During the last decade, metal nanoparticles (MtNPs) have gained immense popularity due to their characteristic physicochemical properties, as well as containing antimicrobial, anti-cancer, catalyzing, optical, electronic and magnetic properties. Primarily, these MtNPs have been synthesized through different physical and chemical methods. However, these conventional methods have various drawbacks, such as high energy consumption, high cost and the involvement of toxic chemical substances. Microbial flora has provided an alternative platform for the biological synthesis of MtNPs in an eco-friendly and cost effective way. In this article we have focused on various microorganisms used for the synthesis of different MtNPs. We also have elaborated on the intracellular and extracellular mechanisms of MtNP synthesis in microorganisms, and have highlighted their advantages along with their challenges. Moreover, due to several advantages over chemically synthesized nanoparticles, the microbial MtNPs, with their exclusive and dynamic characteristics, can be used in different sectors like the agriculture, medicine, cosmetics and biotechnology industries in the near future.

Chronic wounds have emerged as a major cause of mortality, especially in patients with diabetes and other pathologies. Statistics indicate that chronic wounds affect around 6.5 million patients annually, with wound care and management incurring huge economic costs. Growing incidence of chronic wounds and associated pathologies along with the limitations of current therapies have established a strong need for novel and innovative approaches to accelerate wound healing. Conventionally, chronic wounds are addressed using various FDA-approved silver-based formulations and other biomaterials. However, the toxicity associated with these conventional approaches, along with the increased frequency of chronic wound cases, makes the development of alternative therapies for effective wound healing necessary. Recently, researchers have investigated the design and development of nanoparticles, especially inorganic metal nanoparticles, as promising candidates for addressing various pathological conditions, including wound healing. Several research groups, including ours, have designed numerous metal nanoparticles (including silver, gold, zinc oxide, cerium oxide, terbium hydroxide, silica, titanium oxide, copper) and demonstrated their wound-healing properties using in vitro and in vivo models. The rise of nanotechnology-based platforms in wound healing is evidenced by the tremendous impact and number of publications observed in recent years, which has emphasized the robust potential of inorganic nanomedicine for addressing wounds. Therefore, the importance of these inorganic nanomaterial-based interventions for wound-healing applications needs to be emphasized to inform and encourage scientists and young researchers globally to engage with this expanding area of biology and medicine. In this review article, we mainly focus on highlighting the role of inorganic nanomaterials and nanomaterial-based approaches for wound healing and tissue regeneration, along with their mechanistic properties, clinical status, challenges, and future directions.

Electrospun polycaprolactone (PCL) tissue engineering scaffolds have been developed and used for a wide range of tissue engineering applications, where successful incorporation and conservation of the therapeutic activity of the embedded nanoparticles into scaffolds is critically needed for effective tissue engineering. Incorporation of pro-angiogenic nanomaterials to promote vascularization is a novel approach. Our group has well-demonstrated the potent pro-angiogenic properties of europium hydroxide nanorods (EHNs) using in vitro and in vivo systems. In the present study, electrospun PCL tissue engineering scaffolds containing EHNs were fabricated and characterized for various morphological and physico-chemical properties. Furthermore, biological studies showed enhanced cell growth and a greater density of endothelial cells grown on the scaffolds incorporated with EHNs (PCL-EHNs). The PCL-EHNs also exhibited good hemo-compatibility towards blood cells. Fluorescence microscopy and SEM observations showed good endothelial cell adhesion over these scaffolds. The PCL-EHNs demonstrated augmented growth of blood vessels in an in vivo chick embryo angiogenesis model. Furthermore, protein expression studies illustrated promoted angiogenesis of HUVECs on scaffolds in a VEGFR2/Akt mediated signaling cascade. Together, the above observations strongly suggest potent applications of EHN-incorporated PCL scaffolds in promoting angiogenesis/vascularization and their effective use in tissue engineering and vascular disease therapy.

The growth of new blood vessels from the pre-existing vasculature known as angiogenesis has a vital role in various physiological and pathological processes. In the present study, we demonstrate the pro-angiogenic properties of functional nanoconjugates of organosilane functionalized cerium oxide (CeO₂) nanoparticles (nanoceria). Aqueous dispersible CeO₂ and trivalent metal (samarium) ion-doped CeO₂ (SmCeO₂) nanoparticles conjugated with hydrophilic biocompatible and antifouling (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl)triethoxysilane moieties were prepared. These functional nanoconjugates were prepared via an in situ synthesis and functionalization procedure using an ammonia-induced ethylene glycol-assisted precipitation method. The prepared nanoconjugates were thoroughly characterized using various physico-chemical techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, dynamic light scattering (DLS), Fourier-transform infrared (FTIR) spectroscopy, ¹³C high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The pro-angiogenic properties of the prepared nanoconjugates were evaluated by employing various angiogenesis assays (in vitro and in vivo). The results of the present study illustrate that the functional nanoconjugates of SmCeO₂ triggered endothelial cell proliferation and induced the growth of blood vessels in a chick embryo. The enhanced expression of pro-angiogenic markers (p38 MAPK/HIF-1α) by these functional nanoconjugates might be a plausible signaling mechanism underlying their pro-angiogenic properties. Considering all the observations, we believe that (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl)triethoxysilane conjugated SmCeO₂ nanoparticles could be developed as potential candidates for the treatment of cardiovascular, ischemic and ocular diseases where angiogenesis is the principal phenomenon.

Angiogenesis is a vital process that deals with the generation of new blood vessels from pre-existing vasculature and is well known to regulate various physiological as well as pathophysiological processes. We demonstrated that zinc oxide nanoflowers (ZONF) exhibited pro-angiogenic properties in endothelial cells through the production of intracellular reactive oxygen species (ROS), especially H₂O₂ (hydrogen peroxide). The immense importance of angiogenesis in ischemic and cardiovascular diseases highlights an urgent need to comprehend the detailed molecular mechanisms underlying the ZONF induced angiogenesis process. However, the exact mechanism and signaling pathways behind nanoflowers mediated angiogenesis still remain unclear. In the present study, we report that ZONF induce angiogenesis through MAPK/Akt/eNOS mediated nitric oxide formation, which further acts in a cGMP dependent manner. We strongly believe that exploration of the molecular mechanism and signaling pathways of ZONF driven angiogenesis would be helpful for the advancement of alternative and efficient treatment strategies for ischemic and cardiovascular diseases using a nanomedicine approach.