Nature-Inspired Designed Nanostructured Peptides as Molecular Transporters

Dutta, Chiranjit (2018) Nature-Inspired Designed Nanostructured Peptides as Molecular Transporters. PhD thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

The safe and effective intracellular delivery of functional biopharmaceuticals remains a major concern for the pharmaceutical industries. The main aim of this thesis is to develop improved peptide based molecular transporters for intracellular delivery of small molecule and large biopharmaceutical based cargos, in functional form in breast cancer cells. Chapter 1 reviews the current literature of the structural and functional features of molecular transporters and their limitations. This introductory chapter provides a framework for designing peptide based molecular transporters for developing next generation therapeutics. Chapter 2 describes membrane active peptide gramicidin-inspired designed alternating L,D-peptides for delivering hydrophilic and hydrophobic drugs in breast cancer cells. Chapter 3-5 describe natural TAT-peptide inspired designed arginine rich molecular transporters for intracellular delivery of biopharmaceuticals. Here, we have examined the proteolytically stable backbone structures of library of molecular transporters and evaluated their efficacies. In Chapter 3, we have designed protease-resistant arginine-rich facial peptides (SPP8, SPP16 and SPP9) having arginine-sarcosine-arginine (Arg- Sar-Arg) template as molecular transporters. Interestingly, our designed lipopeptide (SPP9) having two stearyl moieties exhibited significantly higher cellular internalization of cargo with only six L-arginine residues compared to linear oligoarginine peptide, R9 and stearylated oligo-nonaarginine (stearyl-R9) peptide. To further enhance the cytosolic cargo internalization, we designed and examined the efficacy of cyclic molecular transporters. In Chapter 4, we have engineered cyclic peptide based molecular transporters (SPP5, SPP10, SPP13 and SPP18) having Arg-Sar- Arg template. Our designed cyclic lipopeptide SPP18 showed better internalization of siRNA than cyclic-Arg9 peptide and commercial transfection agent Hiperfect. However, SPP18 and its linear counterpart, SPP9, showed similar siRNA internalization and exhibited significant gene silencing efficiency as evidenced by RT-PCR experiment. To facilitate the release of cargo from endosomal entrapment and improve the cargo internalization, we examined the effect of insertion of both Land D-histidine residues in designed cyclic peptide backbone. In Chapter 5, we have designed and studied cyclic peptide based molecular transporters (SPP22, SPP21, SPP14 and SPP23) having arginine-(L/D)histidine-arginine (Arg-L/D-His-Arg) motif. We also examined the insertion of linoleic acids as lipophilic moiety in our designed lipopeptide. Interestingly, our designed lipopeptide based molecular transporters, SPP21, SPP22, SPP14 and SPP23 showed higher siRNA delivery efficiency in MDA-MB-231 cell lines than commercially available transfection agent Hiperfect or cyclic-Arg9 peptide. RT-PCR data suggests SPP21, SPP14 and Hiperfect exhibit significant gene silencing inferring functional delivery of siRNA. Double lipidated peptides SPP21 and SPP14 having Arg-D-His-Arg motif exhibited significant cytosolic delivery of cargo compared to double stearylated peptide SPP23 having Arg-L-His-Arg motif. The proteolytic instability of SPP23 probably contributes to reduced cytosolic delivery. We anticipate that cyclic peptides SPP18 and SPP21 and linear peptide SPP9 might be translated into clinics to develop siRNA based nanotherapeutics.

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