Rheological properties of PLGA-PEG-PLGA copolymers for ophthalmic injection

Evaluation of Dose-Response Relationship in Novel Extended Release of Targeted Nucleic Acid Nanocarriers to Treat Secondary Cataracts

Purpose: The present study aimed to determine the dose-response relationship between targeted nanocarriers released from a novel, sustained release formulation and their ability to specifically deplete cells responsible for the development of posterior capsular opacification (PCO) in month-long, dynamic cell cultures. Methods: Injectable, thermosensitive poly(D,L-lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(D,L-lactic-co-glycolic acid) triblock copolymer hydrogels were loaded with either a low or a high dose of doxorubicin-loaded antibody-targeted nanocarriers (G8:3DNA:Dox). Human rhabdomyosarcoma cells, selected for their expression of PCO marker brain-specific angiogenesis inhibitor 1 (BAI1), were kept under dynamic media flow and received either a low or high dose of nanocarriers. Cells were fixed and stained at predetermined time points to evaluate targeted depletion of BAI1+ cells. Results: A lower dose of nanocarriers in hydrogel depleted BAI1+ cells at a slower rate than the higher dose, whereas both reached over 90% BAI1+ cellular nonviability at 28 days. Both treatment groups also significantly lowered the relative abundance of BAI1+ cells in the population compared with the control group. Conclusions: Controlled release of a lower dose of nanocarriers can still achieve therapeutically relevant effects in the prevention of PCO, while avoiding potential secondary effects associated with the administration of a higher dose.

Injectable In-Situ Forming Depot Based on PLGA and PLGA-PEG-PLGA for Sustained-Release of Risperidone: In Vitro Evaluation and Pharmacokinetics in Rabbits

In the current research, novel drug delivery systems based on in situ forming gel (ISFG) (PLGA-PEG-PLGA) and in situ forming implant (ISFI) (PLGA) were developed for one-month risperidone delivery. In vitro release evaluation, pharmacokinetics, and histopathology studies of ISFI, ISFG, and Risperdal CONSTA^® were compared in rabbits. Formulation containing 50% (w/w %) of PLGA-PEG-PLGA triblock revealed sustained release for about one month. Scanning electron microscopy (SEM) showed a porous structure for ISFI, while a structure with fewer pores was observed in the triblock. Cell viability in ISFG formulation in the first days was more than ISFI due to the gradual release of NMP to the release medium. Pharmacokinetic data displayed that optimal PLGA-PEG-PLGA creates a consistent serum level in vitro and in vivo through 30 days, and histopathology results revealed nearly slight to moderate pathological signs in the rabbit's organs. The shelf life of the accelerated stability test didn't affect the results of the release rate test and demonstrated stability in 24 months. This research confirms the better potential of the ISFG system compared with ISFI and Risperdal CONSTA^®, which would increase patients' compliance and avoid problems of further oral therapy.

Blending of PLGA-PEG-PLGA for Improving the Erosion and Drug Release Profile of PCL Microspheres

BACKGROUND

PCL has a long history as an industrialized biomaterial for preparing microspheres, but its hydrophobic property and slow degradation rate often cause drug degeneration, quite slow drug release rate and undesirable tri-phasic release profile.

MATERIALS AND METHODS

In this study, we used the blending material of PLGA-PEG-PLGA and PCL to prepare microspheres. The microspheres degradation and drug release behaviors were evaluated through their molecular weight reduction rate, mass loss rate, morphology erosion and drug release profile. The hydrophilic PLGA-PEG-PLGA is expected to improve the degradation and drug release behaviors of PCL microspheres.

RESULTS

Microspheres in blending materials exhibited faster erosion rates than pure PCL microspheres, forming holes much quickly on the particle's surface for the drug to diffuse out. A higher proportion of PLGA-PEG-PLGA caused faster degradation and erosion rates. The blending microspheres showed much faster drug release rates than pure PCL microspheres.

CONCLUSION

With blending of 25wt% PLGA-PEG-PLGA, the release rate of microspheres speeded up significantly, while, with a further increase of PLGA-PEG-PLGA proportion (50%, 75%, 100%), it accelerated a little. The microspheres with PCL/PLGA-PEG-PLGA of 1/1 exhibited a linear-like drug release profile. The results could be a guideline for preparing microspheres based on blending materials to obtain a desirable release.

Audible Sound from Vibrating Sessile Droplets for Monitoring Chemicals and Reactions in Liquid

To reduce environmental impact and sensor footprint, researchers need cost-effective and small-size surface tension and viscosity measurement devices. New measurement principles are needed for such sensors. We demonstrate that a sessile droplet's mechanical vibration can be transformed to audible sound, by recording the ultrasonic Doppler frequency shift in the form of an acoustic signal. The recorded sound wave reveals a droplet's surface tension and its viscosity, through its frequency spectrum and attenuation rate of the signal, respectively. Based on such sensors, two chemical measurements inside sessile droplets are shown: (I) titration of a Ni²⁺ and Co²⁺ mixture with a surface-active indicator (using surface tension) and (II) measurement of the molecular weight of a polymer in solution (using viscosity). Unlike the commercial technique, our ultrasound-based sensor is cost-effective in terms of equipment price and sample volume.

Synthesis, characterisation and drug release properties of microspheres of polystyrene with aliphatic polyester side-chains

A series of graft copolymers consisting of polystyrene backbone with biocompatible side chains based on (co)polymers of l-lactic acid and glycolic acid were synthesised by combination two controlled polymerisations, namely, nitroxide mediated radical polymerisation (NMRP) and ring opening polymerisation (ROP) with "Click" chemistry. The main goal of this work was to design new biodegradable microspheres using obtained graft copolymers for long-term sustained release of imatinib mesylate (IMM) as a model drug. The IMM loaded microspheres of the graft copolymers, polystyrene-g-poly(lactide-co-glycolide) (PS-g-PLLGA), polystyrene-g-poly(lactic acid) (PS-g-PLLA) and poly(lactic-coglycolic acid) (PLLGA) were then prepared by a modified water-in-oil-in-water (w1/o/w2) double emulsion/solvent evaporation technique. The optimised microspheres were characterised by particle size, encapsulation efficiency, and surface morphology also; their degradation and release properties were studied in vitro. The degradation studies of three different types of microspheres showed that the PS backbone of the graft copolymers slows down the degradation rate compared to PLLGA.