No abstract

Gold nanoparticles (AuNPs) are used for a number of imaging and therapeutic applications in east and western part of the world. For thousands of years, the traditional Indian Ayurvedic approach to healing involves the use of incinerated gold ash, prepared with a variety of plant extracts and minerals depending on the region. Here, we describe the characterization of incinerated gold particles (IAuPs) in HeLa (human cells derived from cervical cancer) and HFF-1 (human foreskin fibroblast cells) in comparison to synthesized citrate-capped gold nanoparticles (AuNPs). We found that while individual IAuP crystallites are around 60 nm in size, they form large aggregates with a mean diameter of 4711.7 nm, some of which can enter cells. Fewer cells appeared to have IAuPs compared to AuNPs, although neither type of particle was toxic to cells. Imaging studies revealed that IAuPs were in vesicles, cytosol, or in the nucleus. We found that their nuclear accumulation likely occurred after nuclear envelope breakdown during cell division. We also found that larger IAuPs entered cells via macropinocytosis, while smaller particles entered via clathrin-dependent receptor-mediated endocytosis.

Micro-photosynthetic power cell (μPSC) is one of the emerging energy harvesting technologies which harvests energy using light (photosynthesis) and carbohydrate metabolism in dark (respiration) for low-power (mW range) applications. μPSC is a green technology that not only uses solar power and algae, but also provides power in both dark and light conditions. This perspective article provides state of the art of μPSC technology in terms of fabrication, mathematical modeling and energy harvesting circuit design. Currently, low power densities and high cost are the factors limiting μPSCs commercialization. Key aspects and methods to enhance the performance and decrease the cost are proposed in this paper.

No abstract

No abstract

In this work, we provide a cost comparison of micro-photosynthetic power cells (µPSC) with the well-established photovoltaic (PV) cells for ultra-low power and low power applications. We also suggest avenues for the performance improvement of µPSC. To perform cost comparison, we considered two case studies, which are development of energy systems for: (i) A typical mobile-phone battery charging (low power application) and (ii) powering a humidity sensor (ultra-low power application). For both the cases, we have elucidated the steps in designing energy systems based on PV and µPSC technologies. Based on the design, we have considered the components needed and their costs to obtain total cost for developing energy systems using both PV and µPSC technologies. Currently, µPSCs based energy systems are costlier compared to their PV counterparts. We have provided the avenues for improving µPSC performance, niche application areas, and aspects in which µPSCs are comparable to PV cells. With a huge potential to develop low-cost and high performing technologies, this emerging technology can share the demand on PV technologies for ultra-low power applications.

The necessity for sustainable energy production has driven the rapid development of technologies to harness solar energy effectively. The microphotosynthetic power cells (μPSC) aim to harness solar energy from living photosynthetic cells. Currently, the power density of the μPSC is low, due to several factors. One of the major impediments and challenges of the μPSC is its lower charge transfer efficiency between the photosynthetic microorganisms and the electrodes. Herein, the proposed strategy explores the interaction of gold nanoparticles (Au NPs) with photosynthetic microorganisms for enhanced power generation from the μPSC. Herein, the intracellular biocompatible, efficient light absorbers in the form of Au NPs are introduced. Translocation of gold colloidal solution of 25 μL of 50 μg mL−1 (253.8 μmol mL−1) concentration into 2 mL whole liquid culture of algal cells (Chlamydomonas reinhardtii: ≈1 million cells mL−1) enhances operational quantum yield (ϕ0) of the algal cells by 30.2% and power generation capability by 15.2% in μPSCs. Internalized Au NPs in the algal cells quench chlorophyll fluorescence, thereby contributing to increased photosynthetic efficiency. With multiple advantages such as light absorption capability, biocompatibility, and ability to transfer the electrons, Au NPs can efficiently harvest sunlight for enhanced power generation from the μPSC.

In the ancient traditional Indian Ayurvedic system of natural healing, gold nanoparticles (Swarna Bhasma, gold ash) have been used for its therapeutic benefits as far back as 2500 B.C. Ayurvedic medicinal preparations are complex mixtures that include many plant-derived products and metals. Bhasmas date as far back as the 8th century and are made by samskaras (processings), such as shodhana (purification and potentiation), jarana (roasting), and marana (incineration, trituration) in the presence of plant products, including juices and concoctions. Previous studies characterized the physical properties of gold ash, and the mechanisms of its entry into human cells, but only preliminary data exist on its toxicity. Before using nanoparticles for therapeutic application, it is extremely important to study their toxicity and cellular internalization. In the present study, various imaging techniques were used to investigate Swarna Bhasma's (gold nanopowder) toxicity in both cancerous and noncancerous cells (HeLa and HFF-1) and to characterize its spectral properties. The results showed that gold ash particles had no impact on the cellular viability of both HeLa and HFF-1 cells, even at high concentrations or long incubation times. Moreover, it was found that the internalization level of Swarna Bhasma to cells may be improved by mechanical breaking of the large aggregates into smaller agglomerates. Hyperspectral images revealed that after breaking, the small agglomerates have different spectral properties in cells, compared to the original aggregates, suggesting that size of particles is instrumental for the subcellular interaction with human cells.