Revolutionizing Wound Healing: Exploring Scarless Solutions through Drug Delivery Innovations

Human skin is the largest organ and outermost surface of the human body, and due to the continuous exposure to various challenges, it is prone to develop injuries, customarily known as wounds. Although various tissue engineering strategies and bioactive wound matrices have been employed to speed up wound healing, scarring remains a significant challenge. The wound environment is harsh due to the presence of degradative enzymes and elevated pH levels, and the physiological processes involved in tissue regeneration operate on distinct time scales. Therefore, there is a need for effective drug delivery systems (DDSs) to address these issues. The objective of this review is to provide a comprehensive exposition of the mechanisms underlying the skin healing process, the factors and materials used in engineering DDSs, and the different DDSs used in wound care. Furthermore, this investigation will delve into the examination of emergent technologies and potential avenues for enhancing the efficacy of wound care devices.

Ferrocene/ β-cyclodextrin based supramolecular nanogels as theranostic systems

A supramolecular redox responsive nanogel (NG) with the ability to sense cancer cells and loaded with a releasing therapeutic agent was synthesized using hostguest interactions between polyethylene glycol-grafted-β-cyclodextrin and ferrocene boronic acid. Cyclic voltammetry matched with other spectroscopy and microscopy methods provided strong indications regarding host-guest interactions and formation of the NG. Moreover, the biological properties of the NG were evaluated using fluorescence silencing, confocal laser scanning microscopy, and cell toxicity assays. Nanogel with spherical core-shell architecture and 100-200 nm sized nanoparticles showed high encapsulation efficiency for doxorubicin (DOX) and luminol (LU) as therapeutic and sensing agents. High therapeutic and sensing efficiencies were manifested by complete release of DOX and dramatic quenching of LU fluorescence triggered by 0.05 mM H2O2 (as an ROS component). The NGs showed high ROS sensitivity. Taking advantage of a high loading capacity, redox sensitivity, and biocompatibility, the NGs can be used as strong theranostic systems in inflammation-associated diseases.

Nano-Gels: Recent Advancement in Fabrication Methods for Mitigation of Skin Cancer

In the 21st century, melanoma and non-melanoma skin cancers have become an epidemic outbreak worldwide. Therefore, the exploration of all potential preventative and therapeutic measures based on either physical or bio-chemical mechanisms is essential via understanding precise pathophysiological pathways (Mitogen-activated protein kinase, Phosphatidylinositol 3-kinase Pathway, and Notch signaling pathway) and other aspects of such skin malignancies. Nano-gel, a three-dimensional polymeric cross-linked porous hydrogel having a diameter of 20-200 nm, possesses dual properties of both hydrogel and nanoparticle. The capacity of high drug entrapment efficiency with greater thermodynamic stability, remarkable solubilization potential, and swelling behavior of nano-gel becomes a promising candidate as a targeted drug delivery system in the treatment of skin cancer. Nano-gel can be either synthetically or architectonically modified for responding to either internal or external stimuli, including radiation, ultrasound, enzyme, magnetic, pH, temperature, and oxidation-reduction to achieve controlled release of pharmaceuticals and several bio-active molecules such as proteins, peptides, genes via amplifying drug aggregation in the active targeted tissue and reducing adverse pharmacological effects. Several drugs, such as anti-neoplastic biomolecules having short biological half-lives and prompt enzyme degradability capacity, must be appropriate for administration employing either chemically bridged or physically constructed nano-gel frameworks. The comprehensive review summarizes the advancement in the preparation and characterization methods of targeted nano-gel with enhanced pharmacological potential and preserved intracellular safety limits for the mitigation of skin malignancies with a special emphasize on skin cancer inducing pathophysiological pathways and prospective research opportunities for skin malignancy targeted nano-gels.

A hybrid thermoresponsive plasmonic nanogel designed for NIR-mediated chemotherapy

Temperature-trigger chemotherapy is one of the state-of-the-art anti-tumoral strategies in nanomedicine. However, this strategy is in close relationship with the effect of the temperature in the tumor tissue. With high temperatures, the ablation of the tumor tissue can hinder a correct chemotherapy approximation. On the other hand, with moderate temperatures a negative vascularization that promotes the tumor growing is produced and competes with the chemotherapeutic effects. We have constructed one nanogel system composed of a thermoresponsive polymer cross-linked by plasmonic gold nanoparticles (AuNPs) for temperature-trigger chemotherapy. Doxorubicin loaded in the porous interior of the nanogel is released when the thermoresponsive network of the nanogel collapses due to the heat generated by the AuNPs upon near infra-red light irradiation. The hybrid nanogel system has been tested in vitro and in vivo, where it was observed that the temperatures reached in the in vivo NIR irradiation have an undesired effect on the inhibition of the tumor growth while the drug loaded systems considerably reduced the tumor sizes. This study shows the importance of design in temperature triggered antitumoral systems, where lower temperatures usually reached in practical situations due to light attenuation produced by the tissue can be positively utilized for enhancing the antitumoral effect of loaded drugs in the system.

Formulation Development and Evaluation of Pravastatin-Loaded Nanogel for Hyperlipidemia Management

Hyperlipidemia is a crucial risk factor for the initiation and progression of atherosclerosis, ultimately leading to cardiovascular disease. The nanogel-based nanoplatform has emerged as an extremely promising drug delivery technology. Pravastatin Sodium (PS) is a cholesterol-lowering drug used to treat hyperlipidemia. This study aimed to fabricate Pravastatin-loaded nanogel for evaluation of its effect in hyperlipidemia treatment. Pravastatin-loaded chitosan nanoparticles (PS-CS-NPs) were prepared by the ionic gelation method; then, these prepared NPs were converted to nanogel by adding a specified amount of 5% poloxamer solution. Various parameters, including drug entrapment efficacy, in vitro drug release, and hemolytic activity of the developed and optimized formulation, were evaluated. The in vitro drug release of the nanogel formulation revealed the sustained release (59.63% in 24 h) of the drug. The drug excipients compatibility studies revealed no interaction between the drug and the screened excipients. Higher drug entrapment efficacy was observed. The hemolytic activity showed lesser toxicity in nanoformulation than the pure drug solution. These findings support the prospective use of orally administered pravastatin-loaded nanogel as an effective and safe nano delivery system in hyperlipidemia treatment.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic-derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Tunable Polyglycerol-Based Redox-Responsive Nanogels for Efficient Cytochrome C Delivery

The sensitivity of therapeutic proteins is a challenge for their use in biomedical applications, as they are prone to degradation and opsonization, thus limiting their potential. This demands for the development of drug delivery systems shielding proteins and releasing them at the site of action. Here, we describe the synthesis of novel polyglycerol-based redox-responsive nanogels and report on their potential as nanocarrier systems for the delivery of cytochrome C (CC). This system is based on an encapsulation protocol of the therapeutic protein into the polymer network. NGs were formed via inverse nanoprecipitation using inverse electron-demand Diels–Alder cyclizations (iEDDA) between methyl tetrazines and norbornenes. Coprecipitation of CC led to high encapsulation efficiencies. Applying physiological reductive conditions of l-glutathione (GSH) led to degradation of the nanogel network, releasing 80% of the loaded CC within 48 h while maintaining protein functionality. Cytotoxicity measurements revealed high potency of CC-loaded NGs for various cancer cell lines with low IC₅₀ values (up to 30 μg·mL⁻¹), whereas free polymer was well tolerated up to a concentration of 1.50 mg·mL⁻¹. Confocal laser scanning microscopy (CLSM) was used to monitor internalization of free and CC-loaded NGs and demonstrate the protein cargo’s release into the cytosol.

Polymer-Based Smart Drug Delivery Systems for Skin Application and Demonstration of Stimuli-Responsiveness

Progress in recent years in the field of stimuli-responsive polymers, whose properties change depending on the intensity of a signal, permitted an increase in smart drug delivery systems (SDDS). SDDS have attracted the attention of the scientific community because they can help meet two current challenges of the pharmaceutical industry: targeted drug delivery and personalized medicine. Controlled release of the active ingredient can be achieved through various stimuli, among which are temperature, pH, redox potential or even enzymes. SDDS, hitherto explored mainly in oncology, are now developed in the fields of dermatology and cosmetics. They are mostly hydrogels or nanosystems, and the most-used stimuli are pH and temperature. This review offers an overview of polymer-based SDDS developed to trigger the release of active ingredients intended to treat skin conditions or pathologies. The methods used to attest to stimuli-responsiveness in vitro, ex vivo and in vivo are discussed.

Vaccination into the Dermal Compartment: Techniques, Challenges, and Prospects

In 2019, an 'influenza pandemic' and 'vaccine hesitancy' were listed as two of the top 10 challenges to global health by the WHO. The skin is a unique vaccination site, due to its immune-rich milieu, which is evolutionarily primed to respond to challenge, and its ability to induce both humoral and cellular immunity. Vaccination into this dermal compartment offers a way of addressing both of the challenges presented by the WHO, as well as opening up avenues for novel vaccine formulation and dose-sparing strategies to enter the clinic. This review will provide an overview of the diverse range of vaccination techniques available to target the dermal compartment, as well as their current state, challenges, and prospects, and touch upon the formulations that have been developed to maximally benefit from these new techniques. These include needle and syringe techniques, microneedles, DNA tattooing, jet and ballistic delivery, and skin permeabilization techniques, including thermal ablation, chemical enhancers, ablation, electroporation, iontophoresis, and sonophoresis.

Thermoresponsive Nanogels Based on Different Polymeric Moieties for Biomedical Applications

Nanogels, or nanostructured hydrogels, are one of the most interesting materials in biomedical engineering. Nanogels are widely used in medical applications, such as in cancer therapy, targeted delivery of proteins, genes and DNAs, and scaffolds in tissue regeneration. One salient feature of nanogels is their tunable responsiveness to external stimuli. In this review, thermosensitive nanogels are discussed, with a focus on moieties in their chemical structure which are responsible for thermosensitivity. These thermosensitive moieties can be classified into four groups, namely, polymers bearing amide groups, ether groups, vinyl ether groups and hydrophilic polymers bearing hydrophobic groups. These novel thermoresponsive nanogels provide effective drug delivery systems and tissue regeneration constructs for treating patients in many clinical applications, such as targeted, sustained and controlled release.

Nanogels for Skin Cancer Therapy via Transdermal Delivery: Current Designs

BACKGROUND

Recently, several strategies have been proposed for skin cancer therapy by transdermal delivery, and particularly the use of nanotechnology.

METHODS

This process disrupts the stratum corneum to deliver a drug through the skin, allowing it to accumulate at the tumor site.

RESULTS

Nanogels are drug delivery systems that can be applied to many diseases. Nanogel engineering has been widely studied for use in drug delivery, particularly in cancer theranostics. This review summarizes specific strategies for using nanogels to treat skin cancer, a topic that is limited in recent literature.

CONCLUSION

Advanced techniques for effective skin cancer therapy based on the nanogel's penetration and cellular uptake abilities will be discussed. Moreover, techniques for penetrating the skin, as well as drug release, permeation studies, and microscopic observations, will also be discussed.

Nanoparticles for topical drug delivery: Potential for skin cancer treatment

Nanoparticles offer new opportunities for the treatment of skin diseases. The barrier function of the skin poses a significant challenge for nanoparticles to permeate into the tissue, although the barrier is partially compromised in case of injury or inflammation, as in the case of skin cancer. This may facilitate the penetration of nanoparticles. Extensive research has gone into developing nanoparticles for topical delivery; however, relatively little progress has been made in translating them to the clinic for treating skin cancers. We summarize the types of skin cancers and practices in current clinical management. The review provides a comprehensive outlook of the various nanoparticle technologies tested for topical therapy of skin cancers and summarizes the obstacles that impede its progress from the bench-to-bedside. The review also aims to provide an understanding of the pathways that govern nanoparticle penetration into the skin and a critical analysis of the approaches used to study nanoparticle interactions within the tissue.

Crossing biological barriers with nanogels to improve drug delivery performance

The current limitations in the use of nanocarriers to treat constantly evolving diseases call for the design of novel and smarter drug delivery systems (DDS). Nanogels (NGs) are three-dimensional crosslinked polymers with dimensions on the nanoscale and with a great potential for use in the biomedical field. Particular interest focuses on their application as DDS to minimize severe toxic effects and increase the therapeutic index of drugs. They have recently gained attention, since they can include responsive modalities within their structure, which enable them to excerpt a therapeutic function on demand. Their bigger sizes and controlled architecture and functionality, when compared to non-crosslinked polymers, make them particularly interesting to explore novel modalities to cross biological barriers. The present review summarizes the most significant developments of NGs as smart carriers, with focus on smart modalities to cross biological barriers such as cellular membrane, tumor stroma, mucose, skin, and blood brain barrier. We discuss the properties of each barrier and highlight the importance that the NG design has on their capability to overcome them and deliver the cargo at the site of action.

Stimulus Sensitive Smart Nanoplatforms: An Emerging Paradigm for the Treatment of Skin Diseases

Background:

Over the past century, the prevalence of skin diseases has substantially increased. These diseases present a significant physical, emotional and socio-economic burden to the society. Such conditions are also associated with a multitude of psychological traumas to the suffering patients. The effective treatment strategy implicates targeting of drugs to the skin. The field of drug targeting has been revolutionized with the advent of nanotechnology. The emergence of stimulus-responsive nanoplatforms has provided remarkable control over fundamental polymer properties for external triggers. This enhanced control has empowered pioneering approaches in the treatment of chronic inflammatory skin diseases.

Objective:

Our aim was to investigate the studies on smart nanoplatforms that exploit the altered skin physiology under diseased conditions and provide site-specific controlled drug delivery.

Method:

All literature search regarding the advances in stimulus sensitive smart nanoplatforms for skin diseases was done using Google Scholar and Pubmed.

Conclusion:

Various stimuli explored lately for such nano platforms are pH, temperature, light and magnet. Although, the scientists have actively taken up this research topic but there are still certain lacunaes associated which have been discussed in this review. Further, an interdisciplinary collaboration between the healthcare providers and pharmacists is a pivotal requirement for such systems to be available for patients.

Supramolecular nanogels fabricated via host-guest molecular recognition as penetration enhancer for dermal drug delivery

Nanogels that are assembled by supramolecular interactions as compared to covalent crosslinked nanogels, exhibit new functionalities with potential for easy processability, recycling and self-healing due to the nature of dynamic and reversible non-covalent interactions. Here we design a supramolecular polymer nanogel that utilize host-guest interactions between the groups pillar [5] arene and alkyl chains on hyperbranched polyglycerol backbone as crosslinking agents for a new dermal drug delivery system. The anti-inflammatory drug Dexamethasone (Dexa) can be efficiently loaded into the nanogels and released from the assemblies. Besides, the supramolecular polymer nanogels exhibit better drug loading capacity and skin penetration enhancement than the individual host polymer and guest polymer. In vitro skin permeation studies show that supramolecular polymer nanogels can improve the Nile red penetration through the skin by up to 9 fold, compared to the individual polymers or a conventional cream formulation on a barrier deficient skin model.

Applying emerging technologies to improve diabetes treatment

Insulin, as the most important drug for the treatment of diabetes, can effectively control the blood glucose concentration in humans. Due to its instability, short half-life, easy denaturation and side effects, the administration way of insulin are limited to subcutaneous injection accompany with poor glucose control and low patient compliance. In recent years, emerging insulin delivery systems have been developed in diabetes research. In this review, a variety of stimuli-responsive insulin delivery systems with their response mechanism and regulation principle are described. Further, the introduction of stem cell transplantation and mobile application based delivery technologies are prudent for the diabetes treatment. This article also discusses the advantages and limitations of current strategies, along with the opportunities and challenges for future insulin therapy.

Fabrication of BSA@AuNC-Based Nanostructures for Cell Fluoresce Imaging and Target Drug Delivery

Drug delivery which can offer efficient and localized drug transportation together with imaging capabilities is highly demanded in the development of cancer theranostic approaches. Herein, we report the construction of bovine serum albumin (BSA) gold nanoclusters (BSA@AuNCs) for cell fluoresce imaging and target drug delivery. BSA@AuNCs were modified with cyclic arginine-glycine-aspartate with the product RGD-BSA@AuNCs to enhance cell internalization of the nanoclusters. Furthermore, doxorubicin hydrochloride or doxorubicin (DOX), a widely used chemotherapy drug, was also used to modify RGD-BSA@AuNCs. The final design of the DOX/RGD-BSA@AuNC system was constructed through the disulfide bond. The physical microstructure and biological characterization of the BSA@AuNCs were realized through high-resolution transmission electron microscopy and confocal laser fluorescence microscopy. As the disulfide bonds were cleaved by glutathione in cancer cells, DOX-SH molecules were released from the nanosystem to inhibit the growth of cancer cells. The as-prepared DOX/RGD-BSA@AuNC system can be used not only to deliver drug but also to achieve the antitumor effect by in vivo imaging, demonstrating its promising applications in cancer treatment.

Drug delivery systems and materials for wound healing applications

Chronic, non-healing wounds place a significant burden on patients and healthcare systems, resulting in impaired mobility, limb amputation, or even death. Chronic wounds result from a disruption in the highly orchestrated cascade of events involved in wound closure. Significant advances in our understanding of the pathophysiology of chronic wounds have resulted in the development of drugs designed to target different aspects of the impaired processes. However, the hostility of the wound environment rich in degradative enzymes and its elevated pH, combined with differences in the time scales of different physiological processes involved in tissue regeneration require the use of effective drug delivery systems. In this review, we will first discuss the pathophysiology of chronic wounds and then the materials used for engineering drug delivery systems. Different passive and active drug delivery systems used in wound care will be reviewed. In addition, the architecture of the delivery platform and its ability to modulate drug delivery are discussed. Emerging technologies and the opportunities for engineering more effective wound care devices are also highlighted.

Optimizing Circulating Tumor Cells' Capture Efficiency of Magnetic Nanogels by Transferrin Decoration

Magnetic nanogels (MNGs) are designed to have all the required features for their use as highly efficient trapping materials in the challenging task of selectively capturing circulating tumor cells (CTCs) from the bloodstream. Advantageously, the discrimination of CTCs from hematological cells, which is a key factor in the capturing process, can be optimized by finely tuning the polymers used to link the targeting moiety to the MNG. We describe herein the relationship between the capturing efficiency of CTCs with overexpressed transferrin receptors and the different strategies on the polymer used as linker to decorate these MNGs with transferrin (Tf). Heterobifunctional polyethylene glycol (PEG) linkers with different molecular weights were coupled to Tf in different ratios. Optimal values over 80% CTC capture efficiency were obtained when 3 PEG linkers with a length of 8 ethylene glycol (EG) units were used, which reveals the important role of the linker in the design of a CTC-sorting system.

Crosslinked casein-based micelles as a dually responsive drug delivery system

Crosslinked casein micelles with a dual pH and protease drug triggered release can be applied as a promising hydrophobic drug carrier material.

Thermoresponsive nanogels with film-forming ability

A one pot semibatch method was proposed for synthesizing poly(N-vinylcaprolactam)-based nanogels with particle coalescence ability.

EPR Technology as Sensitive Method for Oxidative Stress Detection in Primary and Secondary Keratinocytes Induced by Two Selected Nanoparticles

Exogenous factors can cause an imbalance in the redox state of biological systems, promoting the development of oxidative stress, especially reactive oxygen species (ROS). To monitor the intensity of ROS production in secondary keratinocytes (HaCaT) by diesel exhaust particles and thermoresponsive nanogels (tNG), electron paramagnetic resonance (EPR) spectroscopy after 1 and 24 h of incubation, respectively, was applied. Their cytotoxicity was analyzed by a cell viability assay (XTT). For tNG an increase in the cell viability and ROS production of 10% was visible after 24 h, whereas 1 h showed no effect. A ten times lower concentration of diesel exhaust particles exhibited no significant toxic effects on HaCaT cells for both incubation times, thus normal adult human keratinocytes (NHK) were additionally analyzed by XTT and EPR spectroscopy. Here, after 24 h a slight increase of 18% in metabolic activity was observed. However, this effect could not be explained by the ROS formation. A slight increase in the ROS production was only visible after 1 h of incubation time for HaCaT (9%) and NHK (14%).

Biocompatibility and characterization of polyglycerol-based thermoresponsive nanogels designed as novel drug-delivery systems and their intracellular localization in keratinocytes

Novel nanogels that possess the capacity to change their physico-chemical properties in response to external stimuli are promising drug-delivery candidates for the treatment of severe skin diseases. As thermoresponsive nanogels (tNGs) are capable of enhancing penetration through biological barriers such as the stratum corneum and are taken up by keratinocytes of human skin, potential adverse consequences of their exposure must be elucidated. In this study, tNGs were synthesized from dendritic polyglycerol (dPG) and two thermoresponsive polymers. tNG_dPG_tPG are the combination of dPG with poly(glycidyl methyl ether-co-ethyl glycidyl ether) (p(GME-co-EGE)) and tNG_dPG_pNIPAM the one with poly(N-isopropylacrylamide) (pNIPAM). Both thermoresponsive nanogels are able to incorporate high amounts of dexamethasone and tacrolimus, drugs used in the treatment of severe skin diseases. Cellular uptake, intracellular localization and the toxicological properties of the tNGs were comprehensively characterized in primary normal human keratinocytes (NHK) and in spontaneously transformed aneuploid immortal keratinocyte cell line from adult human skin (HaCaT). Laser scanning confocal microscopy revealed fluorescently labeled tNGs entered into the cells and localized predominantly within lysosomal compartments. MTT assay, comet assay and carboxy-H2DCFDA assay, demonstrated neither cytotoxic or genotoxic effects, nor any induction of reactive oxygen species of the tNGs in keratinocytes. In addition, both tNGs were devoid of eye irritation potential as shown by bovine corneal opacity and permeability (BCOP) test and red blood cell (RBC) hemolysis assay. Therefore, our study provides evidence that tNGs are locally well tolerated and underlines their potential for cutaneous drug delivery.

The next generation cell-penetrating peptide and carbon dot conjugated nano-liposome for transdermal delivery of curcumin

To overcome the problems associated with conventional liposomes in transdermal drug delivery like limited penetration ability and poor stability, in this article we report a new generation of cell penetrating peptide polyarginine containing nano-liposomes conjugated with carbon dots. The newly synthesized, cost-effective liposomic precursors were used for the fabrication of liposomes. The resulting liposomes have a bilayer structure like that of conventional liposomes with much smaller size, higher stability, and high penetration ability. The nano-liposomes show high stability at room temperature for three months without any change in size or encapsulation efficiency. The incorporation of carbon dots also opens up their application in fluorescence cell imaging studies, which is very well supported by the fluorescence microscopic analysis of the liposome skin penetration. The as-prepared nano-liposomes do not show any cytotoxicity for MCF-7 cells, even at high concentrations; however, when drug loaded liposomes are applied, they can kill the cancer cells with a high rate. The synthesized nano-liposomes have the potential to be used as an efficient, stable, biocompatible nanocarrier for transdermal drug delivery.

Rational design of dendritic thermoresponsive nanogels that undergo phase transition under endolysosomal conditions

In the last few decades, the synthesis of nanodevices has become a very active research field with many applications in biochemistry, biotechnology, and biomedicine. However, there is still a great need for smart nanomaterials that can sense and respond to environmental changes. Temperature- and pH-responsive nanogels (NGs), which are prepared in a one-pot synthesis from N-isopropylacrylamide (NiPAm) and a Newkome-type dendron (ABC) bearing carboxylic acid groups, are being investigated as multi-responsive drug carriers. As a result, NGs have been developed that are able to undergo a reversible volume phase transition triggered by acidic conditions, like the ones found in endolysosomal compartments of cancer cells. The NGs have been thoroughly characterized using dynamic light scattering and spectroscopies, such as infrared, nuclear magnetic resonance, UV-visible, and stimulated Raman. Strong hydrogen bonds have been detected when the ABC moieties are deprotonated, which has led to changes in the transition temperatures of the NGs and a reversible, pH-dependent aggregation. This pH-dependent phase change was exploited for the effective encapsulation and sustained release of the anticancer drug cisplatin and resulted in a faster release of the drug at endolysosomal pH values. The cisplatin-loaded NGs have exhibited high toxicities against A549 cells in vitro, while the unloaded NGs have been found to be not cytotoxic and hemocompatible.

Dendritic polyglycerol and N-isopropylacrylamide based thermoresponsive nanogels as smart carriers for controlled delivery of drugs through the hair follicle

Nanoparticles with a size of several hundred nanometers can effectively penetrate into the hair follicles and may serve as depots for controlled drug delivery. However, they can neither overcome the hair follicle barrier to reach the viable cells nor release the loaded drug adequately. On the other hand, small drug molecules cannot penetrate deep into the hair follicles. Thus, the most efficient way for drug delivery through the follicular route is to employ nanoparticles that can release the drug close to the target structure upon exposure to some external or internal stimuli. Accordingly, 100-700 nm sized thermoresponsive nanogels with a phase transition temperature of 32-37 °C were synthesized by the precipitation polymerization technique using N-isopropylacrylamide as a monomer, acrylated dendritic polyglycerol as a crosslinker, VA-044 as an initiator, and sodium dodecyl sulphate as a stabilizer. The follicular penetration of the indodicarbocyanine (IDCC) labeled nanogels into the hair follicles and the release of coumarin 6, which was loaded as a model drug, in the hair follicles were assessed ex vivo using porcine ear skin. Confocal laser scanning microscopy (CLSM) enabled independent tracking of the nanogels and the loaded dye, although it is not as precise and accurate as standard analytical methods. The results showed that, unlike smaller nanogels (<100 nm), medium and larger sized nanogels (300-500 nm) penetrated effectively into the hair follicles with penetration depths proportional to the nanogel size. The release of the loaded dye in the hair follicles increased significantly when the investigation on penetration was carried out above the cloud point temperature of the nanogels. The follicular penetration of the nanogels from the colloidal dispersion and a 2.5% hydroxyethyl cellulose gel was not significantly different.

Specific uptake mechanisms of well-tolerated thermoresponsive polyglycerol-based nanogels in antigen-presenting cells of the skin

Engineered nanogels are of high value for a targeted and controlled transport of compounds due to the ability to change their chemical properties by external stimuli. As it has been indicated that nanogels possess a high ability to penetrate the stratum corneum, it cannot be excluded that nanogels interact with dermal dendritic cells, especially in diseased skin. In this study the potential crosstalk of the thermoresponsive nanogels (tNGs) with the dendritic cells of the skin was investigated with the aim to determine the immunotoxicological properties of the nanogels. The investigated tNGs were made of dendritic polyglycerol (dPG) and poly(glycidyl methyl ether-co-ethyl glycidyl ether) (p(GME-co-EGE)), as polymer conferring thermoresponsive properties. Although the tNGs were taken up, they displayed neither cytotoxic and genotoxic effects nor any induction of reactive oxygen species in the tested cells. Interestingly, specific uptake mechanisms of the tNGs by the dendritic cells were depending on the nanogels cloud point temperature (Tcp), which determines the phase transition of the nanoparticle. The study points to caveolae-mediated endocytosis as being the major tNGs uptake mechanism at 37°C, which is above the Tcp of the tNGs. Remarkably, an additional uptake mechanism, beside caveolae-mediated endocytosis, was observed at 29°C, which is the Tcp of the tNGs. At this temperature, which is characterized by two different states of the tNGs, macropinocytosis was involved as well. In summary, our study highlights the impact of thermoresponsivity on the cellular uptake mechanisms which has to be taken into account if the tNGs are used as a drug delivery system.

Overcoming drug resistance with on-demand charged thermoresponsive dendritic nanogels

AIM

To develop nanogels (NG) able to modulate the encapsulation and release of drugs, in order to circumvent drug resistance mechanisms in cancer cells.

MATERIALS & METHODS

Poly-N-isopropylacrylamide-dendritic polyglycerol NG were semi-interpenetrated with 2-acrylamido-2-methylpropane sulfonic acid or (2-dimethylamino) ethyl methacrylate. Physico-chemical properties of the NGs as well as doxorubicin (DOXO) loading and release were characterized. Drug delivery performance was investigated in vitro and in vivo in a multidrug-resistant tumor model.

RESULTS

Both the DOXO loaded semi-interpenetrating polymer network NGs were more efficient in multidrug resistant cancer cell proliferation inhibition studies. In vivo, the DOXO loaded NG semi-interpenetrated with 2-acrylamido-2-methylpropane sulfonic acid was able to overcome drug resistance and reduce the tumor volume to about 25%.

CONCLUSION

The innovative semi-interpenetrating polymer network NGs appear to be promising drug carriers for drug resistant cancer therapy.

Drug delivery across intact and disrupted skin barrier: Identification of cell populations interacting with penetrated thermoresponsive nanogels

Nanoscaled soft particles, such as nanogels, can be designed to incorporate different types of compounds and release them in a controlled and triggered manner. Thermoresponsive nanogels (tNG), releasing their cargo above a defined temperature, are promising carrier systems for inflammatory skin diseases, where the temperature of diseased skin differs from that of healthy skin areas. In this study a polyglycerol-based tNG with diameter of 156nm was investigated for penetration and release properties upon topical application on ex vivo human skin with intact or disrupted barrier. Furthermore, temperature-triggered effects and the internalization of tNG by skin cells upon translocation to the viable skin layers were analyzed. The investigated tNG were tagged with indodicarbocyanine and loaded with fluorescein, so that fluorescent microscopy and flow cytometry could be used to evaluate simultaneously particle penetration and release of the fluorochrome. Topically applied tNG penetrated into the SC of both intact and disrupted skin explants. Only in barrier-disrupted skin significant amounts of released fluorochrome and tNG penetrated in the epidermis and dermis 2h after topical application. When a thermal trigger was applied by infrared radiation (30s, 3.9mJ/cm²), a significantly higher penetration of tNG in the SC and release of the dye in the epidermis were detected with respect to non-triggered samples. Penetrated tNG particles were internalized by skin cells in both epidermis and dermis. Only few CD1a-positive Langerhans cells associated with tNG were found in the epidermis. However, in the dermis a significant percentage of cells associated with tNG were identified to be antigen presenting cells, i.e. HLA-DR+and CD206+cells. Thus, tNG represent promising carrier systems for the treatment of inflammatory skin diseases, not only because of their improved penetration and controlled release properties, but also because of their ability to effectively reach dermal dendritic cells in barrier-disrupted skin.

Correlation between the chemical composition of thermoresponsive nanogels and their interaction with the skin barrier

In this paper we present a comprehensive study for the ability of thermoresponsive nanogels (tNG) to act as cutaneous penetration enhancers. Given the unique properties of such molecular architectures with regard to their chemical composition and thermoresponsive properties, we propose a particular mode of penetration enhancement mechanism, i.e. hydration of the stratum corneum. Different tNG were fabricated using dendritic polyglycerol as a multifunctional crosslinker and three different kinds of thermoresponsive polymers as linear counterpart: poly(N-isopropylacrylamide) (pNIPAM), p(di(ethylene glycol) methyl ether methacrylate - co - oligo ethylene glycol methacrylate) (DEGMA-co-OEGMA475), and poly(glycidyl methyl ether - co - ethyl glycidyl ether) (tPG). Excised human skin was investigated by means of fluorescence microscopy, which enabled the detection of significant increment in the penetration of tNG as well as the encapsulated fluorescein. The morphology of the treated skin samples was thoroughly investigated by transmission electron microscopy and stimulated Raman spectromicroscopy. We found that tNG can perturbate the organization of both proteins and lipids in the skin barrier, which was attributed to tNG hydration effects. Interestingly, different drug delivery properties were detected and the ability of each investigated tNG to enhance skin penetration correlated well with the degree of induced stratum corneum hydration. The differences in the penetration enhancements could be attributed to the chemical structures of the nanogels used in this study. The most effective stratum corneum hydration was detected for nanogels having additional or more exposed polyether structure in their chemical composition.

Core-multishell nanocarriers: Transport and release of dexamethasone probed by soft X-ray spectromicroscopy

Label-free detection of core-multishell (CMS) nanocarriers and the anti-inflammatory drug dexamethasone is reported. Selective excitation by tunable soft X-rays in the O 1s-regime is used for probing either the CMS nanocarrier or the drug. Furthermore, the drug loading efficiency into CMS nanocarriers is determined by X-ray spectroscopy. The drug-loaded nanocarriers were topically applied to human skin explants providing insights into the penetration and drug release processes. It is shown that the core-multishell nanocarriers remain in the stratum corneum when applied for 100min to 1000min. Dexamethasone, if applied topically to human ex vivo skin explants using different formulations, shows a vehicle-dependent penetration behavior. Highest local drug concentrations are found in the stratum corneum as well as in the viable epidermis. If the drug is loaded to core-multishell nanocarriers, the concentration of the free drug is low in the stratum corneum and is enhanced in the viable epidermis as compared to other drug formulations. The present results provide insights into the penetration of drug nanocarriers as well as the mechanisms of controlled drug release from CMS nanocarriers in human skin. They are also compared to related work using dye-labeled nanocarriers and dyes that were used as model drugs.

Near Infrared Dye Conjugated Nanogels for Combined Photodynamic and Photothermal Therapies

There is a need for new and smart formulations that will help overcome the limitations of organic dyes used in photodynamic (PDT) and photothermal (PTT) therapy and significantly accelerate their clinical translation. Therefore the aim of this work was to create a responsive nanogel scaffold as a smart vehicle for dye administration. We developed a methodology that enables the conjugation of organic dyes to thermoresponsive nanogels and yields biocompatible, nanometer-sized products with low polydispersity. The potential of the dye-nanogel conjugate as a photothermal and photodynamic agent has been demonstrated by an in vitro evaluation with a model human carcinoma cell line. Additionally, confocal cell images showed their cellular uptake profile and their potential for bioimaging and intracellular drug delivery. These conjugates are a promising scaffold as a theranostic agents and will enable further applications in combination with controlled drug release.

Water dispersible siloxane nanogels: a novel technique to control surface characteristics and drug release kinetics

Amphiphilic, water-dispersible, crosslinked siloxane nanogels were synthesized and applied as optically clear, functional coatings on the surface of lens substrates to demonstrate the feasibility of siloxane-nanogels to generate covalently tethered coatings and modify the surface properties of intraocular lens substrates.