Translating ultrasound-mediated drug delivery technologies for CNS applications.

Ultrasound enhances drug delivery into the central nervous system (CNS) by opening barriers between the blood and CNS and by triggering release of drugs from carriers. A key challenge in translating setups from in vitro to in vivo settings is achieving equivalent acoustic energy delivery. Multiple devices have now been demonstrated to focus ultrasound to the brain, with concepts emerging to also target the spinal cord. Clinical trials to date have used ultrasound to facilitate the opening of the blood-brain barrier. While most have focused on feasibility and safety considerations, therapeutic benefits are beginning to emerge. To advance translation of these technologies for CNS applications, researchers should standardise exposure protocol and fine-tune ultrasound parameters. Computational modelling should be increasingly used as a core component to develop both in vitro and in vivo setups for delivering accurate and reproducible ultrasound to the CNS. This field holds promise for transformative advancements in the management and pharmacological treatment of complex and challenging CNS disorders.

Luminal Delivery of Pectin-Modified Oxygen Microbubbles Mitigates Rodent Experimental Intestinal Ischemia.

INTRODUCTION: Ischemic gut injury is common in the intensive care unit, impairs gut barrier function, and contributes to multiorgan dysfunction. One novel intervention to mitigate ischemic gut injury is the direct luminal delivery of oxygen microbubbles (OMB). Formulations of OMB can be modified to control the rate of oxygen delivery. This project examined whether luminal delivery of pectin-modified OMB (OMBp5) can reduce ischemic gut injury in a rodent model. METHODS: The OMBp5 formulation was adapted to improve delivery of oxygen along the length of small intestine. Adult Sprague-Dawley rats (n = 24) were randomly allocated to three groups: sham-surgery (SS), intestinal ischemia (II), and intestinal ischemia plus luminal delivery of OMBp5 (II + O). Ischemia-reperfusion injury was induced by superior mesenteric artery occlusion for 45 min followed by reperfusion for 30 min. Outcome data included macroscopic score of mucosal injury, the histological score of gut injury, and plasma biomarkers of intestinal injury. RESULTS: Macroscopic, microscopic data, and intestinal injury biomarker results demonstrated minimal intestinal damage in the SS group and constant damage in the II group. II + O group had a significantly improved macroscopic score throughout the gut mucosa (P = 0.04) than the II. The mean histological score of gut injury for the II + O group was significantly improved on the II group (P ≤ 0.01) in the proximal intestine only, within 30 cm of delivery. No differences were observed in plasma biomarkers of intestinal injury following OMBp5 treatment. CONCLUSIONS: This proof-of-concept study has demonstrated that luminal OMBp5 decreases ischemic injury to the proximal small intestine. There is a need to improve oxygen delivery over the full length of the intestine. These findings support further studies with clinically relevant end points, such as systemic inflammation and vital organ dysfunction.

Management of zygomatico maxillary complex fractures.

Zygomatic bone fractures should be effectively diagnosed and treated because they affect how the face is shaped for both aesthetically and functional reasons. It is possible to compare different surgical techniques and their comorbidities objectively through using outcome quantitative assessments, which call for a treatment programme and long-term follow-up. The purpose of this study was to compare the outcomes of two procedures and the effectiveness of the zygomatic bone following open reduction internal fixation (ORIF) employing two-point fixation and ORIF employing three-point fixation. Two groups of twenty patients each were randomly assigned to. Twenty patients in Group A had ORIF treatment using two-point miniplate fixation technique, and twenty patients in Group B received three-point miniplate fixation treatment. Differences between the two categories were ascertained after they had been evaluated in terms of their advantages and disadvantages. We discovered that the two-point fixation group had the fewest facial complications and neurological side effects. At 1 month follow up, Group B's average radiological evaluation score was 2.47± 0.30, and then at 6 months follow up, it was found out to be 1.87±0.47. A significant statistical distinction between the average radiological evaluations was observed in study participants of Group A at follow up done after one month and six months of procedure. Student's paired t- statistical test was utilized from this statistical analysis. (t = 6.54, P < 0.01). On carrying out follow up after one month of surgery, average neurological assessment score in study participants of group A was found out to be 0.22± 0.42, and then at 6 months follow up, it was 0.61±0.63. The average neurological evaluation score in study participants of Group A on carrying out follow up after one month of surgical procedure and and after six months of surgical procedure months showed a significant statistical distinction when utilizing Student's paired t- statistical test (t = 2.51, P = 0.021).It was determined that the best available rehabilitation for the treatment of zygomaticomaxillary complex fractures is open reduction and internal fixation employing two-point fixation by miniplates.

Loss of epigenetic information as a cause of mammalian aging.

All living things experience an increase in entropy, manifested as a loss of genetic and epigenetic information. In yeast, epigenetic information is lost over time due to the relocalization of chromatin-modifying proteins to DNA breaks, causing cells to lose their identity, a hallmark of yeast aging. Using a system called "ICE" (inducible changes to the epigenome), we find that the act of faithful DNA repair advances aging at physiological, cognitive, and molecular levels, including erosion of the epigenetic landscape, cellular exdifferentiation, senescence, and advancement of the DNA methylation clock, which can be reversed by OSK-mediated rejuvenation. These data are consistent with the information theory of aging, which states that a loss of epigenetic information is a reversible cause of aging.

Investigating the influence of ultrasound parameters on ibuprofen drug release from hydrogels.

Hydrogels are promising ultrasound-responsive drug delivery systems. In this study, we investigated how different ultrasound parameters affected drug release and structural integrity of self-healing hydrogels composed of alginate or poloxamers. The effects of amplitude and duty cycle at low frequency (24 kHz) ultrasound stimulation were first investigated using alginate hydrogels at 2% w/v and 2.5% w/v. Increasing ultrasound amplitude increased drug release from these gels, although high amplitudes caused large variations in release and damaged the gel structure. Increasing duty cycle also increased drug release, although a threshold was observed with the lower pulsed 50% duty cycle achieving similar levels of drug release to a continuous 100% duty cycle. Poloxamer-based hydrogels were also responsive to the optimised parameters at low frequency (24 kHz, 20% amplitude, 50% duty cycle for 30 s) and showed similar drug release results to a 2.5% w/v alginate hydrogel. Weight loss studies demonstrated that the 2% w/v alginate hydrogel underwent significant erosion following ultrasound application, whereas the 2.5% w/v alginate and the poloxamer gels were unaffected by application of the same parameters (24 kHz, 20% amplitude, 50% duty cycle for 30 s). The rheological properties of the hydrogels were also unaffected and the FTIR spectra remained unchanged after low frequency ultrasound stimulation (24 kHz, 20% amplitude, 50% duty cycle for 30 s). Finally, high-frequency ultrasound stimulation (1 MHz, 3 W.cm-2, 50% duty cycle) was also trialled; the alginate gels were less responsive to this frequency, while no statistically significant impact on drug release was observed from the poloxamer gels. This study demonstrates the importance of ultrasound parameters and polymer selection in designing ultrasound-responsive hydrogels.

Broadband-excitation-based mechanical spectroscopy of highly viscous tissue-mimicking phantoms.

Standard rheometers assess mechanical properties of viscoelastic samples up to 100 Hz, which often hinders the assessment of the local-scale dynamics. We demonstrate that high-frequency analysis can be achieved by inducing broadband waves and monitoring their media-dependent propagation using optical coherence tomography. Here, we present a new broadband wave analysis based on two-dimensional Fourier transformation. We validated this method by comparing the mechanical parameters to monochromatic excitation and a standard oscillatory test data. Our method allows for high-frequency mechanical spectroscopy, which could be used to investigate the local-scale dynamics of different biological tissues and the influence of diseases on their microstructure.

A comprehensive update of micro- and nanobubbles as theranostics in oncology.

Advances in diagnostic and imaging capabilities have allowed cancers to be detected earlier and characterized more robustly. These strategies have recently branched into theranostics whereby contrast agents traditionally used for imaging have been co-loaded with therapeutics to simultaneously diagnose and treat cancers in a patient-specific manner. Microbubbles (MBs) and nanobubbles (NBs) are contrast agents which can be modulated to meet theranostic needs particularly in the realm of oncology. The current review focuses on ultrasound-responsive MB/NB platforms used as a theranostic tool in oncology. We discuss in detail the key parameters that influence the utility of MB/NB formulations and implications of such treatment modalities. Recent advances in composition strategies, latest works in the pre-clinical stages and multiple paradigm-shifting innovations in the field of MB/NB are discussed in-depth in this review. The clinical application of MB/NB is currently limited to diagnostic imaging. Surface chemistry modification strategies will help tune the formulations toward therapeutic applications. It is also anticipated that MB/NB will see increased use to deliver gas therapeutics. Scalability and stability considerations will be at the forefront as these particles get introduced into the clinical theranostic toolbox.

Prospective one year study of corneal biomechanical changes following high intensity, accelerated cornea cross-linking in patients with keratoconus using a non-contact tonometer.

PURPOSE: To characterize corneal biomechanical properties utilizing a dynamic ultra-high-speed Scheimpflug camera equipped with a non-contact tonometer (CorVis ST, CST) in keratoconic corneas following continuous high intensity, high irradiance corneal cross-linking. DESIGN: Prospective longitudinal single-centre study at a tertiary referral center. METHODS: Corneal biomechanical properties were measured in patients with progressive keratoconus undergoing high intensity (30 mW/cm2), high irradiance (5.4 J/cm2), accelerated corneal cross-linking with continuous exposure to ultraviolet-A for 4 min. CST was used to assess corneal biomechanical properties pre-operatively and at 1, 3, 6 and 12 months post-operatively. CST output videos were further analyzed using several previously reported algorithms. RESULTS: A total of 25 eyes of 25 participants were examined. The mean age of participants was 20.9 ± 5.3 years; 56% were male and 80% were of Maori or Pacific Island origin. Energy absorbed area (mN mm), was the only significantly changed parameter compared to baseline at all time points measuring 3.61 ± 1.19 preoperatively, 2.81 ± 1.15 at 1 month (p = 0.037), 2.79 ± 0.81 (p = 0.033) at 3 months, 2.76 ± 0.95 (p = 0.028) at 6 months and 2.71 ± 1.18 (p = 0.016) at 12 months. CONCLUSIONS: The significant difference between the pre and post-operative energy absorbed area appears to reflect changes in corneal viscous properties that occur following corneal cross-linking.

Externally triggered release of growth factors - A tissue regeneration approach.

Tissue regeneration aims to achieve functional restoration following injury by creating an environment to enable the body to self-repair. Strategies for regeneration rely on the introduction of biomaterial scaffolding, cells and bioactive molecules into the body, at or near the injury site. Of these bioactive molecules, growth factors (GFs) play a pivotal role in directing regenerative pathways for many cell populations. However, the therapeutic use of GFs has been limited by the complexity of biological injury and repair, and the properties of the GFs themselves, including their short half-life, poor tissue penetration, and off-target side effects. Externally triggered delivery systems have the potential to facilitate the delivery of GFs into the target tissues with considerations of the timing, sequence, amount, and location of GF presentation. This review briefly discusses the challenges facing the therapeutic use of GFs, then, we discuss approaches to externally trigger GF release from delivery systems categorised by stimulation type; ultrasound, temperature, light, magnetic fields and electric fields. Overall, while the use of GFs for tissue regeneration is still in its infancy, externally controlled GF delivery technologies have the potential to achieve robust and effective solutions to present GFs to injured tissues. Future technological developments must occur in conjunction with a comprehensive understanding of the biology at the injury site to ensure translation of promising technologies into real world benefit.

The influence of hyperglycemia on the safety of ultrasound in retinal pigment epithelial cells.

Ultrasound (US) assisted drug delivery is receiving interest in treating posterior eye diseases, such as diabetic retinopathy due to its ability to maximize drug penetration into difficult to reach tissues. Despite its promise, the technique has only been investigated using healthy cell and tissue models, with no evidence to date about its safety in active disease. As a result, the aim of this study was to evaluate the safety of US administration in vitro in retinal pigment epithelial cells under normal and high glucose conditions. US protocols within the presently accepted safety threshold were applied and their influence on cell membrane and tight junction integrity as well as intracellular inflammation was evaluated using lactate dehydrogenase (LDH), zona occludens-1 (ZO-1), fluorescein isothiocyanate (FITC)-dextran dye leak and nuclear factor-kappaB (NF-κB) assays, respectively. Under high glucose conditions, US application increased LDH release and resulted in loss of ZO-1 labeling at 2 h; however, normal levels were restored within 24 h. US within its safety parameters did not induce any FITC-dextran dye leak or NF-κB nuclear translocation in normal or high glucose conditions. In conclusion, our results suggest that while high glucose conditions increase cell susceptibility to US-mediated stress, basal conditions can be restored within 24 h without long-lasting cell damage.

Ex vivo evaluation of the influence of pH on the ophthalmic safety, antibacterial efficacy and storage stability of povidone-iodine.

CLINICAL RELEVANCE: The monitoring and controlling of pH is important when preparing solutions for ophthalmic administration. In the case of povidone-iodine, dilution in an appropriate buffer is needed to improve its ophthalmic safety. BACKGROUND: Povidone-iodine is a broad-spectrum antiseptic agent that is commonly used in ophthalmic applications due to its cost-effectiveness and accessibility. However, native povidone-iodine has a pH of about 4.0 and is known to irritate the ocular surface. This study assessed whether adjusting povidone-iodine formulation pH would influence its ex vivo ophthalmic safety, alongside its impact on antibacterial efficacy and storage stability. METHODS: One per cent w/v povidone-iodine was diluted in normal saline, or 0.1-mol/l citrate or phosphate buffers to yield solutions with a pH ranging from 4.0 to 7.0. Ocular irritancy was evaluated using the bovine cornea opacity and permeability assay. Antibacterial efficacy was assessed by evaluating povidone-iodine minimum inhibitory concentration and minimum bactericidal concentration at varied pH. Storage stability of the preparations was determined over 30-days at room temperature (20-25°C). RESULTS: Combining povidone-iodine with phosphate buffer notably decreased ocular irritancy of the antiseptic. Surprisingly, combining povidone-iodine with citrate buffer potentiated irritant effects of the preparation. Antibacterial efficacy of povidone-iodine was reduced when formulation pH was increased from 4.0 to 7.0, although its general activity was retained. Finally, povidone-iodine remained stable in both normal saline and phosphate buffer over 30-days. CONCLUSION: Ophthalmic application of povidone-iodine can be optimised by adjusting the pH of the formulation to 7.0 using phosphate buffer, reducing irritancy while maintaining adequate antibacterial efficacy and storage stability.

Characterization of Zinc Oxide Nanoparticle Cross-Linked Collagen Hydrogels.

Collagen is the most abundant protein in mammals and possesses high biocompatibility and low antigenicity. These biological properties render it one of the most useful biomaterials for medical applications. This study investigated the mechanical and physical characteristics of collagen hydrogels cross-linked with different ratios of polyvinylpyrrolidone capped zinc oxide nanoparticles (ZPVP). Fourier transform infrared spectroscopy indicated molecular interactions between collagen fibers and ZPVP. Texture analysis revealed a significant increase in gel hardness, adhesiveness, and viscosity after cross-linking with ZPVP. Rheological measurements showed that as the ratio of ZPVP increased, stronger hydrogels were formed which in turn resulted in more sustained release of the model drug, dexamethasone sodium phosphate. We can therefore conclude that the mechanical properties of collagen hydrogels can be modified by controlling the ratio of ZPVP used for cross-linking, offering the potential to develop biocompatible sustained release drug delivery systems.

Ultrasound-responsive lipid microbubbles for drug delivery: A review of preparation techniques to optimise formulation size, stability and drug loading.

Lipid-shelled microbubbles have received extensive interest to enhance ultrasound-responsive drug delivery outcomes due to their high biocompatibility. While therapeutic effectiveness of microbubbles is well established, there remain limitations in sample homogeneity, stability profile and drug loading properties which restrict these formulations from seeing widespread use in the clinical setting. In this review, we evaluate and discuss the most encouraging leads in lipid microbubble design and optimisation. We examine current applications in drug delivery for the systems and subsequently detail shell compositions and preparation strategies that improve monodispersity while retaining ultrasound responsiveness. We review how excipients and storage techniques help maximise stability and introduce different characterisation and drug loading techniques and evaluate their impact on formulation performance. The review concludes with current quality control measures in place to ensure lipid microbubbles can be reproducibly used in drug delivery.

Relationship between rheological properties and transverse relaxation time (T2) of artificial and porcine vitreous humour.

Vitreous liquefactive processes play an integral role in ocular health. Knowledge of the degree of liquefaction would allow better monitoring of ocular disease progression and enable more informed therapeutic dosing for an individual patient. Presently this process cannot be monitored in a non-invasive manner. Here, we evaluated whether magnetic resonance imaging (MRI) could predict the viscoelasticity and in turn liquefactive state of artificial and biological vitreous humour. Gels comprising identical concentrations of hyaluronic acid and agar ranging from 0.125 to 2.25 mg/ml of each polymer were prepared and their T2 was measured using a turbo-spin echo sequence via 3T clinical MRI. The gels were subsequently subjected to rheological frequency and flow sweeps and trends between T2 and rheological parameters were assessed. The relationship between T2 and vitreous humour rheology was further assessed using ex vivo porcine eyes. An optimised imaging technique improved homogeneity of obtained artificial vitreous humour T2 maps. Strong correlations were observed between T2 and various rheological parameters of the gels. Translation to porcine vitreous humour demonstrated that the T2 of biological tissue was related to its viscoelastic properties. This study shows that T2 can be correlated with various rheological parameters within gels. Future investigations will assess the translatability of these findings to live models.

Validation of hyaluronic acid-agar-based hydrogels as vitreous humor mimetics for in vitro drug and particle migration evaluations.

Artificial vitreous humor holds immense potential for use in in vitro intravitreal drug delivery assays. In this study, we investigated rheological properties and drug or nanoparticle migration in hyaluronic acid (HA) - agar based hydrogels and compared these characteristics with bovine vitreous humor. Gel compositions identified in literature containing HA (0.7-5.0 mg/ml) and agar (0.95-4.0 mg/ml) were classified as either high (VH), medium (VM) or low (VL) polymer load. Viscoelastic behavior was evaluated using oscillatory rheology, and migration of differently sized and charged polystyrene nanoparticles (NPs) through the different gels was determined via multiple particle tracking. Comparable rheological behaviour was observed between VL and bovine vitreous. Tracking evaluations revealed that increasing particle size and gel viscosity slowed NP migration. Additionally, 100 nm anionic NPs migrated slower than neutral NPs in VL and VM, while cationic NPs were immobile in all gels. Finally, distribution and clearance of sodium fluorescein was used to model drug mobility through the gels using a custom-built eye model. Flow and angular movement only influenced drug migration in VL and VM, but not VH. Finally, VL and VM demonstrated to have the most similar sodium fluorescein clearance to that of bovine vitreous humor. Together, these evaluations demonstrate that low viscosity HA-agar gels can be used to approximate nanoparticle and drug migration through biological vitreous humor.

Depot formulations to sustain periocular drug delivery to the posterior eye segment.

The periocular space is a promising alternative route for the delivery of drugs to the posterior eye segment, especially when treating conditions in the outer ocular layers. In this review, we discuss the different periocular routes as well as the physiological barriers and elimination mechanisms limiting drug bioavailability at the back of the eye. We then highlight various types of depot formulations, including particulate delivery systems, semisolid formulations, and implants, used to increase the contact time with the ocular tissues. With the additional advantage of sustaining drug release, such depot formulations could enhance periocular drug delivery to the posterior eye segment.

Ex vivo evaluation of the stability, safety and antibacterial efficacy of an extemporaneous povidone-iodine preparation for ophthalmic applications.

BACKGROUND: Povidone-iodine is used as a cost-effective broad-spectrum antiseptic in the prophylaxis and treatment of certain ocular infections. In this study, the stability, ophthalmic irritation potential and antibacterial efficacy of an extemporaneous povidone-iodine preparation was determined using established ex vivo and in vitro assays. METHODS: Extemporaneous iodine was prepared by simple dilution in normal saline. Preparation stability was evaluated by monitoring concentration and pH. Ocular safety was determined using the bovine cornea opacity and permeability assay. Efficacy was assessed by determining the minimum inhibitory and minimum bactericidal concentration of the preparation on Staphylococcus aureus and Pseudomonas aeruginosa. RESULTS: Diluted povidone-iodine maintained its stability over the 28-day evaluation. The formulation caused mild ocular irritation at the lowest prepared concentration (0.5 per cent w/v), with irritation noticeably increased at higher concentrations. The preparation showed minimum bactericidal and inhibitory concentrations of 0.078 and 0.3 per cent w/v on S. aureus and P. aeruginosa, respectively. CONCLUSIONS: This study confirms the stability and broad-spectrum antibacterial efficacy of povidone-iodine, while addressing the ocular irritation potential of this chemical.

Ultrasound-responsive nanobubbles for enhanced intravitreal drug migration: An ex vivo evaluation.

The intravitreal route faces many challenges in rapidly and effectively reaching posterior eye pathology, with administered therapeutics experiencing non-specific distribution around and premature clearance from ocular tissues. Nanobubbles and ultrasound may improve outcomes of intravitreally administered drugs by influencing the directionality of drug-containing particle migration. In this study, we assessed the impact of trans-scleral or corneal ultrasound application on the distribution of intravitreally-injected nanobubbles. Rhodamine-tagged gas entrapped nanobubble formulations were prepared and injected into ex vivo bovine and porcine eyes and subjected to ultrasound (1 MHz, 0-2.5 W/cm2, 50-100% duty, 60 s). Bovine eyes were partially dissected to visualize the vitreous humor and particle migration was evaluated via optical fluorescence spectroscopy. Directional migration in porcine eyes was evaluated using a snap freezing protocol complemented by quantification of regional fluorescence. The impact on nanobubble migration following pars-plana injection and sequential ultrasound cycle application from scleral or corneal-surface positions was also assessed. Administration of ultrasound significantly enhanced the directional migration of nanobubbles in both ex vivo models, with multiple corneal ultrasound cycles promoting greater migration of dye-filled nanobubbles to posterior regions of the vitreous. Moreover, particles moved in a directional manner away from the ultrasound wave source demonstrating an ability to effectively control the rate and path of nanobubble migration. These findings establish an encouraging new and safe modality enabling rapid distribution of intravitreally-injected therapeutics where expeditious therapeutic intervention is warranted.

Evaluation of 2 ex vivo Bovine Cornea Storage Protocols for Drug Delivery Applications.

The use of corneal tissue for ex vivo therapeutic evaluations is limited due to its rapid loss of viability after excision. Optimization of storage conditions may allow prolonged retention of physical tissue properties. In this study, we evaluated how storage in optimized organ culture (OC) medium at 37°C or phosphate-buffered saline (PBS) at 2-8°C impacted physical properties of bovine corneas. Tissue hydration, permeability and histology were monitored at baseline and following 1, 4 and 7 days of storage. Corneas stored in OC demonstrated significantly higher hydration and permeability when compared to those stored in PBS. Histology revealed that storage in OC consistently caused detachment of the epithelial layer by day 4 of storage, whereas both storage conditions caused a significant increase in stromal thickness and tissue vacuolation. This study highlights the limitations of currently available corneal tissue storage approaches for ex vivo drug permeation studies.