Drug release from core-shell type nanoparticles of poly(DL-lactide-co-glycolide)-grafted dextran

This study prepared core-shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran. The synthesis of the PLGA-dextran conjugate was confirmed by Fourier transform-infrared (FT-IR) spectroscopy. The PLGA grafted-dextran was able to form nanoparticles in water by self-assembly and their particle size was 245.3?±?95.1?nm. From fluorescence probe study using pyrene as a hydrophobic probe, critical association concentration (CAC) values were determined from the fluorescence excitation spectra and were found to be 0.006?g?l^?1. Morphological observations using a scanning electron microscope (SEM) showed that the polymeric nanoparticles of the PLGA-dextran conjugate have uniformly spherical shapes. Their size and morphology provide them with acceptable properties for use as a drug-targeting carriers. Drug release from core-shell type nanoparticles was faster in the presence of dextranase, indicating that core-shell type nanoparticles of PLGA grafted-dextran can be used as an oral drug carriers.     

Preparation and in vitro evaluation of thienorphine-loaded PLGA nanoparticles

Poly (d,l-lactic-co-glycolide) nanoparticles (PLGA-NPs) have attracted considerable interest as new delivery vehicles for small molecules, with the potential to overcome issue such as poor drug solubility and cell permeability. However, their negative surface charge decreases bioavailability under oral administration. Recently, cationically modified PLGA-NPs has been introduced as novel carriers for oral delivery. In this study, our aim was to introduce and evaluate the physiochemical characteristics and bioadhesion of positively charged chitosan-coated PLGA-NPs (CS-PLGA-NPs), using thienorphine as a model drug. These results indicated that both CS-PLGA-NPs and PLGA-NPs had a narrow size distribution, averaging less than 130?nm. CS-PLGA-NPs was positively charged (+42.1?±?0.4?mV), exhibiting the cationic nature of chitosan, whereas PLGA-NPs showed a negative surface charge (?2.01?±?0.3?mV). CS-PLGA-NPs exhibited stronger bioadhesive potency than PLGA-NPs. Furthermore, the transport of thienorphine-CS-PLGA-NPs by Caco-2 cells was higher than thienorphine-PLGA-NPs or thienorphine solution. CS-PLGA-NPs were also found to significantly enhance cellular uptake compared with PLGA-NPs on Caco-2 cells. An evaluation of cytotoxicity showed no increase in toxicity in either kind of nanoparticles during the formulation process. The study proves that CS-PLGA-NPs can be used as a vector in oral drug delivery systems for thienorphine due to its positive surface charge and bioadhesive properties.     

Celecoxib-loaded poly(D,L-lactide-co-glycolide) nanoparticles prepared using a novel and controllable combination of diffusion and emulsification steps as part of the salting-out procedure

A novel procedure for the manufacture of celecoxib-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles is described that is based upon combining salting out and emulsion-evaporation steps. An entrapment efficiency, a measure of the actual to theoretical drug content, of 97.3% was achieved, being superior to that achieved when these popular techniques were used separately (emulsion evaporation, 40.1%; salting out, 10.0%). The ratio of a water miscible solvent (acetone) to a non water-miscible solvent (dichloromethane) was shown to be the primary determinants of size and drug loading. Once optimized, using an organic phase of 3?:?1 acetone?:?dichloromethane vol?:?vol ratio, further control on particle parameters could be exerted using modification of acetone diffusion by alterations in MgCl₂?·?6H₂O concentration. This step was shown to have a small effect on both the mean nanoparticle size and entrapment efficiency, but found to reduce the polydispersity considerably. Diffusion control using a 45% w/v MgCl₂?·?6H₂O solution produced nanoparticles with a mean size of 151.4?nm, a polydispersity index of 0.023 and 98.1% entrapment efficiency. Electron microscopy showed the particles to be smooth and spherical. Sheer homogenization during the emulsification step was shown to be not as effective as sonication, with the latter technique able to produce nanoparticles after 1?min of application. Drug release studies across a semi-permeable membrane demonstrated a reduction in the burst effect as the ratio of acetone in the organic phase was increased. Calorimetry studies suggested that celecoxib existed in the nanoparticle as a molecular dispersion, with additional evidence for a strong interaction between the PLGA and the absorbed poly(vinyl alcohol) stabilizer. Formation of a strong interaction between celecoxib and PLGA, together with the formation of a radial drug gradient give a release profile that does not possess the prevalent burst effect seen with other nanoparticulate drug-loaded systems.     

Effect of preparative variables on small interfering RNA loaded Poly(D,L-lactide-co-glycolide)-chitosan submicron particles prepared by emulsification diffusion method

In this study, poly(D,L-lactide-co-glycolide) (PLGA)-chitosan particles were investigated as an effective delivery system for small interfering RNA (siRNA) by emulsification diffusion method. The type, molecular weight and concentration of chitosan, PLGA type as well as centrifugation and freeze-drying process were amongst the investigated variables. PLGA-chitosan particles obtained were positively charged with particle size between ～0.4–1 µm depending on type, molecular weight and concentration of chitosan as well as type of PLGA. A better siRNA loading capacity was observed when a higher degree of ‘uncapped end groups’ were used. The addition of trehalose has also been shown to stabilize these particles from severe aggregation induced by freeze-drying. It was found that physical properties of PLGA-chitosan particles and their siRNA binding capacity were highly influenced by certain preparation parameters. The desired positive charge of submicron size range PLGA-chitosan particles could therefore be obtained by adjusting and optimizing these preparative and formulation parameters.     

Measurement of Protein Diffusion Through Poly(d,l-Lactide-Co-Glycolide)

A novel method was developed for studying the diffusion of proteins through poly(d,l-lactide-co-glycolide) (PLG), using a diffusion cell. To develop improved formulations for the controlled release of encapsulated drugs it is important to understand the underlying release mechanisms. When using low-molecular-weight PLG as the release-controlling polymer, diffusion through the pores is often proposed as the main release mechanism. The experimental set-up and method of determining the diffusion coefficient were thoroughly evaluated with regard to the reliability and the influence of the stirring rate. A procedure for spraying thin films of PLG onto a filter, which could be placed in the diffusion cell, was optimized. The method was then applied to the determination of the diffusion coefficient of human growth hormone (hGH) through a PLG film. The results show that the method enables measurements of the diffusion coefficient through the polymer film. Neither the stirring rate nor the concentration of hGH influenced the diffusion coefficient. The diffusion coefficient of hGH through degraded PLG films was 5.0 · 10^{? 13} m²/s, which is in the range that could be expected, i.e., several orders of magnitude smaller than its the diffusivity in pure water. The reproducibility was good, considering the dynamic properties of PLG, i.e., the difference in diffusion coefficients, at, for example, different stages of degradation and for different compositions of PLG, is expected to be much higher. The variation is probably also present in PLG films used for controlled-release formulations. Although the PLG film contains a large amount of water, a considerable time elapsed before pores of sufficient size formed and diffusion through the film started. In two-component diffusion experiments, the difference in diffusion rate did not correspond to the difference in molecular weight of the solutes, indicating a size exclusion effect. This method can be used to study the effect of changes in the formulation specification. By studying the change in the diffusion coefficient through the degradation process of PLG, or similar polymers, a better understanding of diffusion and, thus, also release mechanisms can be obtained.     

Effect of Divalent Cations on Pore Formation and Degradation of Poly(D,L-lactide-co-glycolide)

Poly(d,l-lactide-co-glycolide) (PLG) is probably the biodegradable polymer most often used for polymeric controlled-release formulations. Different salts have been shown to affect the swelling and degradation of PLG, which, in turn, affect the release of encapsulated drugs. In this investigation the effect of divalent cations was especially investigated. Films of PLG were incubated in phosphate buffer saline (PBS), a buffer containing salts similar to plasma, Hepes buffer, and Hepes buffer with ZnCl₂, CaCl₂, MgCl₂, or Na₂CO₃ added. Pore formation at the surface and inside the film was analyzed by scanning electron microscopy. The samples were also analyzed gravimetrically at predetermined intervals to determine the mass loss, and for some samples the pH within the PLG films was determined by confocal microscopy. Pores were formed faster in the presence of all divalent cations, and the results indicated a greater degradation rate in the presence of Zn²⁺. The catalyzing effect of the divalent cations on degradation was attributed to their ability to act as Lewis acids. Pores were formed more slowly in PBS than in a buffer containing salts similar to plasma, which should be considered when choosing the in vitro release medium.     

Evaluation of the degradation of clonidine-loaded PLGA microspheres

Abstract

Context: The release of an encapsulated drug is dependent on diffusion and/or degradation/erosion processes.

Objective: This work aimed to better understand the degradation mechanism of clonidine-loaded microparticles.

Methods: Gel permeation chromatography was used to evaluate the degradation of the polymer. The water-uptake and the weight loss were determined gravimetrically. The swelling behaviour and the morphological changes of the formulations were observed by microscopy. The glass transition temperature and the crystallinity were also determined by differential scanning calorimetry and X-ray diffraction, respectively. The pH of the medium and inside the microspheres was assessed.

Results: The microspheres captured a large amount of water, allowing a decrease in the molecular weight of the polymer. The pH of the medium decreased after release of the degradation products and the pH inside the microparticles remained constant due to the neutralization of these acidic products.

Conclusion: Clonidine and buffers both had an action on the degradation.     

Three weeks release BCNU loaded hydrophilic-PLGA microspheres for interstitial chemotherapy: Development and activity against human glioblastoma cells

The aim of this study is the development of microspheres of BCNU for intracranial administration, as an alternative to marketed novel Gliadel® Implant in the treatment of brain tumours. H poly-lactide-co-glycolide biodegradable microspheres of BCNU with a mean size of 33.5 ± 1.8 µm were obtained by an oil-in-water emulsion solvent evaporation method. Their small size would allow their intracranial administration through a needle by cerebral stereotaxia if tumour recurrence occurs, without a surgical intervention, as Gliadel® needs. BCNU was released from these microspheres during 21 days, mainly by a mechanism of diffusion from the polymer matrix (K = 2.91 mg days^?½). The cytotoxic effects of these microspheres on human glioblastoma cells were demonstrated all through 21 days and the value of percentage of viable cells was less than 40%. These microspheres should be commercialized as a freeze-dried product to keep at ?20°C. Three hundred and twenty milligrams of microspheres contain 61.6 mg of BCNU, the same amount of BCNU contained in 1600 mg or eight wafers of Gliadel usually implanted after the tumour resection.     

Sustained release of bupivacaine from devices based on chitosan

Chitosan beads loaded with bupivacaine (16+/-3 microg of drug per milligram of beads) were prepared by cross-linking with glutaraldehyde. In vitro drug release at pH and temperature conditions similar to those of the biological systems were studied. Maximum release of bupivacaine was obtained between 100 and 120 h, depending on the presence of lysozyme in the release medium, since the enzyme facilitates the release process. A constant release rate of the drug, between 11 and 15 microg/h, was observed for 30 h. In order to prolong bupivacaine release, the drug-loaded chitosan beads were coated with a poly(DL-lactide-co-glycolide) film. The resulting device allows the drug to be released in a sustained form; a constant release rate between 28.5 and 29.5 microg/h was obtained for 3 days, and the maximum release of bupivacaine took place at day 9. The in vitro results indicate a possible application of these bupivacaine loaded chitosan systems as drug release devices with an analgesic action. Thus, they could be used in the treatment of dental pain in the buccal cavity, where drug release would be made easier by lysozyme of the saliva.     

Preliminary Assessment of the Immune Response to Olea europaea Pollen Extracts Encapsulated into PLGA Microspheres

In this study, poly (d,l-lactide-co-glycolide) (PLGA) microspheres encapsulating Olea europaea pollen extracts were prepared by using the double emulsion (w/o/w) based on a solvent evaporation/extraction method. The resulting microspheres were 1.93 μm in size. The total allergen loading and surface-associated allergen were 8 and 0.64%, respectively. The release of the allergen from the microspheres showed a biphasic profile with an initial burst release followed by a sustained release phase. Finally, the polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the encapsulation process does not affect the stability of the protein. We describe here some preliminary observations concerning the use of these microspheres as parenteral antigen delivery systems for immunization with O. europaea pollen extracts, in a small animal model, the mouse.     

Solubility enhancement and in vitro evaluation of PEG-b-PLA micelles as nanocarrier of semi-synthetic andrographolide analogue for cholangiocarcinoma chemotherapy

Background: Semi-synthetic andrographolide analogue (19-triphenylmethyl ether andrographolide, AG 050) is a C-19 substituted andrographolide which is the major constituent from Andrographis Paniculata Nees (Acanthaceae). The analogue has previously been reported to be highly cytotoxic against several cancer cell lines. Nevertheless, its poor water solubility limits clinical applications of this compound.

Objectives: To improve the aqueous solubility and bioavailability of AG 050 by protonation and encapsulation in poly(ethylene glycol)-b-poly(d,l-lactide) (PEG-b-PLA) polymeric micelles.

Materials and methods: PEG-b-PLA micelle was employed as a nanocarrier for AG 050. The physicochemical properties and in vitro cytotoxicity against cholangiocarcinoma (CCA) (KKU-M213) cell line were done in this study.

Result and discussion: Hydrochloride salt of AG 050 (AG 050-P) greatly enhanced the solubility of this compound (15-fold). PEG-b-PLA was able to encapsulate AG 050-P in hydrophobic core with a significant increase in the amount of AG 050-P in aqueous solution (280-fold). Film sonication method provided greater results in drug-loading study as compared to micelles via solvent evaporation. In addition, the encapsulated AG 050-P exhibited sustained release pattern and excellent cytotoxicity activity against KKU-M213 with IC₅₀ of 3.33?µM.

Conclusion: Nanoencapsulation of AG 050-P implicated its potential development for clinical use in CCA treatment.     

Surface modification of poly (l-lactic acid) microspheres for site-specific delivery of ketoprofen for chronic inflammatory disease

The purpose of this research was to investigate the potential of surface modified Poly (l-lactic acid) (PLA) microspheres as a carrier for site-specific delivery of anti-inflammatory drug, ketoprofen, for the treatment of rheumatoid arthritis. Microspheres were prepared by solvent evaporation method using 20% w/w PLA in methylene chloride and 100 mL of a 2.5% poly vinyl alcohol (PVA) solution. Formulations were optimized for several processing parameters like drug to polymer ratio, stirring rate and volume of preparation medium etc. The surface of PLA microspheres was modified with gelatin to impart fibronectin recognition. The microspheres were characterized by surface morphology, size distribution, encapsulation efficiency, and by in vitro drug release studies. The prepared microspheres were light yellow, discrete, and spherical. Formulation with optimum drug to polymer ratio exhibited smallest vesicle size (43.02), high drug encapsulation efficiency (81.11) and better process yield (83.45). The release of drug was extended up to 24 h with Higuchi pattern of drug release. The in vivo results showed that the gelatin modified formulation reduced paw edema at greater extent than pure drug and PLA microspheres and it could be a promising carrier system for controlled and site-specific delivery of ketoprofen with possible clinical applications.     

l-Cysteine conjugated poly l-lactide nanoparticles containing 5-fluorouracil: formulation,characterization, release and uptake by tissues in vivo

Abstract

Context: Targeted delivery of drugs is still a therapeutic challenge and numerous methods have been reported for the same.

Objective: In this study, emphasis was placed on developing nanoparticles loaded with 5-fluorouracil (FU) and modifying the surface of the nanoparticles by conjugation with amino acid, to improve the distribution of 5-FU in the lungs.

Methods: An emulsion solvent evaporation technique was used to formulate nanoparticles of FU using Poly l-lactide and Pluronic F-68. The nanoparticles were conjugated with l-Cysteine using EDC as the activator of COOH group and were evaluated for product yield, particle size, surface morphology, amount of conjugation by Ellman’s method and in vitro drug release study.

Results and conclusion: The results indicated 60–65% yield with an average particle size of 242.7?±?37.11?nm for the cysteine conjugated nanoparticle (CNP) formulation and more than 70% conjugation of cysteine. The cumulative percentage of drug released over a period of 24?h was found to be 58%. An increase in distribution of the delivery system in lungs (11.4% ID after 1?h) in mice was found indicating the role of l-Cysteine in the transport mechanism to the lungs. In vivo kinetic studies in rats revealed higher circulation time of CNP as compared to pure FU solution. The study helps in designing a colloidal delivery system for increased distribution of drugs to the lungs and may be helpful in delivery of drugs in conditions like non-small cell lung carcinomas.     

The preparation of sustained release erythropoietin microparticle

Purpose: Protein microencapsulation in biodegradable polymers is a promising route to provide for sustained release. The erythropoietin (EPO) microparticles are using human serum albumin (HSA) and poly-L-lysine (PK) as the protection complex to increased EPO integrity, entrapped efficiency and active EPO release by w/o/w solvent evaporation techniques. The optimum formulation development process was also reported by using FITC-OVA as a model protein.

Methods: The model protein FITC-ovalbumin and EPO are protected by human serum albumin and poly-L-lysine complex and encapsulated in 50:50 poly(DL-lactide-co-glycolide) by a w/o/w solvent evaporation method. Protein active integrity and degradation compound is measured by size-exclusion chromatography. Protein-loaded microparticle physical properties and in vitro active and degradation compounds release profile are characterized.

Results: High active integrity protein loading efficiency and particle yield of EPO or OVA-HSA/PK-loaded PLG microparticles are successfully produced by a w/o/w solvent evaporation method. Varied protection protein complex formulations and encapsulation processes are investigated. The high OVA model protein loading efficiency (80.2%), FITC-OVA content (0.24?µg?mg^?1) and yield (72.4%) are obtained by adding 100?µg?mL^?1 FITC-OVA complex with 10% HSA/0.05% PK (Mw 1.5–3?kD) in the initial solution to protect the model protein. In vitro release profiles show more active OVA release from HSA/PK OVA-loaded than OVA-loaded only microparticles and also the amount of degraded protein that comes out after 3 weeks incubated in the PBS medium for OVA-loaded only microparticles is observed. The same formulation and preparation process resulted in EPO loading efficiency (68.4%), EPO content (0.23?µg?mg^?1) and yield (76.1%) for HSA/PK EPO-loaded microparticles. In vitro release profiles show active EPO sustained release over 7 days. Using HSA/PK as carried in the primary emulsion of EPO-loaded microparticles resulted in less burst release% than EPO-loaded only microparticles.     

Preparation of poly-l-lysine-based nanoparticles with pH-sensitive release of curcumin for targeted imaging and therapy of liver cancer in vitro and in vivo

Poly-l-lysine (PLL) nanoparticle (NP) system was prepared for the controlled release of curcumin (CUR) by pH stimuli, and its theranostic efficacy on cancer was compared to that of CUR solution in vitro and in vivo. Deoxycholic acid (DOCA), methoxy polyethylene glycol (MPEG) and cyanine 5.5 (cy5.5) were conjugated to the amine group of PLL through condensation reaction (PLL-DOCA-MPEG-cy5.5), followed by encapsulation of CUR by dialysis method (PLL-DOCA-MPEG-cy5.5/CUR NPs). The composition, morphology and size distribution of PLL-DOCA-MPEG-cy5.5 NPs were characterized by proton nuclear magnetic resonance (¹H NMR), transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. In vitro tests exhibited that changes in the charge and size of the NPs at low pH led to the improved cellular uptake of CUR into human hepatoma Hep3B cell line by electrostatically absorptive endocytosis. PEGylation with MPEG was turn out to be very effective to have a prolonged blood circulation time, in turn increased the EPR effect. In addition, the incorporation of Cy5.5 into NPs provided successful biodistribution images in vivo and ex vivo. Our findings suggest that PLL-DOCA-MPEG-cy5.5/CUR NPs may have promising applications in cancer theranosis.     

l-Peptide functionalized dual-responsive nanoparticles for controlled paclitaxel release and enhanced apoptosis in breast cancer cells

Nanoparticles and macromolecular carriers have been widely used to increase the efficacy of chemotherapeutics, largely through passive accumulation provided by their enhanced permeability and retention effect. However, the therapeutic efficacy of nanoscale anticancer drug delivery systems is severely truncated by their low tumor-targetability and inefficient drug release at the target site. Here, the design and development of novel l-peptide functionalized dual-responsive nanoparticles (l-CS-g-PNIPAM-PTX) for active targeting and effective treatment of GRP78-overexpressing human breast cancer in vitro and in vivo are reported. l-CS-g-PNIPAM-PTX NPs have a relative high drug loading (13.5%) and excellent encapsulation efficiency (74.3%) and an average diameter of 275?nm. The release of PTX is slow at pH 7.4 and 25?°C but greatly accelerated at pH 5.0 and 37?°C. MTT assays and confocal experiments showed that the l-CS-g-PNIPAM-PTX NPs possessed high targetability and antitumor activity toward GRP78 overexpressing MDA-MB-231 human breast cancer cells. As expected, l-CS-g-PNIPAM-PTX NPs could effectively treat mice bearing MDA-MB-231 human breast tumor xenografts with little side effects, resulting in complete inhibition of tumor growth and a high survival rate over an experimental period of 60 days. These results indicate that l-peptide-functionalized acid – and thermally activated – PTX prodrug NPs have a great potential for targeted chemotherapy in breast cancer.     

Sodium fusidate-poly(D,L-lactide-co-glycolide) microspheres: Preparation,characterisation and in vivo evaluation of their effectiveness in the treatment of chronic osteomyelitis

Purpose: The aim of this study was to prepare poly(D,L-lactide-co-glycolide) (PLGA) microspheres containing sodium fusidate (SF) using a double emulsion solvent evaporation method with varying polymer:drug ratios (1:1, 2.5:1, 5:1) and to evaluate its efficiency for the local treatment of chronic osteomyelitis.

Methods: The particle size and distribution, morphological characteristics, thermal behaviour, drug content, encapsulation efficiency and in vitro release assessments of the formulations had been carried out. Sterilized SF-PLGA microspheres were implanted in the proximal tibia of rats with methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. After 3 weeks of treatment, bone samples were analysed with a microbiological assay.

Results: PLGA microspheres between the size ranges of 2.16–4.12?µm were obtained. Production yield of all formulations was found to be higher than 79% and encapsulation efficiencies of 19.8–34.3% were obtained. DSC thermogram showed that the SF was in an amorphous state in the microspheres and the glass transition temperature (T_g) of PLGA was not influenced by the preparation procedure. In vitro drug release studies had indicated that these microspheres had significant burst release and their drug release rates were decreased upon increasing the polymer:drug ratio (p?<?0.05). Based on the in vivo data, rats implanted with SF-PLGA microspheres and empty microspheres showed 1987?±?1196 and 55526?±?49086 colony forming unit of MRSA in 1?g bone samples (CFU/g), respectively (p?<?0.01).

Conclusion: The in vitro and in vivo studies had shown that the implanted SF loaded microspheres were found to be effective for the treatment of chronic osteomyelitis in an animal experimental model. Hence, these microspheres may be potentially useful in the clinical setting.     

Stability of proteins encapsulated in injectable and biodegradable poly(lactide-co-glycolide)-glucose millicylinders

PURPOSE: To characterize protein stability in poly(lactide-co-glycolide) 50/50-glucose star (PLGA-Glu) injectable millicylinders and to compare results with linear PLGA 50/50. METHODS: Bovine serum albumin (BSA), a model protein, was encapsulated in PLGA-Glu and linear PLGA millicylinders by solvent-extrusion and incubated under physiological conditions. Important system properties were characterized, including: polymer molecular weight distribution, soluble acidic residues, polymer morphology, polymer water uptake, microclimate pH, protein content and release, and protein aggregation. The polymer microclimate late in the release incubation was simulated and protein recovery was analyzed by UV280, size exclusion chromatography, amino acid analysis, and a modified Bradford assay. RESULTS: PLGA-Glu contained higher levels of low molecular weight oligomers, more rapidly biodegraded, and exhibited a lower microclimate pH than the linear 50/50 PLGA, which is the most acidic type in the PLGA family. BSA, when encapsulated in PLGA-Glu millicylinders, underwent extensive noncovalent insoluble aggregation over 2 weeks in vitro release, which was almost completely inhibited upon co-encapsulation of Mg(OH)2. However, by 5 weeks release for base-containing formulations, although insoluble aggregation was still suppressed, the soluble fraction of protein in the polymer was unrecoverable by the modified Bradford assay. Polymer microclimate simulations with extensive protein analysis strongly suggested that the low recovery was mostly caused by base-catalyzed hydrolysis of the oligomeric fraction of BSA. CONCLUSIONS: In PLGA-Glu, the acidic microclimate was similarly responsible for insoluble aggregation of encapsulated BSA. BSA aggregation was inhibited in millicylinders by co-incorporation into the polymer an insoluble base, but over a shorter release interval than linear PLGA likely because of a more acidic microclimate in the star polymer.     

Preparation and evaluation of double-walled microparticles prepared with a modified water-in-oil-in-oil-in-water (w1/o/o/w3) method

Abstract

In this study, a modified water-in-oil-in-oil-in-water (w₁/o/o/w₃) method was developed to prepare double-walled microparticles containing ovalbumin (OVA). The microparticles were characterized with respect to their morphology, particle size, encapsulation efficiency, production yield, thermal properties and in vitro drug release. Microscopy observations clearly showed that microparticles have spherical shape and smooth surface. These microparticles were characterized to have double-walled structure, with a cavity in the centre. By using w₁/o/o/w₃ method, a significant decrease in mean particle size and a significant increase in encapsulation efficiency were obtained. The mean particle size and the encapsulation efficiency of double-walled microparticles were also affected by the changing amount of OVA and mass ratio of polymers. Microparticles prepared with two polymers exhibited a significantly lower initial burst release followed by sustained release compared to microparticles made from poly(d,l-lactide-co-glycolide) 50/50 only. It can be concluded that these microparticles can be a potential delivery system for therapeutic proteins.     

Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal delivery

This study investigates the physicochemical properties of glycyl-histidyl-lysine-copper (GHK-Cu) to support the development of a formulation for effective topical delivery. The solubility and distribution coefficients (log D) were investigated using conventional methods and GHK concentrations were quantified with a validated stability-indicating reversed phase high performance liquid chromatography (RP-HPLC) method. In addition, the stability of GHK-Cu under stressed conditions and the compatibility with some potential formulation components were assessed. The peptide was susceptible to hydrolytic cleavage under basic and oxidative stressors and to a lesser extent acidic stress with first-order degradation profiles. Surprisingly, the peptide was stable in water and in pH (4.5–7.4) buffers for at least two weeks at 60 °C. The HPLC in conjunction with mass spectrometry identified three key degradation products, one of which was the constituent amino acid histidine. The distribution coefficients in octanol-phosphate buffered saline indicated the highly hydrophilic nature of GHK-Cu with log D values between ?2.38 and ?2.49 at pH range of 4.5–7.4. Furthermore, GHK-Cu was compatible with Span 60 based niosomes but less stable in the presence of the negatively charged lipid dicetyl phosphate. In summary, the preformulation studies provided information useful to deliver the GHK-Cu complex by carrier.