Stability of cyclosporine-loaded poly-sigma-caprolactone nanoparticles

Freeze-Drying of Pharmaceutical and Nutraceutical Nanoparticles: The Effects of Formulation and Technique Parameters on Nanoparticles Characteristics

Nanoparticles (NPs) are of the most interesting novel vehicles for effective drug delivery to humans. Freeze drying is known as an engaging process to improve the long lasting stability of NPs formulations. This study aims to elucidate the importance of various parameters involving in freeze-drying of the most common pharmaceutical/nutraceutical NPs including nanosuspensions, nanocrystals (NCs), cocrystals/nanococrystals, nanoemulsions (NEs), nanocapsules (NCPs) and nanospheres (NSPs). Regarding this, the therapeutic goals of NPs and specifications of drug must be considered. According to our survey, the most influential factors for achieving optimum results include type and concentration of cryoprotectant/lyoprotectant, stabilizer structure and concentration, the NPs concentration in solution, freezing, annealing, and drying rate, the interaction between protectants and stabilizer, solvent type and antisolvent to solvent ratio. The study shows that for each class of NPs, specific variables are of highest significance and should be optimized. For instance, about NCs, freezing rate and antisolvent/solvent ratio should be particularly considered and for emulsified NPs, the best results have been obtained by 5-20% of saccharides as cryoprotectants. These findings suggest that to obtain a product with the lowest aggregation and particle size (PS), optimization of the effective factors in formulation and lyophilization process are essential.

Converting nanosuspension into inhalable and redispersible nanoparticles by combined in-situ thermal gelation and spray drying

While nanoparticulate drugs for deep lung delivery hold promise for particular disease treatments, their size-related physical instability and tendency of being exhaled during breathing remain major challenges to their inhaled formulation development. Here we report a viable method for converting drug nanosuspensions into inhalable, stable and redispersible nano-agglomerates through combined in-situ thermal gelation and spray drying. Itraconazole (ITZ) nanosuspensions were prepared by flash nanoprecipitation, and co-spray dried with two different grades of the gel-forming polymer, methylcellulose (MC M20 and MC M450) as protectants. MC M20 was found superior in protecting ITZ nanoparticles against thermal stress (through nanoparticle entrapment within its gel network structure) during spray drying. In terms of redispersibility, an S_f/S_i ratio (i.e., ratio of nanoparticle sizes after and before spray drying) of unity (1.02 ± 0.03), reflecting full particle size preservation, was achieved by optimizing the suspending medium content and spray drying parameters. Formulation components, nanosuspension concentration and spray drying parameters all showed a significant impact on the aerosol performance of the resulting agglomerates, but an absence of defined trends or correlations. Overall, the MC-protected nano-agglomerates displayed excellent in-vitro aerosol performance with fine particle fractions higher than 50% and mass median aerodynamic diameters within the 2-3 µm range, which are ideal for deep lung delivery.

Spray coating of foley urinary catheter by chlorhexidine-loadedpoly(ε-caprolactone) nanospheres: effect of lyoprotectants, characteristics, and antibacterial activity evaluation

In this study, chlorhexidine-loaded poly(ε-caprolactone) nanospheres (CHX-NS) were prepared and successfully coated on the urinary catheters. Properties of CHX-NS were evaluated including drug loading content and the nanosphere size. Effects of different lyoprotectants for long-term storage of CHX-NS were also investigated. In vitro release study and antibacterial activity were also conducted using 20 cycles coated-urinary catheters. Results showed that the high-pressure emulsification-solvent evaporation technique provided the drug loading content at 1.14 ± 0.16% and the size of nanospheres was 152 ± 37 nm. The suitable lyoprotectant for long-term storage of CHX-NS was sucrose which provided noticeably no aggregation at the degree of reconstitution at 89.95%. The amount of CHX loading on coated catheters was at 4.55 ± 0.31 mg. Drug release from the coated catheters in artificial urine could be prolonged up to 2 weeks and bacteria proliferation was inhibited up to 14 days. These results suggest that the antimicrobial activity of CHX-NS reduces the adherence of the uropathogens to the catheter surface. Chlorhexidine-loaded polymeric nanospheres were fabricated which can be successfully coated on urinary catheters. These systems have potential use for prolonged antimicrobial applications.

Poly(lactic acid) nanoparticles loaded with ursolic acid: Characterization and in vitro evaluation of radical scavenging activity and cytotoxicity

The purpose of this study was to develop poly(lactic acid) (PLA) nanoparticles containing ursolic acid (UA) by an emulsification-solvent evaporation technique and evaluate the radical scavenging activity over hypochlorous acid (HOCl) and cytotoxicity over erythrocytes and tumor cells. Nanoparticles were successfully obtained and presented mean size of 246nm with spherical or slightly oval morphology, negative zeta potential and 96% of UA encapsulation efficiency. Analyses of FTIR, XRD and DSC-DTG suggest interaction/complexation of UA with PLA matrix and drug amorphization promoted by nanoencapsulation process. Stability study showed that room temperature was the best condition for nanoparticles storage. The in vitro release study showed UA was released from the polymeric matrix over two constants (α, β), suggesting a second order kinetics. After 120h of assay, 60% of UA were released by diffusion. In the HOCl scavenging activity, after 72h of assay UA-loaded nanoparticles presented the same efficacy of free drug. In cytotoxicity test over red blood cells, UA-loaded nanoparticles showed less toxicity on cells than free drug. The cytotoxicity assay over melanoma cells line (B16-F10) showed after 72h that nanoparticles were able to reduce the cell viability in 70%. PLA nanoparticles showed be potential carriers for UA maintaining the antioxidant and antitumor activity of the UA and decreasing its cytotoxicity over normal cells.

Facts and evidences on the lyophilization of polymeric nanoparticles for drug delivery

Lyophilization has been used to improve the long-term stability of polymeric nanoparticles for drug delivery applications, avoiding their instability in suspension. However, this dehydration process may induce stresses to nanoparticles, mitigated by the use of some excipients such as cryo- and lyoprotectants. Still, the lyophilization of polymeric nanoparticles is frequently based in empirical principles, without considering the physical-chemical properties of formulations and the engineering principles of lyophilization. Therefore, the optimization of formulations and the lyophilization cycle is crucial to obtain a good lyophilizate, and guarantee the preservation of nanoparticle stability. The proper characterization of the lyophilizate and nanoparticles has a great importance in achieving these purposes. This review updates the fundaments involved in the optimization procedures for lyophilization of polymeric nanoparticles, with the aim of obtaining the maximum stability of formulations. Different characterization methods to obtain and guarantee a good lyophilized product are also discussed. A special focus is given to encapsulated therapeutic proteins. Overall, this review is a contribution for the understanding of the parameters involved in the lyophilization of polymeric nanoparticles. This may definitely help future works to obtain lyophilized nanoparticles with good quality and with improved therapeutic benefits.

Effect of cryoprotectants on the porosity and stability of insulin-loaded PLGA nanoparticles after freeze-drying

PLGA nanoparticles are useful to protect and deliver proteins in a localized or targeted manner, with a long-term systemic delivery pattern intended to last for a period of time, depending on polymer bioerosion and biodegradability. However, the principal concern regarding these carriers is the hydrolytic instability of polymer in aqueous suspension. Freeze-drying is a commonly used method to stabilize nanoparticles, and cryoprotectants may be also used, to even increase its physical stability. The aim of the present work was to analyze the influence of cryoprotectants on nanoparticle stability and porosity after freeze-drying, which may influence protein release and stability. It was verified that freeze-drying significantly increased the number of pores on PLGA-NP surface, being more evident when cryoprotectants are added. The presence of pores is important in a lyophilizate to facilitate its reconstitution in water, although this may have consequences to protein release and stability. The release profile of insulin encapsulated into PLGA-NP showed an initial burst in the first 2 h and a sustained release up to 48 h. After nanoparticles freeze-drying the insulin release increased about 18% in the first 2 h due to the formation of pores, maintaining a sustained release during time. After freeze-drying with cryoprotectants, the amount of insulin released was higher for trehalose and lower for sucrose, glucose, fructose and sorbitol comparatively to freeze-dried PLGA-NP with no cryoprotectant added. Besides the porosity, the ability of cryoprotectants to be adsorbed on the nanoparticles surface may also play an important role on insulin release and stability.

Hydrogels containing redispersible spray-dried melatonin-loaded nanocapsules: a formulation for transdermal-controlled delivery

The aim of the present study was to develop a transdermal system for controlled delivery of melatonin combining three strategies: nanoencapsulation of melatonin, drying of melatonin-loaded nanocapsules, and incorporation of nanocapsules in a hydrophilic gel. Nanocapsules were prepared by interfacial deposition of the polymer and were spray-dried using water-soluble excipients. In vitro drug release profiles were evaluated by the dialysis bag method, and skin permeation studies were carried out using Franz cells with porcine skin as the membrane. The use of 10% (w/v) water-soluble excipients (lactose or maltodextrin) as spray-drying adjuvants furnished redispersible powders (redispersibility index approximately 1.0) suitable for incorporation into hydrogels. All formulations showed a better controlled in vitro release of melatonin compared with the melatonin solution. The best controlled release results were achieved with hydrogels prepared with dried nanocapsules (hydrogels > redispersed dried nanocapsules > nanocapsule suspension > melatonin solution). The skin permeation studies demonstrated a significant modulation of the transdermal melatonin permeation for hydrogels prepared with redispersible nanocapsules. In this way, the additive effect of the different approaches used in this study (nanoencapsulation, spray-drying, and preparation of semisolid dosage forms) allows not only the control of melatonin release, but also transdermal permeation.

Effect of various formulation parameters on the properties of polymeric nanoparticles prepared by multiple emulsion method

This work evaluates and interprets underlying mechanisms behind various aspects related to preparation and physical characteristics of polymeric nanoparticles (NP). These were prepared from different biodegradable polymers according to a water-in-oil-in-water emulsion solvent evaporation method. Polymers used were poly(lactic-co-glycolic) acid (PLGA), poly (lactic acid) (PLA), (PLA-PEG-PLA) triblock and (PLA-PEG-PLA)n multi-block co-polymers. A model DNA, as an example of a hydrophilic drug, was encapsulated in the internal aqueous phase. The primary emulsion was prepared using a high shear turbine mixer. The secondary emulsion was prepared by high-pressure homogenization. Surface morphology and internal structure were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Influence of process variables on the physical properties of NP has been studied. Release of DNA was evaluated. In addition, changes occurring to NP porosity and surface area during degradation were followed. Nanoparticle size was ranging between 200-700 nm, according to the preparation conditions. Homogenizing pressure, concentration of the emulsifying agent used, polymer concentration and type and the concentration of a cryoprotectant had variable effects on NP size, surface area and porosity. Batches of NP where no emulsifying agent was added were obtained successfully. The release rate of the DNA from NP was mainly dependent on porosity, which varied significantly among used polymers. The preparation technique was efficient in encapsulating the model DNA and will be used for plasmid encapsulation in a future work.

Conjugates of poly(DL-lactide-co-glycolide) on amino cyclodextrins and their nanoparticles as protein delivery system

Poly(DL-lactide-co-glycolide) (PLG) was chemically conjugated on two amino cyclodextrins, mono(6-(2-aminoethyl)amino-6-deoxy)-beta-cyclodextrin and ethylenediamino bridged bis(beta-cyclodextrin), to afford novel amphiphilic conjugates. Those conjugates were then characterized with infrared spectrometry (IR), proton nuclear magnetic resonance ((1)H NMR) and gel permeation chromatography (GPC). A repeat-nanoprecipitation (RP-NP) method was also developed to fabricate the nanoparticles of the conjugates with a water-soluble model protein, bovine serum albumin (BSA). At the end of RP-NP process, the availability of BSA was over 80% while the entrapment efficiency was 40-50% for each nanoprecipitation. The nanoparticles were rigid and spherical with diameters of 110-180 nm determined by transmission electron microscope (TEM), atomic force microscopy (AFM) and particle size analyzer. Nanoparticles possessed good steric stability during freeze-drying and resuspensions due to the existence of cyclodextrins corona. Interactions between BSA and the conjugates in the nanoparticles were then elucidated with IR experiments. About 25% BSA adsorbed on the surface of nanoparticles due to the interaction and was easy to release in the first day. The release of BSA from the nanoparticles was in three phases: a burst effect in the first day, a followed plateau in about a week, and a sustained release of the protein over 14 days. By changing the lactide/glycolide ratio, the degradation time of the conjugates and the release rate of BSA could be controlled. The loss of CDs content was faster than that of overall Mw during degradation since CDs formed outer corona of the nanoparticles. Both the novel biomaterials and the nanosphere fabrication technique contributed to the maintenance of protein structure.

A Practical Approach to the use of Nanoparticles for Vaccine Delivery

The objective of this work was to obtain a nanoparticle formulation that could be sterile filtered, lyophilized, and resuspended to the initial size with excipients appropriate for use as a vaccine formulation. Poly(lactide-co-glycolide) (PLG) polymers were used to create nanoparticles ranging in size from 110 to 230 nm. Protein antigens were adsorbed to the particles; the protein-nanoparticles were then lyophilized with the excipients. Vaccine compatible excipient combinations of sugars alone, surfactants alone, and sugars and surfactants were tested to find conditions where initial particle size was recovered. Sterile filtration of smaller nanoparticles led to minimal PLG losses and allowed the particle preparation to be a nonaseptic process. We found that the smaller nanoparticles of size approximately 120 nm required higher surfactant concentration to resuspend postlyophilization than slightly larger ( approximately 220 nm) particles. To resuspend 120 nm nanoparticles formulations of poly(vinyl alcohol) (PVA) with sucrose/mannitol or dioctyl sodium sulfosuccinate (DSS) with trehalose/mannitol were sufficient. The protein-nanoparticles resuspension with the same excipients was dependent on the protein and protein loading level. The nanoparticle formulations in vivo were either similar or had enhanced immunogenicity compared to aluminum hydroxide formulations. A lyophilized nanoparticle formulation with adsorbed protein antigen and minimal excipients is an effective vaccine delivery system.

Stabilisation by freeze-drying of cationically modified silica nanoparticles for gene delivery

Core shell silica particles with a hydrodynamic diameter of 28nm, an IEP of 7.1 and a zeta potential of +35mV at pH 4.0 were synthesised. The role of freeze-drying for the conservation of zwitterionic nanoparticles and the usefulness of different lyoprotective agents (LPA) for the minimisation of particle aggregation were studied. The activity of the nanoparticles was measured as DNA-binding capacity and transfection efficiency in Cos-1 cells before and after lyophilisation. It was found that massive aggregation occurred in the absence of LPA. Of the various LPAs screened in the present investigations, trehalose and glycerol were found to be well suited for conservation of cationically modified silica nanoparticles with simultaneous preservation of their DNA-binding and transfection activity in Cos-1 cells.

Freeze-drying of polycaprolactone and poly(D,L-lactic-glycolic) nanoparticles induce minor particle size changes affecting the oral pharmacokinetics of loaded drugs

The present study was geared at identifying the conditions to stabilize poly (D,L-lactic-glycolic) (PLGA) and polycaprolactone (PCL) nanoparticles (NP) by freeze-drying with several cryoprotective agents. Differential scanning calorimetry and freeze-thawing studies were used to optimize the lyophilization process. These studies showed that all samples were totally frozen at -45 degrees C and evidenced the necessity of adding sucrose, glucose, trehalose or gelatine to preserve the properties of NP regardless of the freezing procedure. However, only 20% sucrose and 20% glucose exerted an acceptable lyoprotective effect on PLGA and PCL NP, respectively. Nonetheless, the final to initial size ratios ( approximately 1.5) indicated that particle size was slightly affected in both cases. In vivo studies with CyA-loaded PCL NP whose sizes matched those obtained after NP preparation (100 nm) and after being lyophilized (160 nm) showed that the changes of particle size might have some relevance on drug pharmacokinetics. The MRT was significantly (P<0.05) modified after an oral CyA dose of 5 mg/kg and the treatment with 160-nm sized CyA-loaded NP produced a higher drug partition into the liver of Wistar rats potentially affecting the toxic and immunosuppressive profile of the drug. Therefore, although the particle size changes induced by NP lyophilization were slight, they need to be carefully evaluated and cannot be neglected.

Reversion of multidrug resistance by co-encapsulation of doxorubicin and cyclosporin A in polyalkylcyanoacrylate nanoparticles

Individual and combined polyalkylcyanoacrylate nanoparticle formulation of cyclosporin A and doxorubicin were prepared and evaluated in an attempt to show improved growth inhibition efficacy in a resistant cell culture line. The drug loaded nanoparticles were prepared using the well established emulsion polymerization process without using any modification for the hydrophilic doxorubicin drug whereas the incorporation of cyclosporin A needed to wait a moment after the polymerization reaction started. This was necessary to avoid cyclosporin A precipitation and polymer aggregation. Cyclosporin A release from the nanoparticles was rapid probably because the drug was adsorbed onto the nanoparticles surface rather than embedded into the polymeric core. Doxorubicin displayed also a burst effect but with a slower second phase probably related with the nanoparticles bioerosion rate owing to its entrapment in the polymeric network. Finally, it was shown in resistant cell culture experiments that the association of both cyclosporin A and doxorubicin within a single nanoparticle formulation elicited the most effective growth rate inhibition as compared to other combinations of both drugs while using a lower amount of polymer compared to separated nanoparticle formulations. This result was probably due to the synergistic effect achieved by combining the chemo-sensitizing compound cyclosporin A, with an effective cytotoxic drug like doxorubicin.

Stability and freeze-drying of cyclosporine loaded poly(D,L lactide-glycolide) carriers

The present paper describes the stability of poly (D, L-lactide-glycolide) nanoparticles (PLGA NP) and microspheres (MS), either alone or loaded with cyclosporine (CyA), stored at 8 degrees C and room temperature (RT). Freeze-drying of these formulations was evaluated as an alternative method to achieve long term stability. A significant polymer rupture was detected during PLGA MS preparation by solvent evaporation, which correlated with the stirring rates used for the formation of the primary emulsion. On the other hand, the polymer remained unchanged during NP formation. After 6 months of storage, PLGA NP of a size below 80 nm aggregated when stored at RT whereas no changes of particle size were observed for the remaining formulations and experimental conditions. Drug entrapment significantly increased by about 9.5% only during PLGA NP storage at RT. The PLGA molecular weight of NP dropped at RT being these changes related to the initial particle size and amount of CyA incorporated. The same effect was observed at 8 degrees C but only the particle size showed a significant influence. The drop of PLGA molecular weight observed during storage of MS was not dependent on the storage temperature but it was directly related to the molecular weights obtained after MS preparation. Freeze-drying studies revealed that it was not feasible to maintain the initial PLGA NP characteristics after reconstitution. On the other hand, MS lyophilized in the absence of cryoprotectants retained the drug initially entrapped; however, the presence of at least 5% cryoprotectant was essential to keep the initial particle size. Therefore, PLGA NP and MS show a significant instability when stored as suspensions. Freeze-drying offers a good alternative to stabilize polymeric MS but the preservation of the PLGA NP characteristics by freeze-drying needs for further investigations.