Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning pore and ligament sizes. The np-Au electrodes that are prepared using electrochemical techniques are robust and are easier to handle for their use in electrochemical biosensing. Here, we review different electrochemical strategies for the preparation, post-modification, and characterization of np-Au along with the synergistic use of both electrochemistry and np-Au for applications in biosensing.

The glycoalkaloids which are secondary metabolites from plants have proven to be of significant interest for their biological properties both in terms of their roles in plant biology and the effects they exhibit when ingested by humans. The main feature of the action of glycoalkaloids is their strong binding to 3β-hydroxysterols, such as cholesterol, to form complexes with the consequence that membrane structure is significantly perturbed, and leakage or release of contents inside cells or liposomes becomes possible. The glycoalkaloids have been studied for their ability to inhibit the growth of cancer cells and in other roles such as vaccine adjuvants and as synergistic agents when combined with other therapeutics. The glycoalkaloids have rich and complex physical behavior when interacting with model membranes for which many aspects are yet to be understood. This review introduces the general properties of glycoalkaloids and aspects of their behavior, and then summarizes their effects against model membrane systems. While there are many glycoalkaloids that have been identified, most physical or biological studies have focused on the readily available ones from tomatoes (α-tomatine), potatoes (α-chaconine and α-solanine), and eggplant (α-solamargine and α-solasonine).Plants of the Solanaceae family include tomatoes, potatoes, and eggplants, and are well known to produce secondary metabolites known as glycoalkaloids [21]. The glycoalkaloids are produced in the leaves, flowers, and roots of the plant. In the case of potatoes, they are also found in the sprouts [22]. Tomato plants produce the glycoalkaloid α-tomatine, potato plants produce both α-chaconine and α-solanine, and eggplants produce both α-solamargine and α-solasonine (see Figure 1). Green tomatoes can have up to 500 mg kg −1 of tomatine in the fruit, which will decrease to near 5 mg kg −1 upon ripening [5]. The concentration of tomatine in the vines will stay near 500 mg kg −1 . The amount of α-tomatine in red tomatoes consumed by humans is 10-30 mg kg −1 , but if green tomatoes are consumed then the level will be 200-500 mg kg −1 . In eggplants, the average glycoalkaloid concentration for 21 varieties was found to vary from 0.625-20.5 mg kg −1 [23]. The glycoalkaloid content of potatoes varies widely with potato type and conditions of cultivation [24] and will increase in damaged plants [25]. The glycoalkaloid content of normal potato tubers is reported as 12-20 mg kg −1 while green tubers can have 250-280 mg kg −1 and green skin 1500-2200 mg kg −1 [26]. The enzymes involved in the natural synthesis of the oligosaccharides of the glycoalkaloids have been reviewed [27]. Structure of GlycoalkaloidsThe glycoalkaloids consist of a nitrogen-containing steroidal aglycone and an attached oligosaccharide. The prefix αrefers to the compound with fully intact oligosaccharide, whereas removal of one sugar would be denoted by a β-prefix, removal of two sugars by a γ-prefix, and removal of three for a tetrasaccharide by a δ-prefix. The aglycones are referred to as t...

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Nanoparticles (NPs) have been widely explored for delivering doxorubicin (DOX), an anticancer drug, to minimize cardiotoxicity. However, their efficiency is marred by a necessity to chemically modify DOX, NPs, or both and low deposition of the administered NPs on tumors. Therefore, alternative strategies should be developed to improve therapeutic efficacy and decrease toxicity. Here we report the possibility of employing a monolithic nanoporous gold (np-Au) rod as an implant for delivering DOX. The np-Au has very high DOX encapsulation efficiency (>98%) with maximum loading of 93.4 mg cm−3 without any chemical modification required of DOX or np-Au. We provide a plausible mechanism for the high loading of DOX in np-Au. The DOX sustained release for 26 days from np-Au in different pH conditions at 37 °C, which was monitored using UV-Vis spectroscopy. Additionally, we encased the DOX-loaded np-Au with rapamycin (RAPA)-trapped poly(D,L-lactide-co-glycolide) (PLGA) to fabricate an np-Au@PLGA/RAPA implant and optimized the combinatorial release of DOX and RAPA. Further exploiting the effect of the protein corona around np-Au and np-Au@PLGA/RAPA showed zero-order release kinetics of DOX. This work proves that the np-Au-based implant has the potential to be used as a DOX carrier of potential use in cancer treatment.

Nanoporous gold (np-Au) has many interesting and useful properties that make it a material of interest for use in many technological applications. Its biocompatible nature and ability to serve as a support for self-assembled monolayers of alkanethiols and their derivative make it a suitable support for the immobilization of carbohydrates, enzymes, proteins, and DNA. Its chemically inert, physically robust and conductive high-surface area makes it useful for the design of electrochemistry-based chemical/bio-sensors and reactors. Furthermore, it is also used as solid support for organic molecular synthesis and biomolecules separation. Its enhanced optical property has application in design of plasmonics-based sensitive biosensors. In fact, np-Au is one of the few materials that can be used as a transducer for both optical and electrochemical biosensing. Due to the presence of low-coordination surface sites, np-Au shows remarkable catalytic activity for oxidation of molecules like carbon monoxide and methanol. Owing to the importance of np-Au, in this chapter we will highlight different strategies of fabrication of np-Au and its emerging applications based on its unique properties.