Collagen-Based Hydrogels for the Eye: A Comprehensive Review

Collagen-based hydrogels have emerged as a highly promising platform for diverse applications in ophthalmology, spanning from drug delivery systems to biomedical interventions. This review explores the diverse sources of collagen, which give rise to different types of collagen protein. The critical isolation and purification steps are discussed, emphasizing their pivotal role in preparing collagen for biomedical use. To ensure collagen quality and purity, and the suitability of collagen for targeted applications, a comprehensive characterization and quality control are essential, encompassing assessments of its physical, chemical, and biological properties. Also, various cross-linking collagen methods have been examined for providing insight into this crucial process. This comprehensive review delves into every facet of collagen and explores the wide-ranging applications of collagen-based hydrogels, with a particular emphasis on their use in drug delivery systems and their potential in diverse biomedical interventions. By consolidating current knowledge and advancements in the field, this review aims to provide a detailed overview of the utilization of engineered collagen-based hydrogels in ocular therapeutics.

Design of chondroitin sulphate coated proglycosomes for localized delivery of tofacitinib for the treatment of rheumatoid arthritis

Long-term oral tofacitinib (TOF) administration has been linked to serious side effects majorly immunological suppression. The aim of this work was to enhance the therapeutic efficacy of TOF by chondroitin sulphate (CS) coated proglycosomes through the anchoring of high-affinity CS to CD44 receptors on immune cells in the inflammatory region. The CS was coated onto the TOF-loaded proglycosomes (CS-TOF-PG) formulations and they were evaluated for in vitro drug release, ex vivo (permeation, dermatokinetics) studies. In vivo efficacy studies were carried out in Freund's complete adjuvant (CFA) induced arthritis model. The optimized CS-TOF-PG showed particle sizes of 181.13 ± 7.21 nm with an entrapment efficiency of 78.85 ± 3.65 %. Ex-vivo studies of CS-TOF-PG gel exhibited 1.5-fold high flux and 1.4-fold dermal retention compared to FD-gel. The efficacy study revealed that CS-TOF-PG showed a significant (P < 0.001) reduction in inflammation in arthritic rat paws compared to the TOF oral and FD gel. The current study ensured that the CS-TOF-PG topical gel system would provide a safe and effective formulation for localization and site-specific delivery of TOF at the RA site and overcome the adverse effects associated with the TOF.

Insight into the pivotal role of signaling pathways in psoriasis pathogenesis, potential therapeutic molecules and drug delivery approaches

Psoriasis is a multifactorial chronic autoimmune skin disorder, the exact cause of which is still under investigation. It is classified into different types displaying various histopathological features such as hyperproliferation, irregular parakeratosis and vascular infiltration of various immune cells with neutrophils in the epidermis. Over the past few decades, psoriasis pathogenesis has been thoroughly researched, leading to several advances in the treatment using small molecules and biologics. This review focuses on describing the role of various signaling pathways, including PDE-4, JAK-STAT, S1P, A₃AR and NF-κB, in psoriasis pathogenesis and associated new molecules that are either recently approved or under clinical trials. This study has also addressed the relevance of employing nanotherapeutics to boost the efficacy of psoriasis treatment.

Emerging trends in microneedle-based drug delivery strategies for the treatment of rheumatoid arthritis

INTRODUCTION

The current drug therapies for treating Rheumatoid Arthritis (RA) include NSAIDs, DMARDs, or biological products designed to mitigate the symptoms of the disease. These therapies with conventional delivery systems possess limitations such as lack of selectivity and adverse effects in the extra-articular tissues. Microneedles-based transdermal drug delivery gained huge attention that can overcome the limitations associated with conventional preparations.

AREAS COVERED

This review aims to provide detailed information on types of Microneedles (MNs) and their usage in drug delivery for the management of Rheumatoid Arthritis. In addition, it also provides evidence for the effective use of MNs in RA treatment. Various types of MNs, their regulatory status, clinical trials and patents are also compiled in this review.

EXPERT OPINION

Microneedles are small patch-like structures consisting of needles in micron range arranged in array-like structure, used to manage drugs designed to be given via transdermal route. Microneedles provide painless delivery, fast onset of action, bypass the first-pass metabolism and be easily self-administered. In the case of RA treatment, which requires a long-term application of drugs, MNs is a new and emerging way to ease the symptoms of RA.

Revisiting techniques to evaluate drug permeation through skin

INTRODUCTION

Investigating the transportation of a drug molecule through various layers of skin and determining the amount of drug retention in skin layers is of prime importance in transdermal and topical drug delivery. The information regarding drug permeation and retention in skin layers aids in optimizing a formulation and provides insight into the therapeutic efficacy of a formulation.

AREAS COVERED

This perspective covers various methods that have been explored to estimate drug/therapeutics in skin layers using in vitro, ex vivo, and in vivo conditions. In vitro methods such as diffusion techniques, ex vivo methods such as isolated perfused skin models and in vivo techniques including dermato-pharmacokinetics employing tape stripping, and microdialysis are discussed. Application of all techniques at various stages of formulation development where various local and systemic effects need to be considered.

EXPERT OPINION

The void in the existing methodologies necessitates improvement in the field of dermatologic research. Standardization of protocols, experimental setups, regulatory guidelines, and further research provides information to select an alternative for human skin to perform skin permeation experiments to increase the reliability of data generated through the available techniques. There is a need to utilize multiple techniques for appropriate dermato-pharmacokinetics evaluation and formulation's efficacy.

Design of experiment-driven stability-indicating RP-HPLC method for the determination of tofacitinib in nanoparticles and skin matrix

Background

Tofacitinib—an oral JAK inhibitor—has been recently approved by US FDA to treat moderate to severe RA. The delivery of tofacitinib to specific inflammation site at joint via topical route using nanoformulations helps in managing the potential adverse effects. The objective is to develop and validate a simple, specific, and sensitive stability-indicating HPLC method for quantification of tofacitinib in topical nanoformulations and different matrices (adhesive tape, and skin layers, i.e., stratum corneum, viable epidermis, and dermis). The major objective was to avoid use of instruments like LC–MS/MS and to ensure a widespread application of the method.

Result

A 32 factorial ‘design of experiments’ was applied to optimize process variables, to understand the effect of variables on peak properties. The calibration curve showed regression coefficient (R2) 0.9999 and linearity in the concentration range of 50 to 15,000 ng/mL, which is suitable for the analysis of conventional dosage forms and nanoformulations. Method validation was performed as per ICH guideline Q2 (R1). The accuracy by recovery studies ranged between 98.09 and 100.82%. The % relative standard deviations in intraday and interday precisions were in the range of 1.16–1.72 and 1.22–1.80%, respectively. Forced degradation studies indicated the specificity of method and showed stability-indicating potential for tofacitinib peak.

Conclusion

The validated method provides a quantification method of tofacitinib in the presence of formulation excipients, dissolution media, and skin tissues in detail. In addition, the method was successfully utilized for determination of various dermatokinetics profile of tofacitinib.

Repurposing methylene blue in the management of COVID-19: Mechanistic aspects and clinical investigations

The severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is the most recent coronaviruses, which has infected humans, and caused the disease COVID-19. The World Health Organization has declared COVID-19 as a pandemic in March 2020. The SARS-CoV-2 enters human hosts majorly via the respiratory tract, affecting the lungs first. In few critical cases, the infection progresses to failure of the respiratory system known as acute respiratory distress syndrome acute respiratory distress syndrome may be further associated with multi-organ failure and vasoplegic shock. Currently, the treatment of COVID-19 involves use of antiviral and anti-cytokine drugs. However, both the drugs have low efficacy because they cannot inhibit the production of free radicals and cytokines at the same time. Recently, some researchers have reported the use of methylene blue (MB) in COVID-19 management. MB has been used since a long time as a therapeutic agent, and has been approved by the US FDA for the treatment of other diseases. The additional advantage of MB is its low cost. MB is a safe drug when used in the dose of < 2 mg/kg. In this review, the applicability of MB in COVID-19 and its mechanistic aspects have been explored and compiled. The clinical studies have been explained in great detail. Thus, the potential of MB in the management of COVID-19 has been examined.

Quality by design (QbD) in the formulation and optimization of liquid crystalline nanoparticles (LCNPs): A risk based industrial approach

The intersection of lipid-based nanoparticles and lyotropic liquid crystals has provided a novel type of nanocarrier system known as 'lipid-based lyotropic liquid crystals' or 'liquid crystalline nanoparticles' (LCNPs). The unique advantages and immense popularity of LCNPs can be exploited in a better way if the formulation of LCNPs is done using the approach of quality by design (QbD). QbD is a systematic method that can be utilized in formulation development. When QbD is applied to LCNPs formulation, it will proffer many unique advantages, such as better product and process understanding, the flexibility of process within the design space, implementation of more effective and efficient control strategies, easy transfer from bench to bedside, and more robust product. In this work, the application of QbD in the formulation of LCNPs has been explored. The elements of QbD, viz. quality target product profile, critical quality attributes, critical material attributes, critical process parameters, quality risk management, design of experiments, and control strategy for the development of LCNPs have been explained in-depth with case studies. The present work will help the reader to understand the nitty-gritties in the application of QbD in the formulation of LCNPs, and provide a base for QbD-driven formulation of LCNPs with a regulatory perspective.

Spectrophotometric method to quantify tofacitinib in lyotropic liquid crystalline nanoparticles and skin layers: Application in ex vivo dermal distribution studies

Tofacitinib is an oral Janus kinase inhibitor used in the treatment of Rheumatoid arthritis. The topical delivery of novel Tofacitinib loaded liquid crystal nanoparticles (LCNPs) can provide a controlled release, and also targeted drug delivery to inflamed synovium. There is need of UV spectroscopic method which can determine Tofacitinib in designed nanocarriers like LCNPs, that can be applied to evaluate entrapment efficiency, in vitro drug release, and ex vivo skin studies. In the present study, we have developed and validated a simple and sensitive spectrophotometric method for the quantitative determination of Tofacitinib in methanol and phosphate buffer saline. The linearity range in both the media was 5-30 µg/mL (methanol) and 5-40 µg/ mL (phosphate buffer saline) with high correlation coefficient value (>0.9998). This indicates the clear correlation between Tofacitinib concentrations and their absorbance within the test ranges. The repeatability and intermediate precision articulated by the relative standard deviation were less than 2% in the developed method. The method specificity and applicability were also ascertained by performing recovery studies by spiking method, which was 95.85 ± 1.98% with % RSD 1.24 ± 0.045. The method developed in methanol was successfully applied to determine the entrapment efficiency of Tofacitinib in developed LCNPs formulation and skin retention (dermatokinetics). The method developed in pH 7.4 phosphate buffer saline was applied to quantify Tofacitinib from LCNPs in in vitro and ex vivo drug release samples. In conclusion, a simple, sensitive, accurate, and precise UV spectrophotometric method was established to determine Tofacitinib in in vitro and ex vivo skin studies.

Chitosan-based microneedles as a potential platform for drug delivery through the skin: Trends and regulatory aspects

Microneedles (MNs) fabrication using chitosan has gained significant interest due to its ability of film-forming, biodegradability, and biocompatibility, making it suitable for topical and transdermal drug delivery. The presence of amine and hydroxyl functional groups on chitosan permits the modification with tunable properties and functionalities. In this regard, chitosan is the preferred material for fabrication of MNs because it does not produce an immune response in the body and can be tailored as per required strength and functionalities. Therefore, many researchers have attempted to use chitosan as a drug delivery vehicle for hydrophilic drugs, peptides, and hormones. In 2020, the FDA has issued "Regulatory Considerations for Microneedling Products". This official guidance is a sign for future opportunities in the development of MNs. The present review focuses on properties, and modifications of chitosan used in the fabrication of MNs. The therapeutic and diagnostic applications of different types of chitosan-based MNs have been discussed. Further, the regulatory aspects of MN-based devices, and patents related to chitosan-based MNs are discussed.

Magnetic interactions in graphene decorated with iron oxide nanoparticles

We present the studies of structural and magnetic properties of graphene composites prepared with several quantities ofα-Fe₂O₃dopant of 5%, 25% and 50% made with either ethanol or acetone. Our studies showed the presence of a weak magnetic order up to room temperature and saturation magnetization close to 0.2 emu g^-1in pure commercial graphene. With regard to magnetic properties of our graphene + iron oxide samples, the solvent used during the preparation of the composite had a significant influence on them. For graphene + Fe₂O₃samples made with acetone the magnetic properties of pure graphene played a major role in the overall magnetic susceptibility and magnetization. On the other hand, for graphene + iron oxide samples made with ethanol we observed the presence of superparamagnetic blocking atT < 110 K which was due to the additional appearance ofγ-Fe₃O₄nanoparticles. Changes in the synthesis solvent played a major role in the magnetic properties of our graphene + Fe₂O₃nanocomposite samples resulting in much higher saturation magnetization for the samples made with ethanol. Both the shape and the parameters characterizing magnetization hysteresis loops depend strongly on the amount of iron oxide and changes in the preparation method.

Biodegradable microneedles fabricated with carbohydrates and proteins: Revolutionary approach for transdermal drug delivery

There has been a surge in the use of transdermal drug delivery systems (TDDS) for the past few years. The market of TDDS is expected to reach USD 7.1 billion by 2023, from USD 5.7 billion in 2018, at a CAGR of 4.5%. Microneedles (MNs) are a novel class of TDDS with advantages of reduced pain, low infection risk, ease of application, controlled release of therapeutic agents, and enhanced bioavailability. Biodegradable MNs fabricated from natural polymers have become the center of attention among formulation scientists because of their recognized biodegradability, biocompatibility, ease of fabrication, and sustainable character. In this review, we summarize the various polysaccharides and polypeptide based biomaterials that are used to fabricate biodegradable MNs. Particular emphasis is given to cellulose and its derivatives, starch, and complex carbohydrate polymers such as alginates, chitosan, chondroitin sulfate, xanthan gum, pullulan, and hyaluronic acid. Additionally, novel protein-based polymers such as zein, collagen, gelatin, fish scale and silk fibroin (polyamino acid) biopolymers application in transdermal drug delivery have also been discussed. The current review will provide a unique perspective to the readers on the developments of biodegradable MNs composed of carbohydrates and protein polymers with their clinical applications and patent status.

Luliconazole loaded lyotropic liquid crystalline nanoparticles for topical delivery: QbD driven optimization, in-vitro characterization and dermatokinetic assessment

Fungal infections are an important cause of morbidity and pose a serious health concern especially in immunocompromised patients. Luliconazole (LUL) is a topical imidazole antifungal drug with a broad spectrum of activity. To overcome the limitations of conventional dosage forms, LUL loaded lyotropic liquid crystalline nanoparticles (LCNP) were formulated and characterized using a three-factor, five-level Central Composite Design of Response Surface Methodology. LUL loaded LCNP showed particle size of 181 ± 12.3 nm with an entrapment efficiency of 91.49 ± 1.61 %. The LUL-LCNP dispersion in-vitro drug release showed extended release up to 54 h. Ex-vivo skin permeation studies revealed transdermal flux value (J) of LUL-LCNP gel (7.582 μg/h/cm²) 2 folds higher compared to marketed cream (3.3706 μg/h/cm²). The retention of LUL in the stratum corneum was ∼1.5 folds higher and ∼2 folds higher in the epidermis and other deeper layers in comparison to the marketed cream. The total amount of drug penetrated (AUC_0-∞) with LCNP formulation was 4.7 folds higher in epidermis and 6.5 folds higher in dermis than marketed cream. The study's findings vouch that LCNP can be a promising and effective carrier system for the delivery of antifungal drugs with enhanced skin permeation.

Nanostructured Lipid Carriers as Potential Drug Delivery Systems for Skin Disorders

Background:

Skin diseases affect all the age groups of people and have an impact on patients’ physical, mental, and emotional status. Conventional topical preparation is limited with its efficacy due to low permeation, frequent application, and poor adherence to the therapy for prolong time.

Objective:

The objective of this review article is to address the emerging trends of nanotechnology derived lipidic carrier systems for an effective treatment for skin disorders.

Methodology:

Various research and review articles from reputed international journals were referred and compiled.

Results and Discussion:

opical drug delivery systems were found to be more effective than oral and parenteral drug delivery systems for treating skin diseases due to targeted localized applications with reduced side effects. Lipid-based nanoparticles have been found to have the potential in treating skin diseases due to the biocompatibility and the versatility of the lipids. Nanostructured lipid carriers (NLCs) have gained much attention in treating skin diseases due to improved stability of the drugs, enhanced skin permeation, retention, and better therapeutic efficacy. The review summarizes the NLCs characteristics and their application for topical delivery of various therapeutics in skin disorders. NLCs have shown great potential in effective drug delivery for the treatment of psoriasis, dermatitis, bacterial infections, and skin cancer. Its cosmetic application has opened a new area for skincare. Furthermore, safety and clinical status revealed its future commercial acceptability.

Conclusion:

NLCs have been found as effective lipid nanocarriers for the delivery of topical therapeutics.

Emerging Trends in Topical Delivery of Curcumin Through Lipid Nanocarriers: Effectiveness in Skin Disorders

Curcumin is a unique molecule naturally obtained from rhizomes of Curcuma longa. Curcumin has been reported to act on diverse molecular targets like receptors, enzymes, and co-factors; regulate different cellular signaling pathways; and modulate gene expression. It suppresses expression of main inflammatory mediators like interleukins, tumor necrosis factor, and nuclear factor κB which are involved in the regulation of genes causing inflammation in most skin disorders. The topical delivery of curcumin seems to be more advantageous in providing a localized effect in skin diseases. However, its low aqueous solubility, poor skin permeation, and degradation hinder its application for commercial use despite its enormous potential. Lipid-based nanocarrier systems including liposomes, niosomes, solid lipid nanoparticles, nanostructured lipid carriers, lyotropic liquid crystal nanoparticles, lipospheres, and lipid nanocapsules have found potential as carriers to overcome the issues associated with conventional topical dosage forms. Nano-size, lipophilic nature, viscoelastic properties, and occlusive effect of lipid nanocarriers provide high drug loading, hydration of skin, stability, enhanced permeation through the stratum corneum, and slow release of curcumin in the targeted skin layers. This review particularly focuses on the application of lipid nanocarriers for the topical delivery of curcumin in the treatment of various skin diseases. Furthermore, preclinical studies and patents have also indicated the emerging commercialization potential of curcumin-loaded lipid nanocarriers for effective drug delivery in skin disorders. Graphical Abstract.

Psoriasis: pathological mechanisms, current pharmacological therapies, and emerging drug delivery systems

Psoriasis is a chronic autoimmune skin disorder triggered by either genetic factors, environmental factors, life style, or a combination thereof. Clinical investigations have identified pathogenesis, such as T cell and cytokine-mediated, genetic disposition, antimicrobial peptides, lipocalin-2, galectin-3, vaspin, fractalkine, and human neutrophil peptides in the progression of psoriasis. In addition to traditional therapies, newer therapeutics, including phosphodiesterase type 4 (PDE4) inhibitors, Janus kinase (JAK) inhibitors, monoclonal antibodies (mAbs), gene therapy, anti-T cell therapy, and phytoconstituents have been explored. In this review, we highlight nanotechnology-related developments for psoriasis treatment, including patented delivery systems and therapeutics currently in clinical trials.

Insightful exploring of microRNAs in psoriasis and its targeted topical delivery

Psoriasis is a common immune-mediated inflammatory skin disease. It includes multifaceted interaction between the immune system and the keratinocytes. Recent studies depicted the role of microRNAs (miRNAs) in hyperproliferation of keratinocytes and inflammatory cytokine production, which serve as biomarkers for diagnosis, monitoring treatment response, and prognosis. miRNAs are small nucleotide sequenced noncoding RNAs. Deregulation of miRNAs was found to be the most common factor in the studies pertaining to psoriasis. Hence, miRNA-based targeting for psoriasis treatment became the primary field of current research. miRNA due to its spatial and chemical properties offer different challenges in the process of its delivery. The topical delivery of different siRNAs and genes has paved a way to similar delivery of miRNA. The topical delivery of miRNAs to the skin can bring a revolutionary change in the field of psoriasis treatment.

UV spectrophotometric method for simultaneous estimation of betamethasone valerate and tazarotene with absorption factor method: Application for in-vitro and ex-vivo characterization of lipidic nanocarriers for topical delivery

The present study elucidates the development of an accurate, precise and simple simultaneous estimation method for the routine analysis of Betamethasone Valerate (BV) and Tazarotene (TZ). This combination is widely used in the treatment of psoriasis. No method has been reported so far for the simultaneous estimation of BV and TZ in topical dosage forms. The method proposed by this study for the quantification of BV and TZ is the Absorption factor method. The developed method was validated as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) guideline. The validated method was found to be linear in a concentration range of 10-38 μg/mL and 4-14 μg/mL for BV and TZ respectively with a regression coefficient >0.990. The method was validated for accuracy and precision which revealed the recovery of >99.80% with RSD <2.0. The method was found to be precise with RSD <2% for inter and intraday. The developed method was employed for quantification of BV and TZ in lipid based nanocarriers formulation and their in-vitro drug release samples. Further, the developed method was successfully applied for the estimation of BV and TZ in the ex-vivo skin matrix. This showed that the method can sensitively determine the drugs in aqueous and biological samples.

Design of temozolomide-loaded proliposomes and lipid crystal nanoparticles with industrial feasible approaches: comparative assessment of drug loading, entrapment efficiency, and stability at plasma pH

Temozolomide is a drug approved for treating glioblastomas, which has 100% oral bioavailability but gets degraded at physiological pH thus having very short half-life and only 20-30% brain bioavailability. Due to its amphiphilic nature, reported nanoformulations exhibits poor drug loading. The objective of this work was to formulate lipid-based drug delivery systems to enhance the brain bioavailability by prolonging the drug release and circulation time of the drug to overcome the limitations of the existing therapies and possible reduction of side effects. The size of the nanocarriers obtained was less than 300 nm and the PDI obtained was less than 0.3. The designed formulation showed higher entrapment efficiency as compared to the other reported nanocarriers of temozolomide. The designed formulations showed prolonged drug release from 12 to 20 h compared to 6 h for the pure drug. About 95% of the pure drug was degraded at plasma pH at the end of 12 h, whereas only 68% and 77% was degraded when entrapped inside the lipid crystal nanoparticles and proliposomes respectively. Further, pharmacokinetic and animal studies can confirm the potential of these for improvement of brain bioavailability.

UV Spectrophotometric method for characterization of curcumin loaded nanostructured lipid nanocarriers in simulated conditions: Method development, in-vitro and ex-vivo applications in topical delivery

Curcumin the extract obtained from the dried rhizome of turmeric, Curcuma longa is a hydrophobic phenol that delivers numerous pharmacological actions like anti-inflammatory, anti-microbial and anti-oxidant, anti-psoriasis, antidiabetic, anticancer. But curcumin has low bioavailability issues that accompany low aqueous solubility, further, when administered orally, >90% of the drug degrades rapidly in the alkaline medium. Administering the drug topically can bypass the problem as well as first-pass metabolism and therefore delivering the drug at the targeted site of action. Encapsulating curcumin in nanostructured lipid nanocarriers (NLC) is an excellent novel strategy. Further, these NLC provides both the controlled release and helps in the enhanced permeation of the drug through the skin's physiological barrier, stratum corneum. For the NLC characterization, a reliable method must be developed that can accurately and precisely determine the drug content in the formulation and also for its in-vitro and ex-vivo characterization. This experiment describes the analytical validation parameters described as per International Conference of Harmonization guidelines to develop a method using the UV-Visible spectroscopy. The method was developed in two solvent systems i.e. methanol and 6.4 pH phosphate buffer with 1.5% polysorbate 80. Methanol solvent was used for the determination of curcumin in the NLC formulation via determining the encapsulation efficiency and 6.4 pH phosphate buffer with 1.5% polysorbate 80 solvent was used for in-vitro and ex-vivo characterization of the developed NLC formulation (cream and gel). These methods were validated in response to linearity, the limit of detection, the limit of quantification, precision, accuracy, repeatability, and specificity.

Nanocarriers for ocular drug delivery: current status and translational opportunity

Ocular diseases have a significant effect on vision and quality of life. Drug delivery to ocular tissues is a challenge to formulation scientists. The major barriers to delivering drugs to the anterior and posterior segments include physiological barriers (nasolacrimal drainage, blinking), anatomical barriers (static and dynamic), efflux pumps and metabolic barriers. The static barriers comprise the different layers of the cornea, sclera, and blood–aqueous barriers whereas dynamic barriers involve conjunctival blood flow, lymphatic clearance and tear drainage. The tight junctions of the blood–retinal barrier (BRB) restrict systemically administered drugs from entering the retina. Nanocarriers have been found to be effective at overcoming the issues associated with conventional ophthalmic dosage forms. Various nanocarriers, including nanodispersion systems, nanomicelles, lipidic nanocarriers, polymeric nanoparticles, liposomes, niosomes, and dendrimers, have been investigated for improved permeation and effective targeted drug delivery to various ophthalmic sites. In this review, various nanomedicines and their application for ophthalmic delivery of therapeutics are discussed. Additionally, scale-up and clinical status are also addressed to understand the current scenario for ophthalmic drug delivery.

Ocular diseases have a significant effect on vision and quality of life.

Interface phenomena in magnetron sputtered Cu2O/ZnO heterostructures

The interface between ZnO and Cu₂O has been predicted to be a good candidate for use in thin film solar cells. However, the high predicted conversion efficiency has yet to be fully realized experimentally. To explore the underlying causes of this we investigate the interface between ZnO and Cu₂O in magnetron sputtered samples. Two different sample geometries were made: In the first set thin layers of ZnO were deposited on Cu₂O (type A), while in the second set the order was reversed (type B). Using x-ray photoelectron spectroscopy (XPS), an intermediate CuO layer was identified regardless of the order in which the Cu₂O and ZnO layers were deposited. The presence of a CuO layer was supported by transmission electron microscopy (TEM) results. Changes in the electron hole screening conditions were observed in CuO near the interface with ZnO, manifested as changes in the relative peak-to-satellite ratio and the degree of asymmetric broadness in the Cu 2p peak. The suppression of the Cu 2p satellite characteristic of CuO may cause the CuO presence to be overlooked and cause errors in determinations of valence band offsets (VBOs). For the type A samples, we compare four different approaches to XPS-based determination of VBO and find that the most reliable results are obtained when the thin CuO layer and the altered screening conditions at the interface were taken into account. The VBOs were found to range between 2.5 eV and 2.8 eV. For the B type samples a reduction of the Cu 2p-LMM Auger parameter was found as compared to bulk Cu₂O, indicative of quantum confinement in the Cu₂O overlayer.

Nanogel-Conjugated Reverse Transcriptase Inhibitors and Their Combinations as Novel Antiviral Agents with Increased Efficacy against HIV-1 Infection

Nucleoside reverse transcriptase inhibitors (NRTIs) are an integral part of the current antiretroviral therapy (ART), which dramatically reduced the mortality from AIDS and turned the disease from lethal to chronic. The further steps in curing the HIV-1 infection must include more effective targeting of infected cells and virus sanctuaries inside the body and modification of drugs and treatment schedules to reduce common complications of the long-term treatment and increase patient compliancy. Here, we describe novel NRTI prodrugs synthesized from cholesteryl-ε-polylysine (CEPL) nanogels by conjugation with NRTI 5'-succinate derivatives (sNRTI). Biodegradability, small particle size, and high NRTI loading (30% by weight) of these conjugates; extended drug release, which would allow a weekly administration schedule; high therapeutic index (>1000) with a lower toxicity compared to NRTIs; and efficient accumulation in macrophages known as carriers for HIV-1 infection are among the most attractive properties of new nanodrugs. Nanogel conjugates of zidovudine (AZT), lamivudine (3TC), and abacavir (ABC) have been investigated individually and in formulations similar to clinical NRTI cocktails. Nanodrug formulations demonstrated 10-fold suppression of reverse transcriptase activity (EC90) in HIV-infected macrophages at 2-10, 2-4, and 1-2 μM drug levels, respectively, for single nanodrugs and dual and triple nanodrug cocktails. Nanogel conjugate of lamivudine was the most effective single nanodrug (EC90 2 μM). Nanodrugs showed a more favorable pharmacokinetics compared to free NRTIs. Infrequent iv injections of PEGylated CEPL-sAZT alone could efficiently suppress HIV-1 RT activity to background level in humanized mouse (hu-PBL) HIV model.

Isolation rearing significantly perturbs brain metabolism in the thalamus and hippocampus

Psychosocial neglect during childhood severely impairs both behavioral and physical health. The isolation rearing model in rodents has been employed by our group and others to study this clinical problem at a basic level. We previously showed that immediate early gene (IEG) expression in the hippocampus and medial prefrontal cortex (mPFC) is decreased in isolation-reared (IR) compared to group-reared (GR) rats. In the current study, we sought to evaluate: (1) whether these changes in IEG expression would be detected by the measurement of brain glucose metabolism using positron emission tomography (PET) with fluorodeoxyglucose (FDG) and (2) whether PET FDG could illuminate other brain regions with different glucose metabolism in IR compared to GR rats. We found that there were significant differences in FDG uptake in the hippocampus that were consistent with our findings for IEG expression (decreased mean FDG uptake in IR rats). In contrast, in the mPFC, the FDG uptake between IR and GR rats did not differ. Finally, we found decreased mean FDG uptake in the thalamus of the IR rats, a region we had not previously examined. The results suggest that PET FDG has the potential to be utilized as a biomarker of molecular changes in the hippocampus. Further, the differences found in thalamic brain FDG uptake suggest that further investigation of this region at the molecular and cellular levels may provide an important insight into the neurobiological basis of the adverse clinical outcomes found in children exposed to psychosocial deprivation.

Transformation-mediated ductility in CuZr-based bulk metallic glasses

Bulk metallic glasses (BMGs) generally fail in a brittle manner under uniaxial, quasistatic loading at room temperature. The lack of plastic strain is a consequence of shear softening, a phenomenon that originates from shear-induced dilation that causes plastic strain to be highly localized in shear bands. So far, significant tensile ductility has been reported only for microscopic samples of around 100 nm (ref. 4) as well as for high strain rates, and so far no mechanisms are known, which could lead to work hardening and ductility in quasistatic tension in macroscopic BMG samples. In the present work we developed CuZr-based BMGs, which polymorphically precipitate nanocrystals during tensile deformation and subsequently these nanocrystals undergo twinning. The formation of such structural heterogeneities hampers shear band generation and results in macroscopically detectable plastic strain and work hardening. The precipitation of nanocrystals and their subsequent twinning can be understood in terms of a deformation-induced softening of the instantaneous shear modulus. This unique deformation mechanism is believed to be not just limited to CuZr-based BMGs but also to promote ductility in other BMGs.

Characterization of anti-CCR5 ribozyme-transduced CD34+ hematopoietic progenitor cells in vitro and in a SCID-hu mouse model in vivo

The cellular entry of HIV is mediated by the specific interaction of viral envelope glycoproteins with the cell-surface marker CD4 and a chemokine receptor (CCR5 or CXCR4). Individuals with a 32-base-pair (bp) deletion in the CCR5 coding region, which results in a truncated peptide, show resistance to HIV-1 infection. This suggests that the downregulation of CCR5 expression on target cells may prevent HIV infection. Therefore, ribozymes that inhibit the CCR5 expression offer a novel approach for anti-HIV gene therapy. To assess the effect of an anti-CCR5 ribozyme (R5Rbz) on macrophage differentiation, CD34+ hematopoietic progenitor cells were transduced with a retroviral vector carrying RSRbz and allowed to differentiate in the presence of appropriate cytokines. R5Rbz-transduced CD34+ cells differentiated normally into mature macrophages that carried CD14 and CD4 surface markers, expressed the anti-CCR5 ribozyme, and showed significant resistance to viral infection upon challenge with the HIV-1 BaL strain. Using an in vivo thymopoiesis model, the effect of RSRbz on stem cell differentiation into thymocytes was evaluated by reconstituting SCID-hu mice thymic grafts with ribozyme-transduced CD34+ cells. FACS analysis of cell biopsies at 4 and 6 weeks postengraftment for HLA, CD4, and CD8 markers showed comparable levels of reconstitution and similar percentages of subpopulations of thymocytes between grafts receiving R5Rbz-transduced and control CD34+ cells. RT-PCR assays demonstrated the expression of the anti-CCR5 ribozyme in CD4+, CD8+, and CD4+/CD8+ thymocyte subsets derived from RSRbz-transduced CD34+ cells. These results indicate that anti-CCR5 ribozyme can be introduced into hematopoietic stem cells without adverse effects on their subsequent lineage-specific differentiation and maturation. The expression of anti-CCR5 ribozymes in HIV-1 target cells offers a novel gene therapy strategy to control HIV infection.