Confocal laser scanning microscopy to estimate nanoparticles' human skin penetration in vitro

Assessing the Impact of Nanoplastics in Biological Systems: Systematic Review of In Vitro Animal Studies

Nanoplastic (NP) pollution has emerged as a growing concern due to its potential impact on human health, although its adverse effects on different organ systems are not yet fully understood. This systematic scoping review, conducted in accordance with international guidelines, aimed to map the current evidence on the biological effects of NPs. In vitro animal studies assessing cellular damage caused by exposure to any type of NP were searched on PubMed, Web of Science, and Scopus. Data on primary outcomes related to genotoxicity and cytotoxicity (cell viability, oxidative stress, inflammation, DNA and cytoplasmic damage, apoptosis) were extracted from the included studies, and overall reporting quality was assessed. A total of 108 articles published between 2018 and 2024, mostly by China (54%), Spain (14%), and Italy (9%), were included. Polystyrene (PS) was the most frequently studied polymer (85%). NP sizes in solution ranged from 15 to 531 nm, with a higher prevalence in the 40-100 nm range (38%). The overall quality of studies was rated as moderate (60%), with many lacking essential details about cell culture conditions (e.g., pH of the medium, passage number, substances used). A higher frequency of negative effects from NP exposure was observed in respiratory cell lines, while immune, digestive, and hepatic cell lines showed greater resistance. Nervous, urinary, and connective tissue systems were impacted by NPs. Positively charged and smaller PS particles were consistently associated with higher toxicity across all systems. In summary, this review highlights the multifactorial nature of NP toxicity, influenced by size, surface charge, and polymer type. It also reveals a significant knowledge gap, stemming from the predominant use of immortalized monocultures exposed to commercially available PS NPs, the limited use of environmentally relevant particles, and the underutilization of advanced experimental models (e.g., organ-on-chip systems) that better mimic physiological conditions.

Current issues in optical monitoring of drug delivery via hair follicles

Drug delivery via hair follicles has attracted much research attention due to its potential to serve for both local and systemic therapeutic purposes. Recent studies on topical application of various particulate formulations have demonstrated a great role of this delivery route for targeting numerous cell populations located in skin and transporting the encapsulated drug molecules to the bloodstream. Despite a great promise of follicle-targeting carriers, their clinical implementation is very rare, mostly because of their poorer characterization compared to conventional topical dosage forms, such as ointments and creams, which have a history spanning over a century. Gathering as complete information as possible on the intrafollicular penetration depth, storage, degradation/metabolization profiles of such carriers and the release kinetics of drugs they contain, as well as their impact on skin health would significantly contribute to understanding the pros and cons of each carrier type and facilitate the selection of the most suitable candidates for clinical trials. Optical imaging and spectroscopic techniques are extensively applied to study dermal penetration of drugs. Current paper provides the state-of-the-art overview of techniques, which are used in optical monitoring of follicular drug delivery, with a special focus on non-invasive in vivo methods. It discusses key features, advantages and limitations of their use, as well as provide expert perspectives on future directions in this field.

Nanostructured lipid carriers decorated with polyphosphate coated linear and loop cell-penetrating peptides

AIM

This study aimed to evaluate the cellular uptake of nanostructured lipid carriers (NLCs) decorated with polyphosphate coated linear and loop cell-penetrating peptides (CPPs).

METHODS

Linear-CPPs and loop-CPPs were synthesized via ring-opening polymerization and anchored on the surface NLCs, followed by coating with polyphosphate (PP). These nanocarriers (NCs) were characterized in terms of particle size, polydispersity index (PDI), and zeta potential. Cell viability and hemolysis, as well as enzyme-induced charge conversion via phosphate cleavage by free and membrane-bound intestinal alkaline phosphatase (IAP) were investigated. Cellular uptake studies by Caco-2 and HEK cells were quantitatively analyzed by flow cytometry and visualized by confocal microscopy.

RESULTS

A shift in charge from positive to negative was obtained for both linear- and loop-CPPs-NLCs by coating with PP. PP-linear-CPPs-NLCs and PP-loop-CPPs-NLCs exhibited a particle size < 270 nm and a PDI of approximately 0.3. They had a minor effect on cell viability and caused in a concentration of 0.1 % (m/v) around 10 % hemolysis within 24 h. IAP triggered the cleavage and release of monophosphate from the surface of NLCs causing charge conversion from -22.2 mV to + 5.3 mV (Δ27.5 mV) for PP-linear-CPPs-NLCs and from -19.2 mV to + 11.9 mV (Δ31.1 mV) for PP-loop-CPPs-NLCs. Inhibition of alkaline phosphatase activity on Caco-2 and HEK cells confirmed the involvement of this enzyme in charge conversion. PP-linear-CPPs-NLCs showed on Caco-2 cells a higher uptake than PP-loop-CPPs-NLCs, whereas on HEK cells uptake of both types of NLCs was on the same level. The results of cellular uptake were confirmed visually by confocal microscopy.

CONCLUSION

CPPs-NLCs coated with polyphosphate are a promising approach to overcome the polycationic dilemma and to enhance cellular uptake.

Penetration pathways, influencing factors and predictive models for dermal absorption of exobiotic molecules: A critical review

This review provides a comprehensive summary of the skin penetration pathways of xenobiotics, including metals, organic pollutants, and nanoparticles (NPs), with a particular focus on the methodologies employed to elucidate these penetration routes. The impacts of the physicochemical properties of exogenous substances and the properties of solvent carriers on the penetration efficiencies were discussed. Furthermore, the review outlines the steady-state and transient models for predicting the skin permeability of xenobiotics, emphasizing the models which enable realistic visualization of pharmaco-kinetic phenomena via detailed geometric representations of the skin microstructure, such as stratum corneum (SC) (bricks and mortar) and skin appendages (hair follicles and sebaceous gland units). Limitations of published research, gaps in current knowledge, and recommendations for future research are highlighted, providing insight for a better understanding of the skin penetration behavior of xenobiotics and associated health risks in practical application contexts.

Bioarchitectural Design of Bioactive Biopolymers: Structure-Function Paradigm for Diabetic Wound Healing

Chronic wounds such as diabetic ulcers are a major complication in diabetes caused by hyperglycemia, prolonged inflammation, high oxidative stress, and bacterial bioburden. Bioactive biopolymers have been found to have a biological response in wound tissue microenvironments and are used for developing advanced tissue engineering strategies to enhance wound healing. These biopolymers possess innate bioactivity and are biodegradable, with favourable mechanical properties. However, their bioactivity is highly dependent on their structural properties, which need to be carefully considered while developing wound healing strategies. Biopolymers such as alginate, chitosan, hyaluronic acid, and collagen have previously been used in wound healing solutions but the modulation of structural/physico-chemical properties for differential bioactivity have not been the prime focus. Factors such as molecular weight, degree of polymerization, amino acid sequences, and hierarchical structures can have a spectrum of immunomodulatory, anti-bacterial, and anti-oxidant properties that could determine the fate of the wound. The current narrative review addresses the structure-function relationship in bioactive biopolymers for promoting healing in chronic wounds with emphasis on diabetic ulcers. This review highlights the need for characterization of the biopolymers under research while designing biomaterials to maximize the inherent bioactive potency for better tissue regeneration outcomes, especially in the context of diabetic ulcers.

Exploring polysaccharide-based bio-adhesive topical film as a potential platform for wound dressing application: A review

Wound dressings act as a physical barrier between the wound site and the external environment, preventing additional harm; choosing suitable wound dressings is essential for the healing process. Polysaccharide biopolymers have demonstrated encouraging findings and therapeutic prospects in recent decades about wound therapy. Additionally, polysaccharides have bioactive qualities like anti-inflammatory, antibacterial, and antioxidant capabilities that can help the process of healing. Due to their excellent tissue adhesion, swelling, water absorption, bactericidal, and immune-regulating properties, polysaccharide-based bio-adhesive films have recently been investigated as intriguing alternatives in wound management. These films also mimic the structure of the skin and stimulate the regeneration of the skin. This review presented several design standards and functions of suitable bio-adhesive films for the healing of wounds. Additionally, the most recent developments in the use of bio-adhesive films as wound dressings based on polysaccharides, including hyaluronic acid, chondroitin sulfate, dextran, alginate, chitosan, cellulose, konjac glucomannan, gellan gum, xanthan gum, pectin, guar gum, heparin, arabinogalactans, carrageen, and tragacanth gum, are thoroughly discussed. Lastly, to create a road map for the function of polysaccharide-based bio-adhesive films in advanced wound care, their clinical performances and future challenges in making bio-adhesive films by three-dimensional bioprinting are summarized.

The Other Side of Plastics: Bioplastic-Based Nanoparticles for Drug Delivery Systems in the Brain

Plastics have changed human lives, finding a broad range of applications from packaging to medical devices. However, plastics can degrade into microscopic forms known as micro- and nanoplastics, which have raised concerns about their accumulation in the environment but mainly about the potential risk to human health. Recently, biodegradable plastic materials have been introduced on the market. These polymers are biodegradable but also bioresorbable and, indeed, are fundamental tools for drug formulations, thanks to their transient ability to pass through biological barriers and concentrate in specific tissues. However, this "other side" of bioplastics raises concerns about their toxic potential, in the form of micro- and nanoparticles, due to easier and faster tissue accumulation, with unknown long-term biological effects. This review aims to provide an update on bioplastic-based particles by analyzing the advantages and drawbacks of their potential use as components of innovative formulations for brain diseases. However, a critical analysis of the literature indicates the need for further studies to assess the safety of bioplastic micro- and nanoparticles despite they appear as promising tools for several nanomedicine applications.

Methodologies to Evaluate the Hair Follicle-Targeted Drug Delivery Provided by Nanoparticles

Nanotechnology has been investigated for treatments of hair follicle disorders mainly because of the natural accumulation of solid nanoparticles in the follicular openings following a topical application, which provides a drug "targeting effect". Despite the promising results regarding the therapeutic efficacy of topically applied nanoparticles, the literature has often presented controversial results regarding the targeting of hair follicle potential of nanoformulations. A closer look at the published works shows that study parameters such as the type of skin model, skin sections analyzed, employed controls, or even the extraction methodologies differ to a great extent among the studies, producing either unreliable results or precluding comparisons altogether. Hence, the present study proposes to review different skin models and methods for quantitative and qualitative analysis of follicular penetration of nano-entrapped drugs and their influence on the obtained results, as a way of providing more coherent study protocols for the intended application.

Cellular and Systemic Effects of Micro- and Nanoplastics in Mammals-What We Know So Far

Microplastics (MP) and nanoplastics (NP) are accumulating more and more in our environment and have been frequently detected in water and soil, but also in a variety of mainly marine organisms. Polymers such as polyethylene, polypropylene, and polystyrene are those most commonly found. Once in the environment, MP/NP are carriers for many other substances, which often convey toxic effects. Even though intuitively it is thought that ingesting MP/NP cannot be healthy, little is known about their effects on mammalian cells and organisms so far. To better understand the potential hazards of MP/NP on humans and to offer an overview of the already associated pathological effects, we conducted a comprehensive literature review on cellular effects, as well as experimental animal studies on MP/NP in mammals.

Tetrahydrocurcumin Lipid Nanoparticle Based Gel Promotes Penetration into Deeper Skin Layers and Alleviates Atopic Dermatitis in 2,4-Dinitrochlorobenzene (DNCB) Mouse Model

Treatment of atopic dermatitis (AD) is challenging due to its complex pathophysiology. Tetrahydrocurcumin (THC) a polyphenolic, colorless compound that is more polar than curcumin. It possesses superior anti-inflammatory properties and has a clinical advantage over curcumin. The present study investigated the therapeutic effectiveness of THC solid lipid nanoparticle (THC-SLN)-based gels in AD. THC-SLNs prepared using microemulsification resulted in a particle size of 109.2 nm as determined by nanoparticle tracking, and FTIR confirmed the entrapment of drug within the lipid matrix. THC-SLNs greatly enhanced skin hydration when tested both ex vivo and in vivo in Lacca mice. Deeper skin penetration was clearly established using dermatokinetics and CLSM. The in vivo pharmacodynamics of THC-SLNs gel in 2,4-dinitrochlorobenzene (DNCB)-induced AD mice showed enhanced bioactivity; reduced levels of TNF-α and IL-6; and complete healing, as evident from histopathological studies. Thus, the novel topical THC-SLN gel has potential to emerge as a safe alternative to conventional corticosteroids for AD and other skin disorders with overbearing inflammation.

Span 80/TPGS modified lipid-coated chitosan nanocomplexes of acyclovir as a topical delivery system for viral skin infections

Acyclovir (ACR) is considered the gold standard drug for the treatment of skin viral infections caused by the herpes simplex or varicella-zoster virus. However, topical therapy with ACR is hindered by its poor skin penetrability, thus necessitating high doses and frequent administrations. This study was proposed to formulate a modified lipid-coated chitosan nanocomplexes (LCNCs) of acyclovir (ACR), containing span 80 and TPGS, to boost the dermal delivery of ACR and improve the therapeutic outcomes. LCNCs were formulated through a self-assembly method, and the statistical analysis and the optimization were performed via a general 2³ factorial design. Three formulation variables were selected; namely, the amount of chitosan (A), the amount of glyceryl monooleate (GMO) (B), and span 80: D-α-tocopheryl polyethylene glycol succinate (Vitamin ETPGSorTPGS) ratio (C). Four measured attributes were determined; viz., the particle size (PS) in nm, the polydispersity index (PDI), the zeta potential (ZP) in mV, and the entrapment efficiency percentages (EE%). The optimal formulation (LCNCs 8), formulated with 600 mg chitosan, 120 mg GMO, and 3:1 span 80: TPGS ratio, possessed PS of 177.50 ± 1.41 nm, PDI value of 0.28 ± 0.02, ZP of -10.70 ± 0.85 mV, and EE% of 77.20 ± 2.40 %, and was able to sustain ACR release over 24 h. Transmission electron microscopy displayed LCNCs architecture as a polymeric core of chitosan with a lipid coat of GMO, and the solid-state characterization results confirmed the dispersion of ACR in LCNCs. The ex vivo permeation study and the in vivo dermatokinetics profile verified the boosted accumulation of ACR in the skin via LCNCs, while the confocal laser scanning microscopy revealed the heightened penetrability of LCNCs. The topical application of LCNCs demonstrated a safe profile via the modified Draize test and histopathological examinations. Inclusively, ACR-loaded LCNCs could be a promising topical formulation with an advanced dermal delivery status for the treatment of skin viral infections.

Fabrication, optimisation and evaluation of cisplatin-loaded nanostructured carriers for improved urothelium permeability for intravesical administration

AIM

To design microemulsions as carriers to improve cisplatin permeation capability for intravesical administration.

METHOD

The response surface methodology with factorial design was used to investigate and optimise the influence of the compositions e.g. capryol 90 and 5-pentanediol/transcutol mixture on the permeation accumulation amount and tissue deposition amount of cisplatin-loaded microemulsions. The in vitro permeation study and in vivo intravesical test were conducted to prove the effect of microemulsions.

RESULTS

The droplet size and the viscosity of all drug-loaded formulations ranged 235.8-309.3 nm and 550.8-861.7 cps, respectively. The permeation accumulation amounts significantly increased about 26-fold, by used microemulsion as carriers. In vivo study, the cisplatin deposition amount in bladder tissue significantly increased 4.1-fold (p < 0.05) and the penetration depth increased from 60 μm up 120 μm. The nanocarrier showed considerable thermodynamic stability.

CONCLUSION

The designed nanocarrier was considered to be a promising delivery system for cisplatin intravesical administration.

Design and characterization of Nanostructured lipid carriers (NLC) and Nanostructured lipid carrier-based hydrogels containing Passiflora edulis seeds oil

This study aims to design and characterize Nanostructured lipid carriers (NLC) and Nanostructured lipid carrier-based hydrogels with Passiflora edulis seeds oil, a by-product from Madeira Island food industry. NLC were prepared by the ultrasonication technique, using passion fruit seeds oil as a liquid lipid and glyceryl distearate as a solid lipid. These NLC were then gelled with Poly (acrylic acid). Long-term stability studies were conducted with NLC and NLC-based hydrogels stored for 12 months. The following tests were performed: morphology, encapsulation efficiency, particle size analysis, polydispersity index analysis, zeta potential, pH measurement, color analysis, viscosity studies, texture analysis, in vitro occlusion test, ex vivo skin penetration study, tyrosinase inhibition activity, in vitro skin permeation experiments and in vitro cytotoxicity studies. The developed NLC had spherical shape and narrow particle sizes distribution with mean sizes in the range of 150 nm and PDI below 0.3, Zeta potential values around -30 mV and high Encapsulation efficiency. The tyrosinase inhibitory activity and skin retention of the nanoparticles was superior to that of the non-encapsulated oil. The developed formulations did not show cytotoxicity towards HaCat cells and presented suitable viscosity and texture properties for skin application, proving to be good candidates as depigmenting agent.

A review to support the derivation of a worst-case dermal penetration value for nanoparticles

Data on dermal penetration of nanoparticles (NPs) was reviewed with the goal to establish a worst-case dermal penetration value for NPs. To this aim, the main focus was on studies providing quantitative dermal penetration data (29 studies). In vivo dermal penetration studies and ex vivo studies based on skin explants were included. These studies used NPs with different compositions, dimensions, and shapes. The overall results showed that skin is an efficient barrier for NPs, indistinctly of their properties. However, some studies reported that a small percentage of the applied NP dose penetrated the skin surface and reached deeper skin layers. The integrity of the skin layer and the product formulation were more critical determinants of dermal penetration than the NP properties. Most quantitative studies were based on elemental analysis such that it cannot be concluded if detected levels are attributable to a dissolved fraction or to the penetration of particles as such. Results of qualitative imaging studies suggest that at least a fraction of the levels reported in quantitative studies could be due to particle penetration. Altogether, based on the data compiled, we propose that 1% could be used as a worst-case dermal penetration value for nanoparticles within the boundaries of the properties of those included in our analysis.

Tofacitinib Loaded Squalenyl Nanoparticles for Targeted Follicular Delivery in Inflammatory Skin Diseases

Tofacitinib (TFB), a Janus kinase inhibitor, has shown excellent success off-label in treating various dermatological diseases, especially alopecia areata (AA). However, TFB's safe and targeted delivery into hair follicles (HFs) is highly desirable due to its systemic adverse effects. Nanoparticles (NPs) can enhance targeted follicular drug delivery and minimize interfollicular permeation and thereby reduce systemic drug exposure. In this study, we report a facile method to assemble the stable and uniform 240 nm TFB loaded squalenyl derivative (SqD) nanoparticles (TFB SqD NPs) in aqueous solution, which allowed an excellent loading capacity (LC) of 20%. The SqD NPs showed an enhanced TFB delivery into HFs compared to the aqueous formulations of plain drug in an ex vivo pig ear model. Furthermore, the therapeutic efficacy of the TFB SqD NPs was studied in a mouse model of allergic dermatitis by ear swelling reduction and compared to TFB dissolved in a non-aqueous mixture of acetone and DMSO (7:1 v/v). Whereas such formulation would not be acceptable for use in the clinic, the TFB SqD NPs dispersed in water illustrated a better reduction in inflammatory effects than plain TFB's aqueous formulation, implying both encouraging good in vivo efficacy and safety. These findings support the potential of TFB SqD NPs for developing a long-term topical therapy of AA.

Gel-Based Nanocarrier for Intravesical Chemotherapy Delivery: In Vitro and In Vivo Study

Intravesical administration of chemotherapeutic agents can enhance drug accumulation in tumors and reduce systemic side effects. Nanocarriers were developed for intravesical administration and exploit the permeation enhancement effect. In vitro permeation evaluation, the drug transdermal amount and accumulation amounts in the tissue of gemcitabine-loaded nanocarriers through biological membrane significantly increased about 14.8~33.0-fold and 1.5~14.1-fold respectively, when compared to a control group of 1% gemcitabine saline solution. In in vivo intravesical administration, the drug accumulation amount in bladder tissue of nanocarrier of 75.2 ± 5.4 μg was revealed as being comparably higher than that of the control group of 44.8 ± 6.4 μg. In confocal laser scanning microscopy imagery, the penetration depth of fluorescent dyes-rhodamine was increased from 80 μm up to 120 μm when a nanocarrier was used. This result implies that the nanocarrier is a promising drug delivery agent for intravesical administration.

NIR-Emitting Gold Nanoclusters-Modified Gelatin Nanoparticles as a Bioimaging Agent in Tissue

Gold nanocluster (AuNC) synthesis using a well-distinguished polymer for nanoparticle-mediated drug delivery paves the way for developing efficient theranostics based on pharmaceutically accepted materials. Gelatin-stabilized AuNCs are synthesized and modified by glutathione for tuning the emission spectra. Addition of silver ions enhances the fluorescence, reaching also high quantum yield (26.7%). A simplified model can be proposed describing the nanoclusters' properties-structure relationship based on X-ray photoelectron spectroscopy data and synthesis sequence. Furthermore, these modifications improve fluorescence stability toward pH changes and enzymatic degradation, offering different AuNCs for various applications. The impact of nanocluster formation on gelatin structure integrity is investigated by Fourier transform infrared spectrometry and matrix-assisted laser desorption/ionization time of flight mass spectroscopy, being important to further formulate gelatin nanoparticles (GNPs). The 218 nm-sized NPs show no cytotoxicity up to 600 µg mL^-1 and are imaged in skin, as a challenging autofluorescent tissue, by confocal microscopy, when transcutaneously delivered using dissolving microneedles. Linear unmixing allows simultaneous imaging of AuNCs-GNPs and skin with accurate signal separation. This underlines the great potential for bioimaging of this system to better understand nanomaterials' behavior in tissue. Additionally, it is drug delivery system also potentially serving as a theranostic system.

Detection of Intracellular Gold Nanoparticles: An Overview

Photothermal therapy (PTT) takes advantage of unique properties of gold nanoparticles (AuNPs) (nanospheres, nanoshells (AuNSs), nanorods (AuNRs)) to destroy cancer cells or tumor tissues. This is made possible thanks principally to both to the so-called near-infrared biological transparency window, characterized by wavelengths falling in the range 700⁻1100 nm, where light has its maximum depth of penetration in tissue, and to the efficiency of cellular uptake mechanisms of AuNPs. Consequently, the possible identification of intracellular AuNPs plays a key role for estimating the effectiveness of PTT treatments. Here, we review the recognized detection techniques of such intracellular probes with a special emphasis to the exploitation of near-infrared biological transparency window.