On shelf stability of freeze-dried poly(methylidene malonate 2.1.2) nanoparticles

To Protect and to Preserve: Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs.

A review of implantable intravitreal drug delivery technologies for the treatment of posterior segment eye diseases

Intravitreal implantable device technology utilizes engineered materials or devices that could revolutionize the treatment of posterior segment eye diseases by affording localized drug delivery, responding to and interacting with target sites to induce physiological responses while minimizing side-effects. Conventional ophthalmic drug delivery systems such as topical eye-drops, systemic drug administration or direct intravitreal injections do not provide adequate therapeutic drug concentrations that are essential for efficient recovery in posterior segment eye disease, due to limitations posed by the restrictive blood-ocular barriers. This review focuses on various aspects of intravitreal drug delivery such as the impediment of the blood-ocular barriers, the potential sites or intraocular drug delivery device implantation, the various approaches employed for ophthalmic drug delivery and includes a concise critical incursion into specialized intravitreal implantable technologies for the treatment of anterior and posterior segment eye disease. In addition, pertinent future challenges and opportunities in the development of intravitreal implantable devices is discussed and explores their application in clinical ophthalmic science to develop innovative therapeutic modalities for the treatment of various posterior segment eye diseases. The inherent structural and functional properties, the potential for providing rate-modulated drug delivery to the posterior segment of the eye and specific development issues relating to various intravitreal implantable drug delivery devices are also expressed in this review.

Freeze thaw: a simple approach for prediction of optimal cryoprotectant for freeze drying

The present study evaluates freeze thaw as a simple approach for screening the most appropriate cryoprotectant. Freeze-thaw study is based on the principle that an excipient, which protects nanoparticles during the first step of freezing, is likely to be an effective cryoprotectant. Nanoparticles of rifampicin with high entrapment efficiency were prepared by the emulsion-solvent diffusion method using dioctyl sodium sulfosuccinate (AOT) as complexing agent and Gantrez AN-119 as polymer. Freeze-thaw study was carried out using trehalose and fructose as cryoprotectants. The concentration of cryoprotectant, concentration of nanoparticles in the dispersion, and the freezing temperature were varied during the freeze-thaw study. Cryoprotection increased with increase in cryoprotectant concentration. Further, trehalose was superior to fructose at equivalent concentrations and moreover permitted use of more concentrated nanosuspensions for freeze drying. Freezing temperature did not influence the freeze-thaw study. Freeze-dried nanoparticles revealed good redispersibility with a size increase that correlated well with the freeze-thaw study at 20% w/v trehalose and fructose. Transmission electron microscopy revealed round particles with a size approximately 400 nm, which correlated with photon correlation spectroscopic measurements. Differential scanning calorimetry and X-ray diffraction suggested amorphization of rifampicin. Fourier transfer infrared spectroscopy could not confirm interaction of drug with AOT. Nanoparticles exhibited sustained release of rifampicin, which followed diffusion kinetics. Nanoparticles of rifampicin were found to be stable for 12 months. The good correlation between freeze thaw and freeze drying suggests freeze-thaw study as a simple and quick approach for screening optimal cryoprotectant for freeze drying.

Development of alpha-tocopherol acetate nanoparticles: influence of preparative processes

We studied different methods of preparing alpha-tocopherol acetate (ATA) nanoparticles, which are to be used in targeting the lungs as aerosols in order to prevent cigarette smoke toxicity. Poly-(lactide) nanoparticles were prepared using nanoprecipitation and solvent evaporation techniques, which produced, respectively, too small and too large nanoparticles to be aerosolized. The emulsification-diffusion method produced 2 months stable nanoparticles with a size between (500-700 nm). Increasing ATA concentration (1-7 mg/mL) induced a decrease in the association rate (97-93%) and in the adsorbed ATA rate (7-4.5%), which was associated with variations of Zeta potentials (-27.5 to -24.3 mV) and decrease in polymeric wall thickness and density.

Formulation development of freeze-dried oligonucleotide-loaded gelatin nanoparticles

The freeze-drying properties of gelatin nanoparticles were investigated with the goal of providing practicable nanoparticle formulations for in vitro applications or clinical studies. Various excipients and rehydration protocols were assessed, and gelatin nanoparticles loaded with oligonucleotides were successfully freeze-dried and rehydrated. An NF-kappaB decoy oligonucleotide-loaded gelatin nanoparticle formulation was developed and applied in a drug targeting approach in an animal model. The high concentrations of nanoparticles achieved after rehydration with reduced volumes proved to be critical for the in vivo effect. Finally, short term storage stability under accelerated conditions was assessed for dried gelatin nanoparticles formulated in sucrose, trehalose, mannitol, or a mannitol/sucrose mixture. Size, size distribution, and residual moisture content were investigated. Sucrose- and trehalose-containing formulations exhibited the greatest stability, but mannitol-containing formulations also showed notable stabilization despite their crystalline nature.

Biodegradable scleral implants as new triamcinolone acetonide delivery systems

The goal of this study was to develop ocular scleral implants able to release triamcinolone acetonide (TA) overall several months. Scleral discs were manufactured by a compression-molding method using a new synthetic polymer, poly(methylidene malonate) (PMM2.1.2), as matrix. Implants with good mechanical properties adapted for in vivo implantation have been obtained when using high M(w) PMM2.1.2 (100,000 - 150,000 Da) associated with ethoxylated derivatives of stearic acid (Simulsol) or oligomers of methylidene malonate as plasticizer. After implantation in rabbit eyes, scleral implants showed a good ocular biocompatibility. Indeed, the clinical follow-up and ocular inflammation parameters, such as inflammatory cell number and protein content in aqueous humor, demonstrated that implants were well tolerated and did not provoke abnormal inflammation. Implants were able to release significant concentrations of TA in the vitreous and the sclera throughout 5 weeks.

The effect of freeze-drying with different cryoprotectants and gamma-irradiation sterilization on the characteristics of ciprofloxacin HCl-loaded poly(D,L-lactide-glycolide) nanoparticles

In the present study, the influence of freeze-drying with several cryoprotective agents and gamma (gamma)-irradiation sterilization on the physicochemical characteristics of ciprofloxacin HCl-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles was evaluated. Nanoparticles were prepared by W/O/W emulsification solvent evaporation followed by high-pressure homogenization. They were freeze-dried in the presence of 5.0% (w/v) mannitol, trehalose or glucose, with 5.0% (w/v) or 15.0% (w/v) dextran as cryoprotectants. The nanoparticles were irradiated at a dose of 25 kGy using a 60Co source. The following physicochemical properties of the formulations were investigated: the ratio of particle size before (initial) and after freeze-drying, the ease of reconstitution of the nanoparticle suspensions and the drug-release profiles of irradiated and non-irradiated nanoparticles. The antibacterial activity against Pseudomonas aeruginosa was measured. The freeze-drying process induced a significant increase in particle size when no cryoprotectant was employed. Similar results were observed when cryoprotectants were added to the formulation. Only when mannitol was used was no significant size increase measured. Moreover, for formulations with dextran, reconstitution after freeze-drying was difficult by manual agitation and particle size could not be determined because of aggregation. After gamma-sterilization no significant difference in mean particle size was observed, but reconstitution was more difficult and drug release was influenced negatively. Ciprofloxacin HCl incorporated in the nanoparticles was still effective against the micro-organism selected after freeze-drying and gamma-sterilization.

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.