Adenosine-associated delivery systems

Adenosine Encapsulation and Characterization through Layer-by-Layer Assembly of Hydroxypropyl-β-Cyclodextrin and Whey Protein Isolate as Wall Materials

Adenosine, as a water-soluble active substance, has various pharmacological effects. This study proposes a layer-by-layer assembly method of composite wall materials, using hydroxypropyl-β-cyclodextrin as the inner wall and whey protein isolate as the outer wall, to encapsulate adenosine within the core material, aiming to enhance adenosine microcapsules' stability through intermolecular interactions. By combining isothermal titration calorimetry with molecular modeling analysis, it was determined that the core material and the inner wall and the inner wall and the outer wall interact through intermolecular forces. Adenosine and hydroxypropyl-β-cyclodextrin form an optimal 1:1 complex through hydrophobic interactions, while hydroxypropyl-β-cyclodextrin and whey protein isolate interact through hydrogen bonds. The embedding rate of AD/Hp-β-CD/WPI microcapsules was 36.80%, and the 24 h retention rate under the release behavior test was 76.09%. The method of preparing adenosine microcapsules using composite wall materials is environmentally friendly and shows broad application prospects in storage and delivery systems with sustained release properties.

Biomaterials for Protein Delivery: Opportunities and Challenges to Clinical Translation

The development of biomaterials for protein delivery is an emerging field that spans materials science, bioengineering, and medicine. In this review, we highlight the immense potential of protein-delivering biomaterials as therapeutic options and discuss the multifaceted challenges inherent to the field. We address current advancements and approaches in protein delivery that leverage stimuli-responsive materials, harness advanced fabrication techniques like 3D printing, and integrate nanotechnologies for greater targeting and improved stability, efficacy, and tolerability profiles. We also discuss the demand for highly complex delivery systems to maintain structural integrity and functionality of the protein payload. Finally, we discuss barriers to clinical translation, such as biocompatibility, immunogenicity, achieving reliable controlled release, efficient and targeted delivery, stability issues, scalability of production, and navigating the regulatory landscape for such materials. Overall, this review summarizes insights from a survey of the current literature and sheds light on the interplay between innovation and the practical implementation of biomaterials for protein delivery.

An adenosine derivative prevents the alterations observed in metabolic syndrome in a rat model induced by a rich high-fat diet and sucrose supplementation

Metabolic syndrome is a multifactorial disease with high prevalence worldwide. It is related to cardiovascular disease, diabetes, and obesity. Approximately 80% of patients with metabolic syndrome have some degree of fatty liver disease. An adenosine derivative (IFC-305) has been shown to exert protective effects in models of liver damage as well as on elements involved in central metabolism; therefore, here, we evaluated the effect of IFC-305 in an experimental model of metabolic syndrome in rats induced by a high-fat diet and 10% sucrose in drinking water for 18 weeks. We also determined changes in fatty acid uptake in the Huh-7 cell line. In the experimental model, increases in body mass, serum triglycerides and proinflammatory cytokines were induced in rats, and the adenosine derivative significantly prevented these changes. Interestingly, IFC-305 prevented alterations in glucose and insulin tolerance, enabling the regulation of glucose levels in the same way as in the control group. Histologically, the alterations, including mitochondrial morphological changes, observed in response to the high-fat diet were prevented by administration of the adenosine derivative. This compound exerted protective effects against metabolic syndrome, likely due to its action in metabolic regulation, such as in the regulation of glucose blood levels and hepatocyte fatty acid uptake.

Pathophysiological and Molecular Basis of the Side Effects of Ticagrelor: Lessons from a Case Report

Ticagrelor is currently considered a first-line choice in dual antiplatelet therapy (DAPT) following revascularization of acute coronary syndrome (ACS). However, its use is correlated with an increased incidence of two side effects, dyspnea and bradyarrhythmias, whose molecular mechanisms have not yet been defined with certainty and, consequently, neither of the therapeutic decisions they imply. We report the case of a patient with acute myocardial infarction treated with ticagrelor and aspirin as oral antithrombotic therapy after primary percutaneous coronary intervention (PCI), manifesting in a significant bradyarrhythmic episode that required a switch of antiplatelet therapy. Starting from this case report, this article aims to gather the currently available evidence regarding the molecular mechanisms underlying these side effects and propose possible decision-making algorithms regarding their management in clinical practice.

Assessment of Squalene-Adenosine Nanoparticles in Two Rodent Models of Cardiac Ischemia-Reperfusion

Reperfusion injuries after a period of cardiac ischemia are known to lead to pathological modifications or even death. Among the different therapeutic options proposed, adenosine, a small molecule with platelet anti-aggregate and anti-inflammatory properties, has shown encouraging results in clinical trials. However, its clinical use is severely limited because of its very short half-life in the bloodstream. To overcome this limitation, we have proposed a strategy to encapsulate adenosine in squalene-based nanoparticles (NPs), a biocompatible and biodegradable lipid. Thus, the aim of this study was to assess, whether squalene-based nanoparticles loaded with adenosine (SQAd NPs) were cardioprotective in a preclinical cardiac ischemia/reperfusion model. Obtained SQAd NPs were characterized in depth and further evaluated in vitro. The NPs were formulated with a size of about 90 nm and remained stable up to 14 days at both 4 °C and room temperature. Moreover, these NPs did not show any signs of toxicity, neither on HL-1, H9c2 cardiac cell lines, nor on human PBMC and, further retained their inhibitory platelet aggregation properties. In a mouse model with experimental cardiac ischemia-reperfusion, treatment with SQAd NPs showed a reduction of the area at risk, as well as of the infarct area, although not statistically significant. However, we noted a significant reduction of apoptotic cells on cardiac tissue from animals treated with the NPs. Further studies would be interesting to understand how and through which mechanisms these nanoparticles act on cardiac cells.

Extracellular adenosine signaling in bone health and disease

Purinergic signaling is a key molecular pathway in the maintenance of bone health and regeneration. P1 receptor signaling, which is activated by extracellular adenosine, has emerged as a key metabolic pathway that regulates bone tissue formation, function, and homeostasis. Extracellular adenosine is mainly produced by ectonucleotidases, and alterations in the function of these enzymes or compromised adenosine generation can result in bone disorders, such as osteoporosis and impaired fracture healing. This mini review discusses the key role played by adenosine in bone health and how its alterations contribute to bone diseases, as well as potential therapeutic applications of exogenous adenosine to combat bone diseases like osteoporosis and injury.

Epilepsy and Autism Spectrum Disorder (ASD): The Underlying Mechanisms and Therapy Targets Related to Adenosine

Epilepsy and autism spectrum disorder (ASD) are highly mutually comorbid, suggesting potential overlaps in genetic etiology, pathophysiology, and neurodevelopmental abnormalities. Adenosine, an endogenous anticonvulsant and neuroprotective neuromodulator of the brain, has been proved to affect the process of epilepsy and ASD. On the one hand, adenosine plays a crucial role in preventing the progression and development of epilepsy through adenosine receptordependent and -independent ways. On the other hand, adenosine signaling can not only regulate core symptoms but also improve comorbid disorders in ASD. Given the important role of adenosine in epilepsy and ASD, therapeutic strategies related to adenosine, including the ketogenic diet, neuromodulation therapy, and adenosine augmentation therapy, have been suggested for the arrangement of epilepsy and ASD. There are several proposals in this review. Firstly, it is necessary to further discuss the relationship between both diseases based on the comorbid symptoms and mechanisms of epilepsy and ASD. Secondly, it is important to explore the role of adenosine involved in epilepsy and ASD. Lastly, potential therapeutic value and clinical approaches of adenosine-related therapies in treating epilepsy and ASD need to be emphasized.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and M^pro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Suppressed renoprotective purines in COVID-19 patients with acute kidney injury

Acute kidney injury (AKI) is common in patients hospitalized for COVID-19, complicating their clinical course and contributing to worse outcomes. Animal studies show that adenosine, inosine and guanosine protect the kidney against some types of AKI. However, until now there was no evidence in patients supporting the possibility that abnormally low kidney levels of adenosine, inosine and guanosine contribute to AKI. Here, we addressed the question as to whether these renoprotective purines are altered in the urine of COVID-19 patients with AKI. Purines were measured by employing ultra-high-performance liquid chromatography-tandem mass spectrometry with stable-isotope-labeled internal standards for each purine of interest. Compared with COVID-19 patients without AKI (n = 23), COVID-19 patients with AKI (n = 20) had significantly lower urine levels of adenosine (P < 0.0001), inosine (P = 0.0008), and guanosine (P = 0.0008) (medians reduced by 85%, 48% and 61%, respectively) and lower levels (P = 0.0003; median reduced by 67%) of the 2nd messenger for A2A and A2B adenosine receptors, i.e., 3',5'-cAMP. Moreover, in COVID-19 patients with AKI, urine levels of 8-aminoguanine (endogenous inhibitor of inosine and guanosine metabolism) were nearly abolished (P < 0.0001). In contrast, the "upstream" precursors of renoprotective purines, namely 5'-AMP and 5'-GMP, were not significantly altered in COVID-19 patients with AKI, suggesting defective conversion of these precursors by CD73 (converts 5'-AMP to adenosine and 5'-GMP to guanosine). These findings imply that an imbalance in renoprotective purines may contribute to AKI in COVID-19 patients and that pharmacotherapy targeted to restore levels of renoprotective purines may attenuate the risk of AKI in susceptible patients with COVID-19.

pH-Sensitive nanocarrier assisted delivery of adenosine to treat osteoporotic bone loss

Bone tissue undergoes continuous remodeling via osteoclast-mediated bone resorption and osteoblast-mediated bone formation. An imbalance in this process with enhanced osteoclastic activity can lead to excessive bone resorption, resulting in bone thinning. Once activated, osteoclasts bind to the bone surface and acidify the local niche. This acidic environment could serve as a potential trigger for the delivery of therapeutic agents into the osteoporotic bone tissue. To this end, we developed a pH-responsive nanocarrier-based drug delivery system that binds to the bone tissue and delivers an osteoanabolic molecule, adenosine. Adenosine is incorporated into a hyaluronic acid (HA)-based nanocarrier through a pH-sensitive ketal group. The HA-nanocarrier is further functionalized with alendronate moieties to improve binding to the bone tissues. Systemic administration of the nanocarrier containing adenosine attenuated bone loss in ovariectomized mice and showed comparable bone qualities to that of healthy mice. Delivery of osteoanabolic small molecules that can contribute to bone formation and inhibit excessive osteoclast activity by leveraging the tissue-specific milieu could serve as viable therapeutics for osteoporosis.

Recrystallization of Adenosine for Localized Drug Delivery

Adenosine (ADO) is an endogenous metabolite with immense potential to be repurposed as an immunomodulatory therapeutic, as preclinical studies have demonstrated in models of epilepsy, acute respiratory distress syndrome, and traumatic brain injury, among others. The currently licensed products Adenocard and Adenoscan are formulated at 3 mg/mL of ADO for rapid bolus intravenous injection, but the systemic administration of the saline formulations for anti-inflammatory purposes is limited by the nucleoside's profound hemodynamic effects. Moreover, concentrations that can be attained in the airway or the brain through direct instillation or injection are limited by the volumes that can be accommodated in the anatomical space (<5 mL in humans) and the rapid elimination by enzymatic and transport mechanisms in the interstitium (half-life <5 s). As such, highly concentrated formulations of ADO are needed to attain pharmacologically relevant concentrations at sites of tissue injury. Herein, we report a previously uncharacterized crystalline form of ADO (rcADO) in which 6.7 mg/mL of the nucleoside is suspended in water. Importantly, the crystallinity is not diminished in a protein-rich environment, as evidenced by resuspending the crystals in albumin (15% w/v). To the best of our knowledge, this is the first report of crystalline ADO generated using a facile and organic solvent-free method aimed at localized drug delivery. The crystalline suspension may be suitable for developing ADO into injectable formulations for attaining high concentrations of the endogenous nucleoside in inflammatory locales.

Skin Penetration Enhancer-Incorporated Lipid Nanovesicles (SPE-LNV) for Skin Brightening and Wrinkle Treatment

In this work, we utilize skin penetration enhancers (SPEs) such as ceramide and fatty acids in lipid nanovesicles to promote the transdermal delivery of active ingredients. These SPE-incorporated lipid nanovesicles (SPE-LNV) interact with the constituents of skin's outermost stratum corneum (SC) layer, enabling even niacinamide and adenosine with high water solubility to effectively permeate through, leading to enhanced skin efficacy. We demonstrate by both in vitro and in vivo skin permeation studies that the SPE-LNV formulation containing both ceramide and fatty acids (LNV-CF) exhibits deeper penetration depth and faster permeation rate compared to conventional lipid nanovesicles (LNV) without SPE as well as LNV-C with only ceramide. Moreover, in vivo clinical trials were also performed to confirm that LNV-CF most effectively mediates the delivery of niacinamide and adenosine, resulting in a substantial decrease in melanin index as well as skin wrinkle compared to the control groups. We envision that the strategy of incorporating both ceramide and fatty acids in lipid nanovesicles offers a simple and convenient route for the rapid and effective delivery of water-soluble active ingredients across the skin barrier layer.

Gene therapy in epilepsy

Gene therapy may constitute a promising alternative to conventional pharmacological tools and surgeries for epilepsy. For primary epilepsy, a single variant leading to a significant effect is relatively rare, while other forms are considered complex in inheritances with multiple susceptible mutations and impacts from the environment. Gene therapy in preclinical models of epilepsy has attempted to perform antiepileptogenic, anticonvulsant, or disease-modifying effects during epileptogenesis or after establishing the disease. Creating gene vectors tailored for different situations is the key to expanding gene therapy, and choosing the appropriate therapeutic target remains another fundamental problem. A variety of treatment strategies, from overexpressing inhibitory neuropeptides to modulating the expression of neurotransmitters or ion channels, have been tested in animal models. Additionally, emerging new approaches of optogenetics and chemogenetics, as well as genome-editing tools will further boost the prosperity of gene therapy. This review summarizes the experience obtained to date and discusses the challenges and opportunities in clinical translations.

Recent advances on drug delivery nanocarriers for cerebral disorders

Pharmacotherapies for brain disorders are generally faced with obstacles from the blood-brain barrier (BBB). There are a variety of drug delivery systems that have been put forward to cross or bypass the BBB with the access to the central nervous system. Brain drug delivery systems have benefited greatly from the development of nanocarriers, including lipids, polymers and inorganic materials. Consequently, various kinds of brain drug delivery nano-systems have been established, such as liposomes, polymeric nanoparticles (PNPs), nanomicelles, nanohydrogels, dendrimers, mesoporous silica nanoparticles and magnetic iron oxide nanoparticles. The characteristics of their carriers and preparations usually differ from each other, as well as their transportation mechanisms into intracerebral lesions. In this review, different types of brain drug delivery nanocarriers are classified and summarized, especially their significant achievements, to present several recommendations and directions for future strategies of cerebral delivery.

Design and Characterization of Elastic Artificial Skin Containing Adenosine-Loaded Solid Lipid Nanoparticles for Treating Wrinkles

Adenosine (AD), which is used for treating wrinkles, exhibits poor skin permeation. The aim of the present study was to develop a cross-linked silicone-based cellulose elastomer as an elastic artificial skin for the treatment of skin wrinkles, a biocompatible lipid-based nano-carrier for enhancing the skin permeation of AD, and a formulation consisting of the lipid-based carrier incorporated in the elastic artificial skin. AD-loaded solid lipid nanoparticles (SLNs) were prepared using a double-emulsion method. Particle characteristics and mechanical properties of SLNs and elastic artificial skin, respectively, were assessed. Skin permeation was evaluated using SkinEthic RHE tissue, a reconstructed human epidermis model. The mean particle size and zeta potential for SLNs ranged from 123.57 to 248.90 nm and -13.23 to -41.23 mV, respectively. The components of neither SLNs nor the elastic artificial skin were cytotoxic, according to cell- and tissue-viability assays and EU classification. SLNs and the elastic artificial skin exhibited sustained drug release for 48 h. The amount of AD released from SLNs and elastic artificial skin was approximately 10 times and 5 times higher, respectively, than that from AD solution. Therefore, elastic artificial skin incorporated with AD-loaded SLNs may serve as a promising topical delivery system for cosmeceutical treatment of skin wrinkles.

Ticagrelor-Related Severe Dyspnoea: Mechanisms, Characteristic Features, Differential Diagnosis and Treatment

With a growing number of patients on ticagrelor therapy after stent implantation, we observe many cases of side effects of the drug, mostly dyspnoea and bradycardia. In our article we present 2 patients, in which the symptoms were particularly severe. Then we describe possible mechanisms of these complications, explain how to carry out differential diagnosis, discuss when to switch ticagrelor to other antiplatelet drug and finally we present the way to deal with the symptoms.

Polydopamine-assisted one-step modification of nanofiber surfaces with adenosine to tune the osteogenic differentiation of mesenchymal stem cells and the maturation of osteoclasts

Adenosine and its receptors have emerged as alternative targets to control cellular functions for bone healing. However, the soluble delivery of adenosine has not proven effective because of its fast degradation in vivo. We therefore designed a stable coating of adenosine for biomaterial surfaces through polydopamine chemistry to control osteogenesis and osteoclastogenesis via A2bR signaling. First, we prepared electrospun poly (ι-lactic acid) (PLLA) nanofiber sheets, which were modified through a one-step adenosine polydopamine coating process. Scanning electron microscopy (SEM) revealed deposition of particles on the adenosine polydopamine-coated PLLA (AP-PL) sheets compared to the polydopamine-only sheets. Moreover, X-ray photoelectron spectroscopy analysis confirmed an increase in nitrogen signals due to adenosine. Furthermore, adenosine loading efficiency and retention were significantly enhanced in AP-PL sheets compared to polydopamine-only sheets. Human adipose-derived stem cells (hADSCs) cultured on AP-PL expressed A2bR (1.30 ± 0.19 fold) at significantly higher levels than those cultured on polydopamine-only sheets. This in turn significantly elevated the expression of Runx2 (16.94 ± 1.68 and 51.69 ± 0.07 fold), OPN (1.63 ± 0.16 and 30.56 ± 0.25 fold), OCN (1.16 ± 0.13 and 5.23 ± 0.16 fold), and OSX (10.01 ± 0.81 and 62.48 ± 0.25 fold) in cells grown in growth media on days 14 and 21, respectively. Similarly, mineral deposition was enhanced to a greater extent in the AP-PL group than the polydopamine group, while blocking of A2bR significantly downregulated osteogenesis. Finally, osteoclast differentiation of RAW 264.7 cells was significantly inhibited by growth on AP-PL sheets. However, osteoclast differentiation was significantly stimulated after A2bR was blocked. Taken together, we propose that polydopamine-assisted one-step coating of adenosine is a viable method for surface modification of biomaterials to control osteogenic differentiation of stem cells and bone healing.

Milk Metabolomics Reveals Potential Biomarkers for Early Prediction of Pregnancy in Buffaloes Having Undergone Artificial Insemination

This study aimed to identify potential biomarkers for early pregnancy diagnosis in buffaloes subjected to artificial insemination (AI). The study was carried out on 10 pregnant and 10 non-pregnant buffaloes that were synchronized by Ovsynch-Timed Artificial Insemination Program and have undergone the first AI. Furthermore, milk samples were individually collected ten days before AI (the start of the synchronization treatment), on the day of AI, day 7 and 18 after AI, and were analyzed by LC-MS. Statistical analysis was carried out by using Mass Profile Professional (Agilent Technologies, Santa Clara, CA, USA). Metabolomic analysis revealed the presence of several metabolites differentially expressed between pregnant and non-pregnant buffaloes. Among these, a total of five metabolites were identified by comparison with an online database and a standard compound as acetylcarnitine (3-Acetoxy-4-(trimethylammonio)butanoate), arginine-succinic acid hydrate, 5'-O-{[3-({4-[(3aminopropyl)amino]butyl}amino)propyl]carbamoyl}-2'-deoxyadenosine, N-(1-Hydroxy-2-hexadecanyl)pentadecanamide, and N-[2,3-Bis(dodecyloxy)propyl]-L-lysinamide). Interestingly, acetylcarnitine was dominant in milk samples collected from non-pregnant buffaloes. The results obtained from milk metabolic profile and hierarchical clustering analysis revealed significant differences between pregnant and non-pregnant buffaloes, as well as in the metabolite expression. Overall, the findings indicate the potential of milk metabolomics as a powerful tool to identify biomarkers of early pregnancy in buffalo undergoing AI.

Management of tachyarrhythmias in pregnancy - A review

The most common arrhythmias detected during pregnancy include sinus tachycardia, sinus bradycardia, and sinus arrhythmia, identified in 0.1% of pregnancies. Isolated premature atrial or ventricular arrhythmias are observed in 0.03% of pregnancies. Arrhythmias may become more frequent during pregnancy or may manifest for the first time.

Local release of NECA (5'-(N-ethylcarboxamido)adenosine) from implantable polymeric sheets for enhanced islet revascularization in extrahepatic transplantation site

Clinical intraportal pancreatic islet infusion is popular for treating type I diabetes. However, multiple doses of islets and anti-rejection protocols are needed to compensate for early large cell losses post-infusion due to the harsh hepatic environment. Thus, extrahepatic sites are utilized to enable efficient islet engraftment and reduce islet mass. Here, we reported an effective islet revascularization protocol that was based on the co-implantation of islet/fibrin gel construct with poly(lactic-co-glycolic) acid sheet releasing NECA (5'-(N-ethylcarboxamido) adenosine; a potent agonist of adenosine) into mouse epididymal fat pad. Thin, flexible sheets (d = 4 mm) prepared by simple casting exhibited sustained NECA release for up to 21 days, which effectively improved early islet engraftment with a median diabetic reversal time of 18.5 days. Western blotting revealed the facilitative effect of NECA on VEGF expression from islets in vitro and from grafts in vivo. In addition, NECA directly promoted the angiogenic activities of islet-derived endothelial cells by enhancing their proliferation and vessel-like tube formation. As a result, neovasculatures were effectively formed in the engrafted islet vicinity, as evidenced by vasculature imaging and immunofluorescence. Taken together, we suggest NECA-releasing PLGA sheets offer a safe and effective drug delivery system that enhances islet engraftment while reducing islet mass at extrahepatic sites for clinical relevance.

In Vivo Sequestration of Innate Small Molecules to Promote Bone Healing

Approaches that enable innate repair mechanisms hold great potential for tissue repair. Herein, biomaterial-assisted sequestration of small molecules is described to localize pro-regenerative signaling at the injury site. Specifically, a synthetic biomaterial containing boronate molecules is designed to sequester adenosine, a small molecule ubiquitously present in the human body. The biomaterial-assisted sequestration of adenosine leverages the transient surge of extracellular adenosine following injury to prolong local adenosine signaling. It is demonstrated that implantation of the biomaterial patch following injury establishes an in situ stockpile of adenosine, resulting in accelerated healing by promoting both osteoblastogenesis and angiogenesis. The adenosine content within the patch recedes to the physiological level as the tissue regenerates. In addition to sequestering endogenous adenosine, the biomaterial is also able to deliver exogenous adenosine to the site of injury, offering a versatile solution to utilizing adenosine as a potential therapeutic for tissue repair.

Stem cell spheroids incorporating fibers coated with adenosine and polydopamine as a modular building blocks for bone tissue engineering

Although stem cell spheroids offer great potential as functional building blocks for bottom-up bone tissue engineering, delivery of bioactive signals remain challenging. Here, we engineered adenosine-ligand-modified fiber fragments to create a 3D cell-instructive microenvironment for bone. Briefly, the Poly(ι-lactic acid) (PLLA) nanofiber sheet was partially degraded into fragmented fibers (FFs) through aminolysis and adenosine was stably incorporated via one-step polydopamine coating. The SEM and XPS analysis demonstrated that polydopamine assisted adenosine coating efficiency was significantly increased, which led to high coating efficiency of adenosine and its significant retention. The engineered fibers were then assembled into stable spheroids with human-adipose-derived stem cells (hADSCs). The adenosine in the spheroids effectively stimulated A2bR (1.768 ± 0.08) signaling, which further significantly induced the expression of osteogenic markers such as Runx2 (3.216 ± 0.25), OPN (4.136 ± 0.14), OCN (10.16 ± 0.34), and OSX (2.27 ± 0.11) with improved mineral deposition (1.375 ± 0.05 μg per spheroid). In contrast, the adipogenic differentiation of hADSCs was significantly suppressed within the engineered spheroids. Transplantation of engineered spheroids strongly induced osteogenic differentiation of hADSCs in ectopic subcutaneous tissue. Finally, the bone regeneration was significantly enhanced by implanting AP-FF group (59.97 ± 18.33%) as compared to P-FF (27.96 ± 11.14) and defect only (7.97 ± 3.76%). We propose that stem cell spheroids impregnated with engineered fibers enabling adenosine delivery could be promising building blocks for a bottom-up approach to create large tissues for regeneration of damaged bone.

Local delivery of adenosine receptor agonists to promote bone regeneration and defect healing

Adenosine receptor activation has been investigated as a potential therapeutic approach to heal bone. Bone has enhanced regenerative potential when influenced by either direct or indirect adenosine receptor agonism. As investigators continue to elucidate how adenosine influences bone cell homeostasis at the cellular and molecular levels, a small but growing body of literature has reported successful in vivo applications of adenosine delivery. This review summarizes the role adenosine receptor ligation plays in osteoblast and osteoclast biology and remodeling/regeneration. It also reports on all the modalities described in the literature at this point for delivery of adenosine through in vivo models for bone healing and regeneration.

Towards a clinical application of freeze-dried squalene-based nanomedicines

Squalene-adenosine (SQAd) nanoparticles (NPs) were found to display promising pharmacological activity similar to many other nanomedicines, but their long-term stability was still limited, and their preparation required specific know-how and material. These drawbacks represented important restrictions for their potential use in the clinic. Freeze-drying nanoparticles is commonly presented as a solution to allow colloidal stability, but this process needs to be adapted to each nanoformulation. Hence, we aimed at developing a specific protocol for freeze-drying SQAd NPs while preserving their structural features. NPs were lyophilised, resuspended and analysed by dynamic light scattering, atomic force microscopy and small-angle scattering. Among four different cryoprotectants, trehalose was found to be the most efficient in preserving NPs physico-chemical characteristics. Interestingly, we identified residual ethanol in NP suspensions as a key parameter which could severely affect the freeze-drying outcome, leading to NPs aggregation. Long-term stability was also assessed. No significant change in size distribution or zeta potential could be detected after three-month storage at 4 °C. Finally, freeze-dried NPs innocuity was checked in vitro on cultured hepatocytes and in vivo on mice. In conclusion, optimisation of freeze-drying conditions resulted in safe lyophilised SQAd NPs that can be easily stored, shipped and simply reconstituted into an injectable form.

The role of 3D printing in treating craniomaxillofacial congenital anomalies

Craniomaxillofacial congenital anomalies comprise approximately one third of all congenital birth defects and include deformities such as alveolar clefts, craniosynostosis, and microtia. Current surgical treatments commonly require the use of autogenous graft material which are difficult to shape, limited in supply, associated with donor site morbidity and cannot grow with a maturing skeleton. Our group has demonstrated that 3D printed bio-ceramic scaffolds can generate vascularized bone within large, critical-sized defects (defects too large to heal spontaneously) of the craniomaxillofacial skeleton. Furthermore, these scaffolds are also able to function as a delivery vehicle for a new osteogenic agent with a well-established safety profile. The same 3D printers and imaging software platforms have been leveraged by our team to create sterilizable patient-specific intraoperative models for craniofacial reconstruction. For microtia repair, the current standard of care surgical guide is a two-dimensional drawing taken from the contralateral ear. Our laboratory has used 3D printers and open source software platforms to design personalized microtia surgical models. In this review, we report on the advancements in tissue engineering principles, digital imaging software platforms and 3D printing that have culminated in the application of this technology to repair large bone defects in skeletally immature transitional models and provide in-house manufactured, sterilizable patient-specific models for craniofacial reconstruction.