Bacterial nanocellulose-hyaluronic acid microneedle patches for skin applications: In vitro and in vivo evaluation.

The aim of the present study was to develop innovative patches for dermo-cosmetic applications based on dissolvable hyaluronic acid (HA) microneedles (MNs) combined with bacterial nanocellulose (BC) as the back layer. HA was employed as an active biomacromolecule, with hydrating and regenerative properties and volumizing effect, whereas BC was used as support for the incorporation of an additional bioactive molecule. Rutin, a natural antioxidant, was selected as the model bioactive compound to demonstrate the effectiveness of the system. The obtained HA-MNs arrays present homogenous and regular needles, with 200 µm in base width, 450 µm in height and 500 µm tip-to-tip distance, and with sufficient mechanical force to withstand skin insertion with a failure force higher than 0.15 N per needle. The antioxidant activity of rutin was neither affected by its incorporation in the MNs system nor by their storage at room temperature for 6 months. Preliminary in vivo studies in human volunteers unveiled their safety and cutaneous compatibility, as no significant changes in barrier function, stratum corneum hydration nor redness were detected. These results confirm the potentiality of this novel system for skin applications, e.g. cosmetics, taking advantage of the recognized properties of HA and the capacity of BC to control the release of bioactive molecules.

Antibacterial Multi-Layered Nanocellulose-Based Patches Loaded with Dexpanthenol for Wound Healing Applications.

Antibacterial multi-layered patches composed of an oxidized bacterial cellulose (OBC) membrane loaded with dexpanthenol (DEX) and coated with several chitosan (CH) and alginate (ALG) layers were fabricated by spin-assisted layer-by-layer (LbL) assembly. Four patches with a distinct number of layers (5, 11, 17, and 21) were prepared. These nanostructured multi-layered patches reveal a thermal stability up to 200 °C, high mechanical performance (Young's modulus ≥ 4 GPa), and good moisture-uptake capacity (240-250%). Moreover, they inhibited the growth of the skin pathogen Staphylococcus aureus (3.2-log CFU mL-1 reduction) and were non-cytotoxic to human keratinocytes (HaCaT cells). The in vitro release profile of DEX was prolonged with the increasing number of layers, and the time-dependent data imply a diffusion/swelling-controlled drug release mechanism. In addition, the in vitro wound healing assay demonstrated a good cell migration capacity, headed to a complete gap closure after 24 h. These results certify the potential of these multi-layered polysaccharides-based patches toward their application in wound healing.

Pullulan microneedle patches for the efficient transdermal administration of insulin envisioning diabetes treatment.

The present study reports the fabrication of dissolvable microneedle (MN) patches using pullulan (PL), a water-soluble polysaccharide with excellent film-forming ability, for the transdermal administration of insulin, envisioning the non-invasive treatment of diabetes. PL MNs patches were successfully prepared by micromoulding and revealed good thermal stability (Tdmax = 294 °C) and mechanical properties (>0.15 N needle-1), penetrating skin up to 381 µm depth, as revealed by in vitro skin tests. After application into human abdominal skin in vitro, the MNs dissolved within 2 h releasing up to 87% of insulin. When stored at 4, 20 and 40 °C for 4 weeks, insulin was able to retain its secondary structure, as shown by circular dichroism spectropolarimetry. The prepared PL MNs were non-cytotoxic towards human keratinocytes, being suitable for skin application. These findings suggest that PL MNs have potential to deliver insulin transdermally, thus avoiding its subcutaneous administration.

Swellable Gelatin Methacryloyl Microneedles for Extraction of Interstitial Skin Fluid toward Minimally Invasive Monitoring of Urea.

Urea, the main nitrogenous waste product of protein metabolism, is eliminated almost exclusively by the kidney, and hence, displays considerable clinical significance in the assessment of kidney disorders. The aim of this study is to prepare and investigate the potential of swellable cross-linked gelatin methacryloyl (c-GelMA) microneedles (MNs) as a platform for minimally invasive extraction of interstitial skin fluid (ISF) toward straightforward point-of-care healthcare monitoring of renal complaints, by quantification of urea. c-GelMA MNs are successfully prepared by photo-cross-linking and micromolding, faithfully replicating the master molds (387 ± 16 µm height, 200 µm base and 500 µm tip-to-tip distance). These MN patches display good mechanical properties, withstanding more than 0.15 N per needle without breaking. Ex vivo skin insertion assays reveal that the MNs penetrate up to 237 µm depth, reaching the dermis, where they should extract ISF considering a real application. In an in vitro application using an agarose skin model system, the c-GelMA MNs are able to efficiently recover urea (>98%). Additionally, these MNs exhibit noncytotoxic effects toward human keratinocytes. These findings suggest that c-GelMA MNs are promising devices for sampling ISF and offline analysis of urea, opening new avenues for simple point-of-care healthcare monitoring.

A compendium of current developments on polysaccharide and protein-based microneedles.

Microneedles (MNs), i.e. minimally invasive three-dimensional microstructures that penetrate the stratum corneum inducing relatively little or no pain, have been studied as appealing therapeutic vehicles for transdermal drug delivery. Over the last years, the fabrication of MNs using biopolymers, such as polysaccharides and proteins, has sparked the imagination of scientists due to their recognized biocompatibility, biodegradability, ease of fabrication and sustainable character. Owing to their wide range of functional groups, polysaccharides and proteins enable the design and preparation of materials with tunable properties and functionalities. Therefore, these biopolymer-based MNs take a revolutionary step offering great potential not only in drug administration, but also in sensing and response to physiological stimuli. In this review, a critical and comprehensive overview of the polysaccharides and proteins employed in the design and engineering of MNs will be given. The strategies adopted for their preparation, their advantages and disadvantages will be also detailed. In addition, the potential and challenges of using these matrices to deliver drugs, vaccines and other molecules will be discussed. Finally, this appraisal ends with a perspective on the possibilities and challenges in research and development of polysaccharide and protein MNs, envisioning the future advances and clinical translation of these platforms as the next generation of drug delivery systems.

Bioactive Phytochemicals from Wild Arbutus unedo L. Berries from Different Locations in Portugal: Quantification of Lipophilic Components.

The lipophilic composition of wild Arbutus unedo L. berries, collected from six locations in Penacova (center of Portugal), as well as some general chemical parameters, namely total soluble solids, pH, titratable acidity, total phenolic content and antioxidant activity was studied in detail to better understand its potential as a source of bioactive compounds. The chemical composition of the lipophilic extracts, focused on the fatty acids, triterpenoids, sterols, long chain aliphatic alcohols and tocopherols, was investigated by gas chromatography-mass spectrometry (GC-MS) analysis of the dichloromethane extracts. The lipophilic extractives of the ripe A. unedo berries ranged from 0.72% to 1.66% (w/w of dry weight), and consisted mainly of triterpenoids, fatty acids and sterols. Minor amounts of long chain aliphatic alcohols and tocopherols were also identified. Forty-one compounds were identified and among these, ursolic acid, lupeol, α-amyrin, linoleic and α-linolenic acids, and ß-sitosterol were highlighted as the major components. To the best of our knowledge the current research study provides the most detailed phytochemical repository for the lipophilic composition of A. unedo, and offers valuable information for future valuation and exploitation of these berries.