PLGA nanoparticles for intravitreal peptide delivery: statistical optimization, characterization and toxicity evaluation

Multifunctional nano-in-micro delivery systems for targeted therapy in fundus neovascularization diseases

Fundus neovascularization diseases are a series of blinding eye diseases that seriously impair vision worldwide. Currently, the means of treating these diseases in clinical practice are continuously evolving and have rapidly revolutionized treatment opinions. However, key issues such as inadequate treatment effectiveness, high rates of recurrence, and poor patient compliance still need to be urgently addressed. Multifunctional nanomedicine can specifically respond to both endogenous and exogenous microenvironments, effectively deliver drugs to specific targets and participate in activities such as biological imaging and the detection of small molecules. Nano-in-micro (NIM) delivery systems such as metal, metal oxide and up-conversion nanoparticles (NPs), quantum dots, and carbon materials, have shown certain advantages in overcoming the presence of physiological barriers within the eyeball and are widely used in the treatment of ophthalmic diseases. Few studies, however, have evaluated the efficacy of NIM delivery systems in treating fundus neovascular diseases (FNDs). The present study describes the main clinical treatment strategies and the adverse events associated with the treatment of FNDs with NIM delivery systems and summarizes the anatomical obstacles that must be overcome. In this review, we wish to highlight the principle of intraocular microenvironment normalization, aiming to provide a more rational approach for designing new NIM delivery systems to treat specific FNDs.

Enhancing Ocular Drug Delivery: The Effect of Physicochemical Properties of Nanoparticles on the Mechanism of Their Uptake by Human Cornea Epithelial Cells

This study investigates the effect of nanoparticle size and surface chemistry on interactions of the nanoparticles with human cornea epithelial cells (HCECs). Poly(lactic-co-glycolic) acid (PLGA) nanoparticles were synthesized using the emulsion-solvent evaporation method and surface modified with mucoadhesive (alginate [ALG] and chitosan [CHS]) and mucopenetrative (polyethylene glycol [PEG]) polymers. Particles were found to be monodisperse (polydispersity index (PDI) below 0.2), spherical, and with size and zeta potential ranging from 100 to 250 nm and from -25 to +15 mV, respectively. Evaluation of cytotoxicity with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay indicated that incubating cells with nanoparticles for 24 h at concentrations up to 100 μg/mL caused only mild toxicity (70-100% cell viability). Cellular uptake studies were conducted using an in vitro model developed with a monolayer of HCECs integrated with simulated mucosal solution. Evaluation of nanoparticle uptake revealed that energy-dependent endocytosis is the primary uptake mechanism. Among the different nanoparticles studied, 100 nm PLGA NPs and PEG-PLGA-150 NPs showed the highest levels of uptake by HCECs. Additionally, uptake studies in the presence of various inhibitors suggested that macropinocytosis and caveolae-mediated endocytosis are the dominant pathways. While clathrin-mediated endocytosis was found to also be partially responsible for nanoparticle uptake, phagocytosis did not play a role within the studied ranges of size and surface chemistries. These important findings could lead to improved nanoparticle-based formulations that could improve therapies for ocular diseases.

Sialic Acid Mimetic Microglial Sialic Acid-Binding Immunoglobulin-like Lectin Agonism: Potential to Restore Retinal Homeostasis and Regain Visual Function in Age-Related Macular Degeneration

Age-related macular degeneration (AMD), a leading cause of visual loss and dysfunction worldwide, is a disease initiated by genetic polymorphisms that impair the negative regulation of complement. Proteomic investigation points to altered glycosylation and loss of Siglec-mediated glyco-immune checkpoint parainflammatory and inflammatory homeostasis as the main determinant for the vision impairing complications of macular degeneration. The effect of altered glycosylation on microglial maintained retinal para-inflammatory homeostasis and eventual recruitment and polarization of peripheral blood monocyte-derived macrophages (PBMDMs) into the retina can explain the phenotypic variability seen in this clinically heterogenous disease. Restoring glyco-immune checkpoint control with a sialic acid mimetic agonist targeting microglial/macrophage Siglecs to regain retinal para-inflammatory and inflammatory homeostasis is a promising therapeutic that could halt the progression of and improve visual function in all stages of macular degeneration.

Comprehensive Review on the Degradation Chemistry and Toxicity Studies of Functional Materials

In recent decades there has been growing interest of material chemists in the successful development of functional materials for drug delivery, tissue engineering, imaging, diagnosis, theranostic, and other biomedical applications with advanced nanotechnology tools. The efficacy and safety of functional materials are determined by their pharmacological, toxicological, and immunogenic effects. It is essential to consider all degradation pathways of functional materials and to assess plausible intermediates and final products for quality control. This review provides a brief insight into chemical degradation mechanisms of functional materials like oxidation, photodegradation, and physical and enzymatic degradation. The intermediates and products of degradation were confirmed with analytical methods such as proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), UV-vis spectroscopy (UV-vis), infrared spectroscopy (IR), differential scanning calorimetry (DSC), mass spectroscopy, and other sophisticated analytical methods. These analytical methods are also used for regulatory, quality control, and stability purposes in industry. The assessment of degradation is important to predetermine the behavior of functional materials in specific storage conditions and can be relevant to their behavior during in vivo applications. Another important aspect is the evaluation of the toxicity of functional materials. Toxicity can be accessed with various methods using in vitro, in vivo, ex vivo, and in silico models. In vitro cell culture methods are used to determine mitochondrial damage, reactive oxygen species, stress responses, and cellular toxicity. In vitro cellular toxicity can be measured by MTT assay, LDH leakage assay, and hemolysis. In vivo studies are performed using various animal models involving zebrafish, rodents (mice and rats), and nonhuman primates. Ex vivo studies are also used for efficacy and toxicity determinations of functional materials like ex vivo potency assay and precision-cut liver slice (PCLS) models. The in silico tools with computational simulations like quantitative structure-activity relationships (QSAR), pharmacokinetics (PK) and pharmacodynamics (PD), dose and time response, and quantitative cationic-activity relationships ((Q)CARs) are used for prediction of the toxicity of functional materials. In this review, we studied the principle methods used for degradation studies, different degradation pathways, and mechanisms of functional material degradation with prototype examples. We discuss toxicity assessments with different toxicity approaches used for estimation of the safety and efficacy of functional materials.

Effect of Solvents, Stabilizers and the Concentration of Stabilizers on the Physical Properties of Poly(d,l-lactide-co-glycolide) Nanoparticles: Encapsulation, In Vitro Release of Indomethacin and Cytotoxicity against HepG2-Cell

A biocompatible, biodegradable and FDA-approved polymer [Poly lactic-co-glycolic acid (PLGA)] was used to prepare the nanoparticles (NPs) to observe the effect of solvents, stabilizers and their concentrations on the physical properties of the PLGA-NPs, following the encapsulation and in vitro release of Indomethacin (IND). PLGA-NPs were prepared by the single-emulsion solvent evaporation technique using dichloromethane (DCM)/chloroform as the organic phase with Polyvinyl-alcohol (PVA)/Polyvinylpyrrolidone (PVP) as stabilizers to encapsulate IND. The effects of different proportions of PVA/PVP with DCM/chloroform on the physiochemical properties (particle size, the polydispersity index, the zeta potential by Malvern Zetasizer and morphology by SEM) of the NPs were investigated. DSC was used to check the physical state, the possible complexation of PLGA with stabilizer(s) and the crystallinity of the encapsulated drug. Stabilizers at all concentrations produced spherical, regular-shaped, smooth-surfaced discrete NPs. Average size of 273.2–563.9 nm was obtained when PVA (stabilizer) with DCM, whereas it ranged from 317.6 to 588.1 nm with chloroform. The particle size was 273.2–563.9 nm when PVP was the stabilizer with DCM, while it was 381.4–466.6 nm with chloroform. The zeta potentials of PVA-stabilized NPs were low and negative (−0.62 mV) while they were comparatively higher and positive for PVP-stabilized NPs (+17.73 mV). Finally, drug-loaded optimal NPs were composed of PLGA (40 mg) and IND (4 mg) in 1 mL DCM/chloroform with PVA/PVP (1–3%), which resulted in sufficient encapsulation (54.94–74.86%) and drug loading (4.99–6.81%). No endothermic peak of PVA/PVP appeared in the optimized formulation, which indicated the amorphous state of IND in the core of the PLGA-NPs. The in vitro release study indicated a sustained release of IND (32.83–52.16%) from the PLGA-NPs till 72 h and primarily followed the Higuchi matrix release kinetics followed by Korsmeyer–Peppas models. The cell proliferation assay clearly established that the organic solvents used to prepare PLGA-NPs had evaporated. The PLGA-NPs did not show any particular toxicity in the HepG2 cells within the dose range of IND (250–500 µg/mL) and at an equivalent concentration of PLGA-NPs (3571.4–7142.7 µg/mL). The cytotoxicity of the hepatotoxic drug (IND) was reduced by its encapsulation into PLGA-NPs. The outcomes of this investigation could be implemented to prepare PLGA-NPs of acceptable properties for the encapsulation of low/high molecular weight drugs. It would be useful for further in vitro and in vivo applications to use this delivery system.

Sustained release ketamine-loaded porous silicon-PLGA microparticles prepared by an optimized supercritical CO2 process

Ketamine in sub-anaesthetic doses has analgesic properties and an opioid-sparing effect. Intrathecal (i.t.) delivery of analgesics bypasses systemic metabolism and delivers the analgesic agent adjacent to the target receptors in the spinal cord and so small doses are required to achieve effective pain relief. In order to relieve intractable cancer-related pain, sustained-release ketamine formulations are required in combination with a strong opioid because frequent i.t. injection is not practical. In this study, ketamine or ketamine-loaded porous silicon (pSi) were encapsulated into poly(lactic-co-glycolic acid) (PLGA) microparticles by a novel supercritical carbon dioxide (scCO2) method, thereby avoiding the use of organic solvent. Multiple parameters including theoretical drug loading (DL), presence of pSi, size of scCO2 vessel, PLGA type, and use of co-solvent were investigated with a view to obtaining high DL and a sustained-release for an extended period. The most important finding was that the use of a large scCO2 vessel (60 mL) resulted in a much higher encapsulation efficiency (EE) compared with a small vessel (12 mL). In addition, pre-loading ketamine into pSi slightly improved the level of drug incorporation (i.e. EE and DL). Although the in vitro release was mainly affected by the drug payload, the use of the large scCO2 vessel reduced the burst release and extended the release period for PLGA microparticles with 10% or 20% ketamine loading. Together, our findings provide valuable information for optimization of drug delivery systems prepared with the aid of scCO2.

Anti-ageing peptides and proteins for topical applications: a review

Skin ageing is a cumulative result of oxidative stress, predominantly caused by reactive oxygen species (ROS). Respiration, pollutants, toxins, or ultraviolet A (UVA) irradiation produce ROS with 80% of skin damage attributed to UVA irradiation. Anti-ageing peptides and proteins are considered valuable compounds for removing ROS to prevent skin ageing and maintenance of skin health. In this review, skin ageing theory has been illustrated with a focus on the mechanism and relationship with anti-ageing peptides and proteins. The effects, classification, and transport pathways of anti-ageing peptides and proteins across skin are summarized and discussed. Over the last decade, several novel formulations and advanced strategies have been developed to overcome the challenges in the dermal delivery of proteins and peptides for skin ageing. This article also provides an in-depth review of the latest advancements in the dermal delivery of anti-ageing proteins and peptides. Based on these studies, this review prospected several semi-solid dosage forms to achieve topical applicability for anti-ageing peptides and proteins.

Optimisation of a Microfluidic Method for the Delivery of a Small Peptide

Peptides hold promise as therapeutics, as they have high bioactivity and specificity, good aqueous solubility, and low toxicity. However, they typically suffer from short circulation half-lives in the body. To address this issue, here, we have developed a method for encapsulation of an innate-immune targeted hexapeptide into nanoparticles using safe non-toxic FDA-approved materials. Peptide-loaded nanoparticles were formulated using a two-stage microfluidic chip. Microfluidic-related factors (i.e., flow rate, organic solvent, theoretical drug loading, PLGA type, and concentration) that may potentially influence the nanoparticle properties were systematically investigated using dynamic light scattering and transmission electron microscopy. The pharmacokinetic (PK) profile and biodistribution of the optimised nanoparticles were assessed in mice. Peptide-loaded lipid shell-PLGA core nanoparticles with designated size (~400 nm) and a sustained in vitro release profile were further characterized in vivo. In the form of nanoparticles, the elimination half-life of the encapsulated peptide was extended significantly compared with the peptide alone and resulted in a much higher distribution into the lung. These novel nanoparticles with lipid shells have considerable potential for increasing the circulation half-life and improving the biodistribution of therapeutic peptides to improve their clinical utility, including peptides aimed at treating lung-related diseases.

Smart nano-micro platforms for ophthalmological applications: The state-of-the-art and future perspectives

Smart nano-micro platforms have been extensively applied for diverse biomedical applications, mostly focusing on cancer therapy. In comparison with conventional nanotechnology, the smart nano-micro matrix can exhibit specific response to exogenous or endogenous triggers, and thus can achieve multiple functions e.g. site-specific drug delivery, bio-imaging and detection of bio-molecules. These intriguing techniques have expanded into ophthalmology in recent years, yet few works have been summarized in this field. In this work, we provide the state-of-the-art of diverse nano-micro platforms based on both the conventional materials (e.g. natural or synthetic polymers, lipid nanomaterials, metal and metal oxide nanoparticles) and emerging nanomaterials (e.g. up-conversion nanoparticles, quantum dots and carbon materials) in ophthalmology, with some smart nano/micro platformers highlighted. The common ocular diseases studied in the field of nano-micro systems are firstly introduced, and their therapeutic method and the related drawback in clinic treatment are presented. The recent progress of different materials for diverse ocular applications is then demonstrated, with the representative nano- and micro-systems highlighted in detail. At last, an in-depth discussion on the clinical translation challenges faced in this field and the future direction are provided. This review would allow the researchers to design more smart nanomedicines in a more rational manner for specific ophthalmology applications.

Quercetin-loaded nanoparticles enhance cytotoxicity and antioxidant activity on C6 glioma cells

Quercetin (Qu) is a natural flavonoid present in many commonly consumed food items. The dietary phytochemical quercetin prevents tumor proliferation and is a potent therapeutic cancer agent. The purpose of this study was to synthesize and characterize quercetin-loaded poly(lactic-co-glycolic acid) nanoparticles (Qu₁NP, Qu₂NP, and Qu₃NP) with different size and encapsulation properties and to evaluate their in vitro activity on C6 glioma cells. Nanoparticles were synthesized by single emulsion solvent evaporation method. Then, particle size, zeta potential, polydispersity index and encapsulation efficiency of nanoparticles were determined. Particle size of Qu₁NP, Qu₂NP, and Qu₃NPs were determined as 215.2 ± 6.2, 282.3 ± 7.9, and 584.5 ± 15.2 nm respectively. Treating C6 glioma cells with all nanoparticle formulations effectively inhibited the cell proliferation. Qu₁NPs were showed the lowest IC₅₀ value in 48 h with 29.9 μg/ml and achieved higher cellular uptake among other nanoparticles and Qu. Additionally, 48-h treatment with Qu₁NPs significantly decreased MDA level (14.90 nmol/µg protein) on C6 glioma cells which is related to reduced oxidative stress in cells. Findings of this study revealed that quercetin's cellular uptake and anti-oxidant activity is improved by small-sized Qu₁NPs in C6 glioma cells.

Zebrafish, a model to develop nanotherapeutics that control neutrophils response during inflammation

Neutrophils are crucial modulators of the inflammation process, and their uncontrolled response worsens several chronic pathologies. The p38 mitogen-activated protein kinases (MAPKs) activity is critical for normal immune and inflammatory response through the regulation of pro-inflammatory cytokines synthesis. In this work, we study the effect of hybrid lipid-polymer nanoparticles loaded with the p38 MAPK inhibitor SB203580 in an acute and chronic inflammatory model in zebrafish containing a transgenic neutrophil cell line that constitutively expresses a green fluorescent protein. We identify the existence of at least two neutrophils subpopulation involved in the response during the acute inflammation triggered; a first-responder p38α-independent subset and a second-responder p38α-dependent subset. In the case of chronic inflammation, neutrophils recruited in the intestine only during the inflammation process, migrate in a p38α-dependent manner. Likewise, we establish that SB203580-loaded in NPs exerts their action during at least a double period than the inhibitor administers directly in both types of inflammation. Our results demonstrate the exceptional potential of the zebrafish as an inflammatory model for studying novel nanotherapeutics that selectively inhibit the neutrophils response, and to identify functional neutrophils subpopulations involved in the inflammation process.

Ocular Drug Delivery: Role of Degradable Polymeric Nanocarriers for Ophthalmic Application

Ocular drug delivery has been a major challenge for clinical pharmacologists and biomaterial scientists due to intricate and unique anatomical and physiological barriers in the eye. The critical requirement varies from anterior and posterior ocular segments from a drug delivery perspective. Recently, many new drugs with special formulations have been introduced for targeted delivery with modified methods and routes of drug administration to improve drug delivery efficacy. Current developments in nanoformulations of drug carrier systems have become a promising attribute to enhance drug retention/permeation and prolong drug release in ocular tissue. Biodegradable polymers have been explored as the base polymers to prepare nanocarriers for encasing existing drugs to enhance the therapeutic effect with better tissue adherence, prolonged drug action, improved bioavailability, decreased toxicity, and targeted delivery in eye. In this review, we summarized recent studies on sustained ocular drug/gene delivery and emphasized on the nanocarriers made by biodegradable polymers such as liposome, poly lactic-co-glycolic acid (PLGA), chitosan, and gelatin. Moreover, we discussed the bio-distribution of these nanocarriers in the ocular tissue and their therapeutic applications in various ocular diseases.

Intra-vitreal αB crystallin fused to elastin-like polypeptide provides neuroprotection in a mouse model of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe and irreversible central vision loss, and the primary site of AMD pathology is the retinal pigment epithelium (RPE). Geographic atrophy (GA) is an advanced form of AMD characterized by extensive RPE cell loss, subsequent degeneration of photoreceptors, and thinning of retina. This report describes the protective potential of a peptide derived from the αB crystallin protein using a sodium iodate (NaIO₃) induced mouse model of GA. Systemic NaIO₃ challenge causes degeneration of the RPE and neighboring photoreceptors, which have similarities to retinas of GA patients. αB crystallin is an abundant ocular protein that maintains ocular clarity and retinal homeostasis, and a small peptide from this protein (mini cry) displays neuroprotective properties. To retain this peptide for longer in the vitreous, mini cry was fused to an elastin-like polypeptide (ELP). A single intra-vitreal treatment by this crySI fusion significantly inhibits retinal degeneration in comparison to free mini cry. While mini cry is cleared from the eye with a mean residence time of 0.4 days, crySI is retained with a mean residence time of 3.0 days; furthermore, fundus photography reveals evidence of retention at two weeks. Unlike the free mini cry, crySI protects the RPE against NaIO₃ challenge for at least two weeks after administration. CrySI also inhibits RPE apoptosis and caspase-3 activation and protects the retina from cell death up to 1-month post NaIO₃ challenge. These results show that intra-ocular ELP-linked peptides such as crySI hold promise as protective agents to prevent RPE atrophy and progressive retinal degeneration in AMD.

Development of a novel stability indicating RP-HPLC method for quantification of Connexin43 mimetic peptide and determination of its degradation kinetics in biological fluids

Connexin43 mimetic peptide (Cx43MP) has been intensively investigated for its therapeutic effect in the management of inflammatory eye conditions, spinal cord injury, wound healing and ischemia-induced brain damage. Here, we report on a validated stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method for the quantification of Cx43MP under stress conditions. These included exposure to acid/base, light, oxidation and high temperature. In addition, the degradation kinetics of the peptide were evaluated in bovine vitreous and drug-free human plasma at 37 °C. Detection of Cx43MP was carried out at 214 nm with a retention time of 7.5 min. The method showed excellent linearity over the concentration range of 0.9-250 µg/mL (R2 ≥ 0.998), and the limits of detection (LOD) and quantification (LOQ) were found to be 0.90 and 2.98 μg/mL, respectively. The accuracy of the method determined by the mean percentage recovery at 7.8, 62.5 and 250 µg/mL was 96.79%, 98.25% and 99.06% with a RSD of < 2.2%. Accelerated stability studies revealed that Cx43MP was more sensitive to basic conditions and completely degraded within 24 h at 37 °C (0% recovery) and within 12 h at 80 °C (0.34% recovery). Cx43MP was found to be more stable in bovine vitreous (t1/2slow= 171.8 min) compared to human plasma (t1/2slow = 39.3 min) at 37 °C according to the two phase degradation kinetic model. These findings are important for further pre-clinical development of Cx43MP.

Nanoparticle-loaded biodegradable light-responsive in situ forming injectable implants for effective peptide delivery to the posterior segment of the eye

Diseases affecting the posterior segment the eye, such as age-related macular degeneration (AMD), are the leading cause of blindness worldwide. Conventional dosage forms, such as eye drops, have to surmount several elimination mechanisms and complex barriers to achieve therapeutic concentrations at the target site often resulting in low anterior segment bioavailability (ca. 2-5%) with generally none of the drug reaching posterior segment tissues. Thus, frequent intravitreal injections are currently required to treat retinal conditions which have been associated with poor patient compliance due to pain, risk of infection, hemorrhages, retinal detachment and high treatment related costs. To partially overcome these issues, ocular implants have been developed for some posterior segment indications; however, the majority require surgical implantation and removal at the end of the intended treatment period. The transparent nature of the cornea and lens render light-responsive systems an attractive strategy for the management of diseases affecting the back of the eye. Light-responsive in situ forming injectable implants (ISFIs) offer various benefits such as ease of application in a minimally invasive manner and more site specific control over drug release. Moreover, the biodegradable nature of such implants avoids the need for surgical removal after release of the payload. Incorporating drug-loaded polymeric nanoparticles (NPs) into these implants may reduce the high initial burst release from the polymeric matrix and further sustain drug release thus avoiding the need for frequent injections as well as minimizing associated side effects. However, light-responsive systems for ophthalmic application are still in their early stages of development with limited reports on their safety and effectiveness. We hypothesize that the innovative design and properties of NP-containing light-responsive ISFIs can serve as a platform for effective management of ocular diseases requiring long term treatment.