| HS Code | 934554 |
| Product Name | PURASORB PDLG 8531 |
| Chemical Name | Poly(D,L-lactide-co-glycolide) |
| Cas Number | 26780-50-7 |
| Monomer Ratio | 85:15 (D,L-lactide:glycolide) |
| Inherent Viscosity | 0.31 dL/g (nominal) |
| Molecular Weight | Mw 40,000-60,000 Da |
| Glass Transition Temperature | 50-55°C |
| Appearance | White to off-white powder or granules |
| Solubility | Soluble in dichloromethane, chloroform, acetone, ethyl acetate; practically insoluble in water |
| Storage Conditions | Store in a tightly closed container in a cool, dry place; protect from moisture. Recommended storage: -20°C |
| Shelf Life | 24 months |
| End Group | Ester-terminated |
| Residual Monomers | ≤ 0.5% |
| Water Content | ≤ 0.5% |
| Heavy Metals | ≤ 10 ppm |
| Loss On Drying | ≤ 0.5% |
| Ash Content | ≤ 0.1% |
As an accredited PURASORB PDLG 8531 Drug Delivery PLGA Copolymer factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | PURASORB PDLG 8531 drug delivery copolymer is supplied in sealed, moisture-barrier foil pouches, typically packaged as 1 kg quantities. |
| Container Loading (20′ FCL) | 20′ FCL container loading: palletized PURASORB PDLG 8531 PLGA copolymer drums, kept dry, sealed, labeled, and securely stowed for transport. |
| Shipping | PURASORB PDLG 8531 is typically shipped at ambient temperature in sealed, moisture-barrier packaging and is not classified as dangerous goods for transport. Upon receipt, store at -20°C, protected from moisture, heat, and repeated temperature cycling. Equilibrate sealed containers to room temperature before opening and keep containers dry and tightly closed. |
| Storage | Store PURASORB PDLG 8531 in a tightly closed, moisture-proof container under cool, dry, well-ventilated conditions, protected from light and heat. Recommended storage is 2–8°C, or −20°C for longer-term preservation. Let sealed containers equilibrate to room temperature before opening to prevent condensation. Avoid humidity, repeated temperature cycling, incompatible materials, and oxidizing agents. Keep containers dry and clearly labeled. |
| Shelf Life | PURASORB PDLG 8531 typically has a 24-month shelf life when stored unopened at 2–8°C, protected from moisture and light. |
Continuous aqueous-phase extraction in a W/O/W double-emulsion line represents the primary commercial route for converting PDLG 8531 into long-acting injectable microspheres. The 85:15 lactide-to-glycolide ratio and acid-terminated chain ends suppress premature hydration relative to 50:50 copolymers, while the nominal inherent viscosity of 0.31 dL/g measured at 0.1 g/dL in chloroform at 25 °C permits formation of low-viscosity organic phases at polymer loadings that would otherwise restrict atomization and solvent extraction. In process terms, the primary oil phase is compounded at 12–25% w/w PDLG 8531 in dichloromethane, with aqueous peptide solution introduced at a water-to-oil volume ratio of 1:5 to 1:10, and the active pharmaceutical ingredient is loaded at 5–20% w/w of total solids, equivalent to polymer:drug mass ratios of 5:1 to 20:1. The secondary continuous phase contains polyvinyl alcohol at 0.5–2.0% w/v and sodium chloride at 0.5–1.0% w/v, with the NaCl functioning to reduce disperse-phase coalescence during hardening. Compliance for this parenteral dosage form is governed by USP <71> sterility testing, USP <85> bacterial endotoxin limits, USP <790> visible particulate inspection, ICH Q3C residual solvent limits including a methylene chloride permitted daily exposure of 6.0 mg/day, and 21 CFR 210/211 for finished drug product manufacturing, with bulk loading and filling performed under ISO 14644-1:2015 Class 5 conditions. Downstream processing on production-scale equipment typically uses a Silverson rotor-stator homogenizer operating at 5,000–10,000 rpm for secondary emulsification, followed by solvent extraction into 10–15 volumes of water at 15–25 °C, hardening for 3–4 h, and lyophilization with trehalose or sucrose at 2–5% w/v as cryoprotectant. The critical process conflict arises because shear-induced temperature rise in the primary emulsion can exceed the 39.6 °C boiling point of dichloromethane at 101.3 kPa, causing vapor nucleation, inhomogeneous polymer precipitation, and an increase in residual solvent burden; rotor-stator speed is therefore capped below the point at which the organic phase approaches this threshold. Batch-to-batch variance in polyvinyl alcohol degree of hydrolysis alters interfacial tension, mean microsphere diameter, and release lag, requiring gel permeation chromatography and scanning electron microscopy release controls on each lot. Finished product types in this application segment include risperidone depot microspheres, exenatide microspheres, triptorelin acetate microspheres, and octreotide acetate microspheres.
Solvent exchange between N-methyl-2-pyrrolidone and interstitial water dictates implant morphology, release onset, and burst control of PDLG 8531 in in situ forming depots. During subcutaneous administration, the acid-terminated 85:15 copolymer is dissolved in NMP at 30–50% w/w, the active pharmaceutical ingredient is incorporated at 3–10% w/w of total formulation, and the liquid is filled into single-use syringes for injection through a 21 G or 23 G needle. Because the polymer solution undergoes phase inversion at the injection site, water ingress precipitates PDLG 8531 from the periphery inward, producing a depot whose initial release is determined by solvent efflux, polymer concentration, and drug lipophilicity. Regulatory compliance for this parenteral product class includes USP <71>, USP <85>, USP <790>, ICH Q3C, ISO 10993-1:2018 biological evaluation planning, and ISO 10993-6:2016 local effects after implantation; NMP is classed as an ICH Class 2 solvent with a permitted daily exposure of 5.3 mg/day, so syringe fill weight and dosing frequency must be designed to keep total NMP administration below this limit. Manufacturing on production-scale equipment uses a vacuum planetary mixer to degas the polymer-drug solution, filtration through a 0.2 µm PTFE membrane where viscosity allows, and aseptic filling under ISO 14644-1:2015 Class 5. Process boundaries are set by sterilization incompatibility: gamma irradiation above 25 kGy generates measurable chain scission in PLGA and a corresponding drop in inherent viscosity, while steam sterilization triggers hydrolysis and premature precipitation, so terminal sterilization by saturated steam or high-dose gamma is unsuitable; aseptic manufacture or low-dose radiation with release-rate verification is required. Published injection-force data for this exact formulation configuration is limited, and force requirement through a 21 G needle must be measured on each batch rather than inferred from polymer concentration alone. Terminal finished product types include leuprolide acetate depot systems using in situ gelling PLGA/NMP carriers and doxycycline hyclate periodontal depots prepared by the same solvent-exchange mechanism.
In ophthalmic drug delivery, hot-melt compounding of an 85:15 PLGA matrix at a melt temperature below the copolymer thermal degradation onset is the preferred route for intravitreal implants when solvent-casting leaves residual methylene chloride above the ICH Q3C option 1 limit of 6.0 mg/day. The glass transition of the copolymer in the 40–50 °C range permits extrusion through a twin-screw micro-compounder with L/D 20:1 to 30:1, zone temperatures of 80–105 °C, and screw speeds of 50–200 rpm; residence time distribution is narrowed to prevent the high-molecular-weight tail from undergoing thermal degradation and discoloration. Formulation addition ratio is constrained by matrix solubility and drug phase separation: a 0.7 mg dexamethasone payload in a 4.5 mg total implant corresponds to 15.6% w/w drug loading, and the same 85:15 matrix can carry 10–20% w/w corticosteroid without evidence of crystalline growth during cooling. Compliance for sustained-release intravitreal devices requires ISO 10993-1:2018 biological evaluation planning, ISO 10993-5:2009 cytotoxicity, ISO 10993-10:2010 irritation and delayed-type hypersensitivity, USP <789> ophthalmic particulate examination, and ICH Q3B extractables control for the finished implant. Processing on production-scale equipment involves extrusion through a circular die, pelletization to lengths suitable for injection through a 22 G applicator, and automated visual inspection; sterility is achieved either by aseptic processing or by a radiation dose verified below the chain-scission threshold. The main process conflict in hot-melt extrusion is the narrow window between matrix softening and chain degradation: at zone temperatures below 80 °C, melt viscosity produces high motor torque and die pressure variation, while above 105 °C, residual moisture and shear heating can initiate hydrolysis. Terminal finished product types are dexamethasone intravitreal implants of 0.7 mg dose for macular edema and posterior uveitis indications.
When PDLG 8531 replaces higher-lactide grades in drug-eluting stent coatings, the 85:15 composition shifts the hydrolytic degradation profile from the 50:50 copolymers commonly used in sub-90-day eluting matrices toward a 4–6 month persistence window that can delay restenosis without extending the inflammatory phase past endothelialization. Coating formulations dissolve sirolimus or everolimus and PDLG 8531 in acetone/tetrahydrofuran mixtures at polymer concentrations of 1–2% w/w, with drug:polymer ratios of 1:1 to 1:3, and total drug dose is controlled to 100–150 µg/cm² of stent surface area. The downstream production process uses an ultrasonic spray nozzle operating at 25–50 kHz to deposit multiple layers onto a rotating cobalt-chromium or platinum-chromium stent fixture, followed by infrared curing at 40–60 °C to remove residual solvent without deforming the stent or melting the polymer coating; coating thickness is verified by profilometry in the 2–5 µm range and surface morphology by scanning electron microscopy. Compliance for coronary and peripheral stent coatings requires ISO 10993-1:2018, ISO 10993-4:2017 hemocompatibility evaluation, ISO 10993-5:2009 cytotoxicity, ISO 10993-10:2010 sensitization and irritation, ISO 25539-1:2017 vascular stent requirements, and 21 CFR 820 quality system regulation for finished medical devices. Process boundaries include the incompatibility of PDLG 8531 with high residual moisture in the coating chamber: humidity above 30% RH during spray deposition produces surface pores and delamination after stent expansion, so coating is performed under dry nitrogen or controlled dew-point air. In addition, the acid-terminated chain ends can interact with metal ions released from cobalt-chromium substrates under prolonged aqueous conditions, making a primer layer of nondegradable polymer necessary to reduce interface corrosion and localized coating detachment. Terminal finished product types include sirolimus-eluting coronary stents and everolimus-eluting peripheral stent systems in which the PLGA coating functions as the rate-controlling drug reservoir.
For intravenous oncology applications, nanoprecipitation of PDLG 8531 under confined impingement mixing is governed by the Damköhler number of the mixing process relative to the polymer supersaturation time constant. In acetone or tetrahydrofuran at polymer concentrations of 5–20 mg/mL, the acid-terminated 85:15 copolymer precipitates into nanoparticles with mean hydrodynamic diameter 100–200 nm when the aqueous-to-organic flow ratio is 5:1 to 10:1 and the active pharmaceutical ingredient is dissolved in the organic phase at a drug:polymer mass ratio of 1:5 to 1:20. A confined impingement jet mixer with Reynolds number above 2,000 or a microfluidic hydrodynamic focusing cartridge with channel width 50–100 µm provides the rapid antisolvent mixing required to maintain a polydispersity index at or below 0.20 when measured by dynamic light scattering according to ISO 22412:2017. Residual solvent control is governed by ICH Q3C, with acetone classed as a Class 3 solvent having a permitted daily exposure of 50 mg/day, while tetrahydrofuran is classed as a Class 2 solvent with a permitted daily exposure of 7.2 mg/day; solvent removal therefore uses reduced-pressure distillation and tangential flow filtration in cascading operations designed to keep product temperature below 30 °C. The process conflict in this segment is concentration-dependent: increasing polymer concentration above 20 mg/mL raises organic-phase viscosity, slows antisolvent diffusion, and broadens particle size distribution tails that are unacceptable for intravenous administration, while reducing polymer concentration below 5 mg/mL lowers encapsulation efficiency below 40% for poorly water-soluble actives and increases free drug crystals after lyophilization. Batch-to-batch variance in acetone evaporation rate alters residual solvent and nanoparticle aggregation, so the reduced-pressure distillation step must maintain product temperature below 30 °C to prevent glass-transition-induced particle fusion. Sterile filtration through a 0.2 µm polyethersulfone membrane is performed prior to lyophilization with trehalose at 2–5% w/v, and the finished lyophilized cake is tested for bacterial endotoxins under USP <85>, sterility under USP <71>, and subvisible particulate matter under USP <787>. Terminal finished product types include paclitaxel PLGA nanoparticle injections, docetaxel PLGA nanoparticle formulations, and small-molecule kinase inhibitor nanoparticle dispersions intended for intravenous administration.
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PURASORB PDLG 8531 is an acid-terminated poly(D,L-lactide-co-glycolide) drug-delivery copolymer with a nominal lactide-to-glycolide molar ratio of 85:15 and an inherent viscosity midpoint of 0.31 dL/g, measured in chloroform at 25 °C at 0.1 g/dL. The product code identifies the comonomer ratio and the target viscosity midpoint: 85 refers to the lactide fraction, 31 to the intended viscosity. This combination of high lactide content and free carboxylic acid end groups places the material between the fast-degrading 50:50 PLGA grades and the slower ester-capped 85:15 analogues. It is used in parenteral controlled-release systems, including microspheres, in-situ forming implants, and solid implants, where the lactide-rich backbone reduces water uptake and delays bulk erosion.
The acid-terminal architecture is a critical distinction: it provides free carboxyl end groups that increase local hydrophilicity near the chain terminus and promote earlier hydration than an ester-terminated PLGA of the same comonomer ratio. This does not make the product a universal slow-release polymer; it makes it a grade with intermediate wetting and degradation behavior. Selection against PDLG 5002, PDLG 5004, or PDLG 7502 requires experimental confirmation because particle size, drug solubility, and route of administration change the observed release profile.
In phosphate-buffered saline at pH 7.4 and 37 °C, PLGA degrades by random ester hydrolysis followed by autocatalytic acceleration. The 85:15 ratio lowers water uptake relative to 50:50 and 75:25 copolymers, shifting the onset of significant mass loss to later time points. Guide values for PLGA 50:50 low-IV grades place bulk erosion within 2–4 weeks, while 85:15 mid-IV grades often remain mass-loss-limited for 8–12 weeks. Published data for this specific configuration is limited, so these ranges should be confirmed with size-exclusion chromatography and mass-loss measurements under the intended release conditions. The acid-terminal group further modifies this profile because the free carboxyl ends enhance early water interaction, making the initial hydration phase faster than an ester-capped 85:15 grade but slower than a 50:50 acid-terminated grade.
In a depot formulation, this shift is useful when a release duration beyond 1–2 months is required but the formulation cannot tolerate the slower initial wetting of a fully end-capped high-lactide PLGA. The product is therefore evaluated in long-acting injectables where the drug has a narrow therapeutic window and where a pronounced initial lag phase could delay the onset of effective plasma concentrations. In such systems, the formulation scientist typically compares PDLG 8531 with PDLG 7502 and with an ester-terminated 85:15 polymer under identical encapsulation conditions.
The PDLG series includes acid-terminated PLGA grades with different comonomer ratios and molecular weights. The table below lists nominal differentiation parameters for PDLG 8531 against representative lower-lactide products.
| Product | Lactide:Glycolide | Terminal group | Nominal inherent viscosity (dL/g) |
|---|---|---|---|
| PURASORB PDLG 5002 | 50:50 | acid | 0.2 |
| PURASORB PDLG 5004 | 50:50 | acid | 0.4 |
| PURASORB PDLG 7502 | 75:25 | acid | 0.2 |
| PURASORB PDLG 8531 | 85:15 | acid | 0.31 |
PDLG 8531 therefore does not simply duplicate a 75:25 acid-terminated PLGA at higher viscosity. The comonomer shift from 75:25 to 85:15 changes solvent interaction, glass transition, and water penetration. Compared with PDLG 5004, which has a comparable mid-range viscosity but a 50:50 ratio, PDLG 8531 hydrates more slowly and produces a more hydrophobic matrix. Compared with PDLG 7502, it has a higher molecular weight and lower glycolide content, so the solution viscosity increases while the hydrolytic degradation rate decreases. These differences mean that formulation changes cannot be limited to a simple polymer swap; the organic-phase viscosity, evaporation rate, and depot hardening must be re-qualified.
For microsphere manufacturing, PDLG 8531 is dissolved in dichloromethane or ethyl acetate at 10–25 wt% polymer concentration. In oil-in-water emulsification, a Silverson L5M-A rotor-stator mixer with a defined tip speed of 8–15 m/s produces crude emulsions; the resulting solvent removal rate controls particle hardening. Because the 85:15 ratio has a glass transition temperature of approximately 45–55 °C as measured by differential scanning calorimetry at 10 K/min under ASTM E1356, the hardened microspheres remain glassy at room temperature. High shear and moisture must be controlled: residual water in the organic phase above 0.1 wt% can reduce inherent viscosity during solvent evaporation and broaden the particle size distribution.
Solubility in common processing solvents follows the high lactide content. PDLG 8531 dissolves in dichloromethane, chloroform, and tetrahydrofuran; ethyl acetate solutions may require warming because the 85:15 copolymer is less polar than 50:50 grades. In injectable in-situ forming depots, N-methyl-2-pyrrolidone at 30–40 wt% polymer is practical; dimethyl sulfoxide can be used where lower solvent toxicity is required, but the solvent exchange rate and depot shape must be re-qualified. The higher lactide content reduces the polymer’s affinity for water-miscible solvents during phase inversion, which can slow solvent efflux and reduce initial burst but may leave residual solvent in the outer depot layer.
Incoming QC is structured around three risks: comonomer ratio drift, molecular weight loss, and contamination by residual monomers or process solvents. The comonomer ratio is verified by nuclear magnetic resonance spectroscopy or gas chromatography after controlled hydrolysis. Inherent viscosity is determined at 25 °C in chloroform at 0.1 g/dL, consistent with dilute-solution viscometry principles under ISO 1628-1. The manufacturer’s release data provide the acceptance interval. Residual D,L-lactide and glycolide monomers are batch-dependent and are reported on the certificate of analysis, with limits aligned to the intended route of administration. Residual tin, process solvents, and water content are tested by the manufacturer and should be re-tested after transport because the solid is hygroscopic.
For heat-labile or high-moisture operations, pre-use Karl Fischer titration is recommended. The glass transition temperature is typically observed between 45 °C and 55 °C by differential scanning calorimetry at 10 K/min under ASTM E1356; a lower value after drying can indicate plasticization by solvent or residual monomer, while a broadened transition can indicate phase heterogeneity. Residual solvent levels should be assessed against ICH Q3C when the polymer is formulated with solvents that are not removed below their permitted daily exposure limits.
The material is not supplied sterile. For parenteral products, terminal sterilization by gamma irradiation above 25 kGy may reduce molecular weight and alter release, so aseptic filtration of the organic phase or low-dose irradiation should be evaluated with molecular weight testing after treatment. Aseptic filtration of a 10–20 wt% PDLG 8531 solution in dichloromethane through a 0.2 µm hydrophilic membrane is feasible when the solution is maintained at 15–20 °C; however, the exact pressure drop depends on solution concentration and membrane type.
Moisture is the primary destabilizer for melt and warm-solvent processing of PDLG 8531. Karl Fischer titration by USP <921> should be used on the solid and on the prepared organic phase. If residual moisture exceeds 0.1 wt%, hydrolytic chain scission during twin-screw extrusion can reduce inherent viscosity by 0.05–0.1 dL/g per pass in a 16 mm co-rotating twin-screw extruder with L/D 40:1 operating with barrel temperatures between 75 °C and 100 °C. The same moisture threshold applies to injection-molded implants; pre-drying under vacuum at 40 °C for 12 h is used, but the dried polymer must be transferred under dry nitrogen because rehydration occurs quickly at relative humidity above 60%.
High shear also generates local heating. In solvent-based emulsification, tip speeds above 15 m/s may cause the organic phase to heat, accelerating solvent loss and producing viscous gel fragments. In twin-screw compounding, high screw speeds can generate frictional heating above the glass transition, leading to localized yellowing and monomer regeneration. The acid-terminal group lowers thermal stability relative to an ester-capped analogue of equal inherent viscosity because carboxyl groups can catalyse intramolecular ester exchange at elevated temperature; processing above 120 °C should be avoided unless residence time is restricted and the screw profile uses low-shear mixing elements.
An acid-terminated PLGA contains free terminal carboxylic acid groups, while an ester-terminated analogue has the chain ends blocked with an alkyl ester. The acid-terminated grade hydrates more readily and degrades somewhat faster than an ester-capped PLGA of the same comonomer ratio and molecular weight. The free carboxyl groups can interact with basic peptide drugs, and this interaction may alter loading efficiency or induce acylation of primary amine residues. For peptide or protein payloads with nucleophilic side chains, an ester-terminated grade is often evaluated in parallel. Conversely, acid-terminal functionality provides a more hydrophilic surface for wetting and can reduce the organic-phase contact angle in microsphere hardening.
The difference is measured not only by release performance but by stability-indicating assays. Reverse-phase HPLC with UV detection at 210–220 nm is used for peptide content and purity; size-exclusion chromatography with multi-angle light scattering is used for polymer molecular weight. Formulations that show a pH drop below 3 in the microsphere interior during accelerated testing may be unsuitable for acid-labile payloads; the high lactide content of PDLG 8531 delays this pH drop relative to 50:50 PLGA, but the acid-terminal end groups can still create low-pH microdomains.
For long-term storage, sealed containers of PDLG 8531 should be kept at -20 °C or according to the manufacturer’s current labeling. Before opening, the container must be allowed to reach ambient temperature under desiccated conditions to prevent condensation. Avoid exposure to strong bases, primary amines, and moist solvents because base-catalysed ester hydrolysis accelerates molecular weight loss. The product should not be commingled with ester-terminated PLGA batches of the same nominal comonomer ratio without re-qualifying release and stability. In solid implant manufacturing, a laboratory injection-molding setup with a 20 mm screw and clamp force of 100–200 kN is often used for rod-shaped implants, with melt temperature held below 120 °C and total residence time kept under 5 min. Published data for this specific configuration is limited; therefore, molecular weight and residual monomer testing after processing remain critical release controls.
