LACTEL 75:25 DL-PLG (B6007-2) is a biomedical-grade poly(DL-lactide-co-glycolide) copolymer supplied as an amorphous solid. The designation encodes a lactide-to-glycolide molar ratio of approximately 75:25, using a racemic DL-lactide monomer that suppresses crystallinity. B6007-2 is an acid-terminated grade, meaning that polymer chains carry free carboxylic acid end groups rather than ester-capped termini. This chain-end identity influences water uptake, early-stage hydrolysis, and the potential for subsequent chemical conjugation. The copolymer is intended for qualification in absorbable implants, tissue-engineering scaffolds, and parenteral controlled-release formulations. Inherent viscosity is measured in chloroform at 25 °C and 0.5 g/dL; the nominal value for B6007-2 is commonly reported near 0.68 dL/g, but the binding specification is the lot-specific certificate of analysis. Residual lactide, residual glycolide, residual tin catalyst, residual solvents, moisture, and molecular weight polydispersity index should be verified from that document before use.

What Distinguishes B6007-2 from Ester-Terminated 75:25 DL-PLG?

The acid-terminated chain ends on B6007-2 increase the number of ionizable carboxyl groups per chain relative to an ester-capped 75:25 DL-PLG. This difference alters water uptake and early-stage hydrolysis in aqueous environments. The acid-terminated grade is typically selected when faster initial molecular weight reduction is desired, when carboxylic acid end groups are required for conjugation, or when the degradation profile is being tuned by terminal-group chemistry. An ester-capped grade of the same comonomer ratio and molecular weight generally shows lower initial water uptake and a slower early mass loss. The distinction becomes measurable in phosphate-buffered saline at 37 °C, where acid-terminated PLGA may exhibit earlier reduction in weight-average molecular weight by gel permeation chromatography. Selection between B6007-2 and an ester-capped grade should be driven by target release duration, manufacturing route, and regulatory filing history rather than a general preference for one chain-end type.

Moisture control is a primary handling constraint. Hydrolytic degradation begins upon exposure to ambient humidity. Sealed containers should be stored at -20 °C under dry nitrogen or argon. Before opening, containers must be equilibrated to room temperature in a desiccator to prevent condensation on the solid. After weighing, the container should be backfilled with dry nitrogen and resealed. Bulk polymer exposed to ambient air should be dried under vacuum at 25–35 °C for 12–24 h before melt processing; moisture content should be verified by Karl Fischer titration and kept below 0.1 wt%. Drying above the glass transition should be avoided because particle sintering and viscosity loss may occur.

Solubility, Viscosity, and Residual Monomer Specifications for Solvent-Based Processing

The copolymer dissolves in dichloromethane, chloroform, and tetrahydrofuran. Solubility in ethyl acetate is composition- and molecular-weight-dependent and should be confirmed for the specific lot. Inherent viscosity is the primary release specification for process consistency. For B6007-2, a typical manufacturing window of 0.60–0.80 dL/g is suitable for solvent casting, electrospinning, and emulsion-based microsphere production. Sterile filtration through 0.22 µm membranes becomes impractical as solution concentration and molecular weight increase. Solutions of 5–20 wt% in dichloromethane are common for microsphere fabrication. Residual monomers in biomedical PLGA are typically controlled to low parts-per-million levels; the manufacturer’s certificate of analysis should report residual lactide and glycolide, and the values should be compared with the limits in the applicable regulatory file.

In solvent extraction microsphere processes, B6007-2 is frequently dissolved in dichloromethane and emulsified into an aqueous continuous phase containing poly(vinyl alcohol). Droplet breakup is performed with a rotor–stator homogenizer. Tip speeds of 5–15 m/s typically generate mean particle diameters from 10 µm to 80 µm, with the final distribution controlled by continuous-phase viscosity, surfactant concentration, and solvent removal rate. Continuous phase temperature is maintained at 2–8 °C to limit solvent volatility during emulsification. After hardening, microspheres are collected by filtration or centrifugation and washed with water to reduce residual surfactant. Residual dichloromethane is removed by vacuum drying at 25–35 °C; final residual solvent should be below the limit specified in the relevant pharmacopoeial monograph or regulatory dossier. Published data for this specific B6007-2 configuration is limited; process development should rely on design-of-experiment studies with the actual lot.

When Aqueous Terminal Sterilization Is Required for 75:25 DL-PLG Implants

Steam sterilization is generally unsuitable for B6007-2 because the combination of moisture and elevated temperature accelerates hydrolytic chain scission and may reduce molecular weight before implantation. Radiation sterilization by gamma or electron beam is potentially compatible but must be qualified because the amorphous 75:25 copolymer undergoes radiation-induced chain scission. Dose mapping should follow ISO 11137 for radiation sterilization of health care products. Post-irradiation testing should include gel permeation chromatography for molecular weight retention, inherent viscosity measurement, and mechanical testing of the finished device. Ethylene oxide sterilization may be used if residue limits are met under ISO 10993-7; however, ethylene oxide requires aeration at elevated temperature, and residual moisture ingress during humidification must be minimized. Aseptic filtration of concentrated polymer solutions through 0.22 µm membranes is not practical for high-molecular-weight B6007-2. Terminal sterilization or aseptic processing must therefore be selected early in device design.

B6007-2 can be processed by hot-melt extrusion or injection molding when the dried polymer is fed into a twin-screw extruder with a length-to-diameter ratio of at least 25:1. The processing temperature should be set relative to the measured glass transition, typically not exceeding 120–140 °C for short residence times. Barrel temperatures above 160 °C may increase the risk of thermal degradation. Melt viscosity is shear-rate dependent; capillary rheometry at the anticipated extrusion shear rate is recommended before scale-up. For injection molding of small absorbable components, barrel temperatures of 100–140 °C, mold temperatures of 20–35 °C, and injection pressures of 500–1000 bar are representative starting points. Clamp force is selected from projected area and cavity pressure and is usually below 10 metric tons for micro-molded parts. Because PLGA is sensitive to moisture and heat, feed hoppers should be purged with dry nitrogen and residence time should be minimized. Batch-to-batch variation in inherent viscosity can shift melt pressure; barrel pressure and motor torque should be monitored as indicators of lot-to-lot consistency.

Batch-to-Batch Molecular Weight Distribution and Inherent Viscosity Control

Inherent viscosity is determined by polymer concentration, solvent, and temperature specified in the manufacturer’s method; for B6007-2, the usual conditions are chloroform at 25 °C and 0.5 g/dL. Molecular weight is often determined by gel permeation chromatography using polystyrene standards, so the reported weight-average molecular weight is a relative value unless universal calibration is applied. Polydispersity index values for lactide/glycolide copolymers typically range from 1.5 to 2.5, depending on catalyst and polymerization conditions. For controlled-release applications, the polydispersity index can affect the initial release phase; a wider distribution may contain a larger low-molecular-weight fraction that hydrates rapidly. Buyers should request that the certificate of analysis include residual monomer content, residual tin, residual solvents, moisture, and molecular weight distribution in addition to inherent viscosity. If a particular application requires a narrower molecular weight range, the polymer can be reprocessed or fractionated, but that may alter terminal carboxyl content and should be discussed with the supplier.

Karl Fischer titration should be used for moisture measurement. Differential scanning calorimetry at 10 K/min under nitrogen can be used to confirm amorphous character; a 75:25 DL-PLG typically shows only a glass transition, with no melting endotherm. The glass transition temperature is molecular-weight dependent and is commonly observed between 40 °C and 55 °C for medical-grade 75:25 DL-PLG. The exact value is not a release specification but is useful for setting drying and storage conditions. Fourier-transform infrared spectroscopy can confirm ester carbonyl absorbance near 1750 cm⁻¹; nuclear magnetic resonance spectroscopy can confirm the comonomer ratio and chain-end identity. Residual lactide and glycolide monomers are quantified by gas chromatography or high-performance liquid chromatography with external standards.

The B6007-2 Designation Imposes Distinct Chain-End and Ratio Specifications

The B6007-2 product is differentiated from lower-lactide and higher-lactide PLGA grades primarily by degradation rate and mechanical profile. The 75:25 ratio is an intermediate composition between faster-degrading 50:50 PLGA and slower-degrading 85:15 PLGA. The amorphous character is retained across these DL-lactide grades; the difference is in hydrophilicity, water uptake, and mass loss. A comparative view is shown below.

Compliance testing for a medical device containing B6007-2 should be mapped to the applicable regulatory pathway. The following test matrix is representative for bioresorbable polymers; it is not a substitute for product-specific qualification.

The applicability of each standard depends on device classification, patient contact duration, and local regulatory authority. Data from the supplier’s certificate of analysis should be integrated with finished-device testing under the relevant quality management system. For B6007-2, the operational boundary is defined by hydrolytic sensitivity, thermal degradation above 160 °C, and practical limits on sterile filtration. These constraints are material-specific and should not be assumed transferable to other PLGA grades without experimental verification.