Nita Sahai

University of Akron · Department of Polymer Science

Periodontitis and caries, while seemingly innocuous medical conditions, actually pose significant challenges because of their potential etiology with far more serious conditions. Efficacious treatment is hindered by bacterial antibiotic resistance. Standard AgNPs are ineffective against periodontal anaerobic bacteria, because they require oxidative...

The main sources of redox gradients supporting high-productivity life in the Europan and other icy ocean world oceans were proposed to be photolytically derived oxidants, such as reactive oxygen species (ROS) from the icy shell, and reductants (Fe(II), S(-II), CH 4 , H 2 ) from bottom waters reacting with a (ultra)mafic seafloor. Important roadbloc...

Aqueous S[IV] species (HSO3− ${\mathrm{H}\mathrm{S}\mathrm{O}}_{3}^{-}$, SO32− ${\mathrm{S}\mathrm{O}}_{3}^{2-}$) derived from volcanogenic atmospheric SO2 are important to planetary habitability through their roles in proposed origins‐of‐life chemistry and influence on atmospheric sulfur haze formation, but the early cycling of S[IV] is poorly und...

Aqueous S[IV] species (HSO, SO) derived from volcanogenic atmospheric SO are important to planetary habitability through their roles in proposed origins-of-life chemistry and influence on atmospheric sulfur haze formation, but the early cycling of S[IV] is poorly understood. Here, we combine new laboratory constraints on S[IV] disproportionation ki...

Sulfur is important to planetary habitability, but the early sulfur cycle is poorly understood. In particular, S[IV] species (HSO, SO), derived from volcanogenic SO, are critically invoked in recent proposals for origins-of-life chemistry and also influence atmospheric sulfur haze formation, but their abundance in early natural waters is unclear. H...

Primitive cells are believed to have been self-assembled vesicular structures with minimal metabolic components, that were capable of self-maintenance and self-propagation in early Earth geological settings. The coevolution and self-assembly of biomolecules, such as amphiphiles, peptides, and nucleic acids, or their precursors, were essential for p...

Blackberry structure is a type of universal, stable, porous, single layered, hollow, spherical supramolecular structure with sizes from tens to hundreds of nanometers self-assembled by various macroions (1-6 nm-size) in dilute solutions of water or other polar solvents. This self-assembly process is driven by counterion-mediated attraction, and mer...

The self-assembly of chiral Pd12L24 metal-organic cages (MOCs) based on hydrophobic amino acids, including alanine (Ala), valine (Val), and leucine (Leu), into single-layered hollow spherical blackberry-type structures is triggered by nitrates through counterion-mediated attraction. In addition to nitrates, anionic N-(tert-butoxycarbonyl) (Boc)-pro...

The chemical composition of aqueous solutions during the Hadean era determined the availability of essential elements for prebiotic synthesis of the molecular building blocks of life. Here we conducted quantitative reaction path modeling of atmosphere-water-rock interactions over a range of environmental conditions to estimate freshwater and evapor...

Bone biomineralization is a complex process in which type I collagen and associated non-collagenous proteins (NCPs), including glycoproteins and proteoglycans, interact closely with inorganic calcium and phosphate ions to control the precipitation of nanosized, non-stoichiometric hydroxyapatite (HAP, idealized stoichiometry Ca10(PO4)6(OH)2) within...

Understanding prebiotic RNA synthesis is essential to both the RNA world and RNA‐protein co‐evolution theories of the origin of life. Nonenzymatic templated RNA synthesis occurs in solution or by montmorillonite clay heterogenous catalysis but the high magnesium concentrations required are deleterious to protocell membranes. Here, we explore a mult...

The role of chiral counterions on the attraction and self-assembly of chiral Pd12L24 metal organic cages (MOCs) with NO3- being the original counterion is studied by laser light scattering and isothermal titration calorimetry. Nitrates can trigger the self-assembly of macrocationic Pd12L24 into hollow spherical blackberry-type supramolecular struct...

The understanding of calcium phosphate precipitation has been a major interest in different fields of science, including medicine, biomaterials, and physical chemistry. The presence of additive biomacromolecules has been known to influence various stages of precipitation process from nucleation to crystal growth. In the current work, well-defined s...

Proteins and their mimics that contain negatively charged sequences are important in natural and biomimetic mineralization. The mechanism by which these sequences affect calcium phosphate mineralization is not well understood. Here, peptides containing different numbers of repeat units of contiguous glutamic acid residues, oligo(l-glutamic acid) n...

The design of improved materials for orthopedic implants and bone tissue engineering scaffolds relies on materials mimicking the properties of bone. Calcium phosphate (Ca-PO4)-mineralized collagen fibrils arranged in a characteristic hierarchical structure constitute the building blocks of mineralized vertebrate tissues, and control their biomechan...

Lactic acid-functionalized chiral fullerene (C60) molecules are used as models to understand chiral selection in macroionic solutions involving chiral macroions, chiral counterions, and/or chiral co-ions. With the addition of Zn²⁺ cations, the C60 macroions exhibit slow self-assembly behavior into hollow, spherical, blackberry-type structures, as c...

Two important ions, K+ and Na+, are unequally distributed across the contemporary phospholipid-based cell membrane because modern cells evolved a series of sophisticated protein channels and pumps to maintain ion gradients. The earliest life-like entities or protocells did not possess either ion-tight membranes or ion pumps, which would result in t...

Elucidating the structure-activity relationships between biomolecules and hydroxyapatite (HAP) is essential to understanding bone mineralization mechanisms and to developing HAP-based implants as well as designing drug-delivery vectors. Here, four peptides identified by phage were selected as model hydroxyapatite-binding peptides (HBPs) to examine...

Discrepancies have been noted in the solubility constant values of calcium phosphate minerals between various databases employed in widely used aqueous speciation calculation software programs. This can cause serious errors in the calculated speciation of waters when using these software programs. The aim of this communication was to bring to light...

Protocell analogs (lipid vesicles) to modern cell membranes have been postulated as compartments that may have been involved in primordial metabolism during the transition from geochemistry to biochemistry on early Earth. The transduction of light energy into chemical energy for metabolism was a key step in the transition from the earliest metaboli...

The rise in prevalence of antibiotic resistant strains of bacteria is a very significant challenge for treating life-threatening infections worldwide. A source of novel therapeutics that has shown great promise are a class of biomolecules known as antimicrobial peptides. Previously, within our laboratories, we developed a new family of water-solubl...

Nanomaterials in the Earth system Nanomaterials have been part of the Earth system for billions of years, but human activities are changing the nature and amounts of these materials. Hochella Jr. et al. review sources and impacts of natural nanomaterials, which are not created directly through human actions; incidental nanomaterials, which form uni...

Hydroxyapatite (HAP) is an extensively used orthopedic biomaterials because of its high biocompatibility and osteoconductivity. Implant-related infection is a major cause of orthopedic device failure. Previous research showed that silver-doped hydroxyapatite nanoparticles (Ag-HAP NPs) have prominent antimicrobial activity but their biocompatibility...

Nickel–titanium (NiTi) alloy is an attractive material for biomedical implant applications. In this study, the effects of laser shock peening (LSP) on the biocompatibility, corrosion resistance, ion release rate and hardness of NiTi were characterized. The cell culture study indicated that the LSP‐treated NiTi samples had lower cytotoxicity and hig...

Non-enzymatic RNA polymerization, a major challenge in understanding the origin of life on early Earth, was previously achieved in the presence of montmorillonite clay and high magnesium concentrations but the molecular interactions promoting ribonucleotide oligomerization remain unknown. High adsorption capacity of minerals is generally assumed to...

Hierarchical structures on metallic implants can enhance the interaction between cells and implants and thus increase their biocompatibility. However, it is difficult to directly fabricate hierarchical structures on metallic implants. In this study, we used a simple one-step method, ultrasonic nanocrystal surface modification (UNSM), to fabricate h...

Protocells, the first life-like entities, likely contained three molecular components: a membrane, an information-carrying molecule, and catalytic molecules. Minerals have a wide range of properties that might have contributed to the synthesis and self-assembly of these molecular components. Minerals could have mediated the formation and concentrat...

Understanding the molecular mechanism of protein adsorption on solids is critical to their applications in materials synthesis and tissue engineering. Though the water phase at the surface/water interface has been recognized as three types: free water in the bulk region, intermediate water phase and surface-bound water layers adjacent to the surfac...

The nanoscopic structural and thermodynamic basis of biomolecule-regulated assembly and crystallization of inorganic solids have tremendous impact on the rational design of novel functional nanomaterials, but are concealed by many difficulties in molecular-level characterization. Here we demonstrate that the free energy calculation approach, enable...

Much effort has been exerted to unravel bone biomineralization mechanism by which the growth of plate-shaped crystals of hydroxyapatite (HAP) is regulated within a fibrillar collagen matrix. Acidic noncollagenous acidic proteins (NCPs) bearing a large number of carboxylate and phosphorylate amino acid residues are effective regulators of HAP crysta...

Mg alloys offer potential advantages over conventional biomedical implant materials because of their biodegradability and biocompatibility, but could be limited by their poor mechanical properties. In this study, laser shock peening (LSP), a surface processing technique, was applied to improve the mechanical properties of the AZ31B magnesium (Mg) a...

Bone is a hierarchical biocomposite material in which a collagen fibril matrix self-assembled in a three-dimensional (3-D) pseudohexagonal array controls many important processes in mineralization such as providing the pathways...

Early compartmentalization of simple biomolecules by membrane bilayers was, presumably, a critical step in the emergence of the first cell-like entities, protocells. Their membranes were likely composed of single chain amphiphiles (SCAs), but pure SCA membranes especially those with short-chains are highly unstable towards divalent cations, which a...

The increasing incidence of drug resistant strains of bacteria necessitates the development of new classes of antimicrobials. Host defense peptides, also known as antimicrobial peptides, are promising in this regard but have several drawbacks. Herein, we show that peptidomimetic polyurethanes with pendant functional groups that mimic lysine and val...

Magnesium alloys have tremendous potential for biomedical applications due to their good biocompatibility, osteoconductivity, and degradability, but can be limited by their poor mechanical properties and fast corrosion in the physiological environment. In this study, ultrasonic nanocrystal surface modification (UNSM), a recently developed surface p...

The self-assembly of lipid bilayer membranes to enclose functional biomolecules, thus defining a “protocell,” was a seminal moment in the emergence of life on Earth and likely occurred at the micro-environment of the mineral-water interface. Mineral-lipid interactions are also relevant in biomedical, industrial and technological processes. Yet, no...

Following the success of silicate-based glasses as bioactive materials, silicates are believed to play important roles in promoting bone formation and have therefore been considered to provide a hydroxyapatite surface layer capable of binding to bone as well as potentially being a pro-osteoinductive factor. Natural silicate minerals and silicate-su...

Article by Scientia Publications Staff Writer on Dr. Nita Saha's research on the Origins of Life published by Scientia Publications: http://www.scientiapublications.com/

Paradigm-changing discoveries about stellar and planetary evolution, the survival of organic molecules and microorganisms under extreme conditions, and geochemical environments on early Earth and other planets are sparking a synergistic dialogue between geoscientists, chemists, and biologists to understand how life originated. To achieve this goal,...

The onset of life on Earth was preceded by prebiotic chemistry in which complex organic molecules were formed from simpler ones in the presence of energy sources. These prebiotic organics were either synthesized on Earth itself (endogenously) or synthesized extraterrestrially (exogenously) and then delivered to Earth. Organics have been detected in...

The superior biomechanical properties of bone and dentin are dictated, in part, by the unique plate-like morphology of hydroxyapatite (HAP) nanocrysals within a hierarchically-assembled collagen matrix. Understanding the mechanism of crystal growth and, thus, morphology is important to the rational design of bio-inspired apatite nanocrystals for or...

Physical-chemical interactions at the mineral-water-organic interface are ubiquitous in a wide range of biogeochemical processes. For example, biomineralization is directed by highly specific organic-mineral interactions. This chapter describes the challenges and approaches to modeling physical-chemical interactions at the mineral-water-organic int...

In this study, we investigated the mechanical properties of AZ31B Mg alloy before and after laser shock peening (LSP). The hardness of the AZ31B Mg alloy increased from 57 HV to 69 HV after LSP. The yield strength increased from 128 MPa to 152 MPa. Wear resistance was significantly improved after LSP. Immersion testing showed that LSP did not signi...

Understanding the molecular structural and energetic basis of the interactions between peptides and inorganic surfaces is critical to their applications in tissue engineering and biomimetic material synthesis. Despite recent experimental progresses on the identification and functionalization of hydroxyapatite (HAP)-binding peptides, the molecular m...

Statement of significance: Accumulating evidence over 40 years suggests that silicate is beneficial to bone formation. However, the biological role(s) of silicate on bone cells are still unclear and controversial. Here, we report that Si(OH)4, the simplest form of silicate, can stimulate human mesenchymal stem cells osteoblastic differentiation. W...

The mineral component of bone, dentin and calcified parts of avian tendon, hydroxyapatite (HAP), has non-stoichiometric composition (idealized as Ca10(PO4)6(OH)2), plate-like morphology and nanometer size. This unique crystal morphology contributes to the physico-chemical and biochemical properties of bone. Thus, understanding the mechanism for the...

We report herein the effects of Ultrasonic Nano-crystal Surface Modification (UNSM), a severe surface plastic deformation process, on the microstructure, mechanical (hardness, wear), wettability and biocompatibility properties of NiTi shape memory alloy. Complete surface amorphization of NiTi was achieved by this process, which was confirmed by X-r...

Inspired by nature's toughening mechanisms, we designed a new polyhedral oligomeric silsesquioxane (POSS)-derived hybrid glass (PHG) that has covalent interactions on the molecular scale between the inorganic POSS cage and organic phase. These features allow "elastic deformation" of the inorganic POSS cage in limited scale. The final product is a b...

The link between non-enzymatic RNA polymerization and RNA self-replication is a key step towards the "RNA world" and still far from being solved, despite extensive research. Clay minerals, lipids and, more recently, peptides were found to catalyze the non-enzymatic synthesis of RNA oligomers. Herein, a review of the main models for the formation of...

Pathogenic prion protein scrapie (PrP(sc)) may contaminate soils for decades and remain in water in colloidal suspension, providing infection pathways for animals through the inhalation of ingested dust and soil particles, and drinking water. We used molecular dynamics simulations to understand the strong binding mechanism of this pathogenic peptid...

Face-specific interfacial energies and structures of water at ionic crystal surfaces play a dominant role in a wide range of biological, environmental, technological and industrial processes. Nano-sized, plate-shaped crystals of calcium phosphate (CaP) with non-ideal stoichiometry of hydroxyapatite (HAP, ideal stoichiometry Ca10(PO4)6(OH)2) compris...

The interactions of amino acids with mineral surfaces have potential relevance for processes ranging from pre-biotic chemistry to biomineralization to protein adsorption on biomedical implants in vivo. Here, we report the results of experiments investigating the adsorption of l-glutamic (Glu) and l-aspartic (Asp) acids to γ-Al2O3. We examined the e...

The unique, plate-like morphology of hydroxyapatite (HAP) nanocrystals in bone lends to the hierarchical structure and functions of bone. Proteins enriched in phosphoserine (Ser-OPO3 ) and glutamic acid (Glu) residues have been proposed to regulate crystal morphology; however, the atomic-level mechanisms remain unclear. Previous molecular dynamics...

The repair and replacement of damaged or diseased human bone tissue requires a stable interface between the orthopedic implant and living tissue. The ideal material should be both osteoconductive (promote bonding to bone) and osteoinductive (induce osteogenic differentiation of cells and generate new bone). Partially resorbable bioceramic materials...

Bone sialoprotein (BSP), an acidic non-collagenous protein specific to bone, is proposed previously to modulate hydroxyapatite (HAP) nanocrystal growth. Two highly conserved phosphorylated acidic amino-acid sequences in BSP are hypothesized as the functional motifs. Specifically, we choose one of them, (Sp)2E8, where Sp represents a phosphoserine,...

The repair and replacement of damaged or diseased human bone tissue requires a stable interface between the orthopedic implant and living tissue. The ideal material should be both osteoconductive (promote bonding to bone) and osteoinductive (induce osteogenic differentiation of cells and generate new bone). Partially resorbable bioceramic materials...

Life is believed to have originated on Earth B4.4–3.5 Ga ago, via processes in which organic compounds supplied by the environment self-organized, in some geochemical environmental niches, into systems capable of replication with hereditary mutation. This process is generally supposed to have occurred in an aqueous environment and, likely, in the p...

Abstract Modern ecological niches are teeming with an astonishing diversity of microbial life in biofilms closely associated with mineral surfaces, which highlights the remarkable success of microorganisms in conquering the challenges and capitalizing on the benefits presented by the mineral-water interface. Biofilm formation capability likely evol...

Massive sedimentary dolomite formed at near-Earth’s surface temperatures is abundant in the ancient geological rock record compared to modern deposition. Extensive experimental work to synthesize dolomite at low temperature and to reveal the formation mechanism has been attempted previously. Sulfide, the product of bacterial sulfate reduction, has...

Life is believed to have originated on Earth ∼4.4-3.5 Ga ago, via processes in which organic compounds supplied by the environment self-organized, in some geochemical environmental niches, into systems capable of replication with hereditary mutation. This process is generally supposed to have occurred in an aqueous environment and, likely, in the p...

Modern ecological niches are teeming with an astonishing diversity of microbial life closely associated with mineral surfaces, highlighting the remarkable success of microorganisms in conquering the challenges and capitalizing on the benefits presented by the mineral-water interface. Such community-living is enabled by an extracellular, polymeric,...

We worked on four projects consistent with the broad goals of the grant to investigate (i) the potential impacts of mineral surface chemistry and particle size on the stability and viability of cell membranes, bacteria and human cells and (ii) the influence of biomolecules on mineral nucleation and growth. The projects are of relevance to the origi...

Bone sialoprotein (BSP) is an acidic, non-collagenous protein specific to bone proposed previously to promote hydroxyapatite (HAP) nucleation and modulate HAP nanocrystal growth. Specifically, two phosphorylated acidic amino acid sequences in BSP, highly conserved across several vertebrates, are the proposed active sites. We selected one of these s...

Serine- and polysaccharide-enriched organic matrix is associated with biogenic silica such as diatom tests, sponge spicules, and phytoliths. We have used molecular orbital theory to determine the relative stability and 29Si NMR shifts of direct Si-O-C ester-like bonds versus hydrogen bonds between the monomeric silicic acid and the alcohol group on...

We investigated electrostatic effects on the formation of multiple supported phospholipid bilayers (SPB) by varying the oxide substrate, ionic strength, the presence of divalent Ca(2+), and phospholipid (PL) headgroup charge. Whereas the current understanding of processes and forces controlling SPB formation is based primarily on studies involving...

Interaction energies between dipalmitoylphosphatidylcholine (DPPC) bilayers and corundum (α-Al(2)O(3)) or quartz (α-SiO(2)) are calculated according to extended-Derjaguin-Landau-Verwey-Overbeek (DLVO) theory in order to examine oxide-dependent multiple bilayer adsorption. Energies are investigated at two ionic strengths (I=17 or 217 mM) and compare...

We report the effects of two pseudowollastonite (beta-CaSiO(3)) substrates on the attachment, viability, proliferation and osteogenic differentiation of human mesenchymal stem cells (hMSCs), and provide detailed mechanistic links of surface texture, soluble factors and culture media to cell activities. Cell attachment and viability were lower for p...

Bone sialoprotein (BSP) is a highly phosphorylated, acidic, noncollagenous protein in bone matrix. Although BSP has been proposed to be a nucleator of hydroxyapatite (Ca(5)(PO(4))(3)OH), the major mineral component of bone, no detailed mechanism for the nucleation process has been elucidated at the atomic level to date. In the present work, using a...

The broad goals of our study were to identify processes by which organic molecules may have been destroyed or altered on early Earth, thus affecting the total inventory of organics available for prebiotic synthesis reactions.

Our study explored the effects of extracellular polymeric substances (EPS) on the susceptibility to lysis of Pseudomonas aeruginosa in suspensions of oxide particles.