Tendon-mimetic materials with anisotropic assembly of aramid nanofibers

A method for creating a tendon-mimetic anisotropic composite hydrogel (ACH) that emulates the microstructural interplay between aligned collagen fibers and soft proteoglycans in native tissues to provide a useful implant for treatment of a patient, the method comprising:

• mixing an aramid nanofiber (ANF) in dimethyl sulfoxide (DMSO) and stirring for a time sufficient to produce an ANF dispersion in DMSO;
• dissolving polyvinyl alcohol (PVA) in dimethyl sulfoxide (DMSO) and stirring for a time sufficient to produce a PVA dispersion in DMSO;
• mixing together the ANF dispersion in DMSO and the PVA dispersion in DMSO to form a moldable composite dispersion;
• casting the moldable composite dispersion into one or more molds and immersing in deionized water for a time sufficient to produce an isotropic ANF-PVA hydrogel;
• stretching the isotropic ANF-PVA hydrogel to create a stretched hydrogel;
• fixing the length of the stretched hydrogel to create a fixed length;
• drying the stretched hydrogel at the fixed length to create a dried stretched hydrogel;
• and
• reswelling the dried stretched hydrogel to create the ACH.

A tendon-mimetic anisotropic composite hydrogel (ACH) that emulates the microstructural interplay between aligned collagen fibers and soft proteoglycans in native tissues to provide a useful implant for treatment of a patient, the ACH comprising:

• an assembly of stiff aramid nanofibers (ANFs) and flexible polyvinyl alcohol (PVA) molecules attached thereto by intermolecular hydrogen bonding;
• wherein the ACH has a water content between about 60% and about 74% by weight;
• wherein the ACH has a primary fiber orientation direction, and the ACH exhibits an elastic modulus greater than or equal to about 1114 megapascals (MPa) and an ultimate strength greater than or equal to about 72.1;
• the elastic modulus and the ultimate strength, each respectively, measured in a direction parallel to the primary fiber orientation direction;
• wherein the ACH exhibits a fracture energy greater than about 4 kilojoules per square meter (kJ/m2), measured in a direction parallel to the primary fiber orientation direction;
• wherein the ACH exhibits a fracture energy greater than about 6 kJ/m2, measured in a direction perpendicular to the primary fiber orientation direction;
• wherein the ACH exhibits a stiffness anisotropy characterized by the ratio (Ep/En) greater than about 10, wherein the ratio (Ep/En) is calculated between a first respective initial tensile modulus measured parallel (Ep) and a second respective tensile modulus measured perpendicular (En) to the primary fiber orientation direction;
• wherein the ACH is biofunctionalized, and the ACH exhibits:
• an angular frequency distribution with a majority of cells oriented within +/−15 degrees with respect to the primary fiber orientation direction;
• a surface topography measurement by atomic force microscope exhibiting a measured height variation equal to or less than about 500 nano meters (nm) over a measurement area of at least about 36 square micrometers (μm2);
• a statistically significant difference (P<0.05) in mean fluorescent intensity (MFI) for cells having an M1 phenotype when compared to a similarly biofunctionalized isotropic ANF-PVA hydrogel;
• and
• a statistically significant difference (P<0.05) in mean fluorescent intensity (MFI) for cells having an M2 phenotype when compared to a similarly biofunctionalized isotropic ANF-PVA hydrogel;
• and
• wherein the ACH is fitted with one or more integrated multifunctional bioelectronic circuits configured and adapted to obtain one or more measurements selected from the group consisting of electrocardiogram (ECG), electromyogram (EMG), deformation, strain, temperature, resistance, or voltage under cyclic motion up to 50% elongation of the ACH.