Delivery of Molecules into Human Corneal Endothelial Cells by Carbon Nanoparticles Activated by Femtosecond Laser

Influence of the Size and Charge of Carbon Quantum Dots on Their Corneal Penetration and Permeation Enhancing Properties

Reaching the corneal endothelium through the topical administration of therapeutic drugs remains a challenge in ophthalmology. Besides, endothelial cells are not able to regenerate, and diseases at this site can lead to corneal blindness. Targeting the corneal endothelium implies efficient penetration through the three corneal layers, which still remains difficult for small molecules. Carbon quantum dots (CQDs) have demonstrated great potential for ocular nanomedicine. This study focuses on the corneal penetration abilities of differently charged CQDs and their use as permeation enhancers for drugs. Excised whole bovine eyes were used as an ex vivo model to investigate corneal penetration of CQDs derived from glucosamine using β-alanine, ethylenediamine, or spermidine as a passivation agent. It was found that negatively charged CQDs have limited corneal penetration ability, while positively charged CQDs derived from glucosamine hydrochloride and spermidine (CQD-S) penetrate the entire corneal epithelium all the way down to the endothelium. CQD-S were shown to enhance the penetration of FITC-dextran 150 kDa, suggesting that they could be used as efficient penetration enhancers for therapeutic delivery to the corneal endothelium.

Cancer cell-specific protein delivery by optoporation with laser-irradiated gold nanorods

The delivery of macromolecules into living cells is challenging since in most cases molecules are endocytosed and remain in the endo-lysosomal pathway where they are degraded before reaching their target. Here, a method is presented to selectively improve cell membrane permeability by nanosecond laser irradiation of gold nanorods (GNRs) with visible or near-infrared irradiation in order to deliver proteins across the plasma membrane, avoiding the endo lysosomal pathway. GNRs were labeled with the anti-EGFR (epidermal growth factor receptor) antibody Erbitux to target human ovarian carcinoma cells OVCAR-3. Irradiation with nanosecond laser pulses at wavelengths of 532 nm or 730 nm is used for transient permeabilization of the cell membranes. As a result of the irradiation, the uptake of an anti-Ki-67 antibody was observed in about 50 % of the cells. The results of fluorescence lifetime imaging show that the GNR detached from the membrane after irradiation.

[Novel concepts for treatment of the corneal endothelium with nanoparticles]

BACKGROUND

The number of corneal transplantations has increased in Germany in recent years. One reason is an earlier time point of surgery due to less invasive posterior lamellar grafting techniques. To date, penetrating and lamellar corneal transplantations are the only established therapeutic options to treat corneal diseases resulting from endothelial cell pathologies.

AIM

This review article provides an insight into nanoparticle-related translational strategies to improve or to avoid corneal transplantation.

RESULTS

Nanoparticle-based strategies for optimization of the corneal endothelium have different fields of application: 1. during donor cornea cultivation in culture medium, 2. for single cell injection therapies and 3. to treat the patients' own endothelium in an effort to avoid transplantation.

CONCLUSION

Several translational concepts exist to improve or to avoid grafting of a donor cornea. The coming decade will provide established alternatives to conventional corneal transplantation.

Important factors for cell-membrane permeabilization by gold nanoparticles activated by nanosecond-laser irradiation

PURPOSE

Pulsed-laser irradiation of light-absorbing gold nanoparticles (AuNPs) attached to cells transiently increases cell membrane permeability for targeted molecule delivery. Here, we targeted EGFR on the ovarian carcinoma cell line OVCAR-3 with AuNPs. In order to optimize membrane permeability and to demonstrate molecule delivery into adherent OVCAR-3 cells, we systematically investigated different experimental conditions.

MATERIALS AND METHODS

AuNPs (30 nm) were functionalized by conjugation of the antibody cetuximab against EGFR. Selective binding of the particles was demonstrated by silver staining, multiphoton imaging, and fluorescence-lifetime imaging. After laser irradiation, membrane permeability of OVCAR-3 cells was studied under different conditions of AuNP concentration, cell-incubation medium, and cell-AuNP incubation time. Membrane permeability and cell viability were evaluated by flow cytometry, measuring propidium iodide and fluorescein isothiocyanate-dextran uptake.

RESULTS

Adherently growing OVCAR-3 cells can be effectively targeted with EGFR-AuNP. Laser irradiation led to successful permeabilization, and 150 kDa dextran was successfully delivered into cells with about 70% efficiency.

CONCLUSION

Antibody-targeted and laser-irradiated AuNPs can be used to deliver molecules into adherent cells. Efficacy depends not only on laser parameters but also on AuNP:cell ratio, cell-incubation medium, and cell-AuNP incubation time.

Earthicle: The Design of a Conceptually New Type of Particle

The conception and the steps made in the design of a conceptually new type of composite particle, so-called "earthicle", are being described. This particle is meant to roughly mimic the layered structure of the Earth, having zerovalent iron core, silicate mantle, and a thin carbonaceous crust resembling the biosphere and its geological remnants. Particles are made in a stable colloidal form in an aqueous medium, involving chemical precipitation and pyrolysis of citric acid in the solution. The effects of various synthesis parameters were studied, including borohydride and oleate concentrations, APTES/TEOS molar ratio, chemical nature of the carbon precursors, and others. XRD analysis confirmed the predominantly zerovalent iron composition of the core, amorphous silica and crystalline iron silicate/silicide composition of the mesolayer, and the carbonaceous, amorphous graphitic composition of the surface coating. The atomically thin carbon shell was also detected as a distinct shoulder on the broad n-π* absorption resonance and the peak at ∼300 nm, a signature of sp² hybridized electronic orbitals and the result of the interband π-π* transition characteristic of graphitic structures. The irregularity of the shape of generally round Fe⁰ particles has caused the uniformity of the silica shell to be directly proportional to the particle size. The size of the earthicles ranged from 60 to 500 nm depending on the ionic concentration of the precursors and additives. Silica layer effectively prevented the aggregation of the iron core and increased the biocompatibility of the particles. The point of zero charge first increased from the acidic to the neutral range after coating Fe⁰ core with the APTES-functionalized, aminated silica shell and then restored its low value after depositing the carboxylated carbonic crust in a charge-reversal process designed to facilitate the formation of core-multishell structures. Tested on K7M2 osteosarcoma cell line and primary kidney and lung fibroblasts, cytotoxicity was cell-line dependent; however, the trend assessed in both planar and 3D cell culture with respect to the three types of particles, Fe⁰, Fe/SiO₂, and Fe/SiO₂/C, was general and independent of the cell line. Thus, the pronounced toxicity of Fe⁰ alone became neutralized after the silica layer was coated around Fe⁰. The further addition of the carbonic layer reduced the viability as compared to Fe/SiO₂, albeit in a statistically significant manner only for K7M2 cell line when compared against the untreated control. Cell response also varied depending on the formulation: while some formulations exhibited lethal effects on kidney fibroblasts, were harmless to lung fibroblasts, and boosted the proliferation of K7M2 osteosarcoma cells, other formulations exhibited the opposite behavior despite being similar in terms of their core/double-shell structure. Compared across three different cancerous cell lines, K7M2 osteosarcoma and U87 and E297 glioblastoma, a similar cell-line dependency in response was observed, yet the viability reduction was consistent for all Fe/SiO₂/C particles, ranging from 80% to 85% of the untreated control. Carbon surface layer, albeit of graphitic structural nature, was of a markedly more viable character than that of nanosized graphene oxide. The viability of lung fibroblasts incubated with Fe/SiO₂/C particles was reduced in the presence of the alternating magnetic field of 312.75 A/m and 1 MHz, while the viability reduction caused by Fe/SiO₂/C particles in kidney fibroblasts and K7M2 cells was converted from statistically insignificant to significant, suggesting that the composite particles could be used for hyperthermia treatments, although their properties should be optimized for a more intense effect. A single-cell immunofluorescent analysis of the interaction of primary kidney fibroblasts and K7M2 osteosarcoma cells with Fe/SiO₂/C particles demonstrated that the cell uptake and perinuclear localization may be responsible for the necrotic effects. This analysis also showed that composite Fe/SiO₂/C particles may have the ability to cause the rupture of the cancer cell nucleus while having a harmless effect on the primary cells. Such a promising and selective anticancer activity will be investigated in more detail in future studies.

Delivery of macromolecules into the endothelium of whole ex vivo human cornea by femtosecond laser-activated carbon nanoparticles

BACKGROUND

The targeted delivery of drugs or genes into corneal endothelial cells (ECs) during eye banking could help improve graft quality and quantity. Physical methods raising less safety concerns than viral ones, we previously adapted, for in vitro ECs, a recent innovative technique of drug delivery based on the activation of carbon nanoparticles (CNPs) by a femtosecond laser (fsL). The aim of the present pilot study was to adapt this method to enable molecule delivery into the intact endothelium of ex vivo human corneas.

METHODS

ECs from 40 organ-cultured corneas were perforated by photoacoustic reaction induced by irradiation of CNPs by a fsL. This enabled intracellular delivery of Alexa Fluor 488 dextran, a 4000 Da fluorescent macromolecule. The influence of increasing laser fluences (15, 20, 30 and 40 mJ/cm(2)) and of protective additives (ROCK inhibitor and poloxamer 407) on delivery and mortality rates was quantified using ImageJ.

RESULTS

No dextran was delivered with a fluence lower than 20 mJ/cm(2). Dextran was delivered into 3% (range 0%-7%) of cells at 20 mJ/cm(2), 7% (range 2%-12%) at 30 mJ/cm(2) and reaching a median 13% (range 3%-24%) for 40 mJ/cm(2), showing that dextran uptake by ECs increased significantly with fluence. Induced mortality varied from 0% to 53% irrespective of fluence, but likely to be related with the endothelial status (EC density and morphometry, donor age, storage duration and presence of Descemet's folds). ROCK inhibitor slightly increased uptake efficiency, unlike poloxamer. However, none of them decreased the mortality induced by laser.

CONCLUSIONS

This study shows that a macromolecule can be delivered specifically into ECs of a whole organ-cultured human cornea, using fsL-activated CNPs. The delivery rate was relatively high for a non-viral method. Further optimisation is required to understand and reduce variability in cell mortality.

Gold Nanoparticle-Mediated Delivery of Molecules into Primary Human Gingival Fibroblasts Using ns-Laser Pulses: A Pilot Study

Interaction of gold nanoparticles (AuNPs) in the vicinity of cells’ membrane with a pulsed laser (λ = 532 nm, τ = 1 ns) leads to perforation of the cell membrane, thereby allowing extracellular molecules to diffuse into the cell. The objective of this study was to develop an experimental setting to deliver molecules into primary human gingival fibroblasts (pHFIB-G) by using ns-laser pulses interacting with AuNPs (study group). To compare the parameters required for manipulation of pHFIB-G with those needed for cell lines, a canine pleomorphic adenoma cell line (ZMTH3) was used (control group). Non-laser-treated cells incubated with AuNPs and the delivery molecules served as negative control. Laser irradiation (up to 35 mJ/cm²) resulted in a significant proportion of manipulated fibroblasts (up to 85%, compared to non-irradiated cells: p < 0.05), while cell viability (97%) was not reduced significantly. pHFIB-G were perforated as efficiently as ZMTH3. No significant decrease of metabolic cell activity was observed up to 72 h after laser treatment. The fibroblasts took up dextrans with molecular weights up to 500 kDa. Interaction of AuNPs and a pulsed laser beam yields a spatially selective technique for manipulation of even primary cells such as pHFIB-G in high throughput.