Dendrimers in Corneal Drug Delivery: Recent Developments and Translational Opportunities

Dendrimers are biocompatible organic nanomaterials with unique physicochemical properties, making them the focus of recent research in drug delivery. The cornea of the human eye presents a challenge for drug transit due to its inherently impenetrable nature, requiring nanocarrier-mediated targeted drug delivery. This review intends to examine recent advancements in the use of dendrimers for corneal drug delivery, including their properties and their potential for treating various ocular diseases. The review will also highlight the benefit of the novel technologies that have been developed and applied in the field, such as corneal targeting, drug release kinetics, treatments for dry eye disease, antibacterial drug delivery, corneal inflammation, and corneal tissue engineering. The review seeks to provide a comprehensive overview of the current state of research in this field, along with the translational developments in the field of dendrimer-based therapeutics and imaging agents and inspire the potential for future developments and translational opportunities in dendrimers based corneal drug delivery.

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites.

Forkhead Box q1 promotes invasion and metastasis in colorectal cancer by activating the epidermal growth factor receptor pathway

BACKGROUND

Colorectal cancer (CRC) is an extremely malignant tumor with a high mortality rate. Little is known about the mechanism by which forkhead Box q1 (FOXQ1) causes CRC invasion and metastasis through the epidermal growth factor receptor (EGFR) pathway.

AIM

To illuminate the mechanism by which FOXQ1 promotes the invasion and metastasis of CRC by activating the heparin binding epidermal growth factor (HB-EGF)/EGFR pathway.

METHODS

We investigated the differential expression and prognosis of FOXQ1 and HB-EGF in CRC using the Gene Expression Profiling Interactive Analysis (GEPIA) website (http://gepia.cancer-pku.cn/index.html). Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were used to detect the expression of FOXQ1 and HB-EGF in cell lines and tissues, and we constructed a stable low-expressing FOXQ1 cell line and verified it with the above method. The expression changes of membrane-bound HB-EGF (proHB-EGF) and soluble HB-EGF (sHB-EGF) in the low-expressing FOXQ1 cell line were detected by flow cytometry and ELISA. Western blotting was used to detect changes in the expression levels of HB-EGF and EGFR pathway-related downstream genes when exogenous recombinant human HB-EGF was added to FOXQ1 knockdown cells. Proliferation experiments, transwell migration experiments, and scratch experiments were carried out to determine the mechanism by which FOXQ1 activates the EGFR signaling pathway through HB-EGF, and then to evaluate the clinical relevance of FOXQ1 and HB-EGF.

RESULTS

GEPIA showed that the expression of FOXQ1 in CRC tissues was relatively high and was related to a lower overall survival rate. PCR array results showed that FOXQ1 is related to the HB-EGF and EGFR pathways. Knockdown of FOXQ1 suppressed the expression of HB-EGF, and led to a decrease in EGFR and its downstream genes AKT, RAF, KRAS expression levels. After knockdown of FOXQ1 in CRC cell lines, cell proliferation, migration and invasion were attenuated. Adding HB-EGF restored the migration and invasion ability of CRC, but not the cell proliferation ability. Kaplan–Meier survival analysis results showed that the combination of FOXQ1 and HB-EGF may serve to predict CRC survival.

CONCLUSION

Based on these collective data, we propose that FOXQ1 promotes the invasion and metastasis of CRC via the HB-EGF/EGFR pathway.

Collagen/glycosaminoglycan-based matrices for controlling skin cell responses

Wound healing and tissue regeneration are orchestrated by the cellular microenvironment, e.g. the extracellular matrix (ECM). Including ECM components in biomaterials is a promising approach for improving regenerative processes, e.g. wound healing in skin. This review addresses recent findings for enhanced epidermal-dermal regenerative processes on collagen (coll)/glycosaminoglycan (GAG)-based matrices containing sulfated GAG (sGAG) in simple and complex in vitro models. These matrices comprise 2D-coatings, electrospun nanofibrous scaffolds, and photo-crosslinked acrylated hyaluronan (HA-AC)/coll-based hydrogels. They demonstrated to regulate keratinocyte and fibroblast migration and growth, to stimulate melanogenesis in melanocytes from the outer root sheath (ORS) of hair follicles and to enhance the epithelial differentiation of human mesenchymal stem cells (hMSC). The matrices' suitability for delivery of relevant growth factors, like heparin-binding epidermal growth factor like growth factor (HB-EGF), further highlights their potential as bioinspired, functional microenvironments for enhancing skin regeneration.

Glycosaminoglycan-based biomaterials for growth factor and cytokine delivery: Making the right choices

Controlled, localized drug delivery is a long-standing goal of medical research, realization of which could reduce the harmful side-effects of drugs and allow more effective treatment of wounds, cancers, organ damage and other diseases. This is particularly the case for protein "drugs" and other therapeutic biological cargoes, which can be challenging to deliver effectively by conventional systemic administration. However, developing biocompatible materials that can sequester large quantities of protein and release them in a sustained and controlled manner has proven challenging. Glycosaminoglycans (GAGs) represent a promising class of bio-derived materials that possess these key properties and can additionally potentially enhance the biological effects of the delivered protein. They are a diverse group of linear polysaccharides with varied functionalities and suitabilities for different cargoes. However, most investigations so far have focused on a relatively small subset of GAGs - particularly heparin, a readily available, promiscuously-binding GAG. There is emerging evidence that for many applications other GAGs are in fact more suitable for regulated and sustained delivery. In this review, we aim to illuminate the beneficial properties of various GAGs with reference to specific protein cargoes, and to provide guidelines for informed choice of GAGs for therapeutic applications.

Hyaluronan/collagen hydrogels containing sulfated hyaluronan improve wound healing by sustained release of heparin-binding EGF-like growth factor

Functional biomaterials that are able to bind, stabilize and release bioactive proteins in a defined manner are required for the controlled delivery of such to the desired place of action, stimulating wound healing in health-compromised patients. Glycosaminoglycans (GAG) represent a very promising group of components since they may be functionally engineered and are well tolerated by the recipient tissues due to their relative immunological inertness. Ligands of the Epidermal Growth Factor (EGF) receptor (EGFR) activate keratinocytes and dermal fibroblasts and, thus, contribute to skin wound healing. Heparin-binding EGF-like growth factor (HB-EGF) bound to GAG in biomaterials (e.g. hydrogels) might serve as a reservoir that induces prolonged activation of the EGF receptor and to recover disturbed wound healing. Based on previous findings, the capacity of hyaluronan (HA) and its sulfated derivatives (sHA) to bind and release HB-EGF from HA/collagen-based hydrogels was investigated. Docking and molecular dynamics analysis of a molecular model of HB-EGF led to the identification of residues in the heparin-binding domain of the protein being essential for the recognition of GAG derivatives. Furthermore, molecular modeling and surface plasmon resonance (SPR) analyses demonstrated that sulfation of HA increases binding strength to HB-EGF thus providing a rationale for the development of sHA-containing hydrogels. In line with computational observations and in agreement with SPR results, gels containing sHA displayed a retarded HB-EGF release in vitro compared to pure HA/collagen gels. Hydrogels containing HA and collagen or a mixture with sHA were shown to bind and release bioactive HB-EGF over at least 72 h, which induced keratinocyte migration, EGFR-signaling and HGF expression in dermal fibroblasts. Importantly, hydrogels containing sHA strongly increased the effectivity of HB-EGF in inducing epithelial tip growth in epithelial wounds shown in a porcine skin organ culture model. These findings suggest that hydrogels containing HA and sHA can be engineered for smart and effective wound dressings. STATEMENT OF SIGNIFICANCE: Immobilization and sustained release of recombinant proteins from functional biomaterials might overcome the limited success of direct application of non-protected solute growth factors during the treatment of impaired wound healing. We developed HA/collagen-based hydrogels supplemented with acrylated sulfated HA for binding and release of HB-EGF. We analyzed the molecular basis of HB-EGF interaction with HA and its chemical derivatives by in silico modeling and surface plasmon resonance. These hydrogels bind HB-EGF reversibly. Using different in vitro assays and organ culture we demonstrate that the introduction of sulfated HA into the hydrogels significantly increases the effectivity of HB-EGF action on target cells. Therefore, sulfated HA-containing hydrogels are promising functional biomaterials for the development of mediator releasing wound dressings.

Application of drug delivery systems for the controlled delivery of growth factors to treat nervous system injury

Nervous system injury represent the most common injury and was unique clinical challenge. Using of growth factors (GFs) for the treatment of nervous system injury showed effectiveness in halting its process. However, simple application of GFs could not achieve high efficacy because of its rapid diffusion into body fluids and lost from the lesion site. The drug delivery systems (DDSs) construction used to deliver GFs were investigated so that they could surmount its rapid diffusion and retain at the injury site. This study summarizes commonly used DDSs for sustained release of GFs that provide neuroprotection or restoration effects for nervous system injury.

Strategies for local gene therapy of corneal allograft rejection

Penetrating keratoplasty is the most common type of tissue transplant in humans. Irreversible immune rejection leads to loss of vision and graft failure. This complex immune response further predisposes future corneal transplants to rejection and failure. A diverse armamentarium of surgical and pharmacologic tools is available to improve graft survival. In this review, we will discuss the various gene therapeutic strategies aimed at potentiating the anterior chamber-associated immune deviation to extend graft survival.

Controlled delivery of heparin-binding EGF-like growth factor yields fast and comprehensive wound healing

Wound healing is a dynamic process that relies on coordinated signaling molecules to succeed. Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is proven to accelerate healing, however precise control over its application is necessary to reduce side effects and achieve desired therapeutic benefit. To achieve effective growth factor delivery we designed a bioactive heparin-based coacervate. In vitro, HB-EGF released from the coacervate delivery system displayed enhanced bioactivity and promoted human keratinocyte migration while preserving cell proliferative capability. In a mouse excisional full-thickness wound model, controlled release of HB-EGF within the wound significantly accelerated wound closure more effectively than an equal dosage of free HB-EGF. Healing was induced by rapid re-epithelialization, granulation tissue formation, and accompanied by angiogenesis. Consistent with in vitro results, wounds treated with HB-EGF coacervate exhibited enhanced migration of keratinocytes with retained proliferative potential, forming a confluent layer for regained barrier function within 7 days. Collectively, these results suggest that coacervate-based controlled release of HB-EGF may serve as a new therapy to accelerate healing of cutaneous wounds.