Atomic force microscopy methodology and AFMech Suite software for nanomechanics on heterogeneous soft materials.

Atomic force microscopy has proven to be a valuable technique to characterize the mechanical and morphological properties of heterogeneous soft materials such as biological specimens in liquid environment. Here we propose a 3-step method in order to investigate biological specimens where heterogeneity hinder a quantitative characterization: (1) precise AFM calibration, (2) nano-indentation in force volume mode, (3) array of finite element simulations built from AFM indentation events. We combine simulations to determine internal geometries, multi-layer material properties, and interfacial friction. In order to easily perform this analysis from raw AFM data to simulation comparison, we propose a standalone software, AFMech Suite comprising five interacting interfaces for simultaneous calibration, morphology, adhesion, mechanical, and simulation analysis. We test the methodology on soft hydrogels with hard spherical inclusions, as a soft-matter model system. Finally, we apply the method on E. coli bacteria supported on soft/hard hydrogels to prove usefulness in biological field.

Crosslinking hydroxylated reduced graphene oxide with RAFT-CTA: A nano-initiator for preparation of well-defined amino acid-based polymer nanohybrids.

Here, we demonstrate a novel reversible addition-fragmentation chain transfer agent (RAFT-CTA)-modified reduced graphene oxide nanosheets (CTA-rGONSs) by crosslinking rGONSs with a RAFT-CTA via esterification reaction. These nano CTA-rGONSs were used to polymerize a hydrophobic amino acid-based methacrylamide (N-acryloyl-l-phenylalanine methyl ester) monomer with different monomer/initiator ratios. Thermogravimetric analysis showed that the polymer-graphene composites were thermally more stable than GO itself. Mn of the polymers increased with increasing monomer/initiator ratio, while the polydispersity index decreased, indicating controlled polymerization. The composites were stable in DMF even after two months.

Reduced graphene oxide composites with water soluble copolymers having tailored lower critical solution temperatures and unique tube-like structure.

Nanohybrids of graphene with water soluble polymer were synthesized using 'grafting from' method. GO, prepared by modified Hummers' method, was first reacted with sodium azide. Alkyne-terminated RAFT-CTA was synthesized by reaction of propargyl alcohol and S-1-dodecyl-S'-(α,α'-dimethyl-α"-acetic acid) trithiocarbonate. RAFT-CTA was grafted onto the GO sheets by facile click-reaction and subsequently, N-isopropylacrylamide (NIPAM) and N-ethyleacrylamide (NEAM) were polymerized on graphene sheets via RAFT polymerization method. The respective copolymers with different ratios were also prepared. The nanohybrids were characterized by FTIR, XRD, TGA, Raman, SEM, and AFM. Both SEM and AFM clearly showed rod-like structures for rGO-PNEAM. XRD showed a small peak at 2θ = 19.21°, corresponding to d-spacing ≈ 4.6 Å. In addition, the nanohybrids showed a very broad temperature range for the LCST in water between ca. 30 and 70 °C.

Double haploidentical hematopoietic stem cell transplantation results in successful engraftment of bone marrow from both donors without graft-versus-host or graft-versus-graft effects.

We established double-haploidentical (DH) hematopoietic stem cell transplantation (HSCT) murine models to explore competitive engraftment, graft-versus-graft effect and graft-versus-host disease (GVHD). T cell-depleted (TCD) bone marrow (BM) cells from B6SJF1 (donor 1 [D1]) and B6D2F1 (donor 2 [D2]) mice achieved >90% donor engraftment when transplanted into B6CBAF1 mice. B6CBAF1 recipients survived without evidence of GVHD when undergoing HSCT with TCD-BM from 2 haploidentical donors, D1 and D2. DH-HSCT recipients had significantly higher leukocyte and neutrophil counts than single-haploidentical HSCT recipients from either D1 or D2. DH recipients consistently showed successful mixed chimerism in both BM and spleen. Two other DH-HSCT models, B6D2F1 + C3D2F1→B6C3F1 and B6CBAF1 + B6SJLF1→B6D2F1, showed similar engraftment patterns. Low-dose T cell infusion from both D1 and D2 increased the degree of early engraftment of the respective donors in BM and spleen; however, this early engraftment pattern did not determine long-term engraftment dominance. In the long term, minimally engrafted D1 BM recovered and comprised >50% of all donor- derived B, T, and natural killer cells. We conclude that early BM engraftment is determined by donor T cell immunodominance, but long-term engraftment is related to the engraftment potential of stem cells after DH-HSCT.