Peptide Nucleic Acids (PNAs) are the DNA/RNA analogues in which sugar-phosphate backbone is replaced by N-2-aminoethylglycine repeating units. PNA contains neutral backbone hence due to the absence of electrostatic repulsion, its hybridization shows remarkable stability towards complementary oligonucleotides. PNAs are highly resistant to cleavage by chemicals and enzymes due to the substrate specific nature of enzymes and therefore not degraded inside the cells. PNAs are emerging as new tools in the market due to their applications in antisense and antigene therapies by inhibiting translation and transcription respectively. Hence, several methods based on PNAs have been developed for designing various anticancer and antigene drugs, detection of mutations or modulation of PCR reactions. The duplex homopurine sequence of DNA may also be recognized by PNA, forming firm PNA/DNA/PNA triplex through strand invasion with a looped-out DNA strand. PNAs have also been found to replace DNA probes in varied investigative purposes. There are several disadvantages regarding cellular uptake of PNA, so modifications in PNA backbone or covalent coupling with cell penetrating peptides is necessary to improve its delivery inside the cells. In this review, hybridization properties along with potential applications of PNA in the field of diagnostics and pharmaceuticals are elaborated.

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Biosurfactants or microbial surfactants are a diverse group of nonconventional surface active substances synthesized from microorganisms such as bacteria, fungi, and yeast. The hydrophilic moiety of biosurfactants can either be an amino acid, peptide group, phosphate group, carbohydrate (mono‐, di‐, or polysaccharides), or some other compounds, whereas the hydrophobic group is generally made up of long hydrocarbon tail. Commonly, biosurfactants are neutral or anionic in nature. On the basis of their mass, they are broadly classified in two categories namely low‐ and high‐mass biosurfactants. Glycolipids, phospholipids, lipopeptides, lipoproteins, and neutral lipids are low‐mass biosurfactants, whereas polymeric and particulate biosurfactants are high‐mass biosurfactants. Some commonly known examples of biosurfactants are surfactin produced from Bacillus subtilis , rhamnolipids produced from Pseudomonas aeruginosa , emulsan produced from Acinetobacter calcoaceticus , and sophorolipids produced from Candida bombicola . The nature of carbon and nitrogen sources, pH, temperature, and agitation are usually the factors that influence the production of biosurfactants. Their varied surface active properties such as excellent ability to lower the surface tension and interfacial tension, low CMC (critical micelle concentration) values, emulsification and de‐emulsification, HLB (hydrophilic–lipophilic balance), and better pH and thermal stability are due to their specific structure. Low or no toxicity, fast biodegradation, and specific structural properties of biosurfactants label them as green and sustainable materials. These properties make them superior over chemically synthesized counterparts and stimulate the interest of researchers and industry for their extensive use. Their easy dispersability, emulsifying and de‐emulsifying property, good wettability, and corrosion inhibition property are exploited in many industries such as detergent, agriculture, laundry, polymer, pharmaceuticals, cosmetics, food, and in microbial enhanced oil recovery. Despite having a large number of advantages, a few disadvantages are also linked with biosurfactants/microbial surfactants. The two most specific disadvantages are their production cost and purification. Biotechnological processes involved in the synthesis of biosurfactants are pretty expensive, and purification of surfactants is a bit problematic. Various research groups are working especially for the cost cutting of biosurfactants' production by using easily available and renewable bioresources as raw materials for the production of biosurfactants. Use of biosurfactants at commercial level is the need of the hour to reduce of the harmful effects of conventional synthetic surfactants on environment. Disadvantages associated with them are to be surmounted by the scientists. Full potential of these sustainable versatile surfactants may be achieved by the economic balance between their production cost and benefits.

Convenient synthesis, characterization and surface active properties of novel cationic gemini surfactants with carbonate linkage based on C 12 C 18 sat./unsat. fatty acids

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