Co-Amorphous Formation of High-Dose Zwitterionic Compounds with Amino Acids To Improve Solubility and Enable Parenteral Delivery.

Solubilization of parenteral drugs is a high unmet need in both preclinical and clinical drug development. Recently, co-amorphous drug formulation has emerged as a new strategy to solubilize orally dosed drugs. The aim of the present study is to explore the feasibility of using the co-amorphous strategy to enable the dosing of parenteral zwitterionic drugs at a high concentration. A new screening procedure was established with solubility as the indicator for co-amorphous co-former selection, and lyophilization was established as the method for co-amorphous formulation preparation. Various amino acids were screened, and tryptophan was found to be the most powerful in improving the solubility of ofloxacin when lyophilized with ofloxacin at a 1:1 weight ratio, with more than 10 times solubility increase. X-ray powder diffraction showed complete amorphization of both components, and an elevated Tg compared with the theoretical value was observed in differential scanning calorimetry. Fourier transform infrared spectroscopy revealed that hydrogen bonding and π-π stacking were possibly involved in the formation of a co-amorphous system in the solid state. Further solution-state characterization revealed the involvement of ionic interactions and π-π stacking in maintaining a high concentration of ofloxacin in solution. Furthermore, co-amorphous ofloxacin/tryptophan at 1:1 weight ratio was both physically and chemically stable for at least 2 months at 40 °C/75% RH. Lastly, the same screening procedure was validated with two more zwitterionic compounds, showing its promise as a routine screening methodology to solubilize and enable the parenteral delivery of zwitterionic compounds.

Synthesis and characterization of Poloxamer 188-grafted heparin copolymer.

BACKGROUND: Poloxamer 188 is a safe biocompatible polymer that can be used in protein drug delivery system. AIM: In this study, a new heparin-poloxamer 188 conjugate (HP) was synthesized and its physicochemical properties were investigated. HP structure was confirmed by Fourier transform infrared spectroscopy (FTIR) and Hydrogen-1 nuclear magnetic resonance spectroscopy ((1)H-NMR). Content of the conjugated heparin was analyzed using Toluidine Blue. The critical micelle concentration (CMC) of the copolymer was determined by a fluorescence probe technique. The effect of HP on the gelation of poloxamer 188 was characterized by the rheological properties of the HP-poloxamer hydrogels. Solubility and viscosity of HP were also evaluated compared with poloxamer 188. RESULTS: From the results, the solubility of the conjugated heparin was increased compared with free heparin. The content of heparin in HP copolymer was 62.9%. The CMC of HP and poloxamer 188 were 0.483 and 0.743 mg/mL, respectively. The gelation temperature of 0.4 g/mL HP was 43.5 degrees C, whereas that of the same concentration of poloxamer 188 was 37.3 degrees C. With HP content in poloxamer 188 solution increasing, a V-shape change of gelation temperature was observed. CONCLUSION: Considering the importance of poloxamer 188 in functional material, HP may prove to be a facile temperature-sensitive material for protein drug-targeted therapy.

Comparing encapsulation efficiency and ultrasound-triggered release for protein between phospholipid-based microbubbles and liposomes.

This work was to compare the encapsulation efficiency and ultrasound-triggered release for protein between microbubbles and liposomes. Bovine serum albumin (BSA) was used as a model. Final ratios between BSA and HPC in microbubbles and liposomes were 1:5, 1:7 and 1:10, respectively. Morphologic characteristics and contrast enhancement of loaded microbubbles and liposomes were measured. Encapsulation efficiency and ultrasound-stimulated release profile were detected. The mean size of loaded microbubbles and liposomes was 3.4 microm and 1.7 microm, respectively. Encapsulation efficiency of microbubbles had an inverse relationship with the ratio between BSA and HPC, while loaded liposomes remained nearly unchanged in the designed range of the ratio between BSA and HPC. Microbubbles resulted in significant enhancement of CnTi images. After ultrasound, more than 90% of the entrapped BSA was released from microbubbles, but less than 5% of BSA released from liposomes. Microbubbles are a promising delivery system for proteins.

Phospholipid-based ultrasonic microbubbles for loading protein and ultrasound-triggered release.

BACKGROUND: Ultrasonic microbubbles are used as ultrasound-triggered delivery carriers for protein drugs. AIM: This work was to prepare stabilized protein-loaded phospholipid-based ultrasonic microbubbles (PUM) and to determine its value as a protein delivery system. METHOD: Bovine serum albumin (BSA) was used as a model protein drug. BSA-containing PUM were prepared by dissolving lyophilized PUM powder in BSA solution. The particle size and microbubble concentration of BSA-containing PUM were measured. The BSA encapsulation efficiency as a function of BSA concentration was determined. Contrast enhancement of BSA-containing PUM in vivo was detected. The release profile of BSA from PUM was also investigated. RESULTS: The mean particle size and microbubble concentration of PUM were unchanged by the presence of BSA for at least 30 minutes after preparation. The net amount of BSA entrapped in PUM was maintained unchanged with increasing BSA concentration. BSA-containing PUM were shown easily to be visible in in vivo rabbit kidney. There was no difference in echogenicity between the loaded and unloaded PUM. Ultrasound duration had a positive relationship with BSA release. Ultrasound of 30 seconds stimulated 94.1% and 93.3% of BSA release from PUM solutions containing 0.3% and 1.5% BSA, respectively. CONCLUSIONS: Protein-loaded PUM exhibited satisfactory physical characteristics and were potent for using in ultrasound-triggered delivery.

Enhancing chemotherapeutic drug inhibition on tumor growth by ultrasound: an in vivo experiment.

An in vivo study on enhancing epirubicin hydrochloride (EPI) inhibition on tumor growth by ultrasound (US) was reported. Five-week-old male nude mice were used and HL-60 cells were s.c. (subcutaneous injection) inoculated in axilla of these mice. Six groups were designed and five consecutive treatments were applied to investigate the inhibition on tumor growth and body weight growth. US applied locally to the tumor resulted in a substantially increased drug uptake in tumor cells. The inhibition on tumor growth depended on the position of drug injection and phospholipid-based microbubble (PMB) application. Tumor growth rate under group 1 (PMB+US) was similar to that of blank control. The order of the inhibition on tumor volume growth was: group 4 (s.c. EPI+PMB+US) > group 5 intraperitoneal (i.p. EPI+PMB+US) > group 2 (i.p. EPI) > group 3 (s.c. EPI+US) > group 1 (PMB+US). Similar conclusion was obtained from experimental measurements of tumor weight change. The order of animal survival status for EPI administration groups was: group 4 > group 5 > group 2 > group 3. Chemotherapeutic drug inhibition on tumor growth could be enhanced by local US combined with PMB, which might provide a potential application for US-mediated chemotherapy.

Experiment on the factors for enhancing the susceptibility of cancer cells to chemotherapeutic drug by ultrasound microbubbles.

The objective of this study was to investigate the factors for enhancing the susceptibility of cancer cells to chemotherapeutic drug by ultrasound microbubbles. Ultrasound (US) combined with phospholipid-based microbubbles (MB) was used to enhance the susceptibility of colon cancer cell line SWD-620 to anticancer drugs Topotecan hydrochloride (TOP). Experiments were designed to investigate the influence of main factors on cell viability and cell inhibition, such as US intensity, MB concentration, drug combination with MB, asynchronous action between US triggered cavitation and drug entering cell, MB particle size. US exposure for 10 sec with US probe power at 0.6 W/cm(2) had satisfied cell viability. Treated with US combined with 15% MB, cell viability maintained more than 85% and cell inhibition 86.16%. Under optimal US combined with MB, TOP showed much higher cell inhibition than that of only TOP group. Cell inhibition under short delayed time (<2 h) for TOP addition did not show obvious difference. In terms of MB particle size, the order of cell inhibition was: Mixture > Micron bubble part > Nanometer bubble part. US combined with MB can enhance the susceptibility of cancer cells to chemotherapeutic drug, which may provide a potential method for US-mediated tumor chemotherapy.