Glaucoma Drainage Device Coated with Mitomycin C Loaded Opal Shale Microparticles to Inhibit Bleb Fibrosis

Intraocular pressure control efficacy and safety of HA-Mg glaucoma drainage plate implantation in the anterior chamber of rabbit eyes

The current clinical application of glaucoma drainage devices is made of non-degradable materials. These non-degradable drainage devices often trigger inflammatory responses and scar proliferation, possibly leading to surgical failure. We developed a biodegradable material hydroxyapatite-coated magnesium (HA-Mg) as a glaucoma drainage device. Twelve New Zealand white rabbits were randomly assigned to three groups: HA-Mg drainage plate group (6 right eyes), trabeculectomy group (6 right eyes), and control group (12 left eyes). Results showed that all HA-Mg drainage plates were completely degraded ~4 months postoperatively. At the 5th month postoperatively, there was no statistical difference in the corneal endothelium density between the HA-Mg drainage plate group and the control group (p = 0.857). The intraocular pressure (IOP) level in the HA-Mg drainage plate implantation group was lower than in the other two groups. The trypan blue dye still drained from the anterior chamber to the subconjunctiva 5 months after HA-Mg drainage plate implantation. HE staining revealed the scleral linear aqueous humor drainage channel and anterior synechia were observed after drainage plate completely degraded, with no obvious infiltration with the inflammatory cells. This study showed the safety and efficacy of HA-Mg glaucoma drainage plate in controlling IOP after implantation into the anterior chamber of rabbit eyes.

Novel Biomaterials in Glaucoma Treatment

Glaucoma is a significant cause of blindness worldwide, and its treatment remains challenging. The disease progressively leads to damage to the optic disc and thus loss of visual acuity and visual field. High intraocular pressure (IOP) is a common risk factor. There are three major methods to treat this disease: topical, laser, and surgical. None of these are completely satisfactory; therefore, alternatives using new biomaterials are being sought. Since biomaterial engineering has experienced significant growth in recent decades, its products are gradually being introduced to various branches of medicine, with the exception of ophthalmology. Biomaterials, such as glaucoma drainage implants, have been successfully used to treat glaucoma. There is significant ongoing research on biomaterials as drug delivery systems that could overcome the disadvantages of topical glaucoma treatment, such as poor intraocular penetration or frequent drug administration. This article summarizes the use of novel biomaterials for glaucoma treatment presented in the literature. The literature search was based on articles published in English on PubMed.gov, Cochranelibrary.com, and Scopus.com between 2018 and 2023 using the following term "biomaterials in glaucoma." A total of 103 published articles, including twenty-two reviews, were included. Fifty-nine articles were excluded on the basis of their titles and abstracts.

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Renal denervation alleviates chronic obstructive sleep apnea-induced atrial fibrillation via inhibition of atrial fibrosis and sympathetic hyperactivity

OBJECTIVE

Previous studies have reported that renal denervation (RDN) prevents the occurrence of atrial fibrillation (AF) related to obstructive sleep apnea (OSA). However, the effect of RDN on chronic OSA (COSA)-induced AF is still unclear.

METHODS

Healthy beagle dogs were randomized into the OSA group (sham RDN + OSA), OSA-RDN group (RDN + OSA), and CON group (sham RDN + sham OSA). The COSA model was built via repeated apnea and ventilation rounds for 4 h each day lasting 12 weeks, and RDN was employed after 8 weeks of modeling. All dogs were implanted Reveal LINQ™ to detect spontaneous AF and AF burden. Circulating levels of norepinephrine, angiotensin II, and interleukin-6 were determined at baseline and end of the study. In addition, measurements of the left stellate ganglion, AF inducibility, and effective refractory period were conducted. The bilateral renal artery and cortex, left stellate ganglion, and left atrial tissues were collected for molecular analysis.

RESULTS

Of 18 beagles, 6 were randomized to each of the groups described above. RDN remarkably attenuated ERP prolongation and AF episodes and duration. RDN markedly suppressed the LSG hyperactivity and atrial sympathetic innervation, decreased the serum concentrations of Ang II and IL-6, further inhibited fibroblast-to-myofibroblast transformation via the TGF-β1/Smad2/3/α-SMA pathway, and reduced the expression of MMP-9, thus decreasing OSA-induced AF.

CONCLUSIONS

RDN may reduce AF by inhibiting sympathetic hyperactivity and AF in a COSA model.

A graphene-Ag based near-infrared defined accurate anti-scarring strategy for ocular glaucoma surgery

Excessive fibrosis is the major factor in the failure of glaucoma filtration surgery. So far, the dominant approach for inhibiting fibrosis is the use of an antimetabolite drug, but the complications it causes, such as filtering bleb leakage, bacterial endophthalmitis and ocular hypotony, are also inevitable. Herein, a multifunctional anti-scarring platform (PVA@rGO-Ag/5-Fu) integrated with outstanding photothermal, antibacterial and drug delivery abilities is developed. PVA@rGO-Ag shows favorable biocompatibility as well as an accurate regional photothermal killing ability on both conjunctival fibroblasts and bacteria under 808 nm near-infrared (NIR) irradiation. Furthermore, PVA@rGO-Ag/5-Fu improves bleb survival rates and results in the satisfactory reduction of intraocular pressure (IOP) by decreasing the fibrous reaction in vivo. In summary, PVA@rGO-Ag/5-Fu has promising potential as an efficacious and safe anti-scarring agent for filtering surgery.

Modulation of the Blood-Brain Barrier for Drug Delivery to Brain

The blood-brain barrier (BBB) precisely controls brain microenvironment and neural activity by regulating substance transport into and out of the brain. However, it severely hinders drug entry into the brain, and the efficiency of various systemic therapies against brain diseases. Modulation of the BBB via opening tight junctions, inhibiting active efflux and/or enhancing transcytosis, possesses the potential to increase BBB permeability and improve intracranial drug concentrations and systemic therapeutic efficiency. Various strategies of BBB modulation have been reported and investigated preclinically and/or clinically. This review describes conventional and emerging BBB modulation strategies and related mechanisms, and safety issues according to BBB structures and functions, to try to give more promising directions for designing more reasonable preclinical and clinical studies.

Lollipop-Inspired Multilayered Drug Delivery Hydrogel for Dual Effective, Long-Term, and NIR-Defined Glaucoma Treatment

Glaucoma is an ophthalmic disease that is characterized by elevated intraocular pressure (IOP). Eye drops are the preferred choice to reduce IOP for the treatment of glaucoma. However, the bioavailability of eye drops is low (<5%). Their long-term frequent administration cannot ensure patient compliance, which is the main reason for treatment failure. Inspired by lollipop, herein, a multilayered sodium alginate-chitosan (SA-CS) hydrogel ball (HB) decorated by zinc oxide-modified biochar (ZnO-BC) is developed as a new drug delivery system. The multilayer structure encapsulate timolol maleate (TM) and levofloxacin inside the different layers to realize the sustained release of drugs, which can control ocular hypertension and prevent infection effectively. The results show that the release of TM can be sustained in vitro for longer than 2 weeks. Moreover, IOP is also effectively reduced in vivo. Meanwhile, the photothermal conversion activity of ZnO-BC can regulate drug release on demand after stimulation by near-infrared irradiation. More importantly, the designed HB also shows good biocompatibility and antibacterial properties in vitro and in vivo. In summary, ZnO-BC-SA-CS HB can effectively reduce IOP and is expected to replace the classical tedious eye drop strategy, having potential utilization value in the treatment of glaucoma.

A new glaucoma drainage implant with the use of Polytetrafluoroethylene (PTFE). A pilot study

Purpose: To investigate the implantation of Polytetrafluoroethylene (PTFE) as a glaucoma drainage device. Methods: This study has been done in two steps. First, the constructed implants have been used in 4 rabbits and the histopathologic response was evaluated. In the second step, the implants were used in the 6 eyes of 6 patients with end-stage glaucoma with uncontrolled IOP and poor visual acuity. The tube was made of two-layer of PTFE membrane measuring 8 * 6 mm with a thickness of 1.8 mm and a silicone tube. The rabbits and the human eyes underwent surgical implantation of the tube in the anterior chamber. The histopathologic evaluation was done using H&E staining. Visual acuity, intraocular pressure and the number of glaucoma medications were assessed before and after the surgery. Results: In the histopathologic evaluation, subconjunctival polarizing fibers of a synthetic mesh infiltrated by fibrovascular septa was seen. A granulomatous inflammatory reaction composed of histiocytes, lymphocytes, and multinucleated giant cells were seen around and between the synthetic bundles. The average age of patients was 63 ± 5.5 years. The mean IOP reached from 36.6 ± 5.7 mmHg at baseline to 16.2 ± 8.9 mmHg at the final follow-up. Patients were followed for an average of 6.6 ± 4.5 months. One patient found hypotony refractory to medical and surgical treatment, which led to implant removal. One patient had uncontrolled IOP and finally led to phthisis bulbi following slow CPC. The remaining four eyes did well during the follow-up. Conclusion: The use of PTFE as a new polymer in tube shunt construction was reported. Larger studies, modification of the PTFE membranes like changing the porosity amount, and size of PTFE membranes might result in different conclusions.

Prodrug Delivery Using Dual-Targeting Nanoparticles To Treat Breast Cancer Brain Metastases

Brain metastases from breast cancer are the most frequent brain metastasis in women, which are often difficult to be surgically removed due to the multifocal and infiltrative intracranial growth patterns. Cytotoxic drugs have potent anti-breast cancer properties. However, owing to the toxic side effects and the blood-brain barrier (BBB), these drugs cannot be fully and aggressively exploited with systemic administration and hence have very limited application for brain metastases. In this study, hyaluronidase-activated prodrug hyaluronic-doxorubicin (hDOX) was assembled by the BBB and metastatic breast cancer dual-targeting nanoparticles (NPs), which were constructed based on transcytosis-targeting peptide and hyaluronic acid co-modified poly(lactic-co-glycolic acid)-poly(ε-carbobenzoxy-l-lysine). hDOX showed enzyme-recovered DNA insertion, selective cytotoxicity to metastatic breast cancer cells rather than astrocytes, and efficient loading into dual-targeting NPs. hDOX@NPs displayed the ability of dually targeting the BBB and metastatic breast cancer and significantly extended the median survival time of mice with intracranial metastatic breast cancer. Based on these improvements, this prodrug delivery tactic may serve as an important direction for drug therapy against brain metastases.

Old is Gold: Electrolyte Aging Influences the Topography, Chemistry, and Bioactivity of Anodized TiO2 Nanopores

Titanium dioxide (TiO₂) nanostructures including nanopores and nanotubes have been fabricated on titanium (Ti)-based orthopedic/dental implants via electrochemical anodization (EA) to enable local drug release and enhanced bioactivity. EA using organic electrolytes such as ethylene glycol often requires aging (repeated anodization of nontarget Ti) to fabricate stable well-ordered nanotopographies. However, limited information is available with respect to its influence on topography, chemistry, mechanical stability, and bioactivity of the fabricated structures. In the current study, titania nanopores (TNPs) using a similar voltage/time were fabricated using different ages of electrolyte (fresh/0 h to 30 h aged). Current density vs time plots of EA, changes in the electrolyte (pH, conductivity, and Ti/F ion concentration), and topographical, chemical, and mechanical characteristics of the fabricated TNPs were compared. EA using 10-20 h electrolytes resulted in stable TNPs with uniform size and improved alignment (parallel to the underlying substrate microroughness). Additionally, to evaluate bioactivity, primary human gingival fibroblasts (hGFs) were cultured onto various TNPs in vitro. The findings confirmed that the proliferation and morphology of hGFs were enhanced on 10-20 h aged electrolyte anodized TNPs. This pioneering study systematically investigates the optimization of anodization electrolyte toward fabricating nanoporous implants with desirable characteristics.