pH-sensitive polymeric nanoparticles with antioxidant and anti-inflammatory properties against cisplatin-induced hearing loss

Probucol-Ursodeoxycholic Acid Otic Formulations: Stability and In Vitro Assessments for Hearing Loss Treatment

Targeted drug delivery is an ongoing aspect of scientific research that is expanding through the design of micro- and nanoparticles. In this paper, we focus on spray dried microparticles as carriers for a repurposed lipophilic antioxidant (probucol). We characterise the microparticles and quantify probucol prior to assessing cytotoxicity on both control and cisplatin treated hair cells (known as House Ear Institute-Organ of Corti 1; HEI-OC1). The addition of water-soluble polymers to 2% β-cyclodextrin resulted in a stable probucol formulation. Ursodeoxycholic acid (UDCA) used as formulation excipient increases probucol miscibility and microparticle drug content. Formulation characterisations reveals spray drying results in spherical UDCA-drug microparticles with a mean size distribution of ∼5-12 μm. Probucol microparticles show stable short-term storage conditions accounting for only ∼10% loss over seven days. By mimicking cell culture conditions, both UDCA-probucol (67%) and probucol only (82%) microparticles show drug release in the initial two hours. Furthermore, probucol formulations with or without UDCA preserve cell viability and reduce cisplatin-induced oxidative stress. Mitochondrial bioenergetics results in lower basal respiration and non-mitochondrial respiration, with higher maximal respiration, spare capacity, ATP production and proton leak within cisplatin challenged UDCA-probucol groups. Overall, we present a facile method for incorporating lipophilic antioxidant carriers in polymer-based particles that are tolerated by HEI-OC1 cells and show stable drug release, sufficient in reducing cisplatin-induced reactive oxygen species accumulation.

Hyaluronic acid-ibuprofen conjugation: a novel ototherapeutic approach protecting inner ear cells from inflammation-mediated damage

There is a substantial need of effective drugs for the treatment of hearing loss, which affects nearly 500 million individuals globally. Hearing loss can be the result of intense or prolonged noise exposure, ototoxic drugs, infections, and trauma, which trigger inflammatory signaling cascades that lead to irreversible damage to cochlear structures. To address this, we developed and characterized a series of covalent conjugates of anti-inflammatory drugs to hyaluronic acid (HA), for potential use as topical ototherapeutics. These conjugates were tested in in vitro assays designed to mirror physiological processes typically observed with acoustic trauma. Intense noise exposure leads to macrophage recruitment to the cochlea and subsequent inflammatory damage to sensory cells. We therefore first tested our conjugates' ability to reduce the release of inflammatory cytokines in macrophages. This anti-inflammatory effect on macrophages also translated to increased cochlear cell viability. In our initial screening, one conjugate, ibuprofen-HA, demonstrated significantly higher anti-inflammatory potential than its counterparts. Subsequent cytokine release profiling of ibuprofen-HA further confirmed its ability to reduce a wider range of inflammatory markers, to a greater extent than its equivalent unconjugated drug. The conjugate's potential as a topical therapeutic was then assessed in previously developed tympanic and round window membrane tissue permeation models. As expected, our data indicate that the conjugate has limited tympanic membrane model permeability; however, it readily permeated the round window membrane model and to a greater extent than the unconjugated drug. Interestingly, our data also revealed that ibuprofen-HA was well tolerated in cellular and tissue cytocompatibility assays, whereas the unconjugated drug displayed significant cytotoxicity at equivalent concentrations. Moreover, our data highlighted the importance of chemical conjugation of ibuprofen to HA; the conjugate had improved anti-inflammatory effects, significantly reduced cytotoxicity, and is more suitable for therapeutic formulation. Overall, this work suggests that ibuprofen-HA could be a promising safe and effective topical ototherapeutic for inflammation-mediated cochlear damage.

Harnessing astaxanthin-loaded diselenium cross-linked apotransferrin nanoparticles for the treatment of secretory otitis media

Secretory otitis media (SOM) is a clinical condition characterized by the accumulation of fluids and oxidative stress in the middle ear, leading to hearing impairment and infection complications. One potential solution for mitigating oxidative stress associated with SOM is the use of antioxidants such as astaxanthin. However, its effectiveness is limited due to its poor bioavailability and rapid oxidation. Herein, we developed a novel diselenium-crosslinked apotransferrin enriched with astaxanthin (AST@dSe-AFT) nanoparticles to augment the transport of astaxanthin across biological membranes, resulting in increased bioavailability and reduced oxidative stress in SOM. Our research demonstrated that AST@dSe-AFT efficiently accumulated in the middle ear, allowing for controlled delivery of astaxanthin in response to reactive oxygen species and reducing oxidative stress. Additionally, AST@dSe-AFT stimulated macrophages to polarize towards M2 phenotype and neutrophils to polarize towards N2 phenotype, thereby facilitating an anti-inflammatory response and tissue restoration. Importantly, AST@dSe-AFT exhibited no toxicity or adverse effects, suggesting its potential for safety and future clinical translation. Our findings suggested that AST@dSe-AFT represents a promising approach for the treatment of secretory otitis media and other oxidative stress-related disorders.

The diverse effects of cisplatin on tumor microenvironment: Insights and challenges for the delivery of cisplatin by nanoparticles

Cisplatin is a well-known platinum-based chemotherapy medication that is widely utilized for some malignancies. Despite the direct cytotoxic consequences of cisplatin on tumor cells, studies in the recent decade have revealed that cisplatin can also affect different cells and their secretions in the tumor microenvironment (TME). Cisplatin has complex impacts on the TME, which may contribute to its anti-tumor activity or drug resistance mechanisms. These regulatory effects of cisplatin play a paramount function in tumor growth, invasion, and metastasis. This paper aims to review the diverse impacts of cisplatin and nanoparticles loaded with cisplatin on cancer cells and also non-cancerous cells in TME. The impacts of cisplatin on immune cells, tumor stroma, cancer cells, and also hypoxia will be discussed in the current review. Furthermore, we emphasize the challenges and prospects of using cisplatin in combination with other adjuvants and therapeutic modalities that target TME. We also discuss the potential synergistic effects of cisplatin with immune checkpoint inhibitors (ICIs) and other agents with anticancer potentials such as polyphenols and photosensitizers. Furthermore, the potential of nanoparticles for targeting TME and better delivery of cisplatin into tumors will be discussed.

Controlled release of dexamethasone from fibrin sealant for intratympanic administration in inner ear therapy

The aim of the present work was to show the sustainability of fibrin sealant in releasing dexamethasone and adjust the protocol for clinical application of the novel method in the treatment of Meniere's disease (MD) and sudden sensorineural hearing loss (SSHL). Gelation occurred shortly after mixing dexamethasone-containing fibrinogen with thrombin. Dexamethasone was constantly released for at least 16 d at a stable level after 7 d in protocol 1 (low-dose), while it was robustly released within 4 d and slowed afterward until 10 d in protocol 2 (high-dose). There were significant differences among the time points in Protocol 2 (p < 0.01, ANOVA), and the exponential model with the formula y = 15.299 * e-0.483 *t fits the association. The estimated concentration of dexamethasone released on 7 d in protocol 2 was slightly lower than that observed in protocol 1. The fibrin sealant is capable of constantly releasing dexamethasone with adjustable dynamics. Targeted and minimally invasive administration of the material can be achieved in the clinic by sequential injections of the fluids using a soft-tipped catheter.

Space Station-like Composite Nanoparticles for Co-Delivery of Multiple Natural Compounds from Chinese Medicine and Hydrogen in Combating Sensorineural Hearing Loss

Ototoxic drugs such as aminoglycoside antibiotics and cisplatin (CDDP) can cause sensorineural hearing loss (SNHL), which is closely related to oxidative stress and the acidification of the inner ear microenvironment. Effective treatment of SNHL often requires multifaceted approach due to the complex pathology, and drug combination therapy is expected to be at the forefront of modern hearing loss treatment. Here, space-station-like composite nanoparticles (CCC@mPP NPs) with pH/oxidation dual responsiveness and multidrug simultaneous delivery capability were constructed and then loaded with various drugs including panax notoginseng saponins (PNS), tanshinone IIA (TSIIA), and ammonia borane (AB) to provide robust protection against SNHL. Molecular dynamics simulation revealed that carboxymethyl chitosan/calcium carbonate-chitosan (CCC) NPs and monomethoxy poly(ethylene glycol)-PLGA (mPP) NPs can rendezvous and dock primarily by hydrogen bonding, and electrostatic forces may be involved. Moreover, CCC@mPP NPs crossed the round window membrane (RWM) and entered the inner ear through endocytosis and paracellular pathway. The docking state was basically maintained during this process, which created favorable conditions for multidrug delivery. This nanosystem was highly sensitive to pH and reactive oxygen species (ROS) changes, as evidenced by the restricted release of payload at alkaline condition (pH 7.4) without ROS, while significantly promoting the release in acidic condition (pH 5.0 and 6.0) with ROS. TSIIA/PNS/AB-loaded CCC@mPP NPs almost completely preserved the hair cells and remained the hearing threshold shift within normal limits in aminoglycoside- or CDDP-treated guinea pigs. Further experiments demonstrated that the protective mechanisms of TSIIA/PNS/AB-loaded CCC@mPP NPs involved direct and indirect scavenging of excessive ROS, and reduced release of pro-inflammatory cytokines. Both in vitro and in vivo experiments showed the high biocompatibility of the composite NPs, even after long-term administration. Collectively, this work suggests that composite NPs is an ideal multi-drug-delivery vehicle and open new avenues for inner ear disease therapies.

Intratympanic microcrystals of dexamethasone and lipoic acid for the treatment of cisplatin-induced inner ear injury

Steroids (anti-inflammatory drugs) combined with antioxidants are frequently prescribed to treat cisplatin (CP)-induced hearing loss in the clinic. Compared to systemic administration of free drugs, local drug delivery systems offer better therapeutic qualities and patient compliance since they not only can bypass the blood-labyrinth barrier but also can perform sustained release. In this work, dexamethasone (DEX) and lipoic acid (LA) non-spherical microcrystals (MCs) were prepared without complicated chemical modification. Following a series of physical characterizations, including morphology, stability and injectability, dissolution and round window membrane distribution of MCs, DEX MCs, LA MCs and the simple mixture of DEX MCs + LA MCs (combination group) were administered in guinea pigs by intratympanic injection. We found that LA MCs enabled improvement of DEX absorption in the combination group compared to a single dose. In addition, no significant morphological changes or inflammatory responses were observed in cochlear tissue, indicating good biocompatibility. Finally, the combination group also demonstrated synergistic therapeutic effect for protecting hair cells against CP-induced damage. The local co delivery of DEX MCs and LA MCs offers a new strategy for the treatment of CP-induced inner ear injury since they provide sustained anti-inflammatory and antioxidant effects simultaneously.

Core-shell Pluronic F127/chitosan based nanoparticles for effective delivery of methotrexate in the management of rheumatoid arthritis

This study was designed to improve oral bioavailability of the methotrexate (MTX) by sustaining its release profile and integration into core-shell polymeric nanoparticles. The self-micellization and ionotropic gelation technique was employed which resulted into spherical shaped nanoparticles (181-417 nm) with encapsulation efficiency of 80.14% to 85.54%. Furthermore, Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry analyses were carried out to investigate physicochemical and thermal stability of the produced engineered core shell nanoparticles of the methotrexate. . Entrapment of drug in polymeric core was confirmed by X-ray diffraction analysis. In-vitro sustained release behavior of nanoparticles was observed at pH 6.8 for 48 h while low drug release was observed at pH 1.2 due to pH-responsive nature of Pluronic F127. Acute toxicity study confirmed safety and biocompatible profile of nanoparticles. MTX loaded polymeric nanoparticles ameliorated the pharmacokinetic profile (8 folds greater half-life, 6.26 folds higher AUC_0-t and 3.48 folds higher mean residence time). In vivo study conducted in rat model depicted the improved therapeutic efficacy and healing of arthritis through MTX loaded polymeric nanoparticles, preferentially attributable to high accretion of MTX in the inflamed site. In conclusion, MTX loaded polymeric nanoparticles is an attractive drug delivery strategy for an effective management and treatment of rheumatoid arthritis.

The Use of Nanoparticles in Otoprotection

The inner ear can be insulted by various noxious stimuli, including drugs (cisplatin and aminoglycosides) and over-acoustic stimulation. These stimuli damage the hair cells giving rise to progressive hearing loss. Systemic drugs have attempted protection from ototoxicity. Most of these drugs poorly reach the inner ear with consequent ineffective action on hearing. The reason for these failures resides in the poor inner ear blood supply, the presence of the blood-labyrinthine barrier, and the low permeability of the round window membrane (RWM). This article presents a review of the use of nanoparticles (NPs) in otoprotection. NPs were recently used in many fields of medicine because of their ability to deliver drugs to the target organs or cells. The studies included in the review regarded the biocompatibility of the used NPs by in vitro and in vivo experiments. In most studies, NPs proved safe without a significant decrease in cell viability or signs of ototoxicity. Many nano-techniques were used to improve the drugs' kinetics and efficiency. These techniques included encapsulation, polymerization, surface functionalization, and enhanced drug release. In such a way, it improved drug transmission through the RWM with increased and prolonged intra-cochlear drug concentrations. In all studies, the fabricated drug-NPs effectively preserved the hair cells and the functioning hearing from exposure to different ototoxic stimuli, simulating the actual clinical circumstances. Most of these studies regarded cisplatin ototoxicity due to the wide use of this drug in clinical oncology. Dexamethasone (DEX) and antioxidants represent the most used drugs in most studies. These drugs effectively prevented apoptosis and reactive oxygen species (ROS) production caused by ototoxic stimuli. These various successful experiments confirmed the biocompatibility of different NPs and made it successfully to human clinical trials.

Epigallocatechin gallate-loaded tetrahedral DNA nanostructures as a novel inner ear drug delivery system

The study of drug delivery systems to the inner ear is a crucial but challenging field. The sensory organ (in the inner ear) is protected by the petrous bone labyrinth and the membranous labyrinth, both of which need to be overcome during the drug delivery process. The requirements for such a delivery system include small size, appropriate flexibility and biodegradability. DNA nanostructures, biomaterials that can arrange multiple functional components with nanometer precision, exhibit characteristics that are compatible with the requirements for inner ear drug delivery. Herein, we report the development of a novel inner ear drug delivery system based on epigallocatechin gallate (EGCG)-loaded tetrahedral DNA nanostructures (TDNs, EGCG@TDNs). The TDNs self-assembled via base-pairing of four single-stranded DNA constructs and EGCG was loaded into the TDNs through non-covalent interactions. Cy5-labeled TDNs (Cy5-TDNs) were significantly internalized by the House Ear Institute-Organ of Corti 1 cell line, and this endocytosis was energy-, clathrin-, and micropinocytosis-dependent. Cy5-TDNs penetrated the round window membrane (RWM) rapidly in vivo. Local application of EGCG@TDNs onto the RWM of guinea pigs in a single dose continuously released EGCG over 4 hours. Drug concentrations in the perilymph were significantly elevated compared with the administration of free EGCG at the same dose. EGCG@TDNs were found to have favorable biocompatibility and strongly affected the RSL3-induced down-regulation of GPX4 and the generation of reactive oxygen species, on the basis of 2',7'-dichlorodihydrofluorescein diacetate staining. JC-1 staining suggested that EGCG@TDNs successfully reversed the decrease in mitochondrial membrane potential induced by RSL-3 in vitro and rescued cells from apoptosis, as demonstrated by the analysis of Annexin V-FITC/PI staining. Further functional studies showed that a locally administered single-dose of EGCG@TDNs effectively preserved spiral ganglion cells in C57/BL6 mice after noise-induced hearing loss. Hearing loss at 5.6 and 8 kHz frequencies was significantly attenuated when compared with the control EGCG formulation. Histological analyses indicated that the administration of TDNs and EGCG@TDNs did not induce local inflammatory responses. These favorable histological and functional effects resulting from the delivery of EGCG by TDNs through a local intratympanic injection suggest potential for therapeutic benefit in clinical applications.

Superoxide dismutase@zeolite Imidazolate Framework-8 Attenuates Noise-Induced Hearing Loss in Rats

Reactive oxygen species (ROS) and inflammation have been considered major contributors to noise-induced hearing loss (NIHL) that constituted a public health threat worldwide. Nanoantioxidants, with high antioxidant activity and good stability, have been extensively used in the study of ROS-related diseases. In this study, we constructed a superoxide dismutase (SOD)@zeolite imidazolate framework-8 (ZIF-8) nanoparticle based on biomimetic mineralization and applied it to a rat model of NIHL. Our results showed that SOD@ZIF-8 effectively protected the animals from hearing loss and hair cell loss caused by noise. ROS, oxidative damage, and inflammation of noise-damaged cochlea were attenuated considerably after SOD@ZIF-8 administration. Importantly, we found that SOD@ZIF-8 achieved nanotherapy for NIHL in rats via a primary effect on the Sirtuin-3 (SIRT3)/superoxide dismutase2 (SOD2) signaling pathway without obvious adverse side effects. Therefore, our study is expected to open up a new field for NIHL treatment, and lay a foundation for the application of nanomaterials in other ROS-related inner ear diseases.

Nanomaterials for Inner Ear Diseases: Challenges, Limitations and Opportunities

The inner ear is located deep in the temporal bone and has a complex anatomy. It is difficult to observe and obtain pathological tissues directly. Therefore, the diagnosis and treatment of inner ear diseases have always been a major clinical problem. The onset of inner ear disease can be accompanied by symptoms such as hearing loss, dizziness and tinnitus, which seriously affect people's lives. Nanoparticles have the characteristics of small size, high bioavailability and strong plasticity. With the development of related research on nanoparticles in inner ear diseases, nanoparticles have gradually become a research hotspot in inner ear diseases. This review briefly summarizes the research progress, opportunities and challenges of the application of nanoparticles in inner ear diseases.

Novel insights and perspectives for the diagnosis and treatment of hearing loss through the implementation of magnetic nanotheranostics

Hearing loss (HL) is a sensory disability that affects 5% of the world's population. HL predominantly involves damage and death to the cochlear cells. Currently, there is no cure or specific medications for HL. Furthermore, the arrival of therapeutic molecules to the inner ear represents a challenge due to the limited blood supply to the sensory cells and the poor penetration of the blood-cochlear barrier. Superparamagnetic iron oxide nanoparticles (SPIONs) perfectly coordinate with the requirements for controlled drug delivery along with magnetic resonance imaging (MRI) diagnostic and monitoring capabilities. Besides, they are suitable tools to be applied to HL, expecting to be more effective and non-invasive. So far, the published literature only refers to some preclinical studies of SPIONs for HL management. This contribution aims to provide an integrated view of the best options and strategies that can be considered for future research punctually in the field of magnetic nanotechnology applied to HL.

Drug Delivery across Barriers to the Middle and Inner Ear

The prevalence of ear disorders has spurred efforts to develop drug delivery systems to treat these conditions. Here, recent advances in drug delivery systems that access the ear through the tympanic membrane (TM) are reviewed. Such methods are either non-invasive (placed on the surface of the TM), or invasive (placed in the middle ear, ideally on the round window [RW]). The major hurdles to otic drug delivery are identified and highlighted the representative examples of drug delivery systems used for drug delivery across the TM to the middle and (crossing the RW also) inner ear.

Modulation of Inflammatory Mediators by Polymeric Nanoparticles Loaded with Anti-Inflammatory Drugs

The first-line treatment of osteoarthritis is based on anti-inflammatory drugs, the most currently used being nonsteroidal anti-inflammatory drugs, selective cyclooxygenase 2 (COX-2) inhibitors and corticoids. Most of them present cytotoxicity and low bioavailability in physiological conditions, making necessary the administration of high drug concentrations causing several side effects. The goal of this work was to encapsulate three hydrophobic anti-inflammatory drugs of different natures (celecoxib, tenoxicam and dexamethasone) into core-shell terpolymer nanoparticles with potential applications in osteoarthritis. Nanoparticles presented hydrodynamic diameters between 110 and 130 nm and almost neutral surface charges (between −1 and −5 mV). Encapsulation efficiencies were highly dependent on the loaded drug and its water solubility, having higher values for celecoxib (39–72%) followed by tenoxicam (20–24%) and dexamethasone (14–26%). Nanoencapsulation reduced celecoxib and dexamethasone cytotoxicity in human articular chondrocytes and murine RAW264.7 macrophages. Moreover, the three loaded systems did not show cytotoxic effects in a wide range of concentrations. Celecoxib and dexamethasone-loaded nanoparticles reduced the release of different inflammatory mediators (NO, TNF-α, IL-1β, IL-6, PGE₂ and IL-10) by lipopolysaccharide (LPS)-stimulated RAW264.7. Tenoxicam-loaded nanoparticles reduced NO and PGE₂ production, although an overexpression of IL-1β, IL-6 and IL-10 was observed. Finally, all nanoparticles proved to be biocompatible in a subcutaneous injection model in rats. These findings suggest that these loaded nanoparticles could be suitable candidates for the treatment of inflammatory processes associated with osteoarthritis due to their demonstrated in vitro activity as regulators of inflammatory mediator production.

Reactive Oxygen Species-Regulating Strategies Based on Nanomaterials for Disease Treatment

Reactive oxygen species (ROS) play an essential role in physiological and pathological processes. Studies on the regulation of ROS for disease treatments have caused wide concern, mainly involving the topics in ROS-regulating therapy such as antioxidant therapy triggered by ROS scavengers and ROS-induced toxic therapy mediated by ROS-elevation agents. Benefiting from the remarkable advances of nanotechnology, a large number of nanomaterials with the ROS-regulating ability are developed to seek new and effective ROS-related nanotherapeutic modalities or nanomedicines. Although considerable achievements have been made in ROS-based nanomedicines for disease treatments, some fundamental but key questions such as the rational design principle for ROS-related nanomaterials are held in low regard. Here, the design principle can serve as the initial framework for scientists and technicians to design and optimize the ROS-regulating nanomedicines, thereby minimizing the gap of nanomedicines for biomedical application during the design stage. Herein, an overview of the current progress of ROS-associated nanomedicines in disease treatments is summarized. And then, by particularly addressing these known strategies in ROS-associated therapy, several fundamental and key principles for the design of ROS-associated nanomedicines are presented. Finally, future perspectives are also discussed in depth for the development of ROS-associated nanomedicines.

Recent Advances in Antiinflammatory Material Design

Implants and prostheses are widely used to replace damaged tissues or to treat various diseases. However, besides the risk of bacterial or fungal infection, an inflammatory response usually occurs. Here, recent progress in the field of anti-inflammatory biomaterials is described. Different materials and approaches are used to decrease the inflammatory response, including hydrogels, nanoparticles, implant surface coating by polymers, and a variety of systems for anti-inflammatory drug delivery. Complex multifunctional systems dealing with inflammation, microbial infection, bone regeneration, or angiogenesis are also described. New promising stimuli-responsive systems, such as pH- and temperature-responsive materials, are also being developed that would enable an "intelligent" antiinflammatory response when the inflammation occurs. Together, different approaches hold promise for creation of novel multifunctional smart materials allowing better implant integration and tissue regeneration.

Amphiphilic polymeric nanoparticles encapsulating curcumin: Antioxidant, anti-inflammatory and biocompatibility studies

Oxidative stress and inflammation are two related processes common to many diseases. Curcumin is a natural compound with both antioxidant and anti-inflammatory properties, among others, that is recently being used as a natural occurring product alternative to traditional drugs. However, it has a hydrophobic nature that compromises its solubility in physiological fluids and its circulation time and also presents cytotoxicity problems in its free form, limiting the range of concentrations to be used. In order to overcome these drawbacks and taking advantage of the benefits of nanotechnology, the aim of this work is the development of curcumin loaded polymeric nanoparticles that can provide a controlled release of the drug and enlarge their application in the treatment of inflammatory and oxidative stress related diseases. Specifically, the vehicle is a bioactive terpolymer based on a α-tocopheryl methacrylate, 1-vinyl-2-pyrrolidone and N-vinylcaprolactam. Nanoparticles were obtained by nanoprecipitation and characterized in terms of size, morphology, stability, encapsulation efficiency and drug release. In vitro cellular assays were performed in human articular chondrocyte and RAW 264.7 cultures to assess cytotoxicity, cellular uptake, antioxidant and anti-inflammatory properties. The radical scavenging activity of the systems was confirmed by the DPPH test and the quantification of cellular reactive oxygen species. The anti-inflammatory potential of these systems was demonstrated by the reduction of different pro-inflammatory factors such as IL-8, MCP and MIP in chondrocytes; and nitric oxide, IL-6, TNF-α and MCP-1, among others, in RAW 264.7. Finally, the in vivo biocompatibility was confirmed in a rat model by subcutaneously injecting the nanoparticle dispersions. The reduction of curcumin toxicity and the antioxidant, anti-inflammatory and biocompatibility properties open the door to deeper in vitro and in vivo research on these curcumin loaded polymeric nanoparticles to treat inflammation and oxidative stress based diseases.

Nanocarriers for drug delivery to the inner ear: Physicochemical key parameters, biodistribution, safety and efficacy

Despite the high incidence of inner ear disorders, there are still no dedicated medications on the market. Drugs are currently administered by the intratympanic route, the safest way to maximize drug concentration in the inner ear. Nevertheless, therapeutic doses are ensured for only a few minutes/hours using drug solutions or suspensions. The passage through the middle ear barrier strongly depends on drug physicochemical characteristics. For the past 15 years, drug encapsulation into nanocarriers has been developed to overcome this drawback. Nanocarriers are well known to sustain drug release and protect it from degradation. In this review, in vivo studies are detailed concerning nanocarrier biodistribution, their pathway mechanisms in the inner ear and the resulting drug pharmacokinetics. Key parameters influencing nanocarrier biodistribution are identified and discussed: nanocarrier size, concentration, surface composition and shape. Recent advanced strategies that combine nanocarriers with hydrogels, specific tissue targeting or modification of the round window permeability (cell-penetrating peptide, magnetic delivery) are explored. Most of the nanocarriers appear to be safe for the inner ear and provide a significant efficacy over classic formulations in animal models. However, many challenges remain to be overcome for future clinical applications.

Strategies to reduce the risk of platinum containing antineoplastic drug-induced ototoxicity

INTRODUCTION

Cisplatin is a highly effective chemotherapeutic agent against a variety of solid tumors in adults and in children. Unfortunately, a large percentage of patients suffer permanent sensorineural hearing loss. Up to 60% of children and at least 50% of adults suffer this complication that seriously compromises their quality of life. Hearing loss is due to damage to the sensory cells in the inner ear. The mechanisms of cochlear damage are still being investigated. However, it appears that inner ear damage is triggered by reactive oxygen species (ROS) formation and inflammation 34.

AREAS COVERED

We discuss a number of potential therapeutic targets that can be addressed to provide hearing protection. These strategies include enhancing the endogenous antioxidant pathways, heat shock proteins, G protein coupled receptors and counteracting ROS and reactive nitrogen species, and blocking pathways that produce inflammation, including TRPV1 and STAT1 36.

EXPERT OPINION

Numerous potential protective agents show promise in animal models by systemic or local administration. However, clinical trials have not shown much efficacy to date with the exception of sodium thiosulfate. There is an urgent need to discover safe and effective protective agents that do not interfere with the efficacy of cisplatin against tumors yet preserve hearing 151.

Current Strategies to Combat Cisplatin-Induced Ototoxicity

Cisplatin is widely used for the treatment of a number of solid malignant tumors. However, ototoxicity induced by cisplatin is an obstacle to effective treatment of tumors. The basis for this toxicity has not been fully elucidated. It is generally accepted that hearing loss is due to excessive production of reactive oxygen species by cells of the cochlea. In addition, recent data suggest that inflammation may trigger inner ear cell death through endoplasmic reticulum stress, autophagy, and necroptosis, which induce apoptosis. Strategies have been extensively explored by which to prevent, alleviate, and treat cisplatin-induced ototoxicity, which minimize interference with antitumor activity. Of these strategies, none have been approved by the Federal Drug Administration, although several preclinical studies have been promising. This review highlights recent strategies that reduce cisplatin-induced ototoxicity. The focus of this review is to identify candidate agents as novel molecular targets, drug administration routes, delivery systems, and dosage schedules. Animal models of cisplatin ototoxicity are described that have been used to evaluate drug efficacy and side effect prevention. Finally, clinical reports of otoprotection in patients treated with cisplatin are highlighted. For the future, high-quality studies are required to provide reliable data regarding the safety and effectiveness of pharmacological interventions that reduce cisplatin-induced ototoxicity.

Construction of an environmentally friendly octenylsuccinic anhydride modified pH-sensitive chitosan nanoparticle drug delivery system to alleviate inflammation and oxidative stress

An environmentally friendly octenylsuccinic anhydride modified pH-sensitive chitosan-octenylsuccinic anhydride (OSA-CS) was synthesized. The critical micelle concentration (CMC) of the modified chitosan was 27 μg/mL, the graft polymers can form solubilized curcumin (CUR) and quercetin (QUE) nanoparticles. The drug-loaded nanoparticles had high encapsulation efficiency and drug loading content, the self-assembly of graft polymers formed spherical uniform nanoparticles with an approximate diameter of 150-180 nm. The nanoparticles were stable under storage conditions and in serum. The results revealed that OSA-CS exhibited excellent biocompatibility, no cytotoxicity. Additionally, the results of pH sensitivity and drug release experiments showed that the nanoparticles were highly sensitive to weakly acidic conditions (pH 6.0) and showed a faster release rate, while they were reasonably stable at physiological conditions (pH 7.4). The drug-loaded nanoparticles exhibited higher cellular uptake in vitro, and exhibited stronger anti-inflammatory and antioxidant efficacy. Therefore, OSA-CS-based nanoparticles are a promising hydrophobic drug delivery system for pH-response targeting therapy.

Opportunities and challenging issues of nanomaterials in otological fields: an occupational health perspective

Nanotechnology may offer innovative solutions to overcome the physiological and anatomical barriers that make the diagnosis and treatment of ear diseases an extremely challenging issue. However, despite the solutions provided by nano-applications, the still little-known toxicological behavior of nanomaterials raised scientific concerns regarding their biosafety for treated patients and exposed workers. Therefore, this review provides an overview on recent developments and upcoming opportunities in nanoscale otological applications, and critically assesses possible adverse effects of nanosized compounds on ear structures and hearing functionality. Although such preliminary data do not allow to draw definite strategies for the evaluation of nanomaterial ototoxicity, they can still be useful to improve scientific community and workforce awareness regarding possible nanomaterial adverse effects on ear.

Recent Developments in the Reduction of Oxidative Stress through Antioxidant Polymeric Formulations

Reactive oxygen and nitrogen species (RONS) are produced endogenously in our body, or introduced through external factors, such as pollution, cigarette smoke, and excessive sunlight exposure. In normal conditions, there is a physiological balance between pro-oxidant species and antioxidant molecules that are able to counteract the detrimental effect of the former. Nevertheless, when this homeostasis is disrupted, the resulting oxidative stress can lead to several pathological conditions, from inflammation to cancer and neurodegenerative diseases. In this review, we report on the recent developments of different polymeric formulations that are able to reduce the oxidative stress, from natural extracts, to films and hydrogels, and finally to nanoparticles (NPs).

Solid Lipid Nanoparticles Loaded with Glucocorticoids Protect Auditory Cells from Cisplatin-Induced Ototoxicity

Cisplatin is a chemotherapeutic agent that causes the irreversible death of auditory sensory cells, leading to hearing loss. Local administration of cytoprotective drugs is a potentially better option co-therapy for cisplatin, but there are strong limitations due to the difficulty of accessing the inner ear. The use of nanocarriers for the efficient delivery of drugs to auditory cells is a novel approach for this problem. Solid lipid nanoparticles (SLNs) are biodegradable and biocompatible nanocarriers with low solubility in aqueous media. We show here that stearic acid-based SLNs have the adequate particle size, polydispersity index and ζ-potential, to be considered optimal nanocarriers for drug delivery. Stearic acid-based SLNs were loaded with the fluorescent probe rhodamine to show that they are efficiently incorporated by auditory HEI-OC1 (House Ear Institute-Organ of Corti 1) cells. SLNs were not ototoxic over a wide dose range. Glucocorticoids are used to decrease cisplatin-induced ototoxicity. Therefore, to test SLNs’ drug delivery efficiency, dexamethasone and hydrocortisone were tested either alone or loaded into SLNs and tested in a cisplatin-induced ototoxicity in vitro assay. Our results indicate that the encapsulation in SLNs increases the protective effect of low doses of hydrocortisone and lengthens the survival of HEI-OC1 cells treated with cisplatin.

Dexamethasone-loaded injectable silk-polyethylene glycol hydrogel alleviates cisplatin-induced ototoxicity

Background: Cisplatin is an extensively used anti-neoplastic agent for the treatment of various solid tumors. However, a high incidence of severe ototoxicity is accompanied by its use in the clinic. Currently, no drugs or therapeutic strategies have been approved for the treatment of cisplatin-induced ototoxicity by the FDA.

Purpose: The purpose of this study was to investigate the otoprotective effects of dexamethasone (DEX)-loaded silk-polyethylene hydrogel (DEX-SILK) following round window membrane administration in the cisplatin-induced ototoxicity mouse model.

Methods: The morphology, gelation kinetics, viscosity and secondary structure of the DEX-SILK hydrogel were analyzed. DEX concentration in the perilymph was tested at different time points following hydrogel injection on the RWM niche. Cultured cells (HEI-OC1), organ of Corti explants (C57/BL6, P0-2), and cisplatin-induced hearing loss mice model (C57/BL6) were used as in vitro and in vivo models for investigating the otoprotective effects of DEX-SILK hydrogel against cisplatin.

Results: Encapsulation of DEX with a loading of 8% (w/v) did not significantly change the silk gelation time, and DEX was evenly distributed in the Silk-PEG hydrogel as visualized by scanning electron microscopy (SEM). The concentration of Silk majorly influenced DEX distribution, morphological characteristics, viscosity, and gelation time. The optimized DEX-SILK hydrogel (8% w/v loading, 15% silk concentration, 10 μl) was administered directly onto the RWM of the guinea pigs. The DEX concentration in the perilymph was maintained above 1 μg/ml for at least 21 days for the DEX-SILK, while it was maintained for less than 6 h in the control sample of free DEX. DEX-SILK (5-60 ng/ml) exhibited significant protective effects against cisplatin-induced cellular ototoxicity and notably reduced the production of reactive oxygen species (ROS). Eventually, pretreatment with DEX-SILK effectively preserved outer hair cells in the cultured organ of Corti explants and demonstrated significant hearing protection at 4, 8, and 16 kHz in the cisplatin-induced hearing loss mice as compared to the effects noted following pretreatment with DEX.

Conclusion: These results demonstrated the clinical value of DEX-SILK for the therapy of cisplatin-induced ototoxicity.

Methotrexate-based amphiphilic prodrug nanoaggregates for co-administration of multiple therapeutics and synergistic cancer therapy

The goal of nanomedicine is to seek strategies that are more efficient to address various limitations and challenges faced by conventional medicines, including lack of target specificity, poor bioavailability, premature degradability, and undesired side effects. Self-assembling drug amphiphiles represent a prospective nanomedicine for cancer therapy owing to their favorable route of administration and therapeutic efficiency compared with pristine drug counterparts. In this work, we report a class of self-deliverable prodrug amphiphiles consisting of the hydrophilic drug methotrexate (MTX) and the hydrophobic anticancer drugs camptothecin (CPT) and doxorubicin (DOX) for targeted and combinational chemotherapy. The disulfide bond and hydrazone bond, which are subject to stimuli-triggered bond cleavage, were introduced to link these therapeutic agents and form two prodrug amphiphiles, named as MTX-CPT and MTX-DOX, respectively, which could self-assemble into stable prodrug nanoaggregates (NAs) in aqueous media. MTX molecules in the prodrug NAs facilitated NA uptake into tumor cells with high expression of folic acid receptors (FRs). This systemic study provided clear evidence of the synergistic therapeutic effect by co-administrating dual prodrug NAs on various tumor cells in vitro and a xenograft tumor model in vivo. The obtained prodrug amphiphiles provide an efficient strategy for the design of multifunctional drug delivery systems and elaborate therapeutic nanoplatforms for cancer chemotherapy.

STATEMENT OF SIGNIFICANCE

This work presents two kinds of prodrug amphiphiles that are carrier free and integrate targeted drug delivery, stimuli-triggered drug release, synergistic therapy, and theranostic function into a single system. Reduction/acid active prodrug amphiphiles can self-assemble into micellar nanoaggregates (NAs) at a very low critical aggregation concentration. These NAs exhibit superior stability in physiological environment and disassemble in the presence of tumor cells expressing folic acid receptors or the high glutathione or in low pH tumoral endosomal environment. The induced disassembly of prodrug NAs can "switch on" the inherent fluorescence of the internalized camptothecin or doxorubicin for the detection of tumor cells. Compared to a single type of prodrug NA, co-administration of dual prodrug combination can produce an evident synergistic therapeutic effect against various tumor cells in vitro and inhibit xenograft tumor growth in vivo. The methotrexate-based prodrug amphiphiles may provide a potential strategy for developing multifunctional nanoplatforms and delivery of multiple therapeutics in chemotherapy.

Controlled drug release to the inner ear: Concepts, materials, mechanisms, and performance

Progress in drug delivery to the ear has been achieved over the last few years. This review illustrates the main mechanisms of controlled drug release and the resulting geometry- and size-dependent release kinetics. The potency, physicochemical properties, and stability of the drug molecules are key parameters for designing the most suitable drug delivery system. The most important drug delivery systems for the inner ear include solid foams, hydrogels, and different nanoscale drug delivery systems (e.g., nanoparticles, liposomes, lipid nanocapsules, polymersomes). Their main characteristics (i.e., general structure and materials) are discussed, with special attention given to underlining the link between the physicochemical properties (e.g., surface areas, glass transition temperature, microviscosity, size, and shape) and release kinetics. An appropriate characterization of the drug, the excipients used, and the formulated drug delivery systems is necessary to achieve a deeper understanding of the release process and decrease variability originating from the drug delivery system. This task cannot be solved by otologists alone. The interdisciplinary cooperation between otology/neurotology, pharmaceutics, physics, and other disciplines will result in improved drug delivery systems for the inner ear.

Novel SS-31 modified liposomes for improved protective efficacy of minocycline against drug-induced hearing loss

SS-31 modified, minocycline-loaded liposomes significantly increased hair cell survival against chronic exposure to gentamicin in a zebrafish model.