Spinning with exosomes: electrospun nanofibers for efficient targeting of stem cell-derived exosomes in tissue regeneration.

Electrospinning technique converts polymeric solutions into nanoscale fibers using an electric field and can be used for various biomedical and clinical applications. Extracellular vesicles (EVs) are cell-derived small lipid vesicles enriched with biological cargo (proteins and nucleic acids) potential therapeutic applications. In this review, we discuss extending the scope of electrospinning by incorporating stem cell-derived EVs, particularly exosomes, into nanofibers for their effective delivery to target tissues. The parameters used during the electrospinning of biopolymers limit the stability and functional properties of cellular products. However, with careful consideration of process requirements, these can significantly improve stability, leading to longevity, effectiveness, and sustained and localized release. Electrospun nanofibers are known to encapsulate or surface-adsorb biological payloads such as therapeutic EVs, proteins, enzymes, and nucleic acids. Small EVs, specifically exosomes, have recently attracted the attention of researchers working on regeneration and tissue engineering because of their broad distribution and enormous potential as therapeutic agents. This review focuses on current developments in nanofibers for delivering therapeutic cargo molecules, with a special emphasis on exosomes. It also suggests prospective approaches that can be adapted to safely combine these two nanoscale systems and exponentially enhance their benefits in tissue engineering, medical device coating, and drug delivery applications.

Kuragel: A biomimetic hydrogel scaffold designed to promote corneal regeneration.

Cornea-related injuries are the most common cause of blindness worldwide. Transplantation remains the primary approach for addressing corneal blindness, though the demand for donor corneas outmatches the supply by millions. Tissue adhesives employed to seal corneal wounds have shown inefficient healing and incomplete vision restoration. We have developed a biodegradable hydrogel - Kuragel, with the ability to promote corneal regeneration. Functionalized gelatin and hyaluronic acid form photo-crosslinkable hydrogel with transparency and compressive modulus similar to healthy human cornea. Kuragel composition was tuned to achieve sufficient adhesive strength for sutureless integration to host tissue, with minimal swelling post-administration. Studies in the New Zealand rabbit mechanical injury model affecting corneal epithelium and stroma demonstrate that Kuragel efficiently promotes re-epithelialization within 1 month of administration, while stroma and sub-basal nerve plexus regenerate within 3 months. We propose Kuragel as a regenerative treatment for patients suffering from corneal defects including thinning, by restoration of transparency and thickness.

Biopolymeric corneal lenticules by digital light processing based bioprinting: a dynamic substitute for corneal transplant.

Digital light processing (DLP) technology has gained significant attention for its ability to construct intricate structures for various applications in tissue modeling and regeneration. In this study, we aimed to design corneal lenticules using DLP bioprinting technology, utilizing dual network bioinks to mimic the characteristics of the human cornea. The bioink was prepared using methacrylated hyaluronic acid and methacrylated gelatin, where ruthenium salt and sodium persulfate were included for mediating photo-crosslinking while tartrazine was used as a photoabsorber. The bioprinted lenticules were optically transparent (85.45% ± 0.14%), exhibited adhesive strength (58.67 ± 17.5 kPa), and compressive modulus (535.42 ± 29.05 kPa) sufficient for supporting corneal tissue integration and regeneration. Puncture resistance tests and drag force analysis further confirmed the excellent mechanical performance of the lenticules enabling their application as potential corneal implants. Additionally, the lenticules demonstrated outstanding support for re-epithelialization and stromal regeneration when assessed with human corneal stromal cells. We generated implant ready corneal lenticules while optimizing bioink and bioprinting parameters, providing valuable solution for individuals suffering from various corneal defects and waiting for corneal transplants.

Intermittent scavenging of storage lesion from stored red blood cells by electrospun nanofibrous sheets enhances their quality and shelf-life.

Transfusion of healthy red blood cells (RBCs) is a lifesaving process. However, upon storing RBCs, a wide range of damage-associate molecular patterns (DAMPs), such as cell-free DNA, nucleosomes, free-hemoglobin, and poly-unsaturated-fatty-acids are generated. DAMPs can further damage RBCs; thus, the quality of stored RBCs declines during the storage and limits their shelf-life. Since these DAMPs consist of either positive or negative charged species, we developed taurine and acridine containing electrospun-nanofibrous-sheets (Tau-AcrNFS), featuring anionic, cationic charges and an DNA intercalating group on their surfaces. We show that Tau-AcrNFS are efficient in scavenging DAMPs from stored human and mice RBCs ex vivo. We find that intermittent scavenging of DAMPs by Tau-AcrNFS during the storage reduces the loss of RBC membrane integrity and reduces discocytes-to-spheroechinocytes transformation in stored-old-RBCs. We perform RBC-transfusion studies in mice to reveal that intermittent removal of DAMPs enhances the quality of stored-old-RBCs equivalent to freshly collected RBCs, and increases their shelf-life by ~22%. Such prophylactic technology may lead to the development of novel blood bags or medical device, and may therefore impact healthcare by reducing transfusion-related adverse effects.

Cross-linker-free sodium alginate and gelatin hydrogels: a multiscale biomaterial design framework.

Surface functionalization and cross-linking have been adopted extensively by researchers to customize hydrogel properties, especially in the last decade. The clinical translation of such biomaterials is in a poor state due to long-term toxicity, often beyond the periphery of the short-term animal studies. We endeavor to relook at the material development strategy with all FDA-approved biopolymers in their native states, like gelatin and sodium alginate, without using any functionalization and cross-linking. The fabrication of a cross-linker-free hydrogel has remained one of the main challenges in biomaterial design and requires multiscale structuring of the hydrogels. The physical properties of these hydrogels were enhanced by plasticizers (PEG and glycerol) and a monovalent salt (NaCl). An in-depth analysis suggested that PEG forms a plasticizing layer at the sodium alginate and gelatin interface and glycerol alters the overall polymer structure. The results were further complemented by different characterization methods (scattering techniques and infrared spectroscopy) and molecular dynamics simulations. The detailed microstructural analysis surfaced the enthralling integrated swelling mechanism in gelatin chains that led to high-performing hydrogels.

Oral Drug Delivery: Conventional to Long Acting New-Age Designs.

The Oral route of administration forms the heartwood of the ever-growing tree of drug delivery technology. It is one of the most preferred dosage forms among patients and controlled release community. Despite the high patient compliance, the deliveries of anti-cancerous drugs, vaccines, proteins, etc. via the oral route are limited and have recorded a very low bioavailability. The oral administration must overcome the physiological barriers (low solubility, permeation and early degradation) to achieve efficient and sustained delivery. This review aims at highlighting the conventional and modern-age strategies that address some of these physiological barriers. The modern age designs include the 3D printed devices and formulations. The superiority of 3D dosage forms over conventional cargos is summarized with a focus on long-acting designs. The innovations in Pharmaceutical organizations (Lyndra, Assertio and Intec) that have taken giant steps towards commercialization of long-acting vehicles are discussed. The recent advancements made in the arena of oral peptide delivery are also highlighted. The review represents a comprehensive journey from Nano-formulations to micro-fabricated oral implants aiming at specific patient-centric designs.

Microneedles for Extended Transdermal Therapeutics: A Route to Advanced Healthcare.

Sustained release of drugs over a pre-determined period is required to maintain an effective therapeutic dose for variety of drug delivery applications. Transdermal devices such as polymeric microneedle patches and other microneedle-based devices have been utilized for sustained release of their payload. Swift clearing of drugs can be prevented either by designing a slow-degrading polymeric matrix or by providing physiochemical triggers to different microneedle-based devices for on-demand release. These long-acting transdermal devices prevent the burst release of drugs. This review highlights the recent advances of microneedle-based devices for sustained release of vaccines, hormones, and antiretrovirals with their prospective safe clinical translation.

Physicochemical Response of Gelatin in a Coulombic Soup of Monovalent Salt: A Molecular Simulation and Experimental Study.

The effect of salt on the static properties of aqueous solution of gelatin is studied by molecular dynamics simulation at pH = 1.2, 7, and 10. At the isoelectric point (pH = 7), a monotonic increase in size of the polymer is obtained with the addition of sodium chloride ions. In the positive polyelectrolyte regime (pH = 1.2), collapse of gelatin is observed with increase in salt concentration. In the negative polyelectrolyte regime, we observe an interesting collapse-reexpansion behavior. This is due to the screening of repulsion between the excess charges followed by the screening of attraction of oppositely charged ions as the salt concentration is increased. This mechanism is very different from the charge inversion mechanism which causes the reexpansion in the presence of multivalent ions. The location of salt concentration corresponding to the minimum size of the chain is comparable to the theoretical estimate. The shift in the peak of radial distribution function calculated between monomers and salt ions confirms this spatial reorganization. The predictions from the simulation are verified by dynamic light scattering(DLS) and small-angle X-ray scattering (SAXS) experiments. The size of the hydrodynamic "clusters" obtained from DLS confirms the simulation predictions. Persistence length of the gelatin is calculated from SAXS to get single chain statistics, which also agrees well with the simulation results.

Piperine as a Placebo: Stability of Gelatin Capsules without a Cross-Linker.

Gelatin has been the biomaterial of choice for decades now. Its low cost, renewable, nontoxic, and biodegradable properties make it one of the most desirable materials for controlled release applications. However, the usage of gelatin is limited by its poor mechanical/thermal stability and high water solubility. Chemical cross-linkers and hydrophobic modifications of gelatin have solved this problem, but they lead to the problem of toxicity and/or a high processing cost. This research attempts to employ a nontoxic hydrophobic drug molecule to curb early degradation of gelatin in an aqueous environment. We report the design of non-cross-linked gelatin capsules with a high dissolution resistance in an aqueous medium. Piperine, a hydrophobic drug (solubility = 40 mg/L in water), was coated on the gelatin capsules to enhance its stability in an aqueous environment. The hydrophobic piperine molecules repelled the water molecules to intensify its dissolution resistance. This stabilization was used to control the release of naproxen sodium, encapsulated inside the gelatin matrix. Piperine, in this case, acts as a placebo; i.e., it has zero therapeutic effect, but its presence was necessary to control the early degradation of the gelatin matrix. The deposition of piperine was done using the solvent evaporation method where ethanol was used as the solvent. The wettability studies revealed the hydrophobic nature of the surface after the deposition of piperine, while SEM analysis showed the presence of long cylindrical (fiber-like) structures over the gelatin surface. Further investigation (FTIR/ATR and molecular dynamics) revealed that the long fiber structures were due to the crystallization of piperine over the surface of gelatin. This crystallization was triggered by the intermolecular association (hydrogen bond) of ethanol and piperine. These observations enabled us to optimize the piperine loading protocol over the gelatin capsules that helped in achieving a zero-order naproxen release for 32 h.