading and release profiles from polymeric nanoparticles (NPs). AF4 was hyphenated with multiple online detectors, including dynamic and multi-angle light scattering for NP size and shape factor analysis, fluorescence for drug detection, and total organic carbon (TOC) to quantify the NPs and dissolved polymer in nanoformulations. The method was demonstrated on poly(lactic-co-glycolic acid) (PLGA) NPs loaded with coumarin 6 (C6) as a lipophilic drug surrogate. The bulk C6 release profile using AF4 was validated against conventional analysis of drug extracted from the NPs and complemented with high performance liquid chromatography - quadrupole time-of-flight (HPLC-QTOF) mass spectrometry analysis of oligomeric PLGA species. Interpretation of the bulk drug release profile was ambiguous, with several release models yielding reasonable fits. In contrast, the size-resolved release profiles from AF4 provided critical information to confidently establish the release mechanism. Specifically, the C6-loaded NPs exhibited size-independent release rate constants and no significant NP size or shape transformations, suggesting surface desorption rather than diffusion through the PLGA matrix or erosion. This conclusion was supported through comparative experimental evaluation of PLGA NPs carrying a fully entrapped drug, enrofloxacin, which showed size-dependent diffusive release, along with density functional theory (DFT) calculations indicating a higher adsorption affinity of C6 onto PLGA. In summary, the development of the size-resolved AF4 method and data analysis framework fulfills salient analytical gaps to determine drug localization and release mechanisms from nanomedicines.

Impact of dispersion time interval and particle size on release profiles of propranolol HCl and carbamazepines from microparticle blends system

The objective of this study was to investigate the effect of dispersion time interval (DTI) on physicochemical properties of drug following the incorporation of propranolol HCl (Pro) and carbamazepine (CBZ) within ethyl cellulose (EC) microparticle blends using solvent evaporation method. The first Pro emulsion and second CBZ oil phase were dispersed in an external aqueous phase, with DTI of 0 and 60 min. The morphology of microparticle blends were characterized by SEM. The particle size mean of the emulsion droplets/hardened microparticles were monitored by FBRM. Encapsulation efficiency (EE) and in vitro drug release were also investigated. The resulting microparticle blends were spherical and formed two populations. The particle size mean of microparticle blends ranged from 113.27 µm to 122.42 µm. The EE was 77.28% to 78.64% for Pro and 96.48% to 98.64% for CBZ. FBRM studies showed that the size of microparticle blend prepared as W/O/W (Pro) and O/W (CBZ) system with DTI of 60 min and stirring time 4 h were larger than those prepared with DTI of 0 min. In vitro drug release studies after 28 days that revealed the CBZ release (58.72%) was faster than Pro release (43.16%). Investigation on surface morphology by SEM showed that the second drug CBZ which added as the oil phase in the W/O/W emulsion system had blocked the pores on the surface Pro microparticles prepared from the first primary emulsion, therefore affecting the drug release. This blocking effects of second drug (CBZ) on first emulsion microparticles (Pro) depended on the DTI. This phenomenon is only applicable if the first primary emulsion is W/O/W system.

Toward a new generation of vaginal pessaries via 3D-printing: concomitant mechanical support and drug delivery

To improve patient adherence, vaginal pessaries - polymeric structures providing mechanical support to treat stress urinary incontinence (SUI) - greatly benefit from 3D-printing through customization of their mechanics, e.g. infill modifications. However, currently only limited polymers provide both flawless printability and controlled drug release. The current study closes this gap by exploring 3D-printing, more specifically fused filament fabrication, of pharmaceutical grade thermoplastic polyurethanes (TPU) of different hardness and hydrophilicity into complex pessary structures. Next to the pessary mechanics, drug incorporation into such a device was addressed for the first time. Mechanically, the soft hydrophobic TPU was the most promising candidate for pessary customization, as pessaries made thereof covered a broad range of the key mechanical parameter, while allowing self-insertion. From the drug release point of view, the hydrophobic TPUs were superior over the hydrophilic one, as the release levels of the model drug acyclovir were closer to the target value. Summarizing, the fabrication of TPU-based pessaries via 3D-printing is an innovative strategy to create a customized pessary combination product that simultaneously provides mechanical support and pharmacological therapy.

Nanosponge Approach -A Plethora of Opportunities as a Promising Nanocarrier for Novel Drug Delivery

BACKGROUND

Nanotechnology is the need of the hour! The design of nanotechnologyaided carriers as a tool for the delivery of low solubility molecules offers a potential platform to overcome the issues of current clinical treatment and achieve good targeted release and bioaccessibility.

OBJECTIVE

Nanosponges (NS) encapsulate types of nanocarriers capable of carrying both lipophilic and hydrophilic substances. They are synthesized by mixing a solution of polyester, which is biodegradable, with cross-linkers. These tiny, porous structures are round-shaped, having multiple cavities wherein drugs can be housed to offer programmable release.

METHODS

The detailed literature review and patent search summarize the ongoing research on NS. Substances such as poorly soluble drugs, nutraceuticals, gases, proteins and peptides, volatile oils, genetic material, etc., can be loaded on these novel carriers, which are characterized using various analytical techniques. Target-specific drug delivery and controlled drug release are the advantages offered by NS, along with a myriad of other promising applications.

RESULTS

This review stresses the development of cyclodextrin-based NS, the synthetic methods and characterization of NS, along with factors affecting NS formation, their applications and information on the patented work in this area. NS are solid in character and can be formulated in various dosage forms, such as parenteral, topical, oral or inhalation.

CONCLUSION

Therefore, owing to their promising benefits over other nanocarriers in terms of drug loading, adaptability, sustainability, solubility and tailored release profile, NS is an immediate technological revolution for drug entrapment and as novel drug carriers.The authors expect that these fundamental applications of NS could help the researchers to develop and gain insight about NS in novel drug delivery applications.

Asymmetric flow field-flow fractionation (AF4) with fluorescence and multi-detector analysis for direct, real-time, size-resolved measurements of drug release from polymeric nanoparticles

Polymeric nanoparticles (NPs) are typically designed to enhance the efficiency of drug delivery by controlling the drug release rate. Hence, it is critical to obtain an accurate drug release profile. This study presents the first application of asymmetric flow field-flow fractionation (AF4) with fluorescence detection (FLD) to quantify release profiles of fluorescent drugs from polymeric NPs, specifically poly(lactic-co-glycolic acid) NPs loaded with enrofloxacin (PLGA-Enro NPs). In contrast to conventional measurements requiring separation of the NPs and dissolved drugs (typically by dialysis) prior to quantification, AF4 provides in situ removal of unincorporated drugs, while the judicious combination of online FLD and UV detection selectively provides the entrapped drug and PLGA NP concentrations, respectively, and hence the drug loading. NP size and shape factors are simultaneously obtained by online dynamic and multi-angle light scattering (DLS, MALS) detectors. The AF4 and dialysis approaches were compared to evaluate drug release from PLGA-Enro NPs containing a high proportion (≈ 94%) of unincorporated (burst release) drug at three temperatures spanning the glass transition temperature (T_g ≈ 33 °C) of the NPs. The AF4 method clearly captured the temperature dependence of the drug release relative to T_g (from no release at 20 °C to rapid release at 37 °C). In contrast, dialysis was not able to distinguish differences in the extent or rate of release of the entrapped drug because of interferences from the burst release, as well as the dialysis lag time, as supported through a diffusion model and validation experiments on purified NPs with low burst release. Finally, the multi-detector AF4 analysis yielded unique size-dependent release profiles across the entire NP size distribution, with smaller NPs showing faster release consistent with radial diffusion from the NPs. Overall, this study demonstrates the novel application and advantages of multi-detector AF4 methods, particularly AF4-FLD, to obtain direct, size-resolved release profiles of fluorescent drugs from polymeric NPs.

Optimized Taste-Masked Microparticles for Orally Disintegrating Tablets as a Promising Dosage Form for Alzheimer's Disease Patients

The objective of this research was to optimize the tasted-masked microparticles for orally disintegrating tablets containing donepezil hydrochloride using quality risk assessment and design of experiment approaches. The double emulsion solvent evaporation technique using aminoalkyl methacrylate copolymer (AMC) was used to prepare taste-masked microparticles. Factors affecting the quality of the taste-masked microparticles were analyzed using an Ishikawa diagram. A risk-ranking approach was used to rank the formulation and process risks. Furthermore, the effect of AMC quantity, stirring time, and volume of outer water phase on various responses, such as particle size, the amount of drug dissolved at 5 min (Q5) in simulated saliva fluid, and mean dissolution time (MDT) in simulated gastric fluid, was investigated using the Box-Behnken design. The optimized microparticles were then used to prepare orally disintegrating tablets (ODTs) and evaluated by in vitro and in vivo testing. The results demonstrated that particle size was influenced by the AMC amount and stirring time. Q5 was significantly affected by the amount of AMC and the volume of the outer water phase. On the other hand, these two factors had a positive effect on MDT. The optimized microparticles had a particle size of 174.45 ± 18.19 µm, Q5 of 5.04%, and MDT of 5.97 min. The ODTs with taste-masked microparticles showed acceptable in vitro dissolution with an MDT of 5 min. According to the results of a panel of six human volunteers, they greatly improved palatability.

Sustained Release Drug Delivery Applications of Polyurethanes

Since their introduction over 50 years ago, polyurethanes have been applied to nearly every industry. This review describes applications of polyurethanes to the development of modified release drug delivery. Although drug delivery research leveraging polyurethanes has been ongoing for decades, there has been renewed and substantial interest in the field in recent years. The chemistry of polyurethanes and the mechanisms of drug release from sustained release dosage forms are briefly reviewed. Studies to assess the impact of intrinsic drug properties on release from polyurethane-based formulations are considered. The impact of hydrophilic water swelling polyurethanes on drug diffusivity and release rate is discussed. The role of pore formers in modulating drug release rate is examined. Finally, the value of assessing mechanical properties of the dosage form and approaches taken in the literature are described.

In vitro and in vivo evaluation of Δ⁹-tetrahidrocannabinol/PLGA nanoparticles for cancer chemotherapy

Nanoplatforms can optimize the efficacy and safety of chemotherapy, and thus cancer therapy. However, new approaches are encouraged in developing new nanomedicines against malignant cells. In this work, a reproducible methodology is described to prepare Δ(9)-tetrahidrocannabinol (Δ(9)-THC)-loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles against lung cancer. The nanoformulation is further improved by surface functionalization with the biodegradable polymers chitosan and poly(ethylene glycol) (PEG) in order to optimize the biological fate and antitumor effect. Mean nanoparticle size (≈ 290 nm) increased upon coating with PEG, CS, and PEG-CS up to ≈ 590 nm, ≈ 745 nm, and ≈ 790 nm, respectively. Surface electrical charge was controlled by the type of polymeric coating onto the PLGA particles. Drug entrapment efficiencies (≈ 95%) were not affected by any of the polymeric coatings. On the opposite, the characteristic sustained (biphasic) Δ(9)-THC release from the particles can be accelerated or slowed down when using PEG or chitosan, respectively. Blood compatibility studies demonstrated the adequate in vivo safety margin of all of the PLGA-based nanoformulations, while protein adsorption investigations postulated the protective role of PEGylation against opsonization and plasma clearance. Cell viability studies comparing the activity of the nanoformulations against human A-549 and murine LL2 lung adenocarcinoma cells, and human embryo lung fibroblastic MRC-5 cells revealed a statistically significant selective cytotoxic effect toward the lung cancer cell lines. In addition, cytotoxicity assays in A-549 cells demonstrated the more intense anticancer activity of Δ(9)-THC-loaded PEGylated PLGA nanoparticles. These promising results were confirmed by in vivo studies in LL2 lung tumor-bearing immunocompetent C57BL/6 mice.

Preparation and In Vitro Evaluation of Ethylcellulose and Polymethacrylate Resins Loaded Microparticles Containing Hydrophilic Drug

Objective. The purpose of the recent study was to prepare and estimate sustained release of Ethylcellulose (300 cps) and Eudragit (RS 100 and RL 100) microparticles containing Propranolol hydrochloride used as a treatment of cardiovascular system, especially hypertension. Method. Propranolol hydrochloride was microencapsulated with different polymers (Ethylcellulose, Eudragit RS, and Eudragit RL) using modified hydrophobic (O/O) solvent evaporation method using 1 : 1 combination of acetone and isopropanol as the internal phase. Obtained microparticles were showing higher batch yield with higher encapsulation efficiency. Microparticles were prepared with different ratios of 1 : 1, 1 : 3, 1 : 5, and 1 : 7 (%, wt/wt) using span 80 (%, v/v) as a surfactant. Results. The influence of formulation factors like drug: polymer ratio, internal phase, and type of polymers on obtained microparticles was characterized with respect to particle size distribution, encapsulation efficiency, percentage yield, FTIR, and FE-SEM. Higher encapsulation efficiencies were obtained with various polymers like Ethylcellulose (96.63 ± 0.5) compared to Eudragit RS 100 (83.70 ± 0.6) and RL 100 (89.62 ± 0.6). The in vitro release study was characterized by initial burst. Conclusion. The result of study displays that Ethylcellulose and Eudragit loaded microparticles of Propranolol hydrochloride can be effectively prepared using modified hydrophobic emulsification solvent evaporation technique. Therefore, the modified hydrophobic emulsion technique can also be applied to the preparation of microparticles for low molecular weight and highly water soluble drugs.

Cyclodextrin based nanosponges for pharmaceutical use: a review

Nanosponges are a novel class of hyper-crosslinked polymer based colloidal structures consisting of solid nanoparticles with colloidal sizes and nanosized cavities. These nano-sized colloidal carriers have been recently developed and proposed for drug delivery, since their use can solubilize poorly water-soluble drugs and provide prolonged release as well as improve a drug's bioavailability by modifying the pharmacokinetic parameters of actives. Development of nanosponges as drug delivery systems, with special reference to cyclodextrin based nanosponges, is presented in this article. In the current review, attempts have been made to illustrate the features of cyclodextrin based nanosponges and their applications in pharmaceutical formulations. Special emphasis has been placed on discussing the methods of preparation, characterization techniques and applications of these novel drug delivery carriers for therapeutic purposes. Nanosponges can be referred to as solid porous particles having a capacity to load drugs and other actives into their nanocavity; they can be formulated as oral, parenteral, topical or inhalation dosage forms. Nanosponges offer high drug loading compared to other nanocarriers and are thus suitable for solving issues related to stability, solubility and delayed release of actives. Controlled release of the loaded actives and solubility enhancement of poorly water-soluble drugs are major advantages of nanosponge drug delivery systems.

Modeling the response of a biofilm to silver-based antimicrobial

Biofilms are found within the lungs of patients with chronic pulmonary infections, in particular patients with cystic fibrosis, and are the major cause of morbidity and mortality for these patients. The work presented here is part of a large interdisciplinary effort to develop an effective drug delivery system and treatment strategy to kill biofilms growing in the lung. The treatment strategy exploits silver-based antimicrobials, in particular, silver carbene complexes (SCC). This manuscript presents a mathematical model describing the growth of a biofilm and predicts the response of a biofilm to several basic treatment strategies. The continuum model is composed of a set of reaction-diffusion equations for the transport of soluble components (nutrient and antimicrobial), coupled to a set of reaction-advection equations for the particulate components (living, inert, and persister bacteria, extracellular polymeric substance, and void). We explore the efficacy of delivering SCC both in an aqueous solution and in biodegradable polymer nanoparticles. Minimum bactericidal concentration (MBC) levels of antimicrobial in both free and nanoparticle-encapsulated forms are estimated. Antimicrobial treatment demonstrates a biphasic killing phenomenon, where the active bacterial population is killed quickly followed by a slower killing rate, which indicates the presence of a persister population. Finally, our results suggest that a biofilm with a ready supply of nutrient throughout its depth has fewer persister bacteria and hence may be easier to treat than one with less nutrient.

Biodegradable microparticulate drug delivery system of diltiazem HCl

The efficacy of a drug in a specific application requires the maintenance of appropriate drug blood level concentration during a prolonged period of time. Controlled release delivery is available for many routes of administration and offers many advantages (as microparticles and nanoparticles) over immediate release delivery. These advantages include reduced dosing frequency, better therapeutic control, fewer side effects, and, consequently, these dosage forms are well accepted by patients. Advances in polymer material science, particle engineering design, manufacture, and nanotechnology have led the way to the introduction of several marketed controlled release products and several more are in pre-clinical and clinical development. The objective of this work is to prepare and evaluate diltiazem HCl loaded albumin microparticles using a factorial design. Albumin (natural polymer) microparticles were prepared by emulsion heat-stabilization method. Selected formulations were characterized for their entrapment efficiency, particle size, surface morphology, and release behavior. Analysis of variance for entrapment efficiency indicates that entrapment efficiency is best fitted to a response surface linear model. Surface morphology was studied by scanning electron microscopy. Scanning electron microscopy of the microparticles revealed a spherical, nonporous and uniform appearance, with a smooth surface. The geometric mean diameter of the microparticles was found to be 2-9 µm, which more than 75% were below 3.5 µm and drug incorporation efficiency of 59.74 to 72.48% (w/w). In vitro release profile for formulations containing diltiazem HCl loaded BSA microparticles with heat stabilization technique shows slow controlled the release of the drug up to 24 hours. The release pattern was biphasic, characterized by an initial burst effect followed by a slow release. All selected microparticles exhibited a prolonged release for almost 24 hours. On comparing regression-coefficient (r²) values for Hixson Crowel, Higuchi and Peppas kinetic models, different batches of microparticles showed Fickian, non-Fickian, and diffusion kinetics. The release mechanism was regulated by D:P ratio. From the statistical analysis it was observed that as the drug:polymer (D:P) ratio increased, there was a significant increase in the encapsulation efficiency. Based on the particle size, entrapment efficiency and physical appearance, DTM-3 formulations were selected for in vivo release study and stability study. The in vivo result of drug loaded microparticles showed preferential drug targeting to liver followed by lungs, kidneys and spleen. Stability studies showed that maximum drug content and closest in vitro release to initial data were found in the formulation stored at 4 ºC. In present study, diltiazem HCl loaded BSA microparticles were prepared and targeted to various organs to satisfactory level and were found to be stable at 4 ºC.

A chitosan lactate/poloxamer 407-based matrix containing Eudragit RS microparticles for vaginal delivery of econazole: design and in vitro evaluation

A matrix based on chitosan lactate and poloxamer 407 was evaluated as a delivery system for the vaginal administration of the antifungal drug econazole. The matrix was investigated both containing the pure drug and after introducing microparticles of Eudragit RS 100 containing econazole. Eudragit RS 100 microparticles were prepared using an emulsion-extraction method and dispersed in a solution containing chitosan lactate (2% w/w) and poloxamer 407 (1.7% w/w). The microparticles, obtained with a yield of 64% w/w and an encapsulation efficiency of 42% w/w, had a diameter of less than 2 μm and a drug loading of 13% w/w. The compressed matrices, characterized by DSC, swelling, erosion, release and mucoadhesion studies, had behaviours dependent on the relative amounts of the contained microparticles. The matrix without microparticles (MECN) showed zero-order release kinetics, with a maximum drug-release of 60% w/w, while those containing 50 or 75% w/w microparticles showed a diffusion controlled release up to 8 and 16 h, respectively, and a linear trend after those time intervals, caused by the erosion process, which allowed reaching a drug-release of approximately 100% w/w at 22 h. In in vitro experiments, the matrices were mucoadhesive and active in inhibiting the growth of Candida albicans 796.

Prospects of pharmaceuticals and biopharmaceuticals loaded microparticles prepared by double emulsion technique for controlled delivery

Several methods and techniques are potentially useful for the preparation of microparticles in the field of controlled drug delivery. The type and the size of the microparticles, the entrapment, release characteristics and stability of drug in microparticles in the formulations are dependent on the method used. One of the most common methods of preparing microparticles is the single emulsion technique. Poorly soluble, lipophilic drugs are successfully retained within the microparticles prepared by this method. However, the encapsulation of highly water soluble compounds including protein and peptides presents formidable challenges to the researchers. The successful encapsulation of such compounds requires high drug loading in the microparticles, prevention of protein and peptide degradation by the encapsulation method involved and predictable release, both rate and extent, of the drug compound from the microparticles. The above mentioned problems can be overcome by using the double emulsion technique, alternatively called as multiple emulsion technique. Aiming to achieve this various techniques have been examined to prepare stable formulations utilizing w/o/w, s/o/w, w/o/o, and s/o/o type double emulsion methods. This article reviews the current state of the art in double emulsion based technologies for the preparation of microparticles including the investigation of various classes of substances that are pharmaceutically and biopharmaceutically active.

A novel impinging aerosols method for production of propranolol hydrochloride-loaded alginate gel microspheres for oral delivery

Propranolol hydrochloride was directly encapsulated in alginate gel microspheres (40-50 µm in diameter) using a novel method involving impinging aerosols of CaCl(2) cross-linking solution and sodium alginate solution containing the drug. Microspheres formulated using 0.1 M CaCl(2) exhibited the highest drug loading (14%, w/w of dry microspheres) with 66.5% encapsulation efficiency. Less than 4% and 35% propranolol release occurred from hydrated and dried microspheres, respectively, in 2 h in simulated gastric fluid (SGF). The majority of the drug load (90%) was released in 5 and 7 h from hydrated and dried microspheres, respectively, in simulated intestinal fluid (SIF). Prior incubation of hydrated microspheres (cross-linked using 0.5 M CaCl(2)) in SGF prolonged the time of release in SIF to 10 h, which has implications for the design of protocols and correlation with in vivo release behaviour. Restricted propranolol release in SGF and complete extraction in SIF demonstrate the potential of alginate gel microspheres for oral delivery of pharmaceuticals.

Biodegradable microspheres loaded with an anti-Parkinson prodrug: an in vivo pharmacokinetic study

During chronic treatment with L-dopa (LD), Parkinsonian patients often experience uncontrolled motor complications due to fluctuations of the plasmatic levels of LD that result in pulsatile dopaminergic stimulation. To overcome these plasmatic fluctuations, a novel prodrug of LD, L-dopa-α-lipoic acid (LD-LA), has been proposed as a tool for achieving continuous dopaminergic stimulation. Due to slower susceptibility toward enzymatic conversion by LD-degrading enzymes (such as catechol-O-methyltransferase and monoamine oxidase), the plasma half-life of this prodrug is longer than that of LD. Moreover, the higher lipophilicity of LD-LA over LD promotes its delivery to the CNS, where the resulting levels of dopamine (DA) are kept high for a longer time than after equimolar administration of LD. To further reduce fluctuations in plasma levels of LD, LD-LA has been entrapped into biodegradable polymeric microspheres to be used as a depot system with the aim to prevent prodrug degradation and to obtain a sustained release of the intact compound. In the present work, a formulation of LD-LA loaded microspheres (characterized for drug loading, size, morphology, thermal properties, and in vitro prodrug release) has been administered subcutaneously to rats, and the resulting levels of LD and DA in plasma and striatal tissue, respectively, have been monitored. A good correlation between the in vitro release kinetics and the time range during which the formulation alters the LD/DA tissue levels in vivo was observed, suggesting that the polymeric microsphere matrix protects the loaded prodrug from chemical and enzymatic degradation and controls its release. Interestingly, LD-LA microspheres provided sustained levels of DA neurotransmitter in the striatum nucleus for up to 4 days after a single administration. In conclusion, a polymeric microsphere formulation of LD-LA is an attractive medicine for treating Parkinson's disease (PD) symptoms, avoiding motor complications.

Development and in vitro-in vivo evaluation of fenretinide-loaded oral mucoadhesive patches for site-specific chemoprevention of oral cancer

PURPOSE

To develop fenretinide oral mucoadhesive patch formulations and evaluate their in vitro and in vivo release performance for future site-specific chemoprevention of oral cancer.

METHODS

Solubilization of fenretinide in simulated saliva (SS) was studied by incorporating nonionic surfactants (Tween® 20 and 80, and Brij® 35 and 98), bile salts (sodium salt of cholic, taurocholic, glycocholic, and deoxycholic acids), phospholipid (lecithin), and novel polymeric solubilizer (Souplus®). Adhesive (polycarbophil: hydroxypropyl methylcellulose 4KM) and drug release (Fenretinide/Eudragit® RL PO with or without solubilizers) layers were prepared by solvent casting. Oral mucoadhesive patches were formed by attaching drug and adhesive layers onto backing layer (Tegaderm™ film). Physical state of drug in Eudragit® films was examined by X-ray diffraction (XRD). Evaluation of in vitro and in vivo fenretinide release from the patch was conducted in SS containing 5%w/v sodium deoxycholate and rabbits, respectively. Fenretinide was quantified by HPLC.

RESULTS

Tween® 20 and 80, Brij® 98, and sodium deoxycholate exhibited the highest fenretinide solubilization potential among the solubilizers. Drug loading efficiency in Eudragit® films was 90%-97%. XRD suggested fenretinide was amorphous in solubilizer-free and solubilizer-loaded films. Solubilizer-free patch exhibited poor in vitro and in vivo controlled drug release behavior. Increases in drug loading (5-10 wt%) or changes in polymeric matrix permeability did not provide continuous drug release. Co-incorporation of either single or mixed solubilizers in fenretinide/Eudragit® patches, (20 wt% Tween® 20, Tween® 80 and sodium deoxycholate or 20 wt% Tween® 80 + 40 wt% sodium deoxycholate solubilizers) led to significantly improved continuous in vitro/in vivo fenretinide release.

CONCLUSION

Fenretinide/Eudragit® RL PO patches with 20 wt% Tween® 80 + 40 wt% sodium deoxycholate solubilizers exhibit excellent release behavior for further preclinical and/or clinical evaluation in oral cancer chemoprevention.

Drug-carrying albumin film for blood-contacting biomaterials

Surface-induced thrombosis is a major complication in the development of blood-contacting medical devices. Serum albumin has the ability to bind to a wide variety of compounds, including drugs, and neither cells nor proteins adsorb to an albumin-coated surface. These properties of albumin are useful for improving the blood compatibility of biomaterial surfaces. In the present study, we prepared a water-insoluble film by cross-linking pharmaceutical grade recombinant human serum albumin aiming to the clinical applications, and loaded the film with a synthetic antiplatelet drug, cilostazol. The resultant film possessed native albumin characteristics such as drug binding ability and resistance to cell adhesion. Mouse fibroblast L929 cells did not adhere on the albumin film, just as they did not adhere on native albumin-coated surfaces. Furthermore, when the albumin film carrying cilostazol was placed in PBS containing Tween-80, the release of cilostazol was sustained over 144 h. The results indicate that the surface coating with thus prepared albumin film can confer the biomaterials with antithrombogenic surface by virtue of its non-adhesiveness to cells and its release of cilostazol.

Drug-eluting polymer implants in cancer therapy

BACKGROUND

Drug-eluting polymer implants present a compelling parenteral route of administration for cancer chemotherapy. With potential for minimally invasive, image-guided placement and highly localized drug release, these delivery systems are playing an increasingly important role in cancer management. This is particularly true as the use of labile proteins and other bioactive molecules is likely to increase in the upcoming years.

OBJECTIVE

In this review, we present the current trends in the application of Pre-formed and in situ-forming systems as drug-eluting implants for cancer chemotherapy.

METHODS

We outline the clinically available options as well as up-and-coming technologies and their advantages and challenges. We also describe ongoing related innovations with image-guided drug delivery, mathematical modeling of implanted delivery systems and implanted drug delivery in combination with other therapies.

RESULTS/CONCLUSION

Whether used alone or combined with other minimally invasive procedures, drug-eluting polymeric implants will play a significant role in the future of cancer management.

Influence of polymers on the bioavailability of microencapsulated celecoxib

Celecoxib, a selective COX-2 inhibitor, primarily used in treatment of osteoarthritis, rheumatoid arthritis and acute pain was encapsulated in microparticles composed of various polyesters, polymethacrylates or cellulose derivatives used alone or blended. The influence of polymers on microparticle mean diameter, encapsulation efficiency and in vitro and in vivo celecoxib release was investigated. Microparticles were in the size range 11-37 microm. Encapsulation efficiency was optimal due to poor aqueous solubility of celecoxib. Considering in vitro release, microparticles could be divided into drug delivery systems with fast and slow release profiles. Microparticles prepared with poly-epsilon-caprolactone, Eudragit RS and low viscosity ethylcellulose, together with physical mixture of celecoxib with lactose and Celebrex, were tested in vivo. Relative bioavailability of celecoxib was below 20% in all cases and was probably the consequence of a slow in vivo release of celecoxib from microparticles or low wettability in the case of Celebrex and physical mixture.

A mechanistic model of controlled drug release from polymer millirods: Effects of excipients and complex binding

The incorporation of different cyclodextrin (CD) excipients such as HPbeta-CD, beta-CD, gamma-CD or alpha-CD into polymer millirods for complexing beta-lapachone (beta-lap), a potent anti-cancer drug, significantly improved the drug release kinetics with various drug release patterns. However, such a complex system requires a mechanistically based model in order to provide a quantitative understanding of the many molecular events and processes that are essential for the rational development of millirod implants. This study focuses on mathematical modeling of drug release from PLGA cylindrical millirods. This millirod system incorporates multiple components: a PLGA matrix; excipient in free and complex forms; drug in free, bound, and crystalline forms. The model characterizes many dynamic transport and complexation processes that include radial diffusion, excipient complexation and crystalline drug dissolution. Optimal estimates of the model parameters were obtained by minimizing the difference between model simulation and experimentally measured drug release kinetics. The effects of different drug loadings on the drug release rate were simulated and compared with other data to validate this model. Whereas our model can simulate all the experimental data, the Higuchi model can simulate only some of them. Furthermore, our model incorporates mechanisms by which the processes underlying drug release from a polymer matrix can be quantitatively analyzed. These processes include drug entrapment/dissolution in the matrix, drug recrysallization, and supersaturation. This modeling study shows that complex binding capacity, which affects drug initial conditions, drug-polymer interactions, and bound drug behavior in aqueous solution, is crucial in controlling drug release kinetics.

Oil-in-oil microencapsulation technique with an external perfluorohexane phase

Commonly, the microencapsulation of a lipophilic drug in a polymeric matrix via an ordinary oil/oil emulsification allows entrapping limited drug amounts due to its loss into the external phase. In this present paper, a new microencapsultion method describes the use of perfluorohexane as an external oil phase in order to produce microparticles of polyvinylpyrrolidon/vinylacetate (copovidone) and Eudragit RS. Due to its highly non-solvent properties to most compounds, very limited miscibility with organic solvents, and very low toxicity, perfluorohexane (PFH) represents an excellent liquid for an external phase of the emulsion. Copovidone and Eudragit RS microparticles were prepared by an oil/PFH method trapping ibuprofen as a lipophilic model drug and compared to results from conventional methods (oil/water and oil/oil). Morphological analyses of the obtained particles underlined the general matrix structure. The particle size varied between 75microm (oil/oil) and 400microm (oil/PFH) largely influenced by the stirring speed. Although drug release kinetics were principally similar for all preparation methods, it was generally found that encapsulation rates of oil/water and oil/PFH systems (oil/water: 74+/-9%; oil/PFH: 86+/-10%) were superior to ordinary oil/oil emulsification (3+/-1%). The use of PFH was found to be a new promising tool for the preparation of microparticles. This modified emulsification method allowed the entrapment of lipophilic drugs into hydrophilic or lipophilic polymers in the absence of an aqueous phase.

Slow release of molecules in self-assembling peptide nanofiber scaffold

Biological hydrogels consisting of self-assembling peptide nanofibers are potentially excellent materials for various controlled molecular release applications. The individual nanofiber consists of ionic self-complementary peptides with 16 amino acids (RADA16, Ac-RADARADARADARADA-CONH(2)) that are characterized by a stable beta-sheet structure and undergo self-assembly into hydrogels containing approximately 99.5% w/v water. We report here on the diffusion properties of phenol red, bromophenol blue, 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (pyranine, 3-PSA), 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt (4-PSA), and Coomassie Brilliant Blue G-250 (CBBG) through RADA16 hydrogels. The apparent diffusivity (D ) of phenol red (1.05+/-0.08 x 10(-10) m(2) s(-1)) is higher than that of 3-PSA (0.050+/-0.004 x 10(-10) m(2) s(-1)) and 4-PSA (0.007+/-0.002 x 10(-10) m(2) s(-1)). The difference in 3-PSA and 4-PSA diffusivities suggests that the sulfonic acid groups directly facilitate electrostatic interactions with the RADA16 fiber surface. Bromophenol blue and CBBG were not released from the hydrogel, suggesting that they interact strongly with the peptide hydrogel scaffold. The diffusivities (D ) of the dyes decreased with increasing hydrogel peptide concentration, providing an alternate route of controlling release kinetics. These results indicate that release profiles can be tailored through controlling nanofiber-diffusant molecular level interactions.

Evaluation of ciprofloxacin-loaded Eudragit® RS100 or RL100/PLGA nanoparticles

The objective of present study was to prepare positively charged ciprofloxacin-loaded nanoparticles providing a controlled release formulation. The particles were prepared by water-in-oil-in-water (w/o/w) emulsification and solvent evaporation, followed by high-pressure homogenisation. Two non-biodegradable positively charged polymers, Eudragit RS100 and RL100, and the biodegradable polymer poly(lactic-co-glycolic acid) or PLGA were used alone or in combination, with varying ratios. The formulations were evaluated in terms of particle size and zeta potential. Differential scanning calorimetry measurements were carried out on the nanoparticles and on the pure polymers Eudragit and PLGA. Drug loading and release properties of the nanoparticles were examined. The antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus was determined. During solvent evaporation, the size and zeta potential of the nanoparticles did not change significantly. The mean diameter was dependent on the presence of Eudragit and on the viscosity of the organic phase. The zeta potential of all Eudragit containing nanoparticles was positive in ultrapure water (around +21/+25 mV). No burst effect but a prolonged drug release was observed from all formulations. The particles' activity against P. aeruginosa and S. aureus was comparable with an equally concentrated ciprofloxacin solution.

pH-Sensitive Polymer Blends Used as Coating Materials to Control Drug Release from Spherical Beads: Elucidation of the Underlying Mass Transport Mechanisms

PURPOSE

To elucidate the drug release mechanisms from pellets coated with pH-sensitive polymer blends.

METHODS

Verapamil hydrochloride-loaded beads were coated with various blends of a water-insoluble and an enteric polymer, ethylcellulose:Eudragit L and Eudragit NE:Eudragit L, respectively. Both experimental and theoretical techniques were used to characterize the systems before and upon exposure to 0.1 M HCl and phosphate buffer (pH 7.4).

RESULTS

Using analytical solutions of Fick's second law of diffusion, optical and scanning electron microscopy, and mechanical and gravimetric analysis, new insight into the underlying drug release mechanisms could be gained. More importantly, the latter can be effectively altered by varying the type of polymer blend and blend ratio. For example, at low pH drug release is primarily controlled by diffusion through the intact film coatings in Eudragit NE:Eudragit L blends, whereas crack formation is of major importance in ethylcellulose:Eudragit L-coated systems. At high pH, the (partial) leaching of the enteric polymer out of the coatings plays an important role. In all cases, the observed drug release profiles could be explained based on the occurring mass transport processes.

CONCLUSIONS

The obtained new knowledge can be used to effectively adjust desired drug release mechanisms and, thus, release patterns.