Two-dimensional printing of nanoparticles as a promising therapeutic method for personalized drug administration.

The necessity for personalized patient treatment has drastically increased since the contribution of genes to the differences in physiological and metabolic state of individuals have been exposed. Different approaches have been considered so far in order to satisfy all of the diversities in patient needs, yet none of them have been fully implemented thus far. In this framework, various types of 2D printing technologies have been identified to offer some potential solutions for personalized medication, which development is increasing rapidly. Accurate drug-on-demand deposition, the possibility of consuming multiple drug substances in one product and adjusting individual drug concentration are just some of the few benefits over existing bulk pharmaceuticals manufacture, which printing technologies brings. With inclusion of nanotechnology by printing nanoparticles from its dispersions some further opportunities such as controlled and stimuli-responsive drug release or targeted and dose depending on drug delivery were highlighted. Yet, there are still some challenges to be solved before such products can reach the pharmaceutical market. In those terms mostly chemical, physical as well as microbiological stability concerns should be answered, with which 2D printing technology could meet the treatment needs of every individual and fulfill some existing drawbacks of large-scale batch production of pharmaceuticals we possess today.

Development of Simvastatin-Loaded Particles Using Spray Drying Method for Ex Tempore Preparation of Cartridges for 2D Printing Technology.

In this work, a spray drying method was developed to produce drug/polymer (simvastatin/polycaprolactone) microparticles that have the potential to be used as a pre-formulation for ex tempore preparation of 2D printing cartridges. An experimental model was designed with the process parameters set to predict the smallest particle size required for successful 2D printing. Three different types of particles (lactose, nanocellulose/lactose, calcium silicate) were produced, and the average size of the dry particles varied depending on the sampling location (cyclone, collection vessel). The encapsulation efficiency of simvastatin was highest with nanocellulose/lactose from the collection vessel. The one-month stability of simvastatin in the particles showed low content, but the addition of ascorbic acid as an antioxidant increased the chemical stability of the drug. Interestingly, the addition of antioxidants decreased the stability of simvastatin in the calcium silicate particles from the collection vessel. Dispersion of the particles in three different propylene glycol and water mixtures (10/90, 50/50, and 90/10% (v/v)), representing a printable ink medium with three different viscosity and surface tension properties, showed that nanocellulose/lactose was the most suitable antiadhesive in terms of dispersed particle size (˂1 µm). After one month of storage, the dispersed particles remained in the same size range without undesirable particle agglomeration.

Nanocellulose-Based Film-Forming Hydrogels for Improved Outcomes in Atopic Skin.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by impaired skin barrier function. Amongst the various dermal formulations that are being used and/or investigated for AD treatment, one of the advanced approaches is the use of hydrogels as film-forming systems that are applied directly to the skin and have the added value of providing a physical barrier, which is lacking in atopic skin. Novel film-forming hydrogels based on two different nanocrystalline celluloses (NCCs) in combination with one of two natural polymers (alginate or pectin) were developed for incorporation of betamethasone dipropionate (BDP). Initially, the low water solubility of BDP was resolved by prior dissolution in a self-microemulsifying drug delivery system (SMEDDS). The mixture of Kolliphor® EL/Capryol® 90 in a ratio of 8/2 was chosen on the merit of its high BDP-saturated solubility and no BDP precipitation upon water dilution, enabling BDP to remain dissolved after incorporation into hydrogels. The solvent evaporation method was used to prepare the films, and their high water retention capacity was confirmed in vitro on artificial membranes and pig ear skin. The presented results thus confirm NCC-based film-forming hydrogels as a very promising drug delivery system for AD treatment.

Particle properties and drug metastable solubility of simvastatin containing PVP matrix particles prepared by electrospraying technique.

In this work the preparation of drug loaded polymeric nanoparticles using electrospraying method and their subsequent characterization is presented. Our purpose was to incorporate the drug with extremely low solubility and low oxidative stability into polyvinylpyrolidone nanoparticles in order to improve its solubility and preserve its chemical stability and hence evaluate the ability of the technology to stabilize such systems in nanoparticulate form. Through the initial screening and optimization of process parameters and polymer solution properties, we detected different morphologies of electrosprayed product particles, where the use of lower molecular weight polymer resulted in a higher process instability as well as in a broader particle size distribution. On the other hand, the solution containing polyvinylpyrolidone with higher molecular weight showed sensitivity to different flow rates and electric field changes, which again resulted in differing the particle size and morphology. The electrosprayed products, prepared by sufficient process stability and having adequately narrow size distribution span, showed lower initial simvastatin contents than theoretically expected, which indicated an oxidative drug degradation already during the electrospraying process. The addition of antioxidants improved simvastatin chemical stability in the particles, during the process itself as well as after accelerated stability study. With an addition of butylated hydroxyanisole antioxidant mixture into initial polymer solution more than 95% of the drug content was preserved after one month at accelerated conditions, whereas in formulations without antioxidants simvastatin content was less than 6%. Antioxidants addition however did not influence only simvastatin stability but also simvastatin solubility. Surprisingly, antioxidants addition did decrease drug solubility in buffers (pH=4 and pH=6.8) for more than a half without any solid state changes of simvastatin. Potential hydrophobic interaction between simvastatin and antioxidants are hindering the drug solubility in the respective buffer, despite drug being in amorphous state.

Combinations of nanovesicles and physical methods for enhanced transdermal delivery of a model hydrophilic drug.

Here, we combined lipid nanovesicles (ethosomes, liposomes) as the drug carrier systems with two physical methods (electroporation, sonoporation) to enhance transdermal delivery of a hydrophilic model molecule, calcein. First, using different formulations, ethosomes greatly enhanced calcein permeation by passive diffusion compared to liposomes and calcein in buffer, which is most likely due to a synergism between the ethanol action on the stratum corneum lipids and the penetration of the elastic vesicles. Liposomes permeated poorly through the skin and, as also suggested by other authors, seem to remain confined to the outer layers of the skin. By creating localized effects, liposomes would be better suited to topical dermal delivery than transdermal delivery. Using sonoporation as the physical enhancement method, sonication (5 min) showed improvement over passive diffusion; however, only for the ethosome formulation, and not for solution and liposomes. Similarly, electroporation greatly enhanced delivery of calcein, which was again more pronounced for ethosomes than liposomes and calcein in buffer. Finally, three different transdermal delivery enhancement methods were coupled, using ethosomes as carriers, along with both electroporation and sonoporation, to investigate the potential for synergistic effects. However, these combinations failed to achieve not only synergistic effects, but also additive effects. Nevertheless, combination of the ethosome formulation of calcein with either of electroporation or sonoporation achieves significant enhancement of transdermal molecular delivery being safe for potential clinical use.

The effect of pulse duration, power and energy of fractional Er:YAG laser for transdermal delivery of differently sized FITC dextrans.

We studied fractional Er:YAG laser to enhance transdermal drug delivery of compounds possessing different molecular weights: FITC-dextrans (or FD) with average molecular weights of 4, 10 and 20kDa. Vertical glass Franz diffusion cells were used to study molecular transport through dermatomed porcine skin and histological analysis of laser-treated skin was performed after treatment with different laser pulse protocols. We were comparing different pulse durations at constant or varying pulse energies. We found that the energy of the delivered pulses mostly dictates the size/depth of laser-created microchannels, while the duration of the pulses dictates the extent of thermally altered tissue. That is, tissue ablation threshold is lowered at shorter pulse durations with higher power, which is preferred as it lowers thermal effects on viable skin layers. Especially for smaller molecules, transdermal delivery is increased by increasing laser-created microchannel size, but also by making partitioning into tissue easier when less thermal damage is caused on tissue. For large molecules, molecular transport through the remainder of skin tissue becomes increasingly difficult regardless of laser pulse parameters.

Experimental Factors to Be Considered in Electroporation-Mediated Transdermal Diffusion Experiments.

In this paper, we discuss some of the primary experimental factors that should be considered when interpreting and implementing the published results of skin electroporation studies concerning measurements of mass transport across the stratum corneum (SC) in the Franz cell. It is explained that the pulse magnitude should always be considered in the context of pulse shape and that transport measurements should always be presented in the context of the trans-SC potential difference (instead of the voltage between the electrodes). The condition of the SC prior to the application of the long-duration pulse strongly influences the evolution of the local transport region (LTR). This is quantified in a simple analytical investigation of the conditions that affect the thermodynamic response of the skin.

Ultrasound and electric pulses for transdermal drug delivery enhancement: Ex vivo assessment of methods with in vivo oriented experimental protocols.

In our present study we focus on two physical enhancement methods for transdermal drug delivery: ultrasound and electric pulses either alone or in combination. Great emphasis has been given on the design of the experimental system and protocols, so the results and the conclusions drawn from them would have greater relevance for in vivo use and later translation into clinical practice. Our results show a statistically significant enhancement of calcein delivery (after one hour of passive diffusion following treatment) already after 5 minutes of ultrasound application, or only 6 × 100 short high voltage electrical pulses. We also experimented with combinations of the two enhancement methods hoping for synergistic effects, however, the results showed no evident drastic improvement over single method. Looking closer at physics of both methods, this absence of synergy in our in vivo oriented experimental setting is not surprising. The mechanism of action of both methods is the creation of aqueous pathways in the stratum corneum leading to increased skin permeability. However, when used in combination (regardless of the order of methods), the second method was unsuccessful in adding many new aqueous pathways in the stratum corneum, as it acted preferentially near the sites of the existing ones.

Transdermal transport pathway creation: Electroporation pulse order.

In this study we consider the physics underlying electroporation which is administered to skin in order to radically increase transdermal drug delivery. The method involves the application of intense electric fields to alter the structure of the impermeable outer layer, the stratum corneum. A generally held view in the field of skin electroporation is that the skin's drop in resistance (to transport) is proportional to the total power of the pulses (which may be inferred by the number of pulses administered). Contrary to this belief, experiments conducted in this study show that the application of high voltage pulses prior to the application of low voltage pulses result in lower transport than when low voltage pulses alone are applied (when less total pulse power is administered). In order to reconcile these unexpected experimental results, a computational model is used to conduct an analysis which shows that the high density distribution of very small aqueous pathways through the stratum corneum associated with high voltage pulses is detrimental to the evolution of larger pathways that are associated with low voltage pulses.

Skin electroporation for transdermal drug delivery: the influence of the order of different square wave electric pulses.

Electroporation can be used as an active enhancement method for intra- and transdermal drug delivery. Differences in response of skin to electric pulses depend on their amplitude, duration and number and have been a point of interest in the past. While protocols consisting of the same repetitive, mostly exponentially decaying pulses have been used before, this study is focused on comparing different combinations of square wave short high voltage (HV) and longer low voltage (LV) electroporation pulses. Our in vitro experimental results show that longer LV pulses significantly increase subsequent passive transport of calcein through dermatomed pig skin, while short HV pulses alone result in negligible calcein passive transdermal transport. Surprisingly, when the long LV pulses are preceded by short duration HV pulses, the total calcein transported is reduced significantly. This result is explained using a theoretical physics based model of individual local transport region (LTR) evolution during the applied LV pulse. The theoretical model shows that HV pulses alter the structure of the stratum corneum in such a way that when the LV pulses are applied, insufficient thermal energy is generated to initiate LTR expansion. Together, the experimental results and theoretical predictions show that the total pulse energy alone cannot account for total solute transport: that the order of the types of pulses administered must also be considered. Our findings open a direction for further improvement of the method using new protocols.