Kara N. Gange

Multifunctional polymersomes for cytosolic delivery of gemcitabine and doxorubicin to cancer cells

Although liposomes are widely used as carriers of drugs and imaging agents, they suffer from a lack of stability and the slow release of the encapsulated contents at the targeted site. Polymersomes (vesicles of amphiphilic polymers) are considerably more stable compared to liposomes; however, they also demonstrate a slow release for the encapsulated contents, limiting their efficacy as a drug-delivery tool. As a solution, we prepared and characterized echogenic polymersomes, which are programmed to release the encapsulated drugs rapidly when incubated with cytosolic concentrations of glutathione. These vesicles encapsulated air bubbles inside and efficiently reflected diagnostic-frequency ultrasound. Folate-targeted polymersomes showed an enhanced uptake by breast and pancreatic-cancer cells in a monolayer as well as in three-dimensional spheroid cultures. Polymersomes encapsulated with the anticancer drugs gemcitabine and doxorubicin showed significant cytotoxicity to these cells. With further improvements, these vesicles hold the promise to serve as multifunctional nanocarriers, offering a triggered release as well as diagnostic ultrasound imaging.

Ultrasound Enhanced Matrix Metalloproteinase-9 Triggered Release of Contents from Echogenic Liposomes

The extracellular enzyme matrix metalloproteinase-9 (MMP-9) is overexpressed in atherosclerotic plaques and in metastatic cancers. The enzyme is responsible for rupture of the plaques and for the invasion and metastasis of a large number of cancers. The ability of ultrasonic excitation to induce thermal and mechanical effects has been used to release drugs from different carriers. However, the majority of these studies were performed with low frequency ultrasound (LFUS) at kilohertz frequencies. Clinical usage of LFUS excitations will be limited due to harmful biological effects. Herein, we report our results on the release of encapsulated contents from substrate lipopeptide incorporated echogenic liposomes triggered by recombinant human MMP-9. The contents release was further enhanced by the application of diagnostic frequency (3 MHz) ultrasound. The echogenic liposomes were successfully imaged employing a medical ultrasound transducer (4-15 MHz). The conditioned cell culture media from cancer cells (secreting MMP-9) released the encapsulated dye from the liposomes (30-50%), and this release is also increased (50-80%) by applying diagnostic frequency ultrasound (3 MHz) for 3 min. With further developments, these liposomes have the potential to serve as multimodal carriers for triggered release and simultaneous ultrasound imaging.

Polymer Coated Echogenic Lipid Nanoparticles with Dual Release Triggers

Although lipid nanoparticles are promising drug delivery vehicles, passive release of encapsulated contents at the target site is often slow. Herein, we report contents release from targeted, polymer-coated, echogenic lipid nanoparticles in the cell cytoplasm by redox trigger and simultaneously enhanced by diagnostic frequency ultrasound. The lipid nanoparticles were polymerized on the external leaflet using a disulfide cross-linker. In the presence of cytosolic concentrations of glutathione, the lipid nanoparticles released 76% of encapsulated contents. Plasma concentrations of glutathione failed to release the encapsulated contents. Application of 3 MHz ultrasound for 2 min simultaneously with the reducing agent enhanced the release to 96%. Folic acid conjugated, doxorubicin-loaded nanoparticles showed enhanced uptake and higher cytotoxicity in cancer cells overexpressing the folate receptor (compared to the control). With further developments, these lipid nanoparticles have the potential to be used as multimodal nanocarriers for simultaneous targeted drug delivery and ultrasound imaging.

pH-Triggered Echogenicity and Contents Release from Liposomes

Liposomes are representative lipid nanoparticles widely used for delivering anticancer drugs, DNA fragments, or siRNA to cancer cells. Upon targeting, various internal and external triggers have been used to increase the rate for contents release from the liposomes. Among the internal triggers, decreased pH within the cellular lysosomes has been successfully used to enhance the rate for releasing contents. However, imparting pH sensitivity to liposomes requires the synthesis of specialized lipids with structures that are substantially modified at a reduced pH. Herein, we report an alternative strategy to render liposomes pH sensitive by encapsulating a precursor which generates gas bubbles in situ in response to acidic pH. The disturbance created by the escaping gas bubbles leads to the rapid release of the encapsulated contents from the liposomes. Atomic force microscopic studies indicate that the liposomal structure is destroyed at a reduced pH. The gas bubbles also render the liposomes echogenic, allowing ultrasound imaging. To demonstrate the applicability of this strategy, we have successfully targeted doxorubicin-encapsulated liposomes to the pancreatic ductal carcinoma cells that overexpress the folate receptor on the surface. In response to the decreased pH in the lysosomes, the encapsulated anticancer drug is efficiently released. Contents released from these liposomes are further enhanced by the application of continuous wave ultrasound (1 MHz), resulting in substantially reduced viability for the pancreatic cancer cells (14%).

Chronic Plantarflexor Stretching During Ankle Immobilization Helps Preserve Calf Girth, Plantarflexion Peak Torque, and Ankle Dorsiflexion Motion

CONTEXT Chronic plantarflexor (PF) stretching during ankle immobilization helps preserve calf girth, plantarflexion peak torque, and ankle dorsiflexion (DF) motion. Immobilization can lead to decreases in muscle peak torque, muscle size, and joint range of motion (ROM). Recurrent static stretching during a period of immobilization may reduce the extent of these losses. OBJECTIVE To investigate the effects of chronic static stretching on PF peak torque, calf girth, and DF ROM after 2 weeks of ankle immobilization. DESIGN Randomized controlled clinical trial. SETTING Athletic training facility. PARTICIPANTS A total of 36 healthy college-aged (19.81 [2.48]) females. INTERVENTIONS Subjects were randomly assigned to one of 3 groups: control group, immobilized group (IM), and immobilized plus stretching (IM+S) group. Each group participated in a familiarization period, a pretest, and, 2 weeks later, a posttest. The IM group and IM+S group wore the Aircast Foam Pneumatic Walker for 2 weeks on the left leg. During this time, the IM+S group participated in a stretching program, which consisted of two 10-minute stretching procedures each day for the 14 days. MAIN OUTCOME MEASURES One-way analysis of variance was used to determine differences in the change of ankle girth, PF peak torque, and DF ROM between groups with an α level of <.05. RESULTS A significant difference was noted between groups in girth (F2,31 = 5.64, P = .01), DF ROM (F2,31 = 26.13, P < .001), and PF peak torque (F2,31 = 7.74, P = .002). Post hoc testing also showed a significance difference between change in calf girth of the control group compared with the IM group (P = .01) and a significant difference in change of peak torque in the IM+S group and the IM group (P = .001). Also, a significant difference was shown in DF ROM between the control group and IM+S group (P = .01), the control group and the IM group (P < .001), and the IM+S group and the IM group (P < .001). CONCLUSION Chronic static stretching during 2 weeks of immobilization may decrease the loss of calf girth, ankle PF peak torque, and ankle DF ROM.

Acoustic Characterization of Echogenic Polymersomes Prepared From Amphiphilic Block Copolymers

Polymersomes are a class of artificial vesicles prepared from amphiphilic polymers. Like lipid vesicles (liposomes), they too can encapsulate hydrophilic and hydrophobic drug molecules in the aqueous core and the hydrophobic bilayer respectively, but are more stable than liposomes. Although echogenic liposomes have been widely investigated for simultaneous ultrasound imaging and controlled drug delivery, the potential of the polymersomes remains unexplored. We prepared two different echogenic polymersomes from the amphiphilic copolymers polyethylene glycol-poly-DL-lactic acid (PEG-PLA) and polyethylene glycol-poly-L-lactic acid (PEG-PLLA), incorporating multiple freeze-dry cycles in the synthesis protocol to ensure their echogenicity. We investigated acoustic behavior with potential applications in biomedical imaging. We characterized the polymeric vesicles acoustically with three different excitation frequencies of 2.25, 5 and 10 MHz at 500 kPa. The polymersomes exhibited strong echogenicity at all three excitation frequencies (about 50- and 25-dB enhancements in fundamental and subharmonic, respectively, at 5-MHz excitation from 20 µg/mL polymers in solution). Unlike echogenic liposomes, they emitted strong subharmonic responses. The scattering results indicated their potential as contrast agents, which was also confirmed by clinical ultrasound imaging.

Tissue-Penetrating, Hypoxia-Responsive Echogenic Polymersomes For Drug Delivery To Solid Tumors

Hypoxia in solid tumors facilitates the progression of the disease, develops resistance to chemo and radiotherapy, and contributes to relapse. Due to the lack of tumor penetration, most of the reported drug carriers are unable to reach the hypoxic niches of the solid tumors. We have developed tissue-penetrating, hypoxia-responsive echogenic polymersomes to deliver anticancer drugs to solid tumors. The polymersomes are composed of a hypoxia-responsive azobenzene conjugated and a tissue penetrating peptide functionalized polylactic acid-polyethylene glycol polymer. The drug-encapsulated, hypoxia-responsive polymersomes substantially decreased the viability of pancreatic cancer cells in spheroidal cultures. Under normoxic conditions, polymersomes were echogenic at diagnostic ultrasound frequencies but lose the echogenicity under hypoxia. In-vivo imaging studies with xenograft mouse model further confirmed the ability of the polymersomes to target, penetrate, and deliver the encapsulated contents in hypoxic pancreatic tumor tissues.

Effects of 3 Different Elastic Therapeutic Taping Methods on the Subacromial Joint Space

Objective The purpose of this study was to examine the effects of 3 different elastic therapeutic taping methods on the subacromial joint space in healthy adults. Methods Pre‐/post‐test laboratory study method was used in this study. Forty‐eight healthy adults with no prior history of shoulder injury or surgery and no history of dominant shoulder pain in the past 6 months were enrolled in the study. Participants were placed into 3 groups (8 males and 8 females per group) on the basis of a consecutively assigned allocation design. A baseline measurement of the acromiohumeral distance (AHD) was taken by using diagnostic ultrasonography for every participant. On the basis of group assignment, participants were then taped according to the Kinesio Tape (Kinesio Tex Classic Tape) guidelines in one of 3 conditions: (1) taping of the supraspinatus from insertion to origin; (2) taping of the anterior and posterior deltoids from insertion to origin; and (3) a combination of both techniques. After a 5‐minute wait period, the AHD was remeasured with the tape intervention in place, with each participant serving as his or her own control. Results Data analysis showed a statistically significant increase in AHD when using the taping technique over the anterior and posterior deltoids (Condition 2). The subacromial space increased in both males and females when the supraspinatus was taped from insertion to origin (Condition 1), but not at a statistically significant level. Condition 3, in which both taping techniques were used simultaneously, did not show an increase at a statistically significant level. Conclusions The application of the Kinesio Tape from insertion to muscle origin of the supraspinatus or the anterior and posterior deltoid increased the subacromial joint space.