Cellulose acetate butyrate and polycaprolactone for ketoprofen spray-dried microsphere preparation

Synthesis of Cellulose Acetate Butyrate Microspheres as Precursor for Hard Carbon-Based Electrodes in Symmetric Supercapacitors

Cellulose microspheres have a wide range of applications due to their unique properties and versatility. Various preparation methods have been explored to tailor these microspheres for specific applications. Among these methods, the acetate method using cellulose acetate is well known. However, replacement of the acetate group through the butyrate group significantly extends the variety of morphological properties. In the present work, microspheres based on cellulose acetate butyrate are being developed with modified characteristics in terms of particle size, porosity, surface morphology and the inner structure of the microspheres. While the inner structure of cellulose acetate microspheres is predominantly porous, microspheres prepared from cellulose acetate butyrate are mainly filled or contain several smaller microspheres. Carbon materials from cellulose acetate butyrate microspheres exhibit a high specific surface area of 567 m2 g-1, even without further activation. Activation processes can further increase the specific surface area, accompanied by an adaptation of the pore structure. The prepared carbons show promising results in symmetrical supercapacitors with aqueous 6 M KOH electrolytes. Activated carbons derived from cellulose acetate butyrate microspheres demonstrate an energy density of 12 Wh kg-1 at a power density of 0.9 kW kg-1.

Polycaprolactone: How a Well-Known and Futuristic Polymer Has Become an Innovative Collagen-Stimulator in Esthetics

Compared to other domains, tissue engineering and esthetics have dramatically expanded in recent years, leading to both major biomedical advances and futuristic perspectives. The two share a common approach based on biomaterials, especially polymers. This paper illustrates this with the example of polycaprolactone (PCL), a polymer synthesized in the early 1930s, and one of its most recent applications, a PCL-based collagen stimulator, a filler used in esthetics. PCL is biocompatible and biodegradable. Its specific physicochemical and mechanical properties, viscoelasticity and ease of shaping led to the production of PCL-based products with various shapes and durations dependent on its biodegradation kinetics. PCL has been safely used in the biomedical field for more than 70 years, from sutures to tissue and organ replacement by 3D printing. The PCL-based collagen stimulator is composed of PCL microspheres suspended in a carboxymethyl-cellulose gel carrier providing immediate and sustained volumizing effects when injected; the morphology, the biocompatibility of the PCL microspheres embedded with the collagen fibers produced all contribute to the creation of a unique 3D scaffold for a sustained effect. Its safety has been investigated in clinical studies and vigilance surveys. Recently published experts' recommendations on injection modalities and techniques should help further optimize treatment outcome and safety. This paper also integrates reviews and recommendations on the prevention and management of adverse events related to dermal and subdermal fillers including the PCL-based collagen stimulator. In addition, in terms of efficacy and safety, this product benefits from its daily clinical use in esthetics worldwide and continuous extensive fundamental and clinical research, both on it and the PCL polymer. Forthcoming data from further investigations will reinforce knowledge of the product and procedures in the field.

Development of an injectable PHBV microparticles-GG hydrogel hybrid system for regenerative medicine

Uncontrollable displacements that greatly affect the concentration of active agents at the target tissues are among a major limitation of the use of microparticulate drug delivery systems (DDS). Under this context a biphasic injectable DDS combining poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microparticles (MPs) and a gellan gum (GG) injectable hydrogel is herein proposed for the localized delivery and long-term retention of MPs carrying hydrophilic and hydrophobic model active agents. A double emulsion-solvent evaporation method was adopted to develop the PHBV MPs, carrying bovine serum albumin (BSA) or dexamethasone (Dex) as hydrophilic and hydrophobic active agents' models, respectively. Moreover, this method was modified, together with the properties of the hydrogel to tailor the delivery profile of the active agents. Variations of the composition of the organic phase during the process allowed tuning surface topography, particle size distribution and core porosity of the PHBV MPs and, thus, the in vitro release profile of Dex but not of BSA. Besides, after embedding hydrogels of higher GG concentration led to a slower and more sustained release of both active agents, independently of the processing conditions of the microparticulate system.

The pharmacokinetics and pharmacodynamics of lidocaine- loaded biodegradable poly(lactic-co-glycolic acid) microspheres

The purpose of this study was to develop novel lidocaine microspheres. Microspheres were prepared by the oil-in-water (o/w) emulsion technique using poly(D,L-lactide-co-glycolide acid) (PLGA) for the controlled delivery of lidocaine. The average diameter of lidocaine PLGA microspheres was 2.34±0.3 μm. The poly disperse index was 0.21±0.03, and the zeta potential was +0.34±0.02 mV. The encapsulation efficiency and drug loading of the prepared microspheres were 90.5%±4.3% and 11.2%±1.4%. In vitro release indicated that the lidocaine microspheres had a well-sustained release efficacy, and in vivo studies showed that the area under the curve of lidocaine in microspheres was 2.02-2.06-fold that of lidocaine injection (p<0.05). The pharmacodynamics results showed that lidocaine microspheres showed a significant release effect in rats, that the process to achieve efficacy was calm and lasting and that the analgesic effect had a significant dose-dependency.

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.

Preparation and characterization of starch-poly-epsilon-caprolactone microparticles incorporating bioactive agents for drug delivery and tissue engineering applications

One limitation associated with the delivery of bioactive agents concerns the short half-life of these molecules when administered intravenously, which results in their loss from the desired site. Incorporation of bioactive agents into depot vehicles provides a means to increase their persistence at the disease site. Major issues are involved in the development of a proper carrier system able to deliver the correct drug, at the desired dose, place and time. In this work, starch-poly-epsilon-caprolactone (SPCL) microparticles were developed for use in drug delivery and tissue engineering (TE) applications. SPCL microparticles were prepared by using an emulsion solvent extraction/evaporation technique, which was demonstrated to be a successful procedure to obtain particles with a spherical shape (particle size between 5 and 900 microm) and exhibiting different surface morphologies. Their chemical structure was confirmed by Fourier transform infrared spectroscopy. To evaluate the potential of the developed microparticles as a drug delivery system, dexamethasone (DEX) was used as model drug. DEX, a well-known component of osteogenic differentiation media, was entrapped into SPCL microparticles at different percentages up to 93%. The encapsulation efficiency was found to be dependent on the polymer concentration and drug-to-polymer ratio. The initial DEX release seems to be governed mainly by diffusion, and it is expected that the remaining DEX will be released when the polymeric matrix starts to degrade. In this work it was demonstrated that SPCL microparticles containing DEX can be successfully prepared and that these microparticular systems seem to be quite promising for controlled release applications, namely as carriers of important differentiation agents in TE.

Spray-dried microparticles containing polymeric nanocapsules: Formulation aspects, liquid phase interactions and particles characteristics

Up to now, the full potential of polymer-based nanoparticles is not yet exploited because of a lack of stability when conserved in aqueous medium. The present paper reports the water elimination from nanocapsules (NC) dispersions by means of the spray-drying technique with the aim to achieve dried solid forms of interest using colloidal silicon dioxide as drying auxiliary. The influence of formulation parameters on the suspension behaviour and on the powders characteristics was also evaluated. Our findings demonstrated that the mixing protocol, the concentrations of both NC and silica are crucial parameters that affect the feed behaviour and the spray-dried particles characteristics. Interactions occurring in the feed are directed by hydrogen bounds and were more sensitive to the silica concentration than that of NC as evidenced by rheological measurements. The NC are entrapped within solid dried matrixes following their interaction with silica particles in the feed. SEM analyses of the obtained powders showed spherical separated microparticles formed by the association of NC and silica when they are mixed at adequate concentrations in the feed before spray-drying. On the other hand, fused agglomerated particles presenting NC at their surface, characterised by irregular shapes and a strong adhesiveness were prepared when the silica concentration was not sufficient. The surface composition of the spray-dried powders was investigated using the ESCA technique and revealed the NC exclusion from the surface to obtain powders suitable for further handling.

Poly-epsilon-caprolactone microspheres and nanospheres: an overview

Poly-epsilon-caprolactone (PCL) is a biodegradable, biocompatible and semicrystalline polymer having a very low glass transition temperature. Due to its slow degradation, PCL is ideally suitable for long-term delivery extending over a period of more than one year. This has led to its application in the preparation of different delivery systems in the form of microspheres, nanospheres and implants. Various categories of drugs have been encapsulated in PCL for targeted drug delivery and for controlled drug release. Microspheres of PCL either alone or of PCL copolymers have been prepared to obtain the drug release characteristics. This article reviews the advancements made in PCL-based microspheres and nanospheres with special reference to the method of preparation of these and their suitability in developing effective delivery systems.

Microencapsulation of semisolid ketoprofen/polymer microspheres

Ketoprofen controlled release microspheres were prepared, by emulsion/solvent evaporation, at 15 degrees C, in order to avoid the formation of semisolid particles. An identical procedure was carried out at 60 degrees C to speed up the solvent evaporation and the formed semisolid microspheres were directly microencapsulated by complex coacervation and spray-dried in order to recover them as free flowing powder. Microspheres and microcapsules were characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, in vitro dissolution studies, and then used for the preparation of tablets. During this step, the compressibility of the prepared powders was measured. Microspheres and microcapsules showed compaction abilities by far better than those of the corresponding physical mixtures. In fact, it was impossible to obtain tablets by direct compressing drug and polymer physical mixtures, but microspheres and microcapsules were easily transformed into tablets. Finally, in vitro dissolution studies were performed and the release control of the tablets was pointed out. Microspheres were able to control ketoprofen release only after their transformation into tablets. Tablets containing eudragit RS were the most effective in slowing down drug release.

Elution characteristics of tobramycin from polycaprolactone in a rabbit model

This study investigated the elution characteristics of tobramycin from polycaprolactone, a bioabsorbable polymer, in a rabbit model. Sixty rabbits were divided into two groups. Group 1 had polycaprolactone rods impregnated with 6% tobramycin surgically implanted into the proximal femoral intramedullary canal. Group 2 received polymethylmethacrylate rods of like size, shape, and antibiotic concentration. Serum and urine samples were obtained, and tobramycin levels were determined via fluorescent immunosorbent assay. Rabbits were sacrificed as long as 56 days after surgery. Local bone tobramycin concentration was determined using the agar diffusion method. Polycaprolactone delivered a significantly higher peak bone concentration of tobramycin (22.4 microg/mL) than did polymethylmethacrylate (13.59 microg/mL). Polycaprolactone also had a more gradual decrease in local tobramycin concentration than did polymethylmethacrylate. Neither polycaprolactone nor polymethylmethacrylate yielded consistently detectable (> 0.1 microg/mL) serum tobramycin levels. Urine concentrations mirrored those seen in bone, with polycaprolactone achieving significantly higher tobramycin concentrations than did polymethylmethacrylate. Polycaprolactone had superior elution characteristics compared with polymethylmethacrylate in this lapine model, suggesting that polycaprolactone might be a promising local antibiotic delivery vehicle for the treatment of osteomyelitis.

Spray-drying as a method for microparticulate controlled release systems preparation: advantages and limits. I. Water-soluble drugs

Spray-drying was used for the preparation of paracetamol/eudragit RS or RL or ethylcellulose microspheres to verify the possibility of their use in controlled-release solid-dosage forms formulation and try to determine advantages and limits of the technique of such use. Microspheres were first characterized by scanning electron microscopy, differential scanning calorimetry, x-ray diffractometry, and in vitro dissolution studies and then used for the preparation of tablets. During this step, the compressibility of the spray-dried powders was also evaluated. In vitro dissolution studies were performed also on the tablets and their release control was accessed. Although powders were unable to slow down drug release, tablets obtained from microsphere compression showed a good capability of controlling paracetamol release when eudragit RS or ethylcellulose was used, even at low polymer amounts.

Influence of various technological parameters on the preparation of spray-dried poly(epsilon-caprolactone) microparticles containing a model antigen

This work evaluates the efficacy of the spray-drying technique to prepare poly(epsilon-caprolactone) (PCL) microparticles containing an entrapped model antigen (bovine albumin, BSA). The presence of a stabiliser was found to be an important parameter when preparing PCL microparticles containing a hydrophilic antigen. The effect of various technological parameters (concentration of the polymer and protein solutions, organic/aqueous phases ratio, nature of solvents and emulsion parameters such as duration and speed of agitation) on microparticle morphology and size, BSA entrapment and encapsulation efficiency was studied. Microparticles were characterized by a mean size from 9.56+/-0.25 to 24.31+/-2.87 microm and a BSA entrapment from 0.80+/-0.02 to 24.21+/-0.23% (w/w). SDS-PAGE electrophoresis and isoelectric focusing (IEF) confirmed the conservation of the physicochemical characteristics of the BSA entrapped within PCL microparticles produced by spray-drying. Together, these results showed that spray-drying is an efficient technique to overcome the key obstacle that represents the scaling-up of the manufacturing process to produce sufficient quantities of vaccine for clinical trials and, ultimately, commercialization.

Sustained release chitosan microspheres prepared by novel spray drying methods

Modified spray drying methods, especially a novel w/o/w emulsion-spray drying method, were developed to prepare chitosan microspheres with a sustained drug release pattern. Release of the model drugs cimetidine and famotidine, from the microspheres prepared by the emulsion-spray drying methods, was greatly retarded with release lasting for several hours, compared with drug loaded microspheres prepared by conventional-spray drying or emulsion methods where drug release was almost instant. The slow release of drug was partly due to the poor wetting ability of the microspheres which floated on the surface of the dissolution medium. The addition of a wetting agent increased the release rate significantly. The coating of the microspheres with gelatin decreased the rate of release of drug in the presence of wetting agents.

Preparation, characterization and in vitro drug release of poly-epsilon-caprolactone and hydroxypropyl methylcellulose phthalate ketoprofen loaded microspheres

Ketoprofen was encapsulated within poly-epsilon-caprolactone (PCL) and hydroxypropyl methylcellulose phthalate 50 (HPMCP50) microspheres (MS). Scanning electron microscopy (SEM) studies showed spherical particles without surface crystal formation and differential scanning calorimetry (DSC) supported these results. MS of PCL or HPMCP50 had a mean particle size of 10.7 +/- 2.2 and 10.9 +/- 2.0 mu m respectively, whereas a mixture of these polymers increased the MS particle size to 30 mu m. Greater incorporation efficiencies were found for HPMCP50 MS (98.1 +/- 0.7). MS of PCL and HPMCP50 mixtures showed a decreased drug entrapment as the amount of PCL was increased (96.0 +/- 0.2 for 25% PCL, 95.6 +/- 1.8 for 50% PCL, 80.2 +/- 0.7 for 75% PCL and 78.9 +/- 9.0 for 100% PCL). Size exclusion chromatography (SEC) studies revealed a weak interaction between ketoprofen and PCL and some polymer degradation was found during HPMCP50 MS storage, probably by breaking of the phthalic anhydride bond to be anyhydroglucose backbone. Four types of cryoprotectors (glucose, trehalose, mannitol and sorbitol, at 5 and 10% W/V) and two freezing conditions (-196 and -20 degrees C) were evaluated in freeze-drying studies. For HPMCP50, the sizes of MS after reconstitution of liophylizates were nearly the same as the initial ones. For PCL MS only, those formulations with sorbitol or glucose at 10% and frozen at -196 degrees C showed acceptable results. In contrast to the rapid release rate of ketoprofen from PCL MS as a result of carrier porosity (80% released within 15 min), the release from HPMCP50 MS could be controlled by means of pH (40% released in the first 15 min in simulated gastric fluid and nearly 100% ketoprofen delivered in the same time in simulated intestinal fluid).