The main purpose of this theoretical mini-review study is to determine the effects of the braiding production method used in biomaterials for the usage areas of medical yarns in braiding structured biomaterials, considering the types of yarns used and the associated process parameters. Braiding method used in the production of biomaterials provides higher elasticity modulus, higher tensile strength, and higher dimensional stability compared to foam/sponge, non-woven surfaces, weaving, and knitting methods [1].

Furthermore, when a 3-D braiding structure is employed, an increase in yarn count (dtex), braid yarn count, and braid ply number, coupled with a decrease in braid angle (°), enhances the mechanical properties in the axial direction [2,3,4,5,6,7,8,9,10,11,12,13]. Moreover, maximum mechanical values are observed when using yarn counts of 1112 dtex, 1670 dtex, and 3330 dtex [14,15,16,17,18,19,20,21]. When UHMWPE, PET, HT PET, and PP multifilament yarns, which have high elasticity modulus, maximum breaking force, and high mechanical properties in the axial direction, are used, the mechanical values in the axial direction also increase [7,8,9,10,11,12,13,22,23]. When ELA yarn is added, the maximum percent breaking elongation value increases as well [8].

When thermoplastic structured PGA, PLGA, and PDO multifilament yarns with low thermal properties are used, the resorption period is between 2 and 12 months.

Moreover, when thermoplastic structured PA 6, PA 6.6, HDPE, UHMWPE, PP, PET, PVDF, and PTFE multifilament yarns with relatively higher thermal properties are used, the resorption time is permanent [7,8,9,10,11,12,13,22,23]. Biological chemicals such as CHI, COL, and HA add biological functionality to these yarns by impregnation method. This positively influences the development of the tissue-implant interface, thereby shortening the rehabilitation period. The resulting interface is biocompatible, non-toxic, non-carcinogenic, non-allergenic, and does not cause infection, symptoms, or trauma [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30]. These yarns are generally used in artificial surgical sutures, artificial ligaments, artificial tendons and, artificial vein applications [7,8,9,10,11,12,13].

Biomaterials have been officially approved by the FDA of the USA in accordance with internationally valid ISO and ASTM standards, and their main functions are to protect the damaged areas of the body (such as heart, vessel, ligament, tendon, surgical yarn, graft, brain, eye, teeth, hair, skin, neck, spine, hip, cartilage, knee, arm, leg, foot, joint, rib cage, lung, liver, kidney, stomach, intestine, pancreas, genital area, plate or screw) for a certain period of time. They are artificial biological materials that support the development of the cell/tissue-implant interface. They are produced based on biomechanical design criteria, sterilized, and manufactured using various production methods from natural or synthetic raw materials to meet the specific needs of the body [22,24,25,27,29]. Biomaterial applications began with the application of surgical suture in 4000 BC for the first time in world history [1,26]. In another source, surgical suture was used as a biomaterial application for the first time in Egypt in the 1100s BC [18]. Moreover, its value has been increasing in the modern era since the 1960s [23,25]. Chemical sterilization is generally applied to biomaterials with alcohol-based chemicals [1]. Although the design criteria of biomaterials vary depending on the specific needs of the damaged area within the body, they generally include high modulus of elasticity, low Poisson’s ratio, high radial strength, high tensile (rupture, or fracture) strength, high compressive strength, high bending strength, high impact strength, high shear strength and high fatigue strength. Additionally, they require low creep strength, high force carrying capacity, appropriate elasticity, cheapness, fiber distribution, low density (lightness), easy raw material availability, and ease of production and implantation. Other factors include suitable yarn type, suitable yarn count, appropriate yarn cross-section, appropriate yarn structure, appropriate yarn coefficient, appropriate twist amount, appropriate fabric type, appropriate fabric construction, appropriate fabric density values, production method angle, appropriate geometric shape, appropriate porosity, appropriate porosity size, high and homogeneous porosity distribution. Further, biomaterials should exhibit appropriate length, appropriate diameter, high biocompatibility, biodegradability, sometimes high bioinertness depending on the intrabody site, surface roughness, high wear resistance, high corrosion resistance, high chemical resistance, high pH resistance, blood pressure resistance, high dimensional stability, high tissue-implant interface bond, high cell-tissue interface development support, fibroin-based protein support, cell encapsulation support, being able to carry drugs, closing wounds, supporting tissue integration, and supporting cell/tissue adhesion. Moreover, ideal biomaterials should prevent blood clotting, infections, and adverse symptoms; support rapid rehabilitation; and not cause trauma or immunological reactions. They should also be blood-compatible, osteogenic, angiogenic, non-thrombogenic, antimicrobial, antitoxic, anticancer, antitumor, and antipathogenic [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30]. Biomaterials can be produced primarily from polymeric, metallic, ceramic, composite materials and cell-tissue based materials [24]. Polymeric materials are chitosan (CHI), collagen (COL), alginate (ALG), gelatin (GEL), heparin (UFH), hyaluronic acid (HA), chondroitin sulfate (GAG), N-butyl cyanoacrylate, N-butyl cyanoacrylate, agarose (AGA), carbon (C), glass (G), polyparaphenyleneterephthalamide (PPD-T), cotton (CO), silk (SI), spider silk (SSI), linen (LI), hemp (FL), jute (J), ramie (R), viscose rayon (CMD), lyocell (LYO), elastane (EL), ultra-high molecular weight polyethylene (UHMWPE), polyacetal (PAc), polyamide (PA), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyurethane (PU), polystyrene (PS), palmitoylethanolamide (PEA), polyethylene terephthalate (PET), polytriethylene terephthalate (PTT), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polydioxanone (PDS), plastic optical fibers (POF), polydimethylsiloxane (PDMS), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polybutylene adipateterephthalate (PBAT), polyethyleneglycol (PEG), polyvinylpyrrolidone (PVP), polyvinylalcohol (PVA), polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA), polyglactin (PGLA), poly L-lactic acid (PLLA), poly lactic-co-glycolic acid (PLGA), polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyvinylidenedi-fluoride (PVDF), polytetrafluoroethylene (PTFE), polymethylmethacrylate (PMMA), poly(2-hydroxyethyl meth-acrylate) (PHEMA) and polysiloxane materials [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30]. Metallic materials are stainless steel (SS), titanium (Ti), titanium alloys (TiO₂, Ti-6Al-4V, Ti-6Al-7Nb, Ti-15Mo-5Zr-3Al), cobalt-chromium (Co-Cr) alloys (Co-Cr-Mo, Co-Cr-W-Ni, Co-Ni-Cr-Mo, Co-Cr-Ni-Mo-Fe, Co-Ni-Cr-Mo-W-Fe), NiTi, tantalum (Ta)), and tungsten (W) materials [3,17,24,25].

Ceramic materials are mostly calcium phosphate (CaP) based hydroxyapatite (HA), tricalcium phosphate (TCP), high purity alumina (Al), aluminum zirconia rich alumina (ZTA), yttria stabilized zirconia (YSZ), and bioactive glass (BG) materials [24,25,26]. Composite materials are materials produced by combining polymeric, metallic and ceramic materials [20,21,23,24,25,26]. In biomaterial applications, carbon and glass yarns are commonly used with thermal processing (curing) in combination with epoxy, vinyl ester, and unsaturated polyester resins [20]. The production methods of biomaterials vary depending on the type of raw material used such as polymeric, metallic, ceramic or composite materials. Their production methods are monofilament or multi-filament yarns, braiding, weaving, knitting, non-woven surface, embroidery, sol-gel, electrospinning, coating, plasma, various casting methods, various infusion methods, CVD, and 3-D printing methods [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Produced forms of biomaterials are nanorods, rods, cylindrical structures, plates, biofilms, foams, sponges, cheesecloths, yarns, ropes, fabrics, gels, and solid materials with the desired profile geometry [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Effective production process parameters in the production methods of biomaterials are concentration, atom types, interatomic distance, bond types and bond strengths, polymerization degree, molecular weight, molecular chain configuration and conformation, glass transition temperature, crystallization temperature, melting temperature, decomposition temperature, temperature, time, pressure and environmental conditions [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30]. The applications of biomaterials are orthopedic, heart, vein, ligament, tendon, surgical yarn, graft, brain, eye, tooth, hair, skin, neck, spine, hip, cartilage, knee, arm, leg, foot, joint, rib cage, lung, liver, kidney, stomach, intestine, pancreas, genital area, plate and screws [1,2,3,14,15,16,17,18,19,22,23,24,25,26,29,30]. Application areas of biomaterials are presented in Table 1 [26].

Various technical properties of some polymeric-based yarns commonly used in biomaterials are presented in Table 2 [22,23].

The textile structures used in biomaterials are the most commonly used textile structures are braiding, weaving and knitting textile structures. [4,5,7,8,9,10,11,13,14,23,24,25,26,27,28,29,30].

Braiding structures are produced by the mutual sinusoidal movement of braid beds positioned opposite each other at 180° of at least two yarn groups. Moreover, the unit cell structure is more closed and rigid compared to all other textile production methods except weaving [1,2,3,4,5,6,16,18,19,20,21,22,23,27,30]. Braiding structures can be produced by vertical or horizontal production methods in various geometries, especially round, square, rectangular, hexagonal, H, I, J, and T cross-section profiles [2,3,4,5,20,21]. The hexagonal profile enables the production of the densest braiding structures as it ensures that the braiding formation point with braid coils is reduced to a minimum distance [2]. Moreover, although 1 × 1 (diamond), 2 × 2 (regular) and 3 × 3 (hercules) braiding constructions are widely used, they can be also produced as 2-D, or 3-D braiding structures with 5 × 5 braid beds, and different braiding constructions [2,3,4,5,6,7,8,9,10,11,12,13,20,21]. For 3-D braiding structures, either a center yarn or center yarns are added, or a mandrel with various geometric profiles that can be solid or empty is added [2,3,4]. 3-D braiding structures have higher yarn density and tensile strength values compared to 2D braiding structures [14,25,26,27,28]. The most effective production parameters in the production of braiding structures are unit cell cage geometry, number of braid yarns, number of center yarns, fiber and yarn diameters, yarn type, yarn number, cross-section of the yarn, number of filaments in the yarn and twist amount, yarn coefficient, yarn-count, surface area of the yarn intersection, yarn route length, yarn tension, covering factor, braid angle, braid bed geometry, revolution and speed of the head gears in the braid bed and draft ratio of the gears [2,3,4,5,6,7,8,9,10,11,12,13,20,21]. The yarn types used in braiding structures are PA, PE, PP, PET, PAN, PCL, PLLA, ePTFE, C, G, PPD-T, UHMWPE, NiTi, and Al₂O₃ [2,3,4,5,6,7,8,9,10,11,12,13,20,21]. The yarn numbers used in braiding structures can be used in yarn counts of 1112 dtex, 1240 dtex, 1670 dtex, 2200 dtex, 3300 dtex, 3400 dtex, and 10,000 dtex [2,7,8,9,10,11,12,13]. Carbon yarn applications are excluded. 12k filament count is used in biomaterial applications of carbon yarn [2,4,20]. Although the number of braid yarns is commonly produced in the range of 3 to 48 braid yarns, it can also be produced in the number of braid yarns of 24, 32, 48, 64, 80, 96, or 144 depending on the desired biomechanical performance value in the biomaterial application field [2,3,4,5,6,7,8,9,10,11,12,13]. Braiding structures are widely used in artificial surgical suture, artificial ligament, artificial tendon, artificial vessel and artificial bone applications [2,3,7,8,9,10,11,12,13]. Although it is known that braiding structures can theoretically be produced with braid angles between 1° and 179° in the production of biomaterials, it is generally common and recommended to produce them with braid angles of 30°, 45°, and 60° from experimental studies [2,3,4,5,6,20,21]. The 45° braid angle provides maximum tensile strength and yarn density, while the 60° braid angle provides minimum labor and maximum production speed in biomaterial applications of braiding structures [4,6,20]. Moreover, braiding structures are produced in the diameter range of 5 mm to 24 mm, especially for artificial vascular applications [2].

Woven structures are produced by placing at least two yarn groups (warp and weft yarns) against each other at an angle of 90° and combining them with a beat-up motion. Moreover, the unit cell structure is more closed and rigid compared to all other textile production methods [1,16,22,23,27,28,30].

Knitted structures are primarily divided into warp and weft knitting methods. In warp knitting, they are produced by feeding each yarn to the warp knitting machine separately and creating a closed chain loop structure depending on the loop form of the needle bed. Moreover, the unit cell structure is more closed and less elastic compared to weft knitting [1,16,22,23,27,28,30]. In weft knitting, the yarn is fed to the circular knitting machine from a single point, where it forms an integral loop structure based on the loop configuration of the needle bed. Moreover, the unit cell structure is more open and flexible [1,16,22,23,27,28,30]. As the yarn count increases, the fabric density values increase, the skipping behavior of the yarns forming the fabric is minimized, and the yarn intersection points increase, the pore size of the biomaterials decreases, the number of pores increases, and cell adhesion and proliferation increases. Shear (shear) strength decreases while tensile strength increases [1,16,18,19,22,23,26,29,30]. Comparative biomechanical technical analysis of textile structures used in biomaterials is presented in Table 3 [1].

Various yarns produced by the braiding production method in biomaterial applications and their technical properties have been compiled from literature sources [7,8,9,10,11,12,13]. In an artificial surgical suture application, raw samples were produced with SI as yarn type, 124 tex as yarn count, single-layer (x1), 1 × 1 (diamond) as braiding construction, 16 braid yarns and 2-D braiding structure. After this, they were coated with CHI concentration (c%) for its 1, 2, and 3, at used 100 °C temperature for 10 min. According to experimental results, the dynamic friction coefficient was lower in CHI-coated samples compared to non-CHI-coated samples. As the CHI concentration increased, tensile strength, knot strength and anti-microbial activity increased [7]. In an artificial ACL ligament application, raw samples were produced with HT PET, and EL as yarn types, 1670 dtex, 2200 dtex, and 3300 dtex for HT PET as yarn count, and 420 dtex, 960 dtex, and 1280 dtex for EL as yarn count, four-ply (x4), 1 × 1 (diamond) as braiding construction, 1 center yarn and 16 braid yarns, from 40° to 61° braid angle, and 3-D braiding structure. According to experimental results, as the braid angle increased, axial tensile strength values decreased, while the percentage of elongation at break increased. Moreover, these values were much more evident in samples with EL compared to samples with only HT PET. While the axial tensile strength values decreased for both HT PET, and EL yarn types as the yarn count increased, the percent elongation at break values remained almost unchanged for the HT PET yarn but increased for the EL yarn type [8]. In an artificial Achilles tendon application, raw samples were produced with PET, and PP as yarn types, 1112 dtex for PET as yarn count and 1200 dtex for PP as yarn count, double-layer (x2), 1 × 1 (diamond) and 2 × 2 (regular) as braiding constructions, 1 center yarn and 16 braid yarns, 10° to 60° braid angle, and 3-D braiding structure. According to experimental results, as the braid angle increased, the braid diameter decreased. Axial tensile strength, modulus of elasticity, maximum breaking force, and maximum percent elongation at break increased as the number of yarns increased. Moreover, PET as yarn type had all these biomechanical values higher than PP as yarn type. PET as yarn type creep, and fatigue strength values were higher than PP as yarn type [9]. In an artificial ACL ligament application, raw samples were produced with UHMWPE, PPD-T, and HT PET as yarn types, 445 dtex for UHMWPE as yarn count and 1670 dtex for PPD-T, and HT PET as yarn count, single-layer (x1), 1 × 1 (diamond) and 2 × 2 (regular) as braiding constructions, 1 center yarn and 16 braid yarns, 45° braid angle, and 3-D braiding structure. CHI (c = 2%), and GA (c = 25%) chemicals were first dissolved in solution at pH between 5 and 5.5, 70 °C temperature, and 3 hours as a biofinishing process, then they were absorbed and coated for 0.5 h. A biological in-vitro environment was then created using PBS solution. Finally, the materials were sterilized through EtO sterilization. FT-IR chemical technical analysis was performed. According to experimental results, the most common bond formations were observed as HT PET > PPD-T > UHMWPE, respectively. It was reported that the reasons for this were yarn types, chemical structures of the yarns, bond types, molecular weights, crystallinity, reactivity, ease of diffusion and diffusion rate [10]. In an artificial surgical suture application, raw samples were produced with PA 6.6 as yarn type, 44 dtex as yarn count, 23 as filament count, single, double and triple ply (x1, x2 and x3), 1 × 1 (diamond) as braiding construction, 1, 2, and 3 center yarn, and omly 12 and 16 braids, 350 t/m, 500 t/m, and 650 t/m as twist amounts and 3-D braiding structure. According to experimental results, as the number of braid yarns, number of yarn layers and twist amount increased, braid diameter, tensile strength and knot strength values increased. Node activity first decreased, then increased, and finally decreased again. Deformation recovery (elastic recovery) behavior varied [11].

In an artificial ligament and tendon application, raw samples were produced with PCL, and UHMWPE as yarn types, 110 deniers as yarn count and 32 as filament count for PCL and 100 denier 82 as filament count for UMWPE, PCL/UHMWPE ratio 100/0, 75/25, 50/50, 25/75, and 0/100 ratios, respectively. They had also single-layer (x1), 1 × 1 (diamond) as braiding construction, 4 + 4 and 8 braid yarns and a 2-D braiding structure. According to experimental results, as the PCL/UHMWPE ratio went from 100/0 to 0/100, the modulus of elasticity, maximum breaking force, axial tensile strength, creep strength, fatigue strength and knot strength values increased, but the maximum percent elongation at break values decreased. The general result was that the PCL/UHMWPE with 2-D braiding structures for their 50/50 and 25/75 ratios were reported to have optimum mechanical results [12]. In an artificial bone application, raw samples were produced with PLA as yarn type, 75,150 and 300 deniers as yarn numbers, 36 as filament count, double, three and four layers (x2, x3 and x4), 1 × 1 (diamond) as braiding construction, 16 braid yarns, and 2-D braiding structure. Then, they were impregnated and coated with 3% concentration of CHI at pH 7 at a temperature range of 20 °C to 22 °C for 6 hours. According to experimental results, it was determined that 150 denier 4-ply PLA yarn had the maximum elasticity modulus, maximum breaking force and axial maximum tensile strength values. Moreover, it was observed that thermal degradation began after 70 days. It was also determined that CHI-coated PLA samples produced less Ca⁺² ion. It was reported that the reason for this was that CHI vibrated the carbonyl group on the PLA structure at a wavelength of 1730 cm⁻¹, thus accelerating its conversion to Ca⁺² [13].

Biomaterials have increased their importance and use in the body since the 1960s until today. The raw materials used in biomaterials are generally structures in the form of yarns produced by the 3-D braiding production method. In addition to polymeric materials, they can be used in metallic, ceramic and composite materials. The materials produced in this way are typically used in applications such as artificial surgical sutures, artificial ligaments, artificial tendons, artificial blood vessels, and artificial bone. UHMWPE, PPD-T, HT PET, PET, PP, PLA, and PCL yarns are widely used. It has been determined from experimental studies that they are affected by yarn’s chemical, yarn’s mechanical, yarn’s thermal and yarn’s biological properties, yarn type, yarn count, number of yarn layers, twist amount, center and braid yarn count, braid angle, braiding construction and biofinishing process for biomechanical performance values in biomaterials. After production, it must be subjected to a sterilization process. Chemical sterilization, particularly using alcohol-based chemicals, is the most commonly employed sterilization method. When C, G, UHMWPE, PPD-T, HT PET, and PET yarns are used to have high values for biomechanical performance values in biomaterials. When the high biological performance values are desired in biomaterials. It is recommended to use PLA, PGA, PCL, and PLGA yarns. The biomaterials produced should not cause various complications, and symptoms within the body, and should support the rapid rehabilitation process. Official approval is required from the FDA in US.

CHI: Chitosan; COL: Collagen; ALG: Alginat; GEL: Gelatin; UFH: Heparin; HA: Hyaluronic Acid; GAG: Chondroitin Sulfate; AGA: Agarose; C: Carbon; G: Glass; PPD-T: Polyparaphenyleneterephthalamide; CO: Cotton; SI: Silk; SSI: Spider Silk; LI: Linen; HE: Hemp; J: Jute; R: Ramie; CMD: Viscose Rayon; LYO: Lyocell; EL: Elastane; UHMWPE: Ultra High Molecular Weight Polyethylene; Pac: Polyacetal; PA: Polyamide; PC: Polycarbonate; PE: Polyethylene; PP: Polypropylene; PU: Polyurethane; PS: Polystyrene; PEA: Palmitoylethanolamide; PET: Polyethylene Terephthalate; PTT: Polytriethyleneterephthalate; PBT: Polybutyleneterephthalate; PBS: Polybutylenesuccinate; PDS: Polydioxanone; POF: Plastic Optical Fibers; PDMS: Polydimethylsiloxane; PHA: Polyhydroxyalkanoates; PHB: Polyhydroxybutyrate; PHBV: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate); PBAT: Polybutyleneadipateterephthalate; PEG: Polyethyleneglycol; PVP: Polyvinylpyrrolidone; PVA: Polyvinylalcohol; PCL: Polycaprolactone; PLA: Polylactic Acid; PGA: Polyglycolic Acid; PGLA: Polyglactin; PLLA: Poly L-lactic Acid; PLGA: Poly Lactic-co-glycolic Acid; PAEK: Polyaryletherketone; PEEK: Polyetheretherketone; PEKK: Polyetherketoneketone; PVDF: Polyvinylidenedifluoride; PTFE: Polytetrafluoroethylene; PMMA: Polymethylmethacrylate; PHEMA: Poly(2-hydroxyethyl methacrylate); SS: Stainless Steel; Ti: Titanium; Co-Cr: Cobalt-Chrome; NiTi: Nitinol; Ta: Tantalum; W: Tungsten; CaP: Calcium Phosphate; HA: Hydroxyapatite; TCP: Tricalcium Phosphate; Al: High Purity Alumina; ZTA: Aluminum Zirconia Rich Alumina; YSZ: Yttria Stabilized Zirconia; BG: Bioactive Glass