Spray-dried lactose composite particles containing an ion complex of alginate-chitosan for designing a dry-coated tablet having a time-controlled releasing function

Recent research advances on oral colon-specific delivery system of nature bioactive components: A review

Oral colon-specific delivery system (OCDS) is a targeted approach that aims to directly deliver bioactive compounds directly to the colon following oral administration, thereby enhancing the colonic release of bioactive substances and minimizing adverse reactions. The effectiveness of bioactive substances in the colon hinges on the degree of release, which are affected by various factors including pH, mucosal barrier, delivery time and so on. Therefore, this review provides a comprehensive overview of the key factors affecting oral colon-specific release of bioactive components firstly. Considering the oral safety, this review then mainly focuses on the types of carriers with edible OCDS and preparation strategies for OCDS. Finally, several preparation strategies for loading typical natural bioactive ingredients into oral safe OCDS are reviewed, along with future development prospects.

[Particle Design Strategies for Developing Patient Centric Dosage Form Preparations]

Novel dosage form designs aiming at patient centric drug therapy are summarized here based on my carrier research in this field. The common key word for this research is particle design. The topics will be divided into two parts, based on the type of particle: coarse particles (powder) and colloidal particles. The former includes the preparation and characterization of functional particles prepared using a spray dryer. Solid dispersions, solvent deposition particles and dry emulsion systems are described. Polymer coated liposomes are described as a useful drug delivery carrier in several administration routes. As chitosan, a mucoadhesive polymer, was used as a coating polymer, the resultant chitosan-coated liposome was found to work as a good carrier for peptide drugs such as insulin and calcitonin in the gastrointestinal tract after oral administration. In another administration route (inhalation), polymer-coated liposomes enhanced the absorption of the drugs. Liposomal carriers applied to the surface of the eye as eye drops are able to deliver drugs to the posterior part of the eye, such as the retina. As a typical example of patient centric dosage form design, particle designs for the preparation of orally disintegrating tablets and films were introduced in one of our recent studies on oral dosage form design.

Challenges in technology of bilayer and multi-layer tablets: a mini-review

Bilayer and multi-layer tablets are enjoying growing popularity among original drug and generic product manufacturers. Multi-layer tablets have many key benefits compared to classic immediate-release tablets. The use of such solid oral dosage forms simplifies dosing regimens in combination therapy, and thus improves patient compliance. However, the technology of multilayer tablets is demanding and requires precise choice of excipients and production parameters with regard to each technological step. The main benefits of multi-layer tablets, certain aspects of their production and the challenges encountered during the compression process are reviewed in this paper.

Recyclable Fully Biobased Chitosan Adsorbents Spray-Dried in One Pot to Microscopic Size and Enhanced Adsorption Capacity

A facile one-pot spray-drying process was developed for fabrication and in situ crosslinking of chitosan microspheres to improve the adsorption capacity by microscopic design. A fully biobased nature was achieved by utilizing genipin (GP) as a crosslinking agent and chitosan-derived nanographene oxide (nGO) as a property tuner. The produced chitosan microspheres were further proven as powerful adsorbents for common wastewater contaminants such as anionic dyes and pharmaceutical contaminants, here modeled by methyl orange (MO) and diclofenac sodium (DCF). By regulating the amount of GP and nGO, as well as by controlling the process parameters including the spray-drying inlet temperature and postheat treatment, the surface morphology, size, zeta potential, and adsorption efficiency of the microspheres could be tuned accordingly. The adsorption efficiency for MO and DCF reached 98.9 and 100%, respectively. The microspheres retained high DCF adsorption efficiency after six adsorption and desorption cycles, and the recyclability was improved by the incorporated nGO. The fabricated microspheres, thus, have great potential as reusable and eco-friendly adsorbents.

Magnetic iron oxide nanoparticles (MIONs) cross-linked natural polymer-based hybrid gel beads: Controlled nano anti-TB drug delivery application

The nanosized rifampicin (RIF) has been prepared to increase the solubility in aqueous solution, which leads to remarkable enhancement of its bioavailability and their convenient delivery system studied by newly produced nontoxic, biodegradable magnetic iron oxide nanoparticles (MIONs) cross-linked polyethylene glycol hybrid chitosan (mCS-PEG) gel beads. The functionalization of both nano RIF and mCS-PEG gel beads were studied using various spectroscopic and microscopic techniques. The size of prepared nano RIF was found to be 70.20 ± 3.50 nm. The mechanical stability and swelling ratio of the magnetic gel beads increased by the addition of PEG with a maximum swelling ratio of 38.67 ± 0.29 g/g. Interestingly, this magnetic gel bead has dual responsive assets in the nano drug delivery application (pH and the magnetic field). As we expected, magnetic gel beads show higher nano drug releasing efficacy at acidic medium (pH = 5.0) with maximum efficiency of 71.00 ± 0.87%. This efficacy may also be tuned by altering the external magnetic field and the weight percentage (wt%) of PEG. These results suggest that such a dual responsive magnetic gel beads can be used as a potential system in the nano drug delivery applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1039-1050, 2018.

Curcumin encapsulation in submicrometer spray-dried chitosan/Tween 20 particles

Optimal curcumin delivery for medicinal applications requires a drug delivery system that both solubilizes curcumin and prevents degradation. To achieve this, curcumin has been encapsulated in submicrometer chitosan/Tween 20 particles via a benchtop spray-drying process. Spray-drying parameters have been optimized using a Taguchi statistical approach to minimize particle size and to favor spheroid particles with smooth surfaces, as evaluated with scanning electron microscopy (SEM) imaging. Nearly spherical particles with 285 ± 30 nm diameter and 1.21 axial ratio were achieved. Inclusion of curcumin in the spray-drying solution results in complete encapsulation of curcumin within the chitosan/Tween 20 particles. Release studies confirm that curcumin can be released completely from the particles over a 2 h period.

Production of monodisperse epigallocatechin gallate (EGCG) microparticles by spray drying for high antioxidant activity retention

Epigallocatechin gallate (EGCG) originated from green tea is well-known for its pharmaceutical potential and antiproliferating effect on carcinoma cells. For drug delivery, EGCG in a micro-/nanoparticle form is desirable for their optimized chemopreventive effect. In this study, first time reports that EGCG microparticles produced by low temperature spray drying can maintain high antioxidant activity. A monodisperse droplet generation system was used to realize the production of EGCG microparticles. EGCG microparticles were obtained with narrow size distribution and diameter of 30.24 ± 1.88 μM and 43.39 ± 0.69 μM for pure EGCG and lactose-added EGCG, respectively. The EC50 value (the amount of EGCG necessary to scavenge 50% of free radical in the medium) of spray dried pure EGCG particles obtained from different temperature is in the range of 3.029-3.075 μM compared to untreated EGCG with EC50 value of 3.028 μM. Varying the drying temperatures from 70°C and 130°C showed little detrimental effect on EGCG antioxidant activity. NMR spectrum demonstrated the EGCG did not undergo chemical structural change after spray drying. The major protective mechanism was considered to be: (1) the use of low temperature and (2) the heat loss from water evaporation that kept the particle temperature at low level. With further drier optimization, this monodisperse spray drying technique can be used as an efficient and economic approach to produce EGCG micro-/nanoparticles.

Protein micro and nanoencapsulation within glycol-chitosan/Ca²+/alginate matrix by spray drying

Encapsulation of therapeutic peptides and proteins into polymeric micro and nanoparticulates has been proposed as a strategy to overcome limitations to oral protein administration. Particles having diameter less than 5 µm are able to be taken up by the M cells of Peyer's patches found in intestinal mucosa. Current formulation methodologies involve organic solvents and several time consuming steps. In this study, spray drying was investigated to produce protein loaded micro/nanoparticles, as it offers the potential for single step operation, producing dry active-loaded particles within the micro to nano-range. Spherical, smooth surfaced particles were produced from alginate/protein feed solutions. The effect of operational parameters on particle properties such as recovery, residual activity and particle size was studied using subtilisin as model protein. Particle recovery depended on the inlet temperature of the drying air, and mean particle size ranged from 2.2 to 4.5 µm, affected by the feed rate and the alginate concentration in the feed solution. Increase in alginate:protein ratio increased protein stability. Presence of 0.2 g trehalose/g particle increased the residual activity up to 90%. Glycol-chitosan-Ca(2+)alginate particles were produced in a single step operation, with resulting mean diameter of 3.5 μm. Particles showed fluorescein isothiocyanate labeled bovine serum albumin (BSA)-protein entrapment with increasing concentration toward the particle surface. Similar, limited release profiles of BSA, subtilisin and lysozyme were observed in gastric simulation, with ultimate full release of the proteins in gastrointestinal simulation.

Systemic and mucosal delivery of drugs within polymeric microparticles produced by spray drying

Encapsulation of therapeutic and diagnostic materials into polymeric particles is a means to protect and control or target the release of active substances such as drugs, vaccines, and genetic material. In terms of mucosal delivery, polymeric encapsulation can be used to promote absorption of the active substance, while particles can improve the half-life of drugs administered systemically. Spray drying is an attractive technology used to produce such microparticles, because it combines both the encapsulation and drying steps in a rapid, single-step operation. Even so, spray drying is not classically associated with processes used for drug and therapeutic material encapsulation, since elevated temperatures could potentially denature the active substance. However, a comprehensive review of the literature revealed a number of studies demonstrating that spray drying can be used to produce microparticulate formulations with labile therapeutics. Polymers commonly employed include synthetics such as methacrylic copolymers and polyesters, and natural materials including chitosan and alginate. Drugs and active substances are diverse and included antibiotics, anti-inflammatory agents, and chemotherapeutics. Regarding the delivery of spray-dried particles, the pulmonary, oral, colonic, and nasal mucosal routes are often investigated because they offer a convenient means of administration, which promotes physician and patient compliance. In addition, spray drying has been widely used to produce polymeric microparticles for systemic delivery in order to control the delivery of drugs, vaccines, or genetic material that may exhibit poor pharmacokinetic profiles or pose toxicity concerns. This review presents a brief introduction to the technology of spray drying and outlines the delivery routes and the applications of spray-dried polymeric microparticles.

Predictable pulsatile release of tramadol hydrochloride for chronotherapeutics of arthritis

The present investigation deals with the development of a pH and time-dependent press-coated pulsatile drug delivery system for delivering drugs into the colon. The system consists of a drug containing core, coated by a combination of natural polymer Delonix regia gum (DRG) and hydroxypropyl methylcellulose (HPMC K4M) in various proportions, which controls the onset of release. The whole system was coated with methacrylic acid copolymers, which not only prevents the drug release in the stomach, but also prolongs the lag time. Tramadol HCl was used as a model drug and varying combinations of DRG and HPMC K4M were used to achieve the desired lag time before rapid and complete release of the drug in the colon. It was observed that the lag time depends on the coating ratio of DRG to HPMC and also on press coating weight. Drug release was found to be increased by 15-30% in the presence of colonic microbial flora. The results showed the capability of the system in achieving pulsatile release for a programmable period of time and pH-dependent release to attain colon-targeted delivery.

Useful Extend-release Chitosan Tablets with High Antioxidant Activity

The antioxidant properties of different low molecular weight (LMW) chitosans (CS1; 22 kDa, CS2; 38 kDa, CS3; 52 kDa, CS4; 81 kDa) were examined for possible use in extended-release tablets. The criteria used were the ability of the chitosans to reduce Cu2+, and hydroxyl and superoxide radicals and N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl, via the use of ESR spectrometry. CS2 showed the highest scavenging activity. CS1 and CS3, however, were much less effective and CS4 was not a viable antioxidant. The results suggest that CS2 could be useful in combating the development of oxidative stress. A series of chitosan tablets were prepared using a spray drying method and evaluated as an extended-release matrix tablet using theophylline (TPH) as a model drug. The release of TPH from the different MW chitosan tablets increased with increasing MW of the chitosan used. CS2, CS3 and CS4 showed a reasonable release activity, but CS1 showed the shortest release activity. Moreover, the CS2-TPH tablet showed the highest scavenging activity of the three chitosan tablets (CS2-CS4) using 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radicals. These results suggest that a CS2-TPH tablet could be potentially useful in an extended-release matrix tablet with a high antioxidant activity.

Alginate-crosslinked chitosan scaffolds as pentoxifylline delivery carriers

To prevent fibrous encapsulation of implants, measures are taken to suppress inflammatory reactions around them. Sustained anti-inflammatory drug release from the scaffolds can potentially be a way to reduce inflammation around these implants. Alginate-crosslinked chitosan is often used to make biocompatible tissue engineered scaffolds. However, there is a lack of quantitative studies on the drug delivery properties of alginate-crosslinked chitosan scaffolds. For this study, chitosan, crosslinked with different concentrations of alginate, was made into porous scaffolds. Infrared and thermal gravimetric analyses showed polyelectrolyte complex formation between chitosan and alginate units. The alginate-crosslinked chitosan scaffolds were more hydrophilic, showed less swelling, had lower pentoxifylline (PTX) release efficacies, were more favorable for initial cell attachment, and were mechanically stronger and more resistant to enzymatic degradation when compared to non-crosslinked chitosan scaffolds. The differences became more significant as the concentrations of chitosan and alginate increased. Furthermore, in vitro tests showed that when PTX was slowly released from the scaffolds, it became more effective in suppressing the production of TNF-alpha and IL-6 by stimulated macrophage cells.

Formulation and evaluation of press coated tablets for pulsatile drug delivery using hydrophilic and hydrophobic polymers

The aim of present investigation was to develop press coated tablet for pulsatile drug delivery of ketoprofen using hydrophilic and hydrophobic polymers. The drug delivery system was designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis. The press coated tablets containing ketoprofen in the inner core was formulated with an outer shell by different weight ratio of hydrophobic polymer (micronized ethyl cellulose powder) and hydrophilic polymers (glycinemax husk or sodium alginate). The release profile of press coated tablet exhibited a lag time followed by burst release, in which outer shell ruptured into two halves. Authors also investigated factors influencing on lag time such as particle size and viscosity of ethyl cellulose, outer coating weight and paddle rpm. The surface morphology of the tablet was examined by a scanning electron microscopy. Differential scanning calorimeter and Fourier transformed infrared spectroscopy study showed compatibility between ketoprofen and coating material.

Oral pulsatile delivery systems based on swellable hydrophilic polymers

Upon contact with aqueous fluids, swellable hydrophilic polymers undergo typical chain relaxation phenomena that coincide with a glassy-rubbery transition. In the rubbery phase, these polymers may be subject to swelling, dissolution and erosion processes or, alternatively, form an enduring gel barrier when cross-linked networks (hydrogels) are dealt with. Because of the peculiar hydration and biocompatibility properties, such materials are widely exploited in the pharmaceutical field, particularly as far as hydrophilic cellulose derivatives are concerned. In oral delivery, they have for long been employed in the manufacturing of prolonged release matrices and, more recently, for pulsatile (delayed) release devices as well. Pulsatile delivery, which is meant as the liberation of drugs following programmed lag phases, has drawn increasing interest especially in view of emerging chronotherapeutic approaches. In pursuit of pulsatile release, various design strategies have been proposed, chiefly including reservoir, capsular and osmotic formulations. In most cases, water-swellable polymers play a key role in the overall delivery mechanism after being activated by physiological media. Based on these premises, the aim of the present review is to survey the main oral pulsatile delivery systems, for which swelling, dissolution and/or erosion of hydrophilic polymers are primarily involved in the control of release.

Solventless pharmaceutical coating processes: a review

Coatings are an essential part in the formulation of pharmaceutical dosage form to achieve superior aesthetic quality (e.g., color, texture, mouth feel, and taste masking), physical and chemical protection for the drugs in the dosage forms, and modification of drug release characteristics. Most film coatings are applied as aqueous- or organic-based polymer solutions. Both organic and aqueous film coating bring their own disadvantages. Solventless coating technologies can overcome many of the disadvantages associated with the use of solvents (e.g., solvent exposure, solvent disposal, and residual solvent in product) in pharmaceutical coating. Solventless processing reduces the overall cost by eliminating the tedious and expensive processes of solvent disposal/treatment. In addition, it can significantly reduce the processing time because there is no drying/evaporation step. These environment-friendly processes are performed without any heat in most cases (except hot-melt coating) and thus can provide an alternative technology to coat temperature-sensitive drugs. This review discusses and compares six solventless coating methods - compression coating, hot-melt coating, supercritical fluid spray coating, electrostatic coating, dry powder coating, and photocurable coating - that can be used to coat the pharmaceutical dosage forms.

Smart Polymeric Gels: Redefining the Limits of Biomedical Devices

This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations in the use of hydrogels in stimuli-responsive applications is the diffusion rate limited transduction of signals. This can be obviated by engineering interconnected pores in the polymer structure to form capillary networks in the matrix and by downscaling the size of hydrogels to significantly decrease diffusion paths. Reducing the lag time in the induction of smart responses can be highly useful in biomedical devices, such as sensors and actuators. This review also describes molecular imprinting techniques to fabricate hydrogels for specific molecular recognition of target analytes. Additionally, it describes the significant advances in bottom-up nanofabrication strategies, involving supramolecular chemistry. Learning to assemble supramolecular structures from nature has led to the rapid prototyping of functional supramolecular devices. In essence, the barriers in the current performance potential of biomedical devices can be lowered or removed by the rapid convergence of interdisciplinary technologies.

In vitro biodegradation and biocompatibility of gelatin/montmorillonite-chitosan intercalated nanocomposite

The intercalated nanocomposite of gelatin/montmorillonite-chitosan (Gel/MMT-CS) was prepared via the solution intercalation process. In vitro degradation tests showed that the nanocomposite had a lower degradation rate than Gel-CS composite. And the introduced intercalation structure endowed Gel/MMT-CS nanocomposite with a controllable degradation rate when changing the MMT content. Cells attachment, spread and proliferation on the Gel/MMT-CS membranes were investigated by scanning electron microscopy (SEM) and mitochondrial activity assay. The results provided evidences of good adhesion, proliferation and morphology of rat stromal stem cells on Gel/MMT-CS membranes compared to the tissue culture plates (TCPs), making the Gel/MMT-CS nanocomposite a promising candidate towards tissue engineering.

The strength of bilayered tablets

The tensile strength of model materials (dicalcium phosphate dihydrate, microcrystalline cellulose and pregelatinised starch) compacted to form tablets in the form of beams consisting of two layers of equal thickness has been determined by three-point loading. The values of the tensile strength of the materials were sometimes higher and sometimes lower than the tensile strength of beams of the same thickness composed of a single material. Correction of the values for the tensile strength of the layered beams for the differences in the elasticity of the materials in the layered tablets failed to correct for these differences, as did considering the layered beams as beams of half thickness. For a layered tablet with pregelatinised starch at the bottom and microcrystalline cellulose at the top, the value of the tensile strength recorded appeared to be that of the microcrystalline cellulose as the fracture propagated across the boundary between the layers and into microcrystalline cellulose. What appeared to be the important factor was the way the failure of the beam crossed the interface between the two layers.

Polysaccharide-based polymer blends: Methods of their production

The existing methods of preparing polymer blends of cellulose, chitin and chitosan with natural and synthetic polymers and their applications are reviewed. The methods of solid-phase blending of these polymers under conditions of joint action of high pressure and shear deformation are discussed. Normally, under these conditions the processes of dispersion of polymer particles, amorphization, mixing at different levels, depolymerization as well as a chemical interaction resulting in formation of branched and crosslinked structures can take place. The probability and intensity of these processes depend in many respects on the type and magnitude of the external force, but the properties of the polymers are of higher importance. The advantages of the method of joint action of high pressure and shear deformation compared to the conventional techniques of polysaccharides mixtures production are shown.

Time-controlled oral delivery systems for colon targeting

In recent years, many research efforts have been spent in the achievement of selective delivery of drugs into the colon following oral administration. Indeed, colonic release is regarded as a beneficial approach to the pharmacological treatment or prevention of widespread large bowel pathologies, such as inflammatory bowel disease and adenocarcinoma. In addition, it is extensively explored as a potential means of enhancing the oral bioavailability of peptides, proteins and other biotechnological molecules, which are known to be less prone to enzymatic degradation in the large, rather than in the small, intestine. Based on these premises, several formulation strategies have been attempted in pursuit of colonic release, chiefly including microflora-, pH-, pressure- and time-dependent delivery technologies. In particular, this review is focused on the main design features and release performances of time-controlled devices, which rely on the relative constancy that is observed in the small intestinal transit time of dosage forms.

Oral pulsatile drug delivery systems

In the field of modified release, there has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable lag phase from the time of administration. In particular, the recent literature reports on a variety of pulsatile release systems intended for the oral route, which have been recognised as potentially beneficial to the chronotherapy of widespread diseases, such as bronchial asthma or angina pectoris, with mainly night or early morning symptoms. In addition, time-dependent colon delivery may also represent an appealing related application. The delayed liberation of orally administered drugs has been achieved through a range of formulation approaches, including single- or multiple-unit systems provided with release-controlling coatings, capsular devices and osmotic pumps. Based on these premises, the aim of this review is to outline the rational and prominent design strategies behind oral pulsatile delivery.

Colon Targeted Delivery Systems: Review of Polysaccharides for Encapsulation and Delivery

Colon-targeted delivery of bioactives has recently gained importance in addressing specific needs in the therapy of colon-based diseases. Many approaches have been attempted for the development of colon-specific delivery systems, with not much success in the past. Recent research into the utilization of the metabolic activity and the colonic microenvironment in the lower gastrointestinal tract has attained great value in the design of novel colon-targeted delivery systems based on natural biodegradable polymers. In the current article, special emphasis has been placed on polysaccharide systems, with minimal chemical modification, that have been exploitedfor colon targeting. These polysaccharide based encapsulation and targeted delivery systems are envisaged to have an immense potential for the development of food/nutraceutical formulations for colon-based diseases, including colorectal cancer.

Characterization of chitosan acetate as a binder for sustained release tablets

A chitosan derivative as an acetate salt was successfully prepared by using a spray drying technique. Physicochemical characteristics and micromeritic properties of spray-dried chitosan acetate (SD-CSA) were studied as well as drug-polymer and excipient-polymer interaction. SD-CSA was spherical agglomerates with rough surface and less than 75 microm in diameter. The salt was an amorphous solid with slight to moderate hygroscopicity. The results of Fourier transform infrared (FTIR) and solid-state (13)C NMR spectroscopy demonstrated the functional groups of an acetate salt in its molecular structure. DSC and TGA thermograms of SD-CSA as well as FTIR and NMR spectrum of the salt, heated at 120 degrees C for 12 h, revealed the evidence of the conversion of chitosan acetate molecular structure to N-acetylglucosamine at higher temperature. No interaction of SD-CSA with either drugs (salicylic acid and theophylline) or selected pharmaceutical excipients were observed in the study using DSC method. As a wet granulation binder, SD-CSA gave theophylline granules with good flowability (according to the value of angle of repose, Carr's index, and Hausner ratio) and an excellent compressibility profile comparable to a pharmaceutical binder, PVP K30. In vitro release study of theophylline from the tablets containing 3% w/w SD-CSA as a binder demonstrated sustained drug release in all media. Cumulative drug released in 0.1 N HCl, pH 6.8 phosphate buffer and distilled water was nearly 100% within 6, 16 and 24 h, respectively. It was suggested that the simple incorporation of spray-dried chitosan acetate as a tablet binder could give rise to controlled drug delivery systems exhibiting sustained drug release.

Development of dividable one-step dry-coated tablets (dividable-OSDRC) and their evaluation as a new platform for controlled drug release

PURPOSE

The purpose of this study is to develop novel dividable coated tablets that retain their characteristics even after they are divided.

METHODS

We prepared dividable one-step dry-coated tablets (dividable-OSDRC) using our own manufacturing process with double structure punches. The release pattern of the dividable-OSDRC with hydroxypropyl methylcellulose (HPMC) or methacrylic acid copolymer LD (Eudragit) as an outer layer was investigated before and after the division, and dissolution profiles were statistically compared using difference factor f1 and similarity factor f2.

RESULTS

The dividable-OSDRC with HPMC for sustained-release (compression pressure, 150 MPa; crashing strength, 6.1 N; friability, 0.05%; CV of divided tablet weight, 7.8%) showed statistically equivalent release patterns between the one-half and the whole (f1, 13.9; f2, 55.5) and between the one-half and the two-halves (5.5, 72.5). The surface area of the tablets affected the sustained-release profiles. Furthermore, the tablets made with Eudragit LD for timed-release (150 MPa. 12.8 N, 0.18%, 9.6%) also showed approximated release patterns before and after the division.

CONCLUSIONS

We proved that dividable-OSDRC maintain their release characteristics after they are divided. We conclude that the dividable-OSDRC could be used as a new platform for the controlled release of drugs.

Injectable bone using chitosan-alginate gel/mesenchymal stem cells/BMP-2 composites

AIM

Several injectable materials have been used as osteogenic bone substitutes. However, none has gained universal acceptance. This study was performed to investigate whether or not chitosan-alginate gel/mesenchymal stem cells/bone morphogenetic protein-2 composites are potentially injectable materials for new bone formation.

MATERIAL AND METHODS

The composites were injected into the subcutaneous space on the dorsum of nude mice to investigate new bone tissue formation. The composites were examined histologically over a 12-week period.

RESULTS

The composites injected into the mouse were able to stimulate new bone formation, which was trabecular in type.

CONCLUSIONS

This study showed that chitosan-alginate gel/MSCs/BMP-2 composites could become clinically useful injectable materials to generate new bone.

Evaluation of novel one-step dry-coated tablets as a platform for delayed-release tablets

Using a novel one-step dry-coated tablets (OSDRC) manufacturing method, which we have recently invented, we evaluated the possibility of its application to delayed-release tablets. The manufacturing method for OSDRC is different from conventional methods in that dry-coated tablets can be made with only one process. One of the major advantages of OSDRC is that we can expect to produce tablets, which always contain the core exactly in the center of the whole tablet. This characteristic means that the thickness of outer layer is constantly uniform, which is difficult to achieve with the conventional dry-coated tablets. The effects of different outer layer thicknesses and various compression pressures were examined using HPMC to evaluate OSDRC applicability to delayed-release tablets. We proved that the lag-time can be adjusted only by changing the thickness of the outer layer without any arrangement of its ingredients, which is quite different from the conventional approach. Further, the lag-time of each OSDRC prepared in the 100-200 MPa compression pressure range was almost the same, indicating the lag-time of OSDRC under these compression pressures does not vary. The release rate of the drug (acetaminophen) from the OSDRC with 0.5 and 1.0 mm outer layer thicknesses was almost constant independent of compression pressure. On the other hand, the release rate of the OSDRC with a 2.0 mm outer layer thickness was delayed compared to that of other thicknesses. That is, in the tablets with 2.0 mm outer layer thickness, the release rate declined since its outer layer thickness was sufficient to form a gel-layer. In conclusion, OSDRC could be a platform for delayed-release tablets, which do not utilize the conventional method used for dry-coated tablets.

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets

An oral press-coated tablet was developed by means of direct compression to achieve the time-controlled disintegrating or rupturing function with a distinct predetermined lag time. This press-coated tablet containing sodium diclofenac in the inner core was formulated with an outer shell by different weight ratios of hydrophobic polymer of micronized ethylcellulose (EC) powder and hydrophilic excipients such as spray-dried lactose (SDL) or hydroxypropyl methylcellulose (HPMC). The effect of the formulation of an outer shell comprising both hydrophobic polymer and hydrophilic excipients on the time lag of drug release was investigated. The release profile of the press-coated tablet exhibited a time period without drug release (time lag) followed by a rapid and complete release phase, in which the outer shell ruptured or broke into 2 halves. The lag phase was markedly dependent on the weight ratios of EC/SDL or EC/HPMC in the outer shell. Different time lags of the press-coated tablets from 1.0 to 16.3 hours could be modulated by changing the type and amount of the excipients. A semilogarithmic plot of the time lag of the tablet against the weight ratios of EC/SDL or EC/HPMC in the outer shell demonstrated a good linear relationship, with r = 0.976 and r = 0.982, respectively. The predetermined time lag prior to the drug release from a press-coated tablet prepared by using a micronized EC as a retarding coating shell can be adequately scheduled with the addition of hydrophilic excipients according to the time or site requirements.

Formulation design of double-layer in the outer shell of dry-coated tablet to modulate lag time and time-controlled dissolution function: studies on micronized ethylcellulose for dosage form design (VII)

The dry-coated tablet with optimal lag time was designed to simulate the dosing time of drug administration according to the physiological needs. Different compositions of ethylcellulose (EC) powder with a coarse particle (167.5 microm) and several fine particles (< 6 microm), respectively, were mixed to formulate the whole layer of the outer shell of dry-coated tablets. The formulations containing different weight ratios of coarse/fine particles of EC powders or 167.5 microm EC powder/excipient in the upper layer of the outer shell to influence the release behavior of sodium diclofenac from dry-coated tablet were also explored. The results indicate that sodium diclofenac released from all the dry-coated tablets exhibited an initial lag period, followed by a stage of rapid drug release. When the mixture of the coarse/fine particles of EC powders was incorporated into the whole layer, the lag time was almost the same. The outer shell broke into 2 halves to make a rapid drug release after the lag time, which belonged to the time-controlled disruption of release mechanism. When the lower layer in the outer shell was composed of 167.5 microm EC powder and the upper layer was formulated by mixing different weight ratios of 167.5 microm and 6 microm of EC powders, the drug release also exhibited a time-controlled disruption behavior. Its lag time might be freely modulated, depending on the amount of 6 microm EC powder added. Once different excipients were respectively incorporated into the upper layer of the outer shell, different release mechanisms were observed as follows: time-controlled explosion for Explotab, disruption for Avicel and spray-dried lactose, erosion for dibasic calcium phosphate anhydrate, and sigmoidal profile for hydroxypropyl methylcellulose.